Basic and clinical aspects of selection and application of fiber posts

Simone Grandini

UNIVERSITY OF SIENA SCHOOL OF DENTAL MEDICINE

PHD PROGRAM:

“DENTAL MATERIALS AND CLINICAL APPLICATIONS”

PhD THESIS OF: Simone Grandini TITLE “Basic and clinical aspects of selection and application of fiber posts”

ACADEMIC YEAR 2003/2004 18 December 2004 Siena, Italy Committee: Promoter Prof. Marco Ferrari Co-Promoter Prof. Franklin R Tay Prof. Egidio Bertelli Prof. Carel L Davidson Prof. Manuel Toledano Prof. Michel Goldberg Prof. Piero Balleri

TITLE Basic and clinical aspects of selection and application of fiber posts CANDIDATE Simone Grandini

18 December 2004

CONTENTS

Chapter 1 General Introduction……………………………………..…….……...3

1.1 Differences between healthy and root canal treated teeth………………………….4

1.1.1 Changes in the physical and chemical properties of the tissue……….5

1.1.2 Changes in the morphology and in the biomechanical behavior of

teeth under stress…………………………………………………………………….6

1.1.3 Possible elevation of pain threshold and loss of pressoreceptors....…7

1.2 Relation between fracture resistance of the endodontically-treated teeth and

presence of posts………………..…………………...………………………………………8

Chapter 2 The use of fiber posts in dentistry…………………………………....16

2.1 The use of fiber posts………………………………………………………..…………16

2.2 Fabrication process and structure of fiber posts ………………………………16

2.3 Structure and mechanical properties of fibre posts ……………………………18

2.4 Metal posts versus fiber posts…………………………………………………..19

2.5 Role of the final restoration design (ferrule effect)………...………..……………20

Chapter 3 Preparation of root canal dentin to bonding………..………………26

3.1 Evaluation of Glyde File Prep in combination with sodium hypochlorite as root

canal irrigant: a scanning electron microscopic study……………………………...28

Chapter 4 Criteria for selecting fiber posts ……………………………………..41

4.1 Fatigue resistance and structural characteristics of fiber posts: three-point

bending test and SEM evaluation. …………………………………………………41

Chapter 5 Adjusting the length of a post………………………………….60

5.1 Scanning electron microscopic investigation of the surface of fibre posts after

cutting………………………………………………………………………………60

Chapter 6 Selection of clinical luting procedures ..............................................70

6.1 A one step procedure for luting glass fibre posts: an SEM evaluation…………71

Chapter 7 Anatomic Post: an innovative approach…………………………… 85

7.1 SEM evaluation of the cement layer thickness after the luting procedures of two

different posts……………………………………………………………………….85

7.2 Use of Anatomic Post’n Core for reconstructing an endodontically treated tooth:

a case report………………………………………………………………………...94

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Chapter 8 Clinical aspects and future role of fiber posts in dentistry ……...113

8.1. Clinical evaluation of the use of fiber posts and direct resin restorations for

endodontically-treated teeth ………………………………………………………113

Chapter 9 Summary and conclusions …………………………………..129

Riassunto e conclusioni ………………………………………………………….135

Résumé et conclusions …………………………………………………………..142

Schlußfolgerung …………………………………………………………………149

Resumen y conclusiones .......................................................................................155

Sumário e conclusões ............................................................................................162

Complete list of references ……………………………………………………...169

Acknowledgements ……………………………………………………………...183

CURRICULUM VITAE ………………………………………………………...185

2

Chapter 1 General introduction

The restoration of the endodontically-treated teeth has always been a debated topic.

A tooth requires endodontic treatment as a result of caries, repeated restorative

procedures, or trauma. Many changes occur to a tooth after root canal treatment,

including the physical and chemical properties of dentin, its elasticity, resistance to

fatigue, changes in the morphology and biomechanical behaviour. As early as 1746,

Fauchard (Fauchard, 1746) proposed the insertion of wooden dowels (the first real

“fiber post”) in canals of teeth to give support to crown retention. Since then, many

different materials have been proposed for “reinforcement” and retention of the

restorative core.

This thesis contains a study on several different basic and clinical aspects related to

the selection and use of fiber posts.

Starting from the assessment of the differences between healthy and root canal

treated teeth, the next step was to analyse the relationship between the presence of a

post and root fracture. Fiber posts were the first true alternative to metal posts, and

they jeopardized in the dental market in the last 10 years; for this reason an

overview regarding the properties, advantages and disadvantages of fiber reinforced

materials is presented.

A clean and neat root canal is one of the goals pursued during endodontic treatment.

The first objective of this thesis was to evaluate different irrigating regimes to

achieve a clean root canal before guttapercha condensation procedures and

eventually the insertion of the post.

As actually many fiber posts are available on the market, it is important for the

clinician to know the properties of each fiber post available on the market, and to

consequently select the more appropriate. The second was indeed to conduct a study

to assess the fatigue resistance of different types of fiber posts, and to verify the

existence of a correlation between the fatigue resistance exhibited by the different

types of posts and their structural characteristics. These are also very important

when calibrating a post before or after the luting procedures. Another goal of this

thesis was in fact to evaluate if and how three cutting methods can affect integrity of

fibre posts, and analyse the differences in cutting procedures.

3

Bonding procedures are a prerequisite when using fiber posts. Another step of this

thesis was to evaluate the efficacy of a technique (“one-shot”) -alternative to the

well-established procedure- in forming resin tags, adhesive lateral branches and

RDIZ when luting translucent fibre posts into root canal preparations.

Fibre posts went through rapid developments in the last few years, in particular

when dealing with the shape of the post. Interestingly, starting from the double-

cylinder shape, endodontic shapes and then double tapered shapes were presented,

as the adhesive cementation now relies on formation of resin dentin interdiffusion

zone and resin tags (Ferrari et al 2002) even if the good fitting and mechanical

retention of the post inside the root canal contribute to sliding friction as for non

adhesive cements (Goracci et al 2004). As a matter of fact it is pretty common to

face root canals that are not perfectly round after endodontic instrumentation. A

study was conducted regarding the very last brand of fiber post available (Anatomic

Post’n Core, RTD, St Egrève, France), that is able to reduce the cement thickness

and to immediately restore the coronal portion in cases where the root canal is not

round and a huge loss of tooth structure is present.

Finally a possible future use of fiber posts in combination with a direct resin

restoration is examined for the restoration of root canal treated teeth, according to

the aim of the minimal intervention philosophy.

1.1 Differences between healthy and root canal treated teeth

There is substantial literature stating that endodontically-treated teeth differ from

teeth with a viable pulp (Ingle JA 1973, Walton R et al.,1996). As a matter of fact,

tooth fractures often result in severe damages to non-vital teeth (Angmar-Månsson

et al., 1969, Rud et al., 1970, Meister et al., 1980, Morfis, 1990, Testori et al., 1993,

Bergman et al., 1989, Torbjöner et al., 1995, Fuss et al., 1999), and mostl likely, the

only alternative therapy is extraction. Three main aspects can be analyzed regarding

these differences after root canal therapy: 1) changes in the physical properties and

in the chemical composition, 2) changes in the morphology and in the

biomechanical behavior of teeth under stress, 3) possible elevation of pain threshold

and loss of pressoreceptors.

4

1.1.1 Changes in the physical and chemical properties of the tissue

A vital tooth presents with a stiffer structure (enamel) and a more compliant support

underlying it (dentin). Notwithstanding a fracture that can always occur, teeth

usually exhibit microcracking of the enamel as a consequence of wear (tooth-to-

tooth and tooth-to-food wear). Type I mineralized collagen fibrils are abundant

within healthy dentin. Back in 1998, Nakabayashi and Pashley (Nakabayashi et al.,

1998) demonstrated that these fibrils are able to retard the growth of microcracks

(Sakaguchi et al., 1992), and that if they are removed after root canal treatment a

fracture is more likely to occur. The main physical properties of dentin that were

studied during the years were the modulus of elasticity, the tensile strength and the

compressive strength. Unfortunately results differ a lot from tooth to tooth and

within the same type of tooth (Peyton et al., 1952; Tyldesley 1959). The methods in

which elasticity or the dentin hardness were measured have changed through time.

Using a micro-indentation technique, Lewinstein et al. (1981) observed no

difference in the elasticity and dentin hardness between vital teeth and teeth that

were endodontically treated 5 or 10 years before (Lewinstein et al. 1981). Pashley et

al. (1985) showed that the micro-hardness of coronal dentin is higher in superficial

than in deep dentin. This decrease in hardness may be due to a decrease in the

stiffness of the intertubular matrix (Kinney et al., 1996). Many techniques were used

to measure the modulus of elasticity. Some studies reported values between 15 and

19 GPa (Sano et al., 1995; Van Meerbeek et al., 1993), while the ultimate

compressive strength was around 300 MPa. When the microtensile test was used to

measure the ultimate tensile strength of dentin, values around 100 MPa were

reported (Sano et al., 1994). Irrigating solutions that are used in endodontics have

been reported to have a negative effect on the physical properties of dentin. Micro-

hardness is significantly reduced in root canal dentin after the use of H2O2/NaOCl

and EDTA (Saleh et al., 1999). Different concentrations of NaOCl can also reduce

tooth surface strain, even if no difference was found in the strain recorded after

different irrigation regimes (Goldsmith et al., 2002). Chemical changes may also

occur when a tooth is endodontically treated. Healthy dentin can be described as a

“…biological composite of a collagen matrix filled with submicron to nanometer-

sized calcium deficient, carbonate-rich apatite crystallites dispersed between

5

micron–sized hyper-mineralised, collagen-poor hollow cylinders…” (Marshall et al.,

1997). Dentin is about 50% (vol.) mineral, 20% (vol.) water and 30% (vol.) organic

matrix (LeGeros 1991), but the composition may change with position of the tooth

and even within a tooth (Panighi et al., 1993). Age or disease can affect the

composition: coronal dentin has approximately twice the number of tubules of

radicular dentin and also less inorganic substrate and less intertubular dentin, while

radicular dentin contains less moisture. A 9% lower moisture content was found in

pulpless dog teeth when compared with vital dog teeth (Helfer et al., 1972). A later

study (Huang et al., 1992) showed that dehydration of human dentin increased its

Young’s modulus and that wet dentin specimens from treated pulpless teeth

generally showed lower elastic modulus and proportional limit in compression than

those of normal teeth. Using a method of collagen dissolution, Mason (2001)

demonstrated that the percentage of collagen present in crown and root dentin

decreases after the root canal treatment. The percentage of collagen in crown dentin

of healthy teeth is 21.7%. The value was reduced to 20.1% in teeth that had been

endodontically treated for 2 years, and was further reduced to 16.8% in teeth that

had been endodontically for 10 years. In root dentin the percentages are 25.5%,

23.5% and 19.3% respectively. Moreover, a degradation of resin composite and

depletion of collagen fibrils were observed in specimens that were aged in an oral

environment (Hashimoto et al., 2000). These findings were further confirmed in a

recent transmission electron microscopy study, showing a decrease in the

distribution of the collagen fibrils within root dentin 5 years after endodontic

treatment (Ferrari et al., 2004).

1.1.2 Changes in the morphology and in the biomechanical behavior of teeth under

stress

In 1976, Tidmarsh described the intact tooth as a “…hollow, laminated structure that

deforms under load; this structure may undergo permanent deformation following

excessive or sustained loads…”(Tidmarsh 1976) . In his PhD thesis at the University

of Otago, Grimaldi showed that there is a “…direct relationship between the amount

of central tooth structure lost in cavity preparation and the deformation under

load….after endodontic access preparation the tooth can deform to a greater extent

6

under applied load and thus be more susceptible to fracture. It might therefore be

expected that the removal of dental substance during access cavity preparation and

cleaning and shaping procedures would significantly weaken the tooth…” (Grimaldi

1971). On the other hand, in a study comparing MOD cavity preparation with simple

access opening and endodontic procedures in maxillary second premolars, the

reduction in tooth stiffness was 60% versus 5% (Reeh et al., 1989). The highlights

the importance of preserving the marginal crest as a structure that can compensate

for the stresses generated by the occlusal and chewing forces. Other structures, such

as the presence of intact roofs of pulp chambers, are also important in avoiding root

fractures in a healthy tooth (Fuzzi 1993). Usually, pulpless teeth have lost

substantial coronal and radicular tooth structure from pre-existing restorations,

dental caries, and access cavity preparations (Morgano et al., 1993). The endodontic

procedure in itself can also be an explanation for additional morphological changes.

Excessive flaring during endodontic treatment and poor gutta-percha condensation

procedures were considered as possible causes of root fracture (Trabert et al., 1978,

Milot et al., 1992). The introduction of NiTi rotary instruments has led to great

improvements in the effectiveness and speed of root canal instrumentation, and a

more conservative approach is universally adopted in order to reduce the amount of

tooth structure that has to be eliminated during the root canal treatment. These

instruments allow faster (Schafer et al., 2001, Gambill et al., 1996, Glosson et al.,

1995), more centered (Gambill et al., 1996, Glosson et al., 1995, Bertrand et al.,

2001), rounder (Gambill et al., 1996, Glosson et al., 1995) and more conservative

(Schafer et al., 2001, Gambill et al., 1996, Glosson et al., 1995) shapings of the root

canals than stainless steel instruments.

1.1.3 Possible elevation of pain threshold and loss of pressoreceptors.

Another possible cause of weakness of endodontically-treated teeth might be the

loss of pressoreceptors. There is no clear evidence about this topic. When pain

thresholds of vital and endodontically-treated teeth were analysed with a minimal

load (Lowenstein et al., 1955), it was found that the load thresholds were 57%

higher in endodontically-treated teeth compared to vital teeth. An autoradiographic

study of the sensory innervation of rats’ teeth (Pimenidis et al., 1977) showed the

7

presence of structures similar to corpuscular receptors in the pulp, thereby

suggesting that those tissues may be responsive to modalities other than pain, such

as pressure. Another study (Linden 1975) did not support this hypothesis. More

recent studies on the reflex control of human jaw-closing muscles suggested the role

of periodontal and gingival receptors as potential pressoreceptors (Louca et al.,

1996, 1998).

In conclusion, the general loss of tooth structure in the non-vital tooth, together with

the alterations in collagen distribution, may simultaneously contribute to the

increased susceptibility of endodontically-treated teeth to fracture under loading. A

further reduction in micro-hardness can be induced by the use of irrigating solutions

during endodontic treatment. The loss of water, the increase in deformation due to

the loss of load-supporting structure, and the generation of micro-fractures by gutta-

percha condensation procedures may also contribute to the weakness reported in

endodontically-treated teeth.

1.2 Relation between fracture resistance of the endodontically-treated teeth and

presence of posts

It is a common belief that the likelihood of survival of a pulpless tooth is directly

related to the quantity and quality of remaining tooth structure (Assif et al., 1994,

Guttman, 1992, Cohen et al., 1996). For many years, the concept of using a post for

the restoration of endodontically-treated teeth was based upon the philosophy that

the post would “reinforce” the tooth, and that additional retention was needed for the

core restoration. A post was generally placed in an attempt to strengthen the tooth.

However, as dentin has to be sacrified, especially when a metal post is utilized, and

in consideration of other aspect that will be analyzed later, a post does not

strengthen the root, but serves solely to improve retention of the core (Lloyd et al.,

1993, Sorensen et al., 1990, Morgano et al., 1996, Abou-Rass, 1992). Resistance to

fracture of the non-vital tooth is related with the thickness of remaining root dentin,

especially in the bucco-lingual direction (Guzy et al., 1979, Mattison, 1982, Tjan et

al., 1985). Several factors have been identified (Stockton, 1999, Morgano et al.,

8

1999), in both clinical or laboratory studies, to affect the fracture resistance and the

failure modes of post-core restorations.

An important factor is the type of tooth and its position in the dental arch. It was

found that half of the fractured post-retained teeth were maxillary second premolars

(27.2%) and mesial roots of the mandibular molars (24%). The susceptibility of

these teeth to root fracture increased when the residual sound tooth structure was

less than 1-2 mm (Pilo et al., 1998, 2000; Tamse et al., 1999). Moreover, oval-

shaped canals are more prone to root fracture, as there are more spaces that have to

be filled with luting cements. As the cement dissolves, spaces are inadvertently

created for the post to move inside the dowel space. These micro-movements may

eventually result in dislodging of the post, fatigue of the tooth and root fracture

(Chapman et al., 1985).

Post length is important as well. Many different recommendations have been given

to clinicians regarding this issue (one half, two thirds, three quarters of the root,

below the cemento-enamel junction, as long as possible…etc). Sorensen and

Martinhof (1984a, 1984b) reported a high risk of tooth fracture for teeth with short

posts, while other studies indicated that long posts can affect root resistance because

of the removal of tooth structure in the deepest part of the root itself (Guzy et al.,

1979).

Besides the length, the diameter of the post is also significant. This is related to the

remaining tooth structure. As an increase in post diameter did not provide in

increase in post retention, conservation of remaining tooth structure by avoiding the

use of posts with a large diameters have been recommended (Standlee et al., 1978;

Guzy et al., 1979; Standlee et al., 1980).

Three basic types of clinical study are able to provide information on the incidence

of root fracture in endodontically-treated teeth. They include surveys of root

fractured extracted teeth, retrospective studies on the fracture rate of endodontically-

treated restored teeth, and prospective studies on the fracture rate of certain types of

restorations of endodontically-treated teeth.

Initially, corrosion was cited as a cause of root fractures (Angmar-Månsson et al.,

1969; Rud et al., 1970). In these papers maxillary premolars accounted for 61.5% of

the total number of root fractures, the mandibular premolars accounted for 16.3%,

9

and the other tooth types ranged from 0.4% for mandibular incisors to 5.4% for the

first mandibular molars. These percentages may be partially caused by the

observation that some teeth are endodontically treated and restored with posts less

frequently than others, and by the fact that molars were more commonly extracted in

the era in which these studies were conducted. High percentages of endodontically-

treated fractured premolars, 56% and 52% respectively, were also found in two more

recent surveys of 36 (Testori et al., 1993) and of 92 vertically fractured teeth (Tamse

et al., 1999). The mesial roots of mandibular molars were also frequently extracted

because of root fractures (Tamse et al., 1999). Among all the surveys of tooth

extraction due to root fracture, only the study of Testori et al. (1993) included a

statistical analysis of the results. A significantly higher incidence of fractures in

premolars and molars was found. But the majority of studies available on the root

fractures of endodontically-treated teeth are retrospective in nature (Hansen et al.,

1990a, 1990b; Walton, 1997, 1999). The studies by Sorensen and Martinoff (1984 a,

1984b) are often cited when debating this topic. Their conclusions were that coronal

coverage did not significantly improve the rate of clinical success for anterior teeth

while it improved the rate of clinical success for premolars and molars. Among teeth

restored with posts, the parallel-sided serrated dowel with an amalgam or resin

composite core recorded the highest success rate. The tapered cast dowel and core

displayed a higher failure rate than teeth treated without intracoronal reinforcement.

The parallel-sided serrated dowel did not have failures caused by root fracture,

whereas root fractures caused extractions of teeth restored with tapered cast dowels

and cores. The success rate of teeth with a dowel length equal or greater than the

crown length exceeded 97%. One of the authors’ conclusions was that “…a post did

not significantly strengthen endodontically treated teeth…”. Unfortunately no

prospective studies are available to definitely validate all the aspects analyzed. More

prospective studies are required to evaluate post-core restorations in controlled

clinical situations.

10

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Stockton LW. Factors affecting retention of post systems: a literature review. J

Prosthet Dent 1999;81: 380-85.

Tamse A, Fuss Z, Lustig J, Kaplavi J. An evaluation of endodontically treated

vertically fractured teeth. J Endod 1999;25: 506-8.

Testori T, Badino M, Castagnola M. Vertical root fractures in endodontically treated

teeth: a clinical survey of 36 cases. J Endod 1993;19: 87-91.

Tidmarsh BG. Restoration of endodontically treated posterior teeth. J Endod 1976, 2

:374-75.

Tjan AHL, Whang S. Resistance to root fracture of dowel channels with various

thicknesses of buccal dentin walls. J Prosth Dent 1985; 53: 496-500.

Torbjöner A, Karlsson S, Odman PA. Survival rate and failure characteristics for

two post designs. J Prosthet Dent 1995;73: 439-44.

14

Trabert KC, Caputo AA, Abou Rass M. Tooth fracture: a comparison of endodontic

and restorative treatments. J Endod 1978;4: 341-45.

Tyldesley WR. The mechanical properties of human enamel and dentine. Br Dent J

1959;106: 269-78.

Van Meerbeek B, Willems G, Celis JP, Roos JR, Braem M, Lambrechts P,

VanHerle G. Assessment by nano-indentation of the hardness and elasticity of the resin-

dentin-bonding area. J Dent Res 1993;72: 1434-42.

Walton TR. A 10-year longitudinal study of fixed prosthodontics.1 Protocol and

patient profile. Int J Prosthodont 1997;10: 325-31.

Walton TR. A 10-year longitudinal study of fixed prosthodontics: clinical

characteristics and outcome of single unit metal crowns. Int J Prosthodont 1999;12: 519-26.

Walton R, Torabinejad M. Principles and practice of endodontics, 2nd edition, W.B.

Saunders Co., 1996: 212-14.

15

Chapter 2 The use of fiber posts in dentistry

2.1 The use of fiber posts

The potential of fiber reinforced materials in restorative dentistry has been

appreciated for some time (Bradley et al., 1980). With the introduction of fiber posts

(Duret et al., 1990a; 1990b, 1992), a new trend has been established, in the

restoration of the endodontically-treated teeth. Fiber posts can be considered as

composite reinforced materials. A composite is “any material that is composed of

hard, peeble-like filler particles, surrounded by a hard matrix of a second material,

which binds the filler particles together” (Vichi A et al., 2002). The purpose of

making composite structures is to obtain better mechanical characteristics with the

final material when compared to the single components. As far as fiber posts are

concerned, fibers are embedded in a matrix of epoxy-resin, and an interfacial agent

such as silane is used to optimize the link between the two components.

2.2 Fabrication process and structure of fiber posts

To manufacture fiber-reinforced post, the first step is to produce cylindrical barrels

and then these barrels are machined into different shape and diameter. Pultrusion is

the name for this process, frequently it is a continuous and semi-automated process.

Resin-impregnated fibers are pulled through a series of forming dies. The final die is

heated to cure the resin, thereby producing a rigid composite section. The profile is

determined by the die cross-section which could be round, rectangular, square or a

variety of other shapes. The section produced can either be cut into dicrete lengths

after the puller system or wound onto a drum. The speed of travel through the die is

determined by the viscosity, thickness and curing of the resin. The process uses a

hardened (hard-chromed) steel die and a pultrusion machine (Fig 1).

16

Fig 1. The pultrusion process.

The benefits of this process are increased strength/stiffness of the final product,

especially if compared to the two single components alone. High pressure and

temperatures densify the composite, further impregnating the fibers and eliminating

voids. This process offers a high fiber to resin ratio, which translates directly into

superior strength characteristics of the fiber-reinforced material. Any variation in

pressure and temperature values during the process may result in variation of the

mechanical properties of the material. Finally, a post is fabricated that is composed

of fibers (carbon i.e., 66% in weight, diameter of the single fiber around 10-15

microns) and filler (i.e. epoxy resin, 33% in weight). Fibers can be pre-treated with a

silane-coupling agent to obtain a chemical bond between the fibres and the resin.

This applies to glass, quartz and even carbon fibers. As a matter of fact fibers must

be treated just after their manufacturing. Otherwise it is impossible to work with

because fibers will be in all direction, not assembled. They will stick and will not

have enough rigidity for handling (just like a roving of cotton). And one the goal of

the treatment is to allow fibers to be handled, stored in roving. The addition of silane

during the pultrusion process gives more stability to the system, and is the key factor

for success in manufacturing. The importance of this topic will be discussed in

chapter 4. In general, the addition of silane-coated glass fiber to BIS-GMA resin

increases the elastic modulus, tensile and compressive strengths compared with non-

treated fibers. The use of carbon fibers for the reinforcement of

polymethylmethacrylate used for the construction of denture bases was first

suggested by Schreiber in 1971. When a fiber post is manufactured, the “composite”

17

that is formed is anisotropic: as a consequence mechanical properties differ

according to the direction of measurement.

2.3 Structure and mechanical properties of fibre posts

The Composipost (RTD, St Egrève, France) is the most studied carbon-fiber post. It

was described by its inventors as a post fabricated from continuous, unidirectional

high performance, pyrolytic carbon fibers, 8 µm in diameter uniformly embedded in

an epoxy-resin matrix (Duret et al., 1990a, 1990b). The fibers constitute 64% by

volume of the post. A coupling agent, that is usually called “silane”, is used to link

the fibers to the epoxy resin matrix. It is usually a mixture containg silane but not

only silane (with wetting agent, coupling amino agent for example). “Silane” is a

general word”. A silane is a chemical component with two extremities (at least), one

is really silane (OH) and the other is epoxy if the manufacturer wants to use it with

epoxy resin. But this extremity can be methacrylate when the resin matrix is

methacrylate. Definitely the “silane” must be selected to be suitable with the resin

matrix. This “silanisation” is made by the manufacturer at a temperature of 160-

180°C. There’s first a heat treatment and then a chemical treatment to fix coupling

agent (like silane). Manufacturers do not give much details but the first treatment is

a physical treatment to enhance the power of the silanisation.

The epoxy resin matrix is injected into the pre-tensioned fiber bundle. The original

Composipost was not radio-opaque; the radio-opacity was obtained in the second

generation of these posts (Composipost Radio-opaque, RTD) by the injection of a

high-molecular weight element powder into the un-polymerized post structure.

Many different types of carbon, quartz, silica-zirconium and glass fibers are now

available in the market: carbon was the first material used for manufacturing fiber

posts. These posts represented the first true alternative to cast post and cores, and to

pre-fabricated metal posts.

The following chart shows the mechanical properties of these kinds of posts. COMPOSIPOST No radiopaque TENSILE STRENGTH* 2900 MPa TENSILE MODULUS OF ELASTICITY* AT 30° 17-18 GPa FLEXURAL STRENGTH** 1900 MPa FLEXURAL MODULUS OF ELASTICITY** 135 GPa INTERLAMINATE SHEAR STRENGTH** 65-95 MPa * values determined by calculations. ** values determined by testing raw material

18

The use of glass and quartz fibers was initially proposed as an alternative to the dark

colour of carbon posts. Even though a ceramo-metal crown, and often even a full

ceramic crown is able to mask the dark colour of the post underlying the restoration

(Vichi et al., 2000), “esthetic” posts eventually gained popularity (Ferrari et al.,

2001). Moreover, during the preparation of the abutment (when a carbon fiber post

was selected), a dark powder was spread all around the mouth of the patients, who

sometimes complained because of this fact. As far as esthetics is concerned, several

brands of translucent glass fiber posts are available. They are better accepted than

carbon fiber posts, especially for anterior roots that provide support to all-ceramic

coronal restorations. The mechanical behaviours of these newer generations of posts

do not seem to differ from the first generation of fiber posts (Mannocci et al., 1999;

Grandini et al., 2004). By further adding a component usually in the resin matrix,

radiopaque posts can be obtained. Finally, translucent fiber posts are now available

to be used in combination with a dual curing resin cement and to take advantage of

light passing through the post for polymerization.

2.4 Metal posts versus fiber posts

The technique for the preparation of cast post and cores requires the clinician to

prepare the dowel space in order to finally have a length equal to two thirds of the

root, a width equal to one third of the root and 3-4 mm of root canal filling left at the

apex of the root (Shillimburg et al., 1982). In the last decades many opinion leaders

stressed the fact that a well-performed cast post and core could work for years

(Shillimburg et al., 1982). However, this kind of restoration has a failure rate

ranging from 6 to 10% in the literature (Morgano et al., 1993, Sorensen et al., 1984,

Torbjoner et al., 1995). Failure rate can even be worse as far as pre-fabricated metal

posts are analyzed (Tjan et al., 1985, Fuss et al., 1999). It was previously thought

that in order to achieve success with post-retained restorations, the post had to be as

strong, as long and as stiff as possible (Shillimburg et al., 1982, Sorensen et al.,

1984, Morgano et al., 1993, Torbjoner et al., 1995). However, metal posts can only

be successful if they do not overpass the elastic limit of the dentin (Desort et al.,

1983, Leary et al., 1987). As “…retention often requires the removal of tooth

structure…it is a procedure that may reduce the strength of the root…when placing a

19

post, the dentist must evaluate each tooth individually to determine the best

approach to obtaining the maximal fracture resistance…” (Stockton, 1999). In a

study comparing cast post and cores and carbon fiber posts, 200 patients were

examined. The failure rate for cast post and cores (Group 1, high modulus

restorations in terms of modulus of elasticity) and fiber posts (Group 2, low modulus

restorations) was totally different. Group 1 had 84% clinical success, 2% excluded

for non-compliance, and 9% root fracture (no need to inderline), 2% dislodgement

of crown, 3% endodontic failures. Conversely Group 2 had 95% clinical success,

3% excluded for non-compliance, 2% endodontic failures. The difference between

the two groups was highly statistically significant (Ferrari et al., 2000). For this

reason, clinical acceptance of fiber posts is now higher than it was before. The

advantage of having no root fracture is very important. Failure can occur as a

“debonding” of the post, especially at the time of removing the temporary

restoration, but this failure can easily be dealt with by repeating the adhesive

procedures. When fiber posts and a core and metal posts and a core were compared,

it became more and more obvious that the first ones functioned more satisfactorily.

As far as the mechanism of failure is concerned, metallic posts on failure tend to

produce an irreversible root fracture. Conversely, in the presence of a fiber post, root

fracture that occurs is usually located more coronally and is more easily retreatable

(Reagan et al., 1999, Ukon et al., 2000, Cornier et al., 2001). This type of failure

may be due to the wider amount of tooth structure must be sacrificed when a

metallic post is placed (Stankiewicz et al., 2002). Two recent papers underlined the

concept mentioned above: even if a crown is made, when a failure occurs, favorable

fractures are seen in teeth restored with fiber posts and resin cores, whereas

unfavorable fractures or failures are usually encountered with the use of a metal

post, or a fiber post of bad quality (Heydecke et al., 2002, Akkayan et al., 2002).

2.5 Role of the final restoration design (ferrule effect)

It is known that post luting in a way brings to the transportation of stresses in the

root canal and eventually to vertical root fractures (Guzy and Nicholls 1979).

Coronal coverage has always been considered a very important factor for preventing

root fractures in endodontically treated teeth (Frank 1959). Many years ago it was

20

suggested (Rosen 1961) that a sub-gingival collar might provide an extra-coronal

bracing able to prevent fractures of the root. The term “ferrule effect” was used for

the first time in 1987 by Eissman and Radke and it indicates a 360-degree ring of

cast metal that embraces the tooth.

A ferrule is defined as a metal ring or cap used to strengthen the end of a stick or

tube (Glossary of Prosthodontic terms). The effect of a metal collar on stress

distribution with cast post and cores was studied by using three-dimensional

photoelastic models of maxillary canine teeth of average dimensions. Standardized

parallel post and cores cemented into the models were used, with half of the samples

incorporating a 1.5 mm metal collar, and a 400 gm load was applied to the cingulum

of the cores. Stresses were then calculated and, on a point by point basis, a better

distribution was found in the collared specimens (Loney et al 1990). Another

simulation study was designed to compare the effect of different corono-radicular

reconstruction methods on stress transmission to dental tissues. Whatever the type of

stress (tensile or compressive), the greatest stress was observed in the cervical

region, regardless of the model. The absence of a cervical ferrule was found to be a

determining negative factor, giving rise to considerably higher stress levels.

Nevertheless, the peripheral ferrule seemed to cancel the mechanical effect of the

reconstruction material on the intensity of the stresses. Moreover, when a ferrule

effect was achieved, the choice of reconstruction material had no impact on the level

of cervical stress (Pierrisnard et al 2002). In another in vitro study it was

demonstrated that increasing the ferrule length of the endodontically treated teeth

from 1 mm to 1.5 mm in specimens restored with quartz-fiber and glass-fiber dowels

did not produce significant increases in the failure loads. No significant difference

was detected between glass-fiber and glass-fiber plus zirconia dowels with 1.5-mm

and 2.0-mm ferrules. However, fracture thresholds were higher for all 4 dowel

systems tested in the study when the specimens were prepared with a 2.0-mm ferrule

length (P<.001) (Akkayan 2004). Also among clinicians the ferrule effect was

perceived as an important factor; responses to a questionnaire sent to 1000 dentists

in Switzerland showed that most of the answering dentists strove to stabilize the

remaining tooth structure by circular enclosure of the tooth structure by the later

crown (ferrule effect) (Tinner et al 2001). In a recent literature review Stankiewicz

21

underlined that a ferrule effect occurs owing to the artificial crown bracing against

the dentine extending coronal to the crown margin. Overall, the author concluded

that a ferrule is desirable, but should not be provided at the expense of the remaining

tooth/root structure. (Stankiewicz et al 2002). Another important factor is the height

of the remaining tooth structure between the core and the crown margin: this is a

much more significant factor in determining the fracture resistance of teeth (Hunter

et al 1991). For this reason the crown lengthening surgical procedure has been taken

into account to obtain a consistent height of the remaining tooth structure and

eventually a desirable ferrule effect (Gegauff 2000).

In conclusion, a ferrule effect is desirable when restoring compromised

endodontically treated teeth. Crown lengthening can be considered as one of the

therapeutic options, and a positive crown/root ratio is an important factor for

predicting success of the treatment.

22

References

Akkayan B, Gulmez T. Resistance to fracture of endodontically treated teeth

restored with different post systems. J Prosthet Dent 2002; 87: 431-437.

Akkayan B. An in vitro study evaluating the effect of ferrule length on fracture

resistance of endodontically treated teeth restored with fiber-reinforced and zirconia dowel

systems. J Prosthet Dent. 2004 Aug;92(2):155-62.

Bradley JS, Hastings GW, Johnson-Nurse C. Carbon fibre reinforced epoxy as a

high strength, low modulus material for internal fixation plates. Biomaterials 1980;1, 38-40.

Cornier CJ, Burns DR, Moon P. In vitro comparison of the fracture resistance and

failure mode of fiber, ceramic and conventional post systems at variuos stages of restorations.

J Prosthodont 2001; 10: 26-36.

Desort KD. The prosthodontic use of endodontically treated teeth: theory and

biomechanics of post preparation. J Prosthet Dent 1983;49:203-6.

Duret B, Reynaud M, Duret F (1990 a) Un noveau concept de reconstitution

coronoradiculaire: le Composipost 1°. Le Chir Dent de France 540:131-41.

Duret B, Reynaud M, Duret F (1990 b) Un noveau concept de reconstitution

coronoradiculaire: le Composipost 2°. Le Chir Dent de France 542: 69-77.

Duret B, Reynaud M, Duret F (1992) Intérêt des materiaux á structure

unidirectionnelle dans les reconstitutions corono-radiculaires. Journal de Biomateriaux

Dentaires 7:45-57.

Eissman HF, Radke RA. Postendodontic restoration. In Cohen S, Burns RC, editors.

Pathways of the pulp 4th ed. St Louis CV Mosby 1987:640-43.

Ferrari M, Vichi A, Garcia Godoy F. A retrospective study of fiber-reinforced

epoxy resin posts vs. cast post and cores: a four year recall. Am J Dent 2000;13:9B-14B.

Ferrari M, Vichi A, Grandini S, Goracci C. Efficacy of a self-curing adesive-resin

cement system on luting glass-fiber posts into root canals: an SEM investigation. Int J

Prosthod 2001;14:543-9.

Frank AL. Protective coverage of pulpless teeth. J Am Dent Assoc 1959;59: 895-

900.

Fuss Z, Lustig J, Tamse A. Prevalence of vertical root fractures in extracted

endodontically treated teeth. Int Endod J 1999;32: 283-86.

Gegauff AG. Effect of crown lengthening and ferrule placement on static load

failure of cemented cast post-cores and crowns. J Prosthet Dent. 2000 Aug;84(2):169-79.

23

Grandini S, Goracci C, Monticelli F, Tay FR, Ferrari M. Fatigue resistance and

structural characteristics of fiber posts: three-point bending test and SEM evaluation. Dent

Mat 2004, in press.

Guzy GE, Nicholls JI. In vitro comparison of intact endodontically treated teeth

with and without endo-post reinforcement. J Prosthet Dent 1979;42: 39-44.

Heydecke G, Butz F, Hussein A, Strub JR. Fracture strength after dynamic loading

of endodontically treated teeth restored with different post-and-core systems. J Prosthet Dent

2002; 87: 438-445.

Hunter AJ, Hunter AR. The treatment of endodontically treated teeth. Curr Opin

Dent. 1991 Apr;1(2):199-205.

Leary JM, Aquilino SA, Svare CW. An evaluation of post length within the elastic

limits of dentin. J Prosthet Dent 1987;57:277-81.

Loney RW, Kotowicz WE, McDowell GC. Three-dimensional photoelastic stress

analysis of the ferrule effect in cast post and cores. J Prosthet Dent. 1990 May;63(5):506-12.

Mannocci F, Ferrari M, Watson TF. Intermittent loading of teeth restored using

quartz fiber, carbon-quartz fiber, and zirconium dioxide ceramic root canal posts. J Adhes

Dent. 1999;1:153-8.

Morgano SM, Milot P. Clinical success of cast metal post and cores. J Prosthet Dent

1993; 70:11-6.

Pierrisnard L, Bohin F, Renault P, Barquins M. Corono-radicular reconstruction of

pulpless teeth: a mechanical study using finite element analysis. J Prosthet Dent 2002

Oct;88(4):442-8.

Reagan SE, Fruits TJ, Van Brunt CL, Ward CK. Effects of cycling loading on

selected post-and-core systems. Quintessence Int 1999; 30: 61-67.

Rosen H. Operative procedures in mutilated endodontically treated teeth. J Prosthet

Dent 1961;11: 973-86.

Schillimburg HT, Kessler JC. Restoration of endodontically treated teeth.

Quintessence Publishing Co Inc Chicago 1982.

Schreiber CK. Polymethylmetacrilate reinforced with carbon fibres. Br Dent J 1971;130: 29-

30.

Sorensen JA, Martinoff JT. Intracoronal reinforcement and coronal coverage: a

study of endodontically treated teeth. J Prosthet Dent 1984;51: 780-84.

Stankiewicz NR, Wilson PR. The ferrule effect: a literature review. Int J Endod

2002; 35: 575-581.

24

Stockton LW. Factors affecting retention of post systems: A literature review. J

Prosthet Dent 1999; 81: 380-5.

Tinner D, Marinello C, Kerschbaum T. The preprosthetic preparation of the

endodontically treated abutment tooth. Post and core technique: a questionnaire analysis.

Schweiz Monatsschr Zahnmed 2001;111(4):402-9.

Tjan AHL, Whang S. Resistance to root fracture of dowel channels with various

thicknesses of buccal dentin walls. J Prosthet Dent 1985; 53: 496-500.

Torbjöner A, Karlsson S, Odman PA. Survival rate and failure characteristics for

two post designs. J Prosthet Dent 1995;73: 439-44.

Ukon S, Moroi H, Okimoto K. Influence of different elastic moduli of dowel and

core on stress distribution in root. Dent Mater 2000; 19: 50-64.

Vichi A. A study into application of fiber technology into fiber posts. PhD thesis,

Amsterdam 2002.

Vichi A, Ferrari M, Davidson CL. Influence of ceramic and cement thickness on the

masking of various types of opaque posts. J Prosthet Dent 2000; 83: 412-7.

25

Chapter 3 Preparation of root canal dentin to bonding

Success in endodontic treatment is a key factor to allow success in the restoration of

root canal treated teeth. A well performed endodontic treatment is based on the

removal of debris and organic material inside the root canal (Castellucci 1993) and

on the mechanical preparation of the canal itself to receive an obturation material

(Ingle 1993). The importance of apical seal has been already underlined in the

literature (Walton et al 1996). More recently coronal seal has acquired the same

importance, and many authors concluded that exposure to the oral cavity of a well

performed endodontic treatment (not preventing from coronal leakage) inevitably

brings to a re-infection and in conclusion to a failure (Madison et al 1987 and 1988,

Swanson et al 1987). In 1985 Saunders evaluated the long-term coronal leakage in

root fillings achieved by 2 gutta-percha techniques using 2 calcium hydroxide-

containing sealers. Coronal leakage was then determined with an India ink tracer

and a clearing technique. The extent of coronal leakage was measured with a

magnification device and the authors concluded that all the techniques analyzed

were subjected to extended leakage (Saunders et al 1985). In another study three

common sealers were evaluated for coronal leakage using an animal model in vivo.

After 45 days exposure to the oral cavity, none of the sealers was capable of

preventing leakage and coronal dye penetration (Kopper et al 2003).

The detrimental effect of eugenol on adhesion of resinous cements has been taken

into consideration (Tjan et al 1992, Schwartz et al 1998). Resin composites

polymerise by the addition of free radicals; this process may be inhibited by

phenolic compounds, such as eugenol (2-methoxy-4-allyphenol) that is contained in

the vast majority of endodontic sealers and temporary filling materials, and can

penetrate into the root canal walls (Kielbassa et al 1997). The contact of eugenol

with the dentinal walls significantly altered the dentin penetration of dentin bonding

system (Mayer et al 1997). For these reasons the persistence of eugenol into the root

canal walls has been advocated as a cause of some inconsistent results of posts

cemented with adhesive resins. Unfortunately, the results of the studies about post

retention are not reliable because they were performed on root canals that were

different in shape and sizes. As a consequence it is not possible to establish whether

26

the force needed to remove the post was the result of adhesion of the cement to root

dentin or of the different degree of adaptation of the post to the varying

morphologies of the root canals of the teeth used. The adhesive strength of resin

composites to tooth structure may be simply influenced by the cleanliness of tooth

surface; in two recent investigations (Watanabe et al 1997) on temporary cement

remnants as adhesion inhibiting factors in the interface between resin cements and

bovine dentin, the temporary cement application significantly decreased the tensile

bond strength of all adhesive systems employed. The contamination with various

agents of enamel and dentin surface lowered the bond strength of resin composite

restorations performed with different bonding agents (Xie et al 1993). Both eugenol

containing and eugenol free temporary cements decreased the tensile bond strength

of resin luting cements to bovine teeth (Terata 1993). No difference was reported in

leakage of resin luted inlays when the cavity preparations were treated with either

eugenol-containing or eugenol-free temporary cements (Woody et al 1992).

Definitely, as the effect of eugenol is generally limited to superficial dentin, and as a

certain removal of tooth structure always happens during preparation for post

placement, it is likely to happen that the eventually inhibited layer is removed, and a

lack of adhesion can be explained differently. The preparation for post placement

can be performed in two ways: with hot pluggers and with burs (Ferrari et al 2003).

Burs are usually preferred as they are faster and allow a higher removal of debris,

leaving a cleaner dowel space where adhesive luting can be performed. Recently

Serafino evaluated the cleanness of root dentin walls after mechanical preparation

and etching procedure. All the tested procedures showed a clean walls’ surface.

Pieces of guttapercha remained along the canal walls where the drill shape did not

follow the root canal shape. Endodontic cement and small amount of guttapercha

were noted closing dentinal tubules in some areas of the root walls (Serafino et al

2004). It is obvious then that high accuracy has to be put when preparing the dowel

space, and that a rotating brush could improve the cleanness of the post space. But

the starting point is always that the endodontic procedure has to be well performed if

we look for success in restoring root canal treated teeth. The following SEM study

regards different irrigating regimes used during endodontic treatment to achieve a

clean root canal before guttapercha condensation procedures.

27

3.1 Evaluation of Glyde File Prep in combination with sodium hypochlorite as

root canal irrigant: a scanning electron microscopic study.

It is well known that the irrigation of the root canal plays a critic role in the

determination of success in the endodontic therapy (Walton et al 1996). Several

studies demonstrated that the quantity of debris found after the instrumentation is

higher in canals prepared without irrigating solutions than in cases where irrigating

solutions have been used (Goldman et al, 1981). Even in canals where a proper

preparation had been performed, Davids et al (1972) experimentally demonstrated

that there were not instrumented areas where organic and inorganic debris could be

found. On the other hand dentin instrumentation always causes the formation of a

thin smear layer which recovers the whole surface of the root canal. Ostby (1957)

was the first one to use EDTA as an irrigating solution, with a chelating action, to

remove the inorganic component. With the same purpose solutions of sodium

hypochlorite have been later proposed, varying the concentration from 2% to 5%

(Mc Comb et al 1975, Brannstrom et al 1974, Pashley et al 1981). So far EDTA was

considered the best irrigating for removing the inorganic component of the smear-

layer and, in association with sodium hypochlorite, showed the best results

(Goldman et al 1984, Aktener et al 1993).

Different morphological observations can be performed to evaluate smear layer and

remained debris after endodontic instrumentation and irrigation of the root canal

(Peters et al 2000). Barbakov et al (1998) proposed a quantitative evaluation of

smear layer and debris presence along root canal walls, based on serial

photomicrographs placed next to each other, forming a continuous horizontal

examination strip at three levels (2-, 6-, 10-mm from the apex) of the canal walls.

Recently a new chelating agent (Glyde File Prep, Dentsply-Maillefer, Ballaigues,

Switzerland) containing EDTA has been proposed.

The aim of the present study was to evaluate 1. the smear layer, debris and tubule

orifices of root canal walls after being instrumented and irrigated by Glyde File Prep

and 2. the null hypothesis that different irrigating techniques can not determine any

difference on amount of debris along root canal walls.

28

3.2 Materials and Methods

Forty mandibular anterior teeth (incisors and canines), stored in 0.1% thymol, were

randomly selected for this study from the department’s stock of extracted teeth.

Canal morphology was verified from radiographs (70 kV and 0.08 s) taken both

buccolingually and mesiodistally (Kodak, USA). The crowns were resected to

ensure good visibility of the canal and optimal access.

Final working lengths were set by deducting 1 mm from lengths recorded when tips

of size 10 or 15 K-files (Dentsply-Maillefer, Ballaigues, Switzerland) were visible at

the apical foramina. All working lengths were confirmed radiographically. The

coronal 3 to 4 mm of the canals were prepared with Gates-Glidden burs (sizes 2

through 4). The teeth of all groups were shaped with Ni-Ti (Profile 0.4-0.6 –

Maillefer) instruments. The instrumentation was performed exactly according to the

manufacturer’s instructions. ProFile (PF, Dentsply-Maillefer) instruments were used

in a modified crown-down approach after using Gates-Glidden burs and the step-

down technique. The coronal two-thirds were enlarged using PF sizes 5, 4 and 3,

sequentially. The size 2 instrument was used in most canals, but the size 1 PF was

not used at all. Apical preparations were then completed using nos. 3, 4, 5 and 6 PF

instruments. Finally, canals were stepped-back using PF instruments nos. 7, 8 and 9.

Each set of PF instruments was discarded after preparing 10 canals.

The specimens were randomly assigned to four equal groups of 10 each (Table 1).

Table1: Type of irrigant used in the different groups Group Irrigant

Group A Physiological solution

Group B NaOCl 2.5%

Group C NaOCl 2.5% and GFP

Group D NaOCl 2.5% and GFP (PP)

Legends: NaOCL= Sodium Hypochlorite, GFP= Glyde File Prep, PP= Paper points

All canals were flushed with 10 ml of the test irrigant using disposable syringes and

27-gauge needles. The total time of irrigation has been 30 minutes per canal. Group

A was irrigated with physiological solution; Group B with sodium hypochlorite

2.5%; Group C with sodium hypochlorite 2.5% and Glyde File Prep alternately.

Group D was irrigated with sodium hypochlorite 2.5% during the preparation, the

29

root canals were then dried and Glyde File Prep applied with sterile paper points

(Mynol) and left for five minutes. At the end a further irrigation with sodium

hypochlorite 2.5% was performed. It must be noticed that in Group C Glyde File

Prep has been used following manufacturer’s instructions, while in Group D a

modified technique has been performed. In Group C Glyde File Prep was used

alternating it as irrigant with sodium hypochlorite during the preparation. In Group

D, instead, only sodium hypochlorite was used during the preparation, and after that

Glyde File Prep was applied with a paper point and left for five minutes. At the end

a further irrigation with sodium hypochlorite was performed.

After preparing the canals, the teeth were sectioned along their buccal and lingual

surfaces, using a low speed diamond saw (Isomet, Buhler, Lake Bluff, NY, USA).

The root halves were coded and examined in a stereomicroscope (Nikon, Germany).

The coded, halved specimens were then dried, mounted on metallic stubs, gold-

sputtered (Balzers CSD 030, Balzers, Liechtenstein), and evaluated using a scanning

electron microscope (SEM) at low (x10 and x 15) and higher (x200 and x500)

magnifications (Philips, 515, Amsterdam, The Netherlands) at the apical, middle and

coronal levels. Serial SEM photomicrographs at x500 original magnification were

taken of the canal walls at the 2-, 6-, and 10-mm levels. The serial photomicrographs

were placed next to each other, forming a continuous horizontal examination strip at

three levels (Fig. 1). Irrespective of the number of photomicrographs needed to form

a complete strip, each strip was subdivided into eight “assessment units” (Barbakow

et al 1998).

The amounts of debris, smear layer and the visibility of open tubules were rated

using a 4-step scale method by the same person (M.F.) who was unaware of the

coding system to exclude observer bias. Evaluation was repeated twice for the first

20 specimens to ensure intraexaminer consistency. The amount of debris present at

x500 magnification was graded between 0 and 3 (Table 2a).

Table 2a : Debris scores Score 0 1 2 3

Description No debris Few debris particles,

with a diameter

< 20 microns

Many debris particles,

with a diameter

< 20 microns

Many debris particles,

with a diameter

> 20 microns

30

A debris score of 0 was assigned when no debris was present. A score of 1 was

assigned when few debris particles were present, whose largest diameter was less

than 20 microns. A score of 2 was recorded when large quantities of debris particles

were present, whose diameter was less than 20 microns. A score of 3 was assigned

when large amounts of debris particles were present, whose diameters were greater

than 20 microns in any direction. The amount of smear layer and the opening of the

dentinal tubules were graded between 0 and 3 (Table 2b).

Table 2b: Smear layer and dentinal tubules scores Score 0 1 2 3

Description Open dentinal tubules.

No smear layer nor

calcospherites

Some open dentinal

tubules. A thin

smear layer is

present

All dentinal tubules

covered by a thin

smear layer

All dentinal tubules

closed by a thick

smear layer

A score of 0 was assigned when all dentinal tubules were open and no smear layer

was present or not instrumented calcospherites were noted. A score of 1 was

recorded when some dentinal tubules were open and a thin smear layer covered the

openings of the cut dentinal tubules. A score of 2 was recorded when all dentinal

tubules were covered by a thin smear layer. A score of 3 was assigned when all the

dentinal tubules were closed by a thick smear layer.

Mean debris, smear layer and open tubules scores were calculated for Groups A, B,

C and D and statistically evaluated using the Kruskal-Wallis and Mann-Whitney U

tests at p 0.001 level.

3.3 Results

The mean amounts of debris, smear layer and open tubules found at the 2-, 6- and

10-mm levels in the test groups are listed in Tables 3 and 4 respectively.

To indicate the distribution of the individual scores, medians are recorded for the

debris, smear layer and open tubules in Tables 3 and 4 respectively.

Mean debris scores for Group A and B were significantly higher than those found in

Groups C and D. Lower debris scores were recorded in Groups C and D, in those

Groups in which Glyde File Prep was used (Table 3).

31

Table 3: Debris scores (The groups with the same letter did not show statistically significant differences).

Group A (Scores) 0 1 2 3 Median

Apical level / / 1 9a 2.9

Medium level / / 1 9a 2.9

Coronal level / / 2 8a 2.8

Group B (Scores) 0 1 2 3 Median

Apical level / / 4 6a 2.6

Medium level / 1 4 5ab 2.4

Coronal level / 2 4 4b 2.2

Group C (Scores) 0 1 2 3 Median

Apical level 2 3 2 3bc 1.9

Medium level 3 3 3 1d 1.2

Coronal level 5 2 1 2d 1.0

Group D (Scores) 0 1 2 3 Median

Apical level 3 3 3 1d 1.2

Medium level 4 2 2 2d 1.2

Coronal level 6 2 2 /e 0.6

Differences in the mean amounts of debris between Group A and the different

irrigation regimes (Group B, C and D) were highly significant (p < 0.001).

Mean smear layer and open tubules scores for the four groups are listed in Table 4. Table 4: Smear layer and open tubules scores (The groups with the same letter did not show statistically

significant differences).

Group A (Scores) 0 1 2 3 Median

Apical level / / / 10a 3

Medium level / / / 10a 3

Coronal level / / / 10a 3

Group B (Scores) 0 1 2 3 Median

Apical level / 2 3 5b 2.3

Medium level / 2 4 4b 2.2

Coronal level / 4 2 4b 2.0

Group C (Scores) 0 1 2 3 Median

Apical level 3 3 2 2d 1.3

Medium level 4 4 2 /e 0.8

Coronal level 6 3 1 /e 0.5

Group D (Scores) 0 1 2 3 Median

Apical level 4 3 3 0de 0.9

Medium level 5 4 / 1e 0.7

Coronal level 6 2 2 /e 0.6

32

A high amount of smear layer and no visibility of tubules on the prepared canal

walls were found when physiological solution was used as the only irrigant (Group

A). Mean amounts of smear layer scores in Group A reached the maximum score of

3. When sodium hypochlorite 2.5% was used (Group B) as irrigant, the samples

showed less smear layer and more open tubules compared with Group A samples.

When Glyde File Prep was used, in both tested techniques, the lowest scores were

noted, and Group C and D had significantly less smear layer and more open tubules

on the canal walls at the apical, mid-third and coronal levels, respectively, compared

with Group A and B samples. Although there is not a statistically significant

difference between Group C and D, Group D showed better scores than Group C.

3.4 Discussion

Smear layer is produced every time a canal is instrumented. The smear layer,

which is mainly inorganic, is also made up by a slight organic component (proteinic

agglomerates, vital or non-vital pulp tissue, odontoblastic processes, bacteria and

blood cells) (2,5). The thickness and composition of smear layer can vary depending

on the kind of dentin and the instruments used (Mader et al 1984, Davis et al 1972,

Mc Comb et al 1975). The smear layer can be organized in two layers: superficial

smear-layer, made up by a 1-2 microns layer above the intertubular dentin, adhering

on it and becoming indistinguishable from it, and smear-plugs within dentinal

tubules, deepening for about 2-40 microns with a fingerlike or small-tube segments

aspect (Mader et al 1984).

There is a rich but conflicting scientific data regarding the choice between

removing or leaving the smear-layer from the dentinal wall. Some authors reported

that the smear layer remaining on the canal walls should have two positive effects:

to reduce the dentin permeability (about 40%) and to block the way through the

tubules for bacteria and endotoxins in a mechanical way (13,14). Other authors

emphasize the need of creating smear free canalar surfaces. Brannstrom e Nyborg

(1974) demonstrated that the smear-layer can give shelter to anaerobic

microorganisms, thus creating a chronic focus of irritating substances. In 1982

Akpata and Blechman (1982) confirmed the smear layer permeability to

streptococcus. Moreover Williams and Goldman (1985) demonstrated that the

33

smear-layer can slow, but not block the way of microorganisms through the dentinal

tubules. In 1993 Nissan et al. (1993) noticed that bacterial products, such as

polysaccharidic endotoxin, can easily permeate human dentin, even when smear-

layer was present. Besides it is known that the smear-layer negatively affects the

adaptation of the materials used to fill the canal, and reduces the diffusion through

the tubules, and as a consequence the efficacy, of many intracanalar medicaments.

Nevertheless smear-layer has the potential to harbor microorganisms: the choice of

eliminating the smear-layer is essentially derived from the need of sealing the open

dentinal tubules.(Behrend et al 1996, Goldman et al 1984).

Usually microscopic investigations are performed under laboratory conditions in

order to predict the clinical behavior of new irrigating solutions. Unfortunately,

SEM evaluation do not permit numeric data collection and consequently statistical

analysis. Only a few studies have reported on quantitative evaluation of

morphological observations of root canals (Peters et al 2000, barbakow et al 1998).

In this way, a repeatable method was introduced.

The results of this study confirm that the irrigation with sodium hypochlorite alone

is not able to totally remove the smear-layer, as its action is mainly directed to the

organic debris. In order to obtain the total removal of the smear-layer, both organic

and inorganic components, the combined use of sodium hypochlorite and EDTA is

recommended (Group C and D) (Aktener et al 1993, Dippel et al 1984). The

chelating agent somehow “prepares” the canal walls surfaces so that irrigants and

medicaments are really effective with their anti-bacterial action.

The role of EDTA during the instrumentation is mainly directed to the creation of

smear free canalar surfaces. Glyde File Prep contains EDTA. Because of its acidity,

no matter how EDTA is used as irrigant, it needs a last flush with hypochlorite in

order to neutralize its acid effect. The technique used for teeth in Group D probably

lets EDTA act in the deepest part of the canal, and this may explain why in the

apical portion the best results were obtained by this Group.

Other substances have been used to remove the smear-layer, such as 20%

polyacrylic acid, 10% citric acid, ortophosphoric and maleic acid (Goldman et al

1981, Wayman et al 1979, Takeda et al 1999). However this acid substances are

clinically not easy to handle, as the effect varies according to the kind of acid used,

34

the concentration and the time of application; besides the low pH (1,5) could have a

harmful effect on the periapical tissues (Takeda et al 1999, Garberoglio et al 1994).

As alternative to irrigant solutions, Laser (CO2 and Er:YAG) has also been

successfully proposed to remove the smear-layer; however further studies are

needed about the thermal effects before the clinical use of lasers can be

recommended (Takeda et al 1999).

In conclusion, none of the techniques used in this study showed a perfect removal of

smear layer and debris. The significantly lower debris and smear layer scores in

Group C and D is probably due to the better effect, as irrigant, of Glyde File Prep

combined with sodium hypochlorite 2.5%.

The null hypothesis tested in this study was not confirmed: differences in the

amount of debris along root canal walls after different irrigation regimes were noted.

35

Fig. 1: Composite picture showing a horizontal examination strip at the coronal level of a

Group A sample.

Fig. 2: Tooth irrigated with physiological solution (Group A, apical portion) (x 500). An

amorphous layer with debris can be noted on the canal wall. No tubule openings are visible.

Fig. 3: Tooth irrigated with NaOCl (Group B, apical portion) (x 500). Smear layer can be

noted, with less amount of debris than in Fig. 2. No openings of dental tubule are visible.

36

Fig. 4: Tooth irrigated with NaOCl and Glyde File Prep (Group C, apical portion) (x 500).

Smear layer is not present. The openings of tubule orifices are visible.

Fig. 5: Tooth irrigated with NaOCl and Glyde File Prep applied at the end of the preparation

(Group D, apical portion) (x 500). No smear layer is present. The tubule orifices are visible.

37

References

Akpata ES, Blechman H. Bacterial invasion of pulpar dentin wall in vitro. J Dent

Res 1982; 61: 435-8.

Aktener BO, Bikay U. Smear layer removal with different concentrations of EDTA

mixtures. J Endod 1993; 19: 228-31.

Barbakov F, Peters O, Havranek L. Effects of Nd:YAG lasers on root canal walls: a

light and scanning electron microscopic study. Quint Int 1998: 837-45.

Behrend GD, Cutler CW, Gutmann JL. An in-vitro study of smear layer removal

and microbial leakage along root canal fillings. Int End J 1996; 29(2): 99-107.

Brannstrom M, Nyborg H. Bacterial growth and pulpar changes under inlays

cemented with zinc phosphate and epoxylate CBA 9080. J Prosth Dent 1974; 31: 556-65.

Castellucci A. Endodontics, Ed Martina, Milano, 1993.

Davis SR, Brayton SM, Goldman M. The morphology of the prepared root canal: a

study utilizing injectable silicone. Oral Surg 1972; 34: 642-8.

Dippel H, Borggreven J, Hoppenbrouvers PMM. Morphology and permeability of

the dentin smear layer. J Prosthet Dent 1984; 52: 657-62.

Ferrari M, Scotti R. Fiber posts: clinical and research aspects. Masson Ed, Milano

2002.

Garberoglio R, Becce C. Smear layer removal by root canal irrigants. Oral Surg

Oral Med Oral Pathol 1994; 78: 358-66.

Goldman M, Devitre R, Pier M. Effect of the dentin smeared layer on tensile

strength of cemented post. J Prosthet Dent 1984; 52: 485-8.

Goldman M, Goldman LB, Kronman JH, Lin PS. The efficacy of several irrigating

solutions for endodontics: a scanning electron microscopic study. Oral Surg 1981; 52: 197-

204.

Ingle JA. Endodonzia. Piccin Editore, 1993, Padova, Italy 29-40.

Kielbassa AM, Attin T, Hellwigg E. Diffusion behaviour of eugenol from zinc

oxide eugenol mixtures through human and bovine dentin in vitro. Oper Dent 1997;22: 15-20.

Kopper PM, Figueiredo JA, Della Bona A, Vanni JR, Bier CA, Bopp S.

Comparative in vivo analysis of the sealing ability of three endodontic sealers in post-

prepared root canals. Int Endod J 2003 Dec;36(12):857-63.

Madison S, Wilcox LR. An evaluation of coronal microleakage in endodontically

treated teeth. Part III. In vivo study. J Endod. 1988 Sep;14(9):455-8.

Madison S, Swanson K, Chiles SA.An evaluation of coronal microleakage in

endodontically treated teeth. Part II. Sealer types. J Endod. 1987 Mar;13(3):109-12.

38

Mader LL, Baumgarter JC, Peters DD. A scanning electron microscopic

investigation of the smear layer on root canal walls. J Endod 1984; 10: 477-83.

Mayer T, Pioch T, Duschner H, Stahele HJ. Dentinal adhesion and histomorphology

of two dentinal bonding agents under the influence of eugenol. Quintess Int 1997;28: 57-62.

Mc Comb D, Smith DC. A preliminary scanning electron microscope study of root

canals after endodontic procedures. J Endod 1975; 1: 238-42.

Nissan R, Sehal H, Pashley DH, Trowbridge H. Ability of bacterial endotoxin to

permeate human dentin. J Dent Res 1993; 92: 127.

Otsby BN. Chelation in root canal therapy. EDTA for cleaning and widening of root

canals. Odontal. Tidskz. 1957; 65: 3-11.

Pashley DH, Michelich V, Kehl T. Dentin permeability: effect of smear layer

removal. J Prosthet Dent 1981; 46: 531-7.

Peters O, Barbakov F. Effects of irrigation on debris and smear layer on canal walls

prepared by two rotary techniques: a scanning electron microscopic study. J Endod 2000; 1:

6-10.

Saunders EM, Saunders WP. Long-term coronal leakage of JS Quickfill root fillings

with Sealapex and Apexit sealers. Endod Dent Traumatol. 1995 Aug;11(4):181-5.

Schwartz RS, Murchison DF, Walker WA 3rd. Effects of eugenol and non eugenol

endodontic sealer cements on post retention. J Endod 1998;24:564-67.

Serafino C, Gallina G, Cumbo E, Ferrari M. Surface debris of canal walls after post

space preparation in endodontically treated teeth: a scanning electron microscopic study. Oral

Surg Oral Med Oral Pathol Oral Radiol Endod. 2004 Mar;97(3):381-7.

Swanson K, Madison S.An evaluation of coronal microleakage in endodontically

treated teeth. Part I. Time periods. J Endod. 1987 Feb;13(2):56-9.

Takeda FH, Harashima T, Kimura Y, Matsumoto K. A comparative study of smear

layer by three endodontic irrigants and two types of laser. Int End J 1999; 32: 32-9.

Terata R. Characterization of enamel and dentin surfaces after removal of temporary

cement. Dent Mater J 1993:12:18-28.

Tjan AHL, Nemetz H. Effect of eugenol-containing endodontic sealer on the

retention of prefabricated posts luted with an adhesive composite luting cement. Quintessence

Int 1992;23:839-44.

Walton R, Torabinejad M. Principles and practice of endodontics, 2nd edition, W.B.

Saunders Co., 1996.

39

Watanabe EK, Yamashita A, Imai M, Suzuki K. Temporary cements remnants as an

adhesion inhibiting factor in the interface between resin cements and bovine dentin. Int J

Prosthodont 1997;10: 440-52.

Wayman BE, Kopp WM, Pinero GJ, Lazzari EP. Citric and lactic acids as root canal

irrigants in vitro. J Endod 1979; 5: 258-60.

Williams S, Goldman M. Penetrability of the smeared layer by strain of proteus

vulgaris. J Endod 1985; 11: 385-8.

Woody TL, Davis RD. The effect of eugenol-containing and eugenol free temporary

cements on microleakage in resin bonded restorations. Oper Dent 1992;17: 175-80.

Xie J, Powers JM, Mc Guckin RS. In vitro bond strength of two adhesives to

enamel and dentin under normal and contaminated conditions. Dent Mater 1993;9: 295-99.

40

Chapter 4 Criteria for selecting fiber posts

Actually many fiber posts are available on the market. Their huge success among

clinician brought many manufacturers to produce their own fiber post. For this

reason it is important for the clinician to know the properties of each fiber post

available on the market, and to consequently select the more appropriate.

Composition and shape of the post are usually the first criteria. Carbon, glass or

quartz fibers are available, and after the first double cylinder shape endodontic and

double tapered shape became available. Depending on the type of root canal and of

tooth the clinician can decide which one can be more appropriate. Also the

combination with an appropriate bonding system acquires high importance: it is

known that materials give better results if they are employed following

manufacturer’s instructions and if proprietary resin cement and adhesives are used

(Ferrari et al 2002). Also the cost can be a factor: some of the posts available on the

market are cheaper than others, but we have to keep in mind that a cost/benefit ratio

should be taken into account when deciding what kind of material we should employ

(Monticelli et al 2003). Probably the most important factor to take into account is

the experimental and clinical evaluation of the behaviour of fiber post/adhesive

material/resin cement/core material used (Monticelli et al 2003, Ferrari et al 2002,

Vichi et al 2001 and 2002). The following study regards a comparison among some

post actually available on the market when resistance to fatigue is considered.

4.1 Fatigue resistance and structural characteristics of fiber posts: three-point

bending test and SEM evaluation.

Over the recent years a rapid development has occurred in the area of fiber posts.

The introduction of carbon fiber posts in 1990 (Duret et al 1990) provided the dental

profession with the first true alternative to cast or prefabricated metal posts. The

elastic moduli of fiber posts are closer to dentin than that of any metal post

(Asmussen et al 1999), and their clinical trials yielded convincing results

(Fredriksson et al 1998, Ferrari et al 2000b, Ferrari et al 2000a, Malferrari et al

2002, Scotti et al 2002, Dallari et al 1998). However, the earlier generations of fiber

posts had some limitations to their universal use, as they were radiolucent and

41

difficult to mask under all-ceramic or composite restorations (Vichi et al 2000).

Later, radiopaque fiber posts, and more esthetic posts were made. These

improvements brought about a drastic change in the acceptance of fiber posts by the

dental profession. As a consequence of practitioners finding esthetic fiber posts a

viable alternative to metal posts (Drummond et al 1999), a number of different fiber

posts were quickly introduced into the market. Many studies are available on the

adhesion of fiber posts to root canal substrates (Nakabayashi et al 1998, Chappel et

al 1994, Mjor et al 1996), on the different luting procedures (Ferrari et al 2000c,

Vichi et al 2002) and the abutment build-up (Gateau et al 1999 ,Cohen et al 1996,

Freedman et al 2001), and all of them demonstrate the quality performances of fiber

posts (Dietschi et al 1996 and 1997). The rapid influx of these new esthetic fiber

posts has imposed the need for a systematic evaluation of their mechanical

properties and clinical performances. For that purpose, scanning electron

microscopy (SEM) and fatigue test can provide an indication of what type of post

would perform better under clinical conditions. Also, SEM observations can be

useful to assess the fiber/resin matrix ratio, as well as the fiber diameter and the

global integrity of the posts. Fatigue is considered as one of the main causes of

structural failure in restorative dentistry (Hsu et al 2002, Baran et al 2001, Fan et al

1995, Yamamoto et al 1995). It has been reported that dental restorations fail much

more frequently under cyclic loading that are well below the ultimate flexural

strength of these materials, than under application of a single, relatively high force

(Kahn et al 1996). Fatigue tests can reveal the resistance level of each type of post

under cyclic loading that simulates the normal occlusal and masticatory function

(Gateau et al 1999, Cohen et al 1997, Reagan et al 1999). Since fiber posts are in

essence composite materials, it seems logical to expect that their mechanical

properties would increase as a result of an increase in fiber content. The objectives

of the present study were to assess the fatigue resistance of different types of fiber

posts, and to verify the existence of a correlation between the fatigue resistance

exhibited by the different types of posts and their structural characteristics. The null

hypotheses tested were: 1. there is no difference in the structural characteristics and

in the fiber/resin ratio of the posts, 2. there is no difference in the fatigue resistance

among different kinds of fiber posts.

42

4.2 Materials and Methods

Eight types of esthetic posts were selected for this study (Table I). Table I.. This table shows the structural characteristics of the eight groups of tested posts

Group

number

Type of post Post

diameter

(mm)

Fiber

diameter

(µm)

Fiber

density

(number

of fibers

per mm2)

Surface

occupied by

fibers per

mm2 of post

surface (%)

Group 1 Easypost 1.6 12 29 34.8

Group 2 Para Post Fiber White 1.5 6 18 10.8

Group 3 FibreKor 1.5 18 28 50.4

Group 4 Ghimas White 1.8 12 30 36.0

Group 5 DT Light-post radiopaque 2.0 12 32 38.4

Group 6 FRC Postec 2.0 12 25 30.0

Group 7 Luscent Anchors 1.7 15 29 43.5

Group 8 Snowpost 1.6 7 36 25.2

They were Easypost (Krugg, Milano, Italy; Group 1, carbon fibers), Para Post Fiber

White (Coltene/Whaledent, Mawhaw, NJ, USA; Group 2, glass fibers), FibreKor

(Jeneric/Pentron, Wallingsford, CT, USA; Group 3, glass fibers), Ghimas White

(Ghimas, Casalecchio di Reno, Bologna, Italy: Group 4, glass fibers), DT Light-Post

radiopaque (RTD, Grenoble, France; Group 5, pre-tensioned glass fibers), FRC

Postec (Ivoclar-Vivadent, Schaan, Liechtenstein; Group 6, glass fibers), Luscent

Anchors (Dentatus, New York, NY, USA; Group 7, glass fibers), Snowpost

(Carbotech, Ganges, France, Group 8, silica fibers). From each group fifteen posts

of the largest available size (Table I) were collected. The size of the post in the

different groups varied from 1.5 mm to 2.0 mm. Ten of them, randomly chosen,

were used for fatigue test, whereas the other five were processed for microscopic

evaluation.

4.2.1 Fatigue test

Ten posts from each group were tested in a fatigue machine (Procyon systemes,

France). This device has a counter that measures the number of cycles and stops

when the specimen breaks (Fig. 1). The three-point bending method of loading was

43

applied, with a loading angle of 90° at a frequency of 3Hz. As the posts in the eight

groups had different diameters, a calculation was done to establish the load to be

applied on the different posts, according to the diameter itself.

( )( )

( )( )

δπ

δ

=××

×

= =

=

=

=

83

F Id

stress N mm MPaF load or force NewtonI span mmd diameter mm

/ ²

The load was applied according to the diameter of post

IdF

3

8×

××

=πδ

The two supports and the punch had a 3-mm diameter, and the distance between the

two supports was 9 mm. All the tests were carried out at a room temperature of

approximately 22°C. The machine was set to carry out 2,000,000 cycles, the

assumption being that, as teeth normally come into contact once a minute, this

number of cycles would simulate about four years of physiologic occlusal and

masticatory activity (Ferrari et al 2000b, Scotti et al 2002).

For those fiber posts that failed prior to reaching the projected cycle count, the

actual number of resisted cycles as counted by the fatigue machine was recorded.

The differences among the tested posts in the number of resisted cycles were tested

for statistical significance with the One-Way ANOVA, followed by the Bonferroni

test for multiple comparisons. The level of significance was set at p<0.05.

At the completion of the fatigue test, the posts were processed for a SEM evaluation,

which was aimed at verifying whether any changes had occurred in the structure of

the post as a result of loading. The detected modifications were documented through

microphotographs.

4.2.2 SEM evaluation

Each post was cross-sectioned into two halves using a diamond saw (Isomet,

Buehler, Lake Bluff, NY). One half was used for the observation of the surface

44

exposed by the cross-sectional cut, whereas the other half was again sectioned

longitudinally (with the same diamond saw described above), in order to examine

the fibers along their longitudinal axes. The external surface of this half of each

sectioned fiber post was also examined. The specimens were mounted on metallic

stubs, and sputtered with gold in an ion-sputtering device (Balzers Ltd., London,

Great Britain). Then the specimens were analyzed under a scanning electron

microscope (Philips 505, Eindoven, The Netherlands), and microphotographs were

taken for documenting the morphologic characteristics of posts. The diameter of the

fibers, the number of fibers per mm2, and the surface occupied by fibers per square

millimeter of post surface were measured. Three micrographs were taken for

evaluating each post, and the result was obtained calculating the mean of the score

assigned to the three single micrographs. Also, the presence of voids/bubbles within

the post and on its outer surface was assessed and expressed through a three-step

scoring system, which was defined as: 0 = no voids or bubbles visible; 1 = micro

voids or bubbles can be detected (diameter < 20 microns); 2 = voids or bubbles

(diameter > 20 microns) are evident and/or fiber detachments due to a loose bond

within the resin matrix. The scoring method allowed for a quantitative evaluation of

the structural integrity of the posts, as well as for a statistical evaluation of the

differences among the various types of post. SEM scores were assigned by two

different operators, who separately examined the micrographs taken from the

specimens. In case of disagreement between the two investigators on the score

assigned to a specimen, the worse score was chosen for the statistical analysis. The

observations were repeated twice to verify the inter-examiner reliability. The

differences in the scores recorded for the eight groups of posts were tested for

statistical significance with the Kruskal Wallis ANOVA on ranks, followed by the

Mann-Whitney U test for multiple comparisons. The level of statistical significance

was set at p<0.05.

4.2.3 Correlation analyses

A further objective of the investigation was to verify the existence of a correlation

between the fatigue resistance exhibited by the different types of posts and their

structural characteristics, namely fiber diameter, fiber density, and the surface

occupied by fibers per square millimetre of post surface. For that purpose, the

45

strength of the correlation between the number of resisted cycles and each one of the

mentioned structural variables of the posts was measured by calculating the

Pearson’s correlation coefficients. The statistical significance of the correlations was

also assessed (p<0.05).

4.3. Results

4.3.1 Fatigue tests

Table II reports the means and standard deviations of the number of cycles that the

different types of posts were able to withstand before breaking. Table II. Mean and standard deviation of the number of cycles that each type of post proved able to

withstand before breaking.

Group

number

Type of post Mean number of resisted cycles Standard

deviation

Group 1 Easypost 931750.2 829005.8

Group 2 Para Post Fiber White 84915.7 106039.0

Group 3 FibreKor 29687.8 24327.5

Group 4 Ghimas White 440952.9 160671.8

Group 5 DT Light-post radiopaque 2000000 0

Group 6 FRC Postec 1837138.7 371387

Group 7 Luscent Anchors 807242.9 2008

Group 8 Snowpost 6763.1 780

The results of the statistical analysis performed on these data are summarized in

Figure 2.

The highest resistance to cyclic loads was exhibited by the DT Light-post group

(Group 5), followed by the FRC Postec group (Group 6). None of the specimens

from the DT Light-Post group was broken after two million cycles, whereas among

the FRC Postec posts only one failure occurred. From a statistical standpoint the

results given by these two groups were similar (Fig. 2). Conversely, Snowpost,

FibreKor, and Para Post (Groups 8, 3, and 2) showed fatigue resistance that were

significantly lower than that of any other post tested (Fig. 2).

4.3.2 Structural integrity

The scores assigned to the different types of posts in order to quantify their

structural integrity, as revealed by SEM observations, are summarized in Table III.

46

Table III. Median values of the scores assigned to the different types of posts, providing an estimate of

posts’ structural integrity, as shown by scanning electron microscopy.

Group number Scores

Type of post

Cross

section of

the post

Longitudinal

section of

the post

External surface of

the post

Group 1 Easypost 2 2 2

Group 2 Para Post Fiber White 2 2 1

Group 3 FibreKor 0 1 1

Group 4 Ghimas White 0 0 0

Group 5 DT Light-post radiopaque 0 0 0

Group 6 FRC Postec 0 0 0

Group 7 Luscent Anchors 1 2 1

Group 8 Snowpost 0 1 0

The specimens from the Easypost, Para Post, and Luscent groups (Groups 1, 2, and

7) exhibited voids and/or bubbles within the post structure on both the cross and the

longitudinal sections. The specimens from the Easypost group (Group 1) also

showed gaps between the fibers and the resin matrix, in particular in the peripheral

area and on the external surface of the post. The Easypost and Para Post groups

recorded scores that were significantly higher than those of any other type of post

(p<0.05; Fig. 3). Only on the specimens from DT Light-post (Group 5), FRC Postec

(Group 6), and Ghimas White (Group 4) were no structural defects visible either on

the cross and longitudinal sections or on the outer surface of the post. The scores

assigned to these three types of posts were significantly lower than those of any

other group (p<0.05; Fig. 3).

When the posts that were fractured after load cycling were observed under the SEM,

their loss of structural integrity was evident (Fig 4). On the other hand, the DT

Light-post and the FRC Postec posts, which were able to withstand the fatigue test,

exhibited only a small circumferential depression in the area of contact of the

loading punch (Fig 5).

47

4.3.3 Correlation analyses

The data expressing the strength of the correlation between fatigue resistance and

structural characteristics of the posts are summarized in Table IV. No correlation

was found to be statistically significant (p>0.05). Table IV. Strength and statistical significance of the correlation between fatigue resistance of the posts

and their structural characteristics.

Variable Variable

Fibers diameter Fibers density Surface occupied by fibers per

square millimeter of post

surface

Pearson’s

correlation

coefficient

r = 0.167 r = 0.069 r = 0.171

Mean

number of

resisted cycles

Statistical

significance

p = 0.693 p = 0.871 p = 0.685

4.4 Discussion

As fiber-reinforced composite materials, fiber posts owe their mechanical properties

not only to the characteristics of fibers and matrix, but also to the strength of the

bond at the interface between these components and to the geometry of

reinforcement, such as fiber length, orientation and concentration (Callister et al

1997). The addition of fibers to a polymer matrix leads to a significant increment in

fracture toughness, stiffness, and fatigue resistance of the material. Since fibers

represent the stiffer component in a post, as compared with the resin matrix, the

posts that exhibit a higher fiber density (Figure 4) would be expected to yield a

greater fracture resistance than those with lower fiber densities (Figure 5) (Callister

et al 1997). Any fiber direction diverging from the longitudinal axis of the post

results in a stress transmission to the matrix. For this reason, posts with parallel

fibers should, at least theoretically, withstand loads more efficiently than posts

containing obliquely-oriented fibers (Callister et al 1997).

In the fabrication of endodontic posts, glass, quartz, carbon, and ceramic fibers have

been used (Drummond et al 1999, Asmussen et al 1999). The posts produced by

RTD and Ivoclar-Vivadent contain silanized glass fibers and an epoxy resin. During

48

the manufacturing process of RTD posts, the fibers are pre-stressed in tension and

then soaked in resin, which is finally polymerized. On the final cure of the resin, the

tension in the fibers is released and, as a result, the resin surface is placed under

compression. For this reason, when the post is subjected to a flexural force, the

tensile stresses which are introduced can easily be absorbed. For the Ivoclar-

Vivadent posts, they are made following the Vectris technology (Vichi et al 2001).

The methods of fabrication of DT Light-post and FRC Postec can provide an

explanation for the significantly higher resistance to fracture under cyclic bending

forces. Unfortunately manufacturers do not declare the modulus of elasticity of the

resin employed as the resin matrices of these posts: it could eventually play an

important role in the determination of the fatigue resistance of the post. Another

important factor is whether the fibers are silanized prior to embedding in the resin

matrices: in particular, it can affect both the resistance of these fiber posts to the

fatigue tests as well as the structural integrity of these posts. Good interfacial

bonding ensures load transfer from the matrix to the reinforcement, and is a primary

requirement for effective use of reinforcement properties (Gu 1997).

During normal occlusal and masticatory function, both the natural and the restored

teeth are subjected to cyclic loading. Thus, failure due to fatigue stress is a

phenomenon of paramount importance from a clinical standpoint (Dietschi et al

1996 and 1997, Hsu et al 2002), as failure commences from a small structural defect

such as a void or microcrack within the material. From this area of weakness a crack

front can gradually propagate through the material, finally resulting in catastrophic

failure (Griffith et al 1920). Potential areas of weakness in a fiber-reinforced post

can be seen in the voids present within the resin or in the discontinuities along the

interfaces between fibers and matrix. Thus, a solid void-free post with evenly

distributed and parallel-oriented fibers seems to be critical for their clinical success.

Areas of potential weakness may also be found in regions where the section of the

post has an abrupt change (Baran et al 2001). For this reason, the addition of a notch

on the post for the purpose of retention does not seem to benefit the post’s fatigue

resistance. The SEM observation of posts that fractured under load showed how

their structure was altered by the fatigue stress.

49

In the fatigue test, as in a repeated masticatory action, the load varies between a

minimum (Kmin) and a maximum (Kmax). Theoretically the moment in which a

rapid fracture occurs has to be related to the Kmax value. On the other hand, the

difference between the maximum and the minimum values (K) corresponds to the

cyclic dissipation of stress energy. The two different values (Kmax and K)

combined provide important information, and are likely to be simulating what really

happens in the mouth (Wiskott et al 1997).

In the present study a load ranging from 20 to 100 N was applied at a frequency of

3 Hz. With the 20-N force, the loading unit was kept in stable contact with the

specimen. In fatigue tests, Kmax does not usually exceed 50% of the ultimate

strength of the material (Cohen et al 1996). This criterion was applied also in the

present study, and the results showed that specimen failure could occur when a

cyclic force as low as one half of the material’s ultimate strength was exerted.

The stress acts on the matrix particularly when a compressive force is exerted on the

post or when the forces are directed obliquely or diagonally to the post’s

longitudinal axis. The high stresses on the fiber/resin interface are responsible for a

gradual inelastic behaviour, which occurs as a consequence of interface detachment

between the fibers and the matrix. Also plastic deformation of the matrix and resin

microcracking occur. Such stresses are minimum in the equidistant areas of the

fibers, and maximum immediately next to the same fibers (Grandini et al 2002a).

Regarding the fracture mode of the post, it is speculated that when failure

commences under compression the more brittle fibers break due to variability in

individual fiber surface defects. This leads to interfacial slip between the broken

fiber and the matrix, and consequently stress magnification in the adjacent fibers.

As the interfacial bond is probably still effective, tensile stress in the broken fiber

along the bond transfer length will gradually build-up. If the bond strength is

exceeded, delamination of the fiber from the matrix will commence and propagate

(Grandini et al 2002a). With interfacial bond lost progressive fiber fracture will

occur leading to overall catastrophic failure. Further detailed fractographic analysis

should be performed to validate the results of this study.

The overall results of this study require rejection of both null hypotheses.

Differences exist among different brands of fiber posts in terms of their structural

50

characteristics and fatigue resistance, although little correlation was observed

between these two attributes. DT Light-post and FRC Postec can be expected to

function efficiently in their ability to resist fatigue stresses. This factor adds to the

reliability of these materials when used clinically for the restoration of

endodontically treated teeth.

In conclusion, the overall results of this study require rejection of both null

hypotheses. Differences exist among different brands of fiber posts in terms of their

structural characteristics and fatigue resistance, although little correlation was

observed between these two attributes. Wiskott et al. (1997) indicated that the

number of cycles in fatigue testing should be at least one million cycles. In the

present study, a maximum of two millions cycles was applied, with the intention of

simulating about four years of normal occlusal and masticatory activity (Ferrari et al

2000b, Scotti et al 2002). It should be pointed out that the cyclic fatigue test

performed in this study most likely exposed the specimens to higher tensile stresses

than those that would have actually been transmitted to an endodontic post cemented

inside a root, as failure of the bonding cement could have occurred prior to post

fracture. For this reason, in order to have a fatigue resistance appraisal that is closer

to clinical reality, the same study should be repeated on roots with cemented posts

instead of just posts. This requires a completely different study design that does not

involve three-point bending test.

51

Fig. 1. The post ready to be tested.

52

Para Post, FibreKor, Snowpost vs * (-)Light-post, Postec, Easypost, Luscent Anchors

Ghimas vs * (-)Light-post, Postec

Easypost, Luscent Anchors vs * (-)Light-post, Postec

* Snowpost, FibreKor, Para Post

FRC Postec, DT Light-post vs * Snowpost, FibreKor, Para Post, Ghimas, Luscent,

Easypost

Mean number of resisted loading cycles for different types of posts

0

500000

1000000

1500000

2000000

2500000

type of post

mean number of cycles

FototechFibreKorParapostGhimasLuscentEasypostPostecLight-Post

Fig. 2. Graph representing the mean number of cycles that each type of post was

able to resist before failing. Columns underlined by the same line represent groups

which gave statistically similar results. In the table, the star sign indicates that the

difference between the groups was statistically significant. The minus sign indicates

that the difference between the two mean values was negative.

53

Mean rank of scores for the different types of posts

24,5 24,533

68,1 68,174,2

95,8 95,8

0

20

40

60

80

100

120

mean rank of scores

Light-postPostecGhimasFibreKorSnowpostLuscent EasypostParapost

Fig. 3 Mean of the ranks that the statistical analysis (Kruskall Wallis test) assigned

to the scores of each group of posts. The columns underlined by the same line

represent groups of post that recorded statistically similar scores.

54

Fig. 4 A sample from group 7. The fatigue test caused the breaking of the post.

55

Fig. 5 Group 5 sample. After 2.000.000 cycles the post is still unbroken. The point

where the loading punch worked is evident.

56

References

Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit, and strength of

newer types of endodontics posts. J Dent 1999;27:275-278.

Baran G, Boberick K, McCool J. Fatigue of restorative materials. Crit Rev Oral Biol

Med 2001;12:350-356.

Callister WD Jr. Materials Science and engineering. An introduction. 3rd Edition.

Chapter 17. Composites. Wiley: New York; 1997; 513-541.Chappel RP, Cobb CM, Spencer

P. Dentinal tubule anastomosis: A potential factor in adhesive bonding? J Prosthet Dent 1994;

72: 183-188.

Cohen BI, Pagnillo MK, Condos S, Deutsch AS. Four different core materials

measured for fracture strength in combination with five different designs of endodontic posts.

J Prosthet Dent 1996;76:487-495.

Cohen BI, Pagnillo MK, Newman I, Musikant BL, Deutsch AS. Cyclic fatigue

testing of five endodontic post designs supported by four core materials. J Prosthet Dent

1997;78:458-464.

Dallari A, Rovatti L. Six years of in vitro/in vivo experience with Composipost.

Compendium 1998;20:S57-S63.

Dietschi D, Romelli M, Goretti A. Evaluation of post and cores in the laboratory:

rationale for developing a fatigue test and preliminary results. Compend Contin Educ Dent

Suppl 1996;20:S65-S73.

Dietschi D, Romelli M, Goretti A. Adaptation of adhesive posts and cores to dentin

after fatigue testing. Int J Prosthodont 1997;10:498-507.Drummond JL, Toepke RS, King TJ.

Thermal and cycling loading of endodontic posts. Eur J Oral Sci 1999;107:220-224.

Duret B, Reynaud M, Duret F. Un nouveau concept de reconstitution corono-

radiculaire: le composiposte (1). Chir Dent France 1990;540:131-141.

Fan P, Nicholls JI, Kois JC. Load fatigue of five restoration modalities in

structurally compromised premolars. Int J Prosthodont 1995;8:213-220.

Ferrari M, Scotti R. Fiber posts: clinical and research aspects. Masson Ed, Milano

2002.

Ferrari M, Vichi A, Mannocci F, Mason PN. Retrospective study of clinical

performance of fiber posts. Am J Dent 2000a;13:9B-14B.

Ferrari M, Vichi A, García-Godoy F. A retrospective study of fiber-reinforced

epoxy resin posts vs. cast posts and cores: a four year recall. Am J Dent 2000b;13:B9-B14.

Ferrari M, Mannocci F, Vichi A, Cagidiaco MC, Mjör IA. Bonding to root canal:

Structural characteristics of the substrate. Am J Dent 2000c;13:380-386.

57

Fredriksson M, Astback J, Pamenius M, et al. A retrospective study on 236 patients

with teeth restored by carbon fiber-reinforced epoxy resin posts. J Prosthet Dent 1998;80:151-

7.

Freedman GA. Esthetic post and core treatment. Dent Clin North Am

2001;45:1:103-116.

Gateau P, Sabek M, Dailey B. Fatigue testing and microscopic evaluation of post

and core restorations under artificial crowns. J Prosthet Dent 1999;82:341-347.

Grandini S, Balleri P, Ferrari M. Scanning electron microscopic investigation of the

surface of fiber posts after cutting. J Endod. 2002; 28:610-612.

Griffith AA. The phenomena of rupture and flow in solids. Philosophical

Transactions of the Royal Society of London (Series A) 1920; A221: 168-198.

Hsu YB, Nicholls JI, Phillips KM, Libman WJ. Effect of core bonding on fatigue

failure of compromised teeth. Int J Prosthodont 2002;15:175-178.

Gu W. Interfacial Adhesion Evaluation of Uniaxial Fiber-Reinforced-Polymer

Composites by Vibration Damping of Cantilever Beam. PhD thesis at Virginia Polytechnic

Institute and State University. 1997; 11-13.

Kahn FH, Rosenberg PA, Schulman A, Pines M. Comparison of fatigue for three

prefabricated threaded post systems. J Prosthet Dent 1996;75:148-153.

Malferrari S, Baldissara P, Arcidiacono A. Translucent quartz fiber posts: a 20

months in vivo study. IADR 80th General Session, S.Diego, 2002, abstract n° 2656.

Monticelli F, Grandini S, Goracci C, Ferrari M. Clinical behaviour of translucent

fiber posts and luting and restorative materials: a 2-year report. Int J Prosthod

2003;16,(6):593-6.

Mjör IA, Nordhal I. The density and branching of dentinal tubules in human teeth.

Archs Oral Biol 1996; 41: 401-412.

Nakabayashi N, Pashley DH. Hybridization of dental hard tissue. Berlin:

Quintessence Co. Publ., 1998.

Reagan SE, Fruits TJ, Van Brunt CL, Ward CK. Effects of cyclic loading on

selected post-and-core systems. Quintessence Int 1999; 30:61-67.

Scotti S, Malferrari S, Monaco C. Clinical evaluation of quartz fiber posts: a 30

months results. IADR 80th General Session, S.Diego, 2002, abstract n° 2657.

Vichi A, Ferrari M, Davidson CL. Influence of ceramic and cement thickness on the

masking of various types of opaque posts. J Prosthet Dent. 2000;83:412-7.

Vichi A, Grandini S, Ferrari M, Clinical procedure for luting Vectris fiber posts. J

Adhes Dent 2001; 3: 353-359.

58

Vichi A Grandini S, Ferrari M. Comparison between two clinical procedures for

bonding fiber posts into a root canal: a microscopic investigation. J. Endod 2002;28:355-360.

Wiskott HW, Nicholls JI, Belser UC. The effect of tooth preparation height and

diameter on the resistance of complete crowns to fatigue loading. Int J Prosthodont

1997;10:207-215.

Yamamoto M, Takahashi H. Tensile fatigue strength of light cure composite resins

for posterior teeth. Dent Mater J 1995 ;14:175-184.

59

Chapter 5 Adjusting the length of a post

As the wear properties of fiber posts are inferior if compared to resin composite

materials, it is not safe to have them exposed to the tooth to tooth and tooth to food

wear. If a crown is placed, the exposed fiber post is protected by the crown itself. If

a direct restoration is made, it is convenient to cut the post before the luting

procedures of the post itself (Ferrari et al 2002). As a matter of fact fiber posts are

pre-fabricated, so they have to be adapted to the root and to the crown length. The

following study regards a comparison between different techniques for cutting fiber

posts.

5.1 Scanning electron microscopic investigation of the surface of fibre posts

after cutting

At the beginning of 1990 carbon fibre posts were proposed as alternative to metallic

posts (Duret et al 1990). In the last 10 years, different types of fiber posts were

proposed to improve mechanical and esthetic properties of fibre posts (Fredrikson et

al 1998, Dallari et al 1998, Ferrari et al 2000a). Initially hybrid posts and almost

simultaneously white quartz posts were proposed (Scotti et al 2000, Ferrari et al

2000b). More recently, translucent posts became available. As the development of

fibre posts was very quick, all these types of posts are still in the market and are

routinely used by practitioners. Recently, clinical efficacy and performances of 3

different types of fibre posts were documented (Fredrikson et al 1998, Dallari et al

1998, Ferrari et al 2000a, Scotti et al 2000, Ferrari et al 2000b). All different types

of fibre posts have a similar strength and stiffness (Asmussen et al 1999). The

stiffness (or modulus of elasticity) of the posts is similar to that of dentin and, for

that, the risk of root fracture became much lower than that noted when metallic posts

were used (Ferrari et al 2000a). In addition, bonding between different types of posts

and resin cements has been demonstrated (Mannocci et al 1999, Ferrari et al 2001,

Vichi et al 2002).

Fibre posts are made in a standardised length in order to be adapted to the length of

different roots. Each post must be tried in and then cut at the most convenient length

in order to avoid exposition of the post along the surface of the abutment/restoration.

60

This is due to the fact that the exposition of the post in to the oral environment might

determine degradation of the resin with a consequent loss of its mechanical

properties during clinical service. However, in order to have a sufficient rigidity of

the abutment at the coronal level, the post must keep its integrity and mechanical

properties after being cut.

In clinical practice, three different methods for cutting fibre posts might be used: 1.

Diamond bur mounted in a turbine handpiece, 2. Carborundum disc mounted in a

handpiece and 3. Scissors.

The aim of this study was to evaluate 1. if and how three cutting methods can affect

integrity of fibre posts and 2. to test the null hypothesis that the type of cutting

procedure can not affect the integrity of post’s surface.

5.2 Materials and Methods

Among those available in the market, six types of fibre posts were selected for this

study: Caron Fibre Posts (RTD, St Egreve, France) as control, Quartz Fibre Posts

(RTD), Aesthetic Posts (RTD), Aesthetic Plus Posts (RTD), Translucent Posts

(Dentatus, Zurich, Switzerland), FRC Postec Posts

(Ivoclar-Vivadent, Schaan, Liecthenstein). Fifteen posts of each type were used. A

total of 90 posts were evaluated.

All fiber posts had a diameter between 1.2 and 1.4 mm and a standardised length

(between 14-16 mm). Each group was divided into three subgroups, according to the

cutting method: a. Diamond bur, b. Carborundum disk and c. Scissors (Fig 1).

5.2.1 Subgroup a (diamond bur): Five samples of all six groups were cut

approximately between medium and coronal third using a diamond bur (2979,

Komet, Zurich, Switzerland) mounted in a turbine handpiece under water spray.

Both sections of each sample were collected and then mounted in a metallic stub to

observe the cut surfaces. Then, the samples were gold-coated (Edwards Co, London,

GB), evaluated using a scanning electron microscope (Philips 515, Amsterdam, The

Netherlands) and microphotographs were taken at different magnifications (x36,

200, 500, 1010) in order to properly document their cut surfaces.

5.2.2 Subgroup b (carborundum disc): Other five samples of each group were used.

The posts were cut using a carborundum disk mounted in a handpiece (L.I.M.A.,

61

Torino, Italy). Then the samples were processed microscopically (for SEM

observations) as described for Subgroup a.

5.2.3 Subgroup c (scissors): The last five samples of each group were cut using

scissors (Dentronix Inc., New York, NY, USA). Then, both halves of each post were

processed as described above for subgroup a and b.

5.3 Results

Analysis of the fibre posts after being cut showed different features mainly due to

the cutting procedures. Uniform results were found according to the type of cutting

procedure.

At low magnifications, no microscopic differences were found among the samples

of group 1-4 and 6. Only samples of group 5 showed more irregular surfaces after

being cut with the two procedures providing rotary instruments (subgroup a and b).

All groups showed evident differences between cut surface of subgroup c samples

and those of group a and b.

In subgroup a, posts showed regular surfaces after cutting with diamond bur (Fig. 2).

Cutting with a carborundum disc (subgroup b) brought to an almost regular surface,

but in all groups with some burs and sometime ‘burns’ close to the surface borders.

In subgroup c, in which the posts were cut using scissors, the cut surfaces of all

samples showed two plane and convergent flanges (Fig. 3); also due to formation of

fracture lines, these posts loose their integrity not only at the cutting surface but also

along their length.

At higher magnifications, the structure of all type of posts, based on fibres

embedded in a resin matrix, was observed. Also, in subgroup a and b samples the

cutting procedure produced a smear layer mainly covering the cut post surface.

5.4 Discussion

Cutting fibre post procedure is commonly performed before luting procedures

or/and during build- up and final preparation of the abutment. During this clinical

step, a good adaptation of the post at the coronal third of the root canal preparation

and a proper adhesion to the resin cement and composite material used for build up

of the tooth at the coronal level is desirable.

62

The findings of this study revealed significant differences in post surfaces after

cutting, similarly to those already described for guttapercha cones (Lopes et al

2000).

The loss of integrity of the posts noted after having been cut with scissors might

negatively affect the adaptation of the post to apical and medium thirds of the root

preparation and to the resin composite used for the coronal build-up. Also, the loss

of integrity of the posts after cutting using scissors can probably reduce their

mechanical properties (Fig 4).

In Subgroup a, samples of groups 1-4 and 6 showed regular cut surfaces. The cut

using diamond bur creates shear stress in the cross-section of the post, but the speed

of the handpiece reduces the plastic deformation of the post. Therefore the stress

tensions induced by the diamond bur allow the development of an almost plane cut

surface, which is perpendicular to the direction of displacement of the cut

instrument. In Subgroup b, posts of groups 1-4 and 6 also showed a regular cut

surfaces. The tips of the posts were irregular and some burs were observed close to

the surface boarders. These probably occurred because the posts were not cut against

a surface, which could create a mechanical resistance load opposed to the cut

direction. In Group 5 a less regular cut surface was noted for the two procedures

based on high speed cutting (subgroup a and b). This can be due to the different

stiffness of the posts and their fibre disposition. As a matter of fact, in group 5

samples, the density of the fibres might be less uniform than that of the other groups

and this fact can determine a different plasticity of the post and consequently the

irregular cut. When subgroup a and b were compared, a more regular cut surface

was observed in subgroup a. This difference might be due to the fact that water

cooling was only used in combination with turbine handpiece, and also to the higher

speed of this cutting procedure. In Subgroup c, in which the posts were cut using

scissors, the cut surfaces of the samples of all groups showed two plane and

convergent flangers. The magnitude of the post deformation after cutting depends on

both scissors shape and post plasticity. Also, the posts showed an area of cut

surfaces where fibres were irregularly cut at different lengths and a deattachment

between fibres and resin matrix was evident along their length.

63

Fig. 12 shows the kind of loading applied on the post during cutting with scissors.

At point P and P’, plastic deformation of the posts occurs. As the load increases, the

post is moved through the two blade surfaces of the scissors, producing two different

inclined planes. Other studies have reported similar results when guttapercha cones

were cut (Lopes at al 2000).

However, every time a fibre post is cut, the cut of the post occurs by the application

of a shear stress in the transverse section of the post. The cutting procedure induces

an elastic compression/deformation of the material. Close to the cut surface, post

fibres bend in a direction that is similar to the movement applied by the cutting

instrument. When the applied pressure overcomes the elastic resistance of the

material, the fibre post is separated.

As the cutting with the carborundum disk (subgroup b) might be associated with

irregularities in the cut post surface, a second cut might be desirable to repair the

defects. Thus, whereas the first cut allowed the calibration of the post, the second

cut can regularise the post surface (Fig 5).

Probably the speed of bur/disc mounted on the handpiece played a role such as also

the stiffness of the posts. It may happen that a “burn out” phenomenon takes place if

excessive heating is applied (Fig 6). The posts of group 1-4 are made by the same

company following the same procedure: for that the similar behaviour during cutting

posts of Group 1-4 can be related to their structure and stiffness. Posts of group 6

have similar stiffness (modulus of elasticity) than that of RTD posts (group 1-4) and

because of that they might show similar cut surface.

Also, when different posts have similar stiffness, the speed of the bur/disc played a

key role in subgroups a and b to obtain better results.

Cutting procedures can have clinical implications. After the coronal build-up, the

abutment can be prepared in order to finalise its shape to receive a crown or to refine

the anatomy of the coronal portion of the tooth. In these clinical steps the quality of

bonding between the post and the resin composite used for building it up is critical:

it must be without discontinuity between the two portions and the length of the post

at the coronal level must be sufficient to held occlusal stress. If the post presents a

superficial and internal loss of its integrity due to the cutting procedure, the bonding

between the post and the resin composite is less uniform, discontinuity might be

64

easily present in between, and the possibility of a fracture of the abutment highly

increases.

The cutting procedure using scissors must be avoided. It must be considered that

cutting the post is usually performed after trying-in into the root canal space and

before luting it. If the cutting procedure is performed at this clinical step, the rotary

cutting procedures tested in subgroups a and b might be used. If the cutting

procedure is performed after luting the post, it is strongly suggested to reduce the

length of the post with a diamond bur (as tested in subgroup a) after building-up the

abutment and during its final preparation.

The results of this study indicated that fibre posts can be regularly cut off using a

diamond bur mounted in a handpiece under copious water cooling. Although

carborundum disc cutting procedure (subgroup b) showed a less regular post surface,

it can be speculated that it might be clinically acceptable. The results of this study

might be extrapolated to other fibre posts with similar properties already available in

the market.

The null hypothesis tested in this study was not confirmed, because post surface

morphology was related to the type of cutting procedure.

65

Fig. 1: Fibre posts were cut with diamond bur, carborundum disc or scissors.

Fig. 2: Cutting procedure with diamond bur often created a flat and regular surface

(x 36).

66

Fig. 3: Cutting procedure with scissors. Two planes and convergent flanges are

visible (x 36). Loss of integrity and morphology of the post is clearly noted.

Fig. 4: Cutting procedure with scissors. The loss of integrity is clearly visible (x 25).

67

Fig. 5: A second cut can help making more regular the cut end (x 36)

Fig. 6: Excessive heating of the post (x 36)

68

References

Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit, and strength of

newer types of endodontics posts. J Dent 1999;27:275-278.

Dallari A, Rovatti L. Six years of an in vitro/in vivo experience with Composipost.

Compendium 1998; 20 (suppl): S57-S63.

Duret B, Reynaud M, Duret F. Un nouveau concept de reconstitution corono-

radiculaire: le composiposte (1). Chirurg Dent France 1990;540:131-141.

Ferrari M, Vichi A, Garcia-Godoy F. A retrospective study of fiber-reinforced

epoxy resin posts vs. cast posts and cores: a four year recall. Am J Dent 2000a;13:B9-B14.

Ferrari M, Vichi A, Mannocci F, Mason PN. Retrospective study of clinical

behavior of several types of fiber posts. Am J Dent 2000b;13:B15-B18.

Ferrari M., Vichi A, Grandini S, Goracci C. Efficacy of a self-curing adhesive/resin

cement system on luting glass-fibre posts into root canals: an SEM investigation. Int J

Prosthod, 2001.

Ferrari M, Scotti R. Fibre posts: clinical and research aspects. Masson Ed, Milano

2002.

Fredriksson M, Astback J, Pamenius M, Ardvidson K. A retrospective study on 236

patients with teeth restored by carbon fiber-reinforced epoxy resin posts. J Prosthet Dent

1998;80:151-157.

Lopes HP, Siqueira GF, Elias CN. Scanning electron microscopic investigation of

the surface of Gutta-Percha cones after cutting. J Endod 2000; 26: 418-420.

Mannocci F, Innocenti M, Ferrari M, Watson T. Confocal and scanning electron

microscopic study of teeth restored with fiber posts, metal posts, and composite resins. J

Endod 1999;25:789-794.

Scotti R. Ricostruzioni preprotesiche con perni in fibra di quarzo: esperienza clinica

a 18 mesi. Odontoiatria adesiva e ricostruttiva, S. Margherita Ligure, 2000; 21-27.

Vichi A, Grandini S, Davidson CL, Ferrari M. An SEM evaluation of several

adhesive systems used for bonding fiber posts under clinical conditions. Dental Materials

2002 Nov;18(7):495-502.

69

Chapter 6 Selection of clinical luting procedures

When fiber posts are employed proper luting is a prerequisite. Depending on what

type of fibers are involved, different options can be taken into account. The first step

is the removal of the guttapercha and the preparation of the dowel space, usually

enlarged with a low-speed bur provided by the manufacturer. The depth of the post

space preparation is around 9-10 mm. Then the post has to be tried into the canal, so

to avoid imperfect fitting and excess of cement at the tip end of the post; if this

happens the post cannot be seated in the correct position. The root canal walls are

etched with phosphoric acid (usually 37%) for 15 (or 30) seconds, washed with

water spray and then gently air-dried. The excess water is removed from the post

space using paper points. Subsequently, adhesive is applied with a microbrush,

gently air-dried and the pooled adhesive left in the post space removed using a paper

point before light curing for 20 seconds. Then a dual-cure resin cement (for

translucent posts) or a self-curing resin cement (for non-translucent posts) is used to

complete the luting procedure. According to the diameter and the shape of the canal,

different brands and sizes can be utilized. The cement is applied with a lentulo spiral

into the post space, and the post inserted into the canal. Resin cement excess is

removed with a clean microbrush and then the cement light-cured for 40 seconds

(Monticelli et al 2003, Vichi et al 2002a and 2002b, Ferrari et al 2002). Some

clinicians suggest to use the same material for the cementation of the post and the

build up of the abutment: it is actually difficult to obtain a material that is hard

enough to be used as a core and that at the same time can flow in the canal like a

cement. Recently new simplified materials appeared on the market (RelyX Unicem,

3M Espe, St Paul, MN, USA) that have also been proposed for bonding fiber posts

into root canals. The bonding mechanism of this self – adhesive resin cement is still

debated, but it has been recently proven that if the substrate is non etched dentin and

if a certain pressure is applied during the luting procedures (the situation we find in

the root canal) there are encouraging results (De Munck et al 2004).

In this chapter an alternative to the well established procedure described above is

discussed.

70

6.1 A one step procedure for luting glass fibre posts: an SEM evaluation

The potential of fibre reinforced materials in restorative dentistry has been

appreciated for some time (Bradley et al. 1980). However, the concept of carbon

fibre posts as a method for reconstructing root filled teeth was not described until

later (Duret et al. 1990). Subsequent research confirmed the retention potential of

carbon fibre posts (Drummond et al. 1999, Asmussen et al. 1999), the low stressing

behaviour of the fibre post-resin cement complex, and its good clinical performance

(Fredrikson et al. 1998, Ferrari et al. 2000a, Malferrari et al. 2002, Scotti et al.

2002).

Various changes have been made to fibre post composition, radiopacity, and shape

(Love & Purton 1996, Asmussen et al. 1999, Vichi et al. 2002a). For example,

carbon has been replaced by quartz in the fibre composition, and then by glass. The

manufacturers have recently developed posts that are radiopaque, allowing the

clinician them to be seen on radiography. Several modifications have been made to

post configuration, with the aim of achieving better adaptation to root canal shape.

It is possible to transmit light through a glass fibre post that is translucent. Light

transmission through the post might permit a bonding procedure, in combination

with an acid-etching technique, based on a light curing adhesive system (as for the

other posts) and a dual curing resin cement (Vichi et al. 2002a). The translucent

fibre post has a modulus of elasticity similar to that of the other fibre posts and of

dentin, and offers adequate mechanical properties (Dietschi et al. 1997, Asmussen et

al. 1999). Transmission of light through the post also makes it possible to light-cure

the resin cement and the bonding system in only one clinical step (“one-shot”), thus

simplifying and shortening the clinical procedure (Lui 1994).

Evaluation of the efficacy of an adhesive system can be performed by observing the

uniformity of the resin dentin interdiffusion zone (RDIZ), resin tags, and adhesive

lateral branches (Nakabayashi & Pashley 1998), and by recording the presence of

voids/bubbles within the luting material or at the interface between the cavity wall

and the post (Ferrari et al. 2001a). An evaluation of the quality of the RDIZ is not

possible using scanning electron microscopy (SEM), rather TEM is the appropriate

way to assess it (Tay et al. 1995).

71

Recently, the so called ‘one bottle’ adhesive systems have been proposed for

bonding a fibre post into a root canal (Ferrari et al. 2001b). In order to perform

reproducible studies and to apply a statistical analysis, a method for scoring resin

tags, adhesive lateral branches, and RDIZ into root canal etched dentin has been

proposed (Ferrari et al. 2001a).

The aim of this study was to evaluate the efficacy of a one-step technique (“one-

shot”) in forming resin tags, adhesive lateral branches and RDIZ when luting

translucent fibre posts into root canal preparations. The null hypothesis that the one-

step technique creates the same bonding mechanism into root canal dentin than the

more traditional two-step luting procedure was tested.

6.2 Materials and Methods

Forty mandibular anterior teeth (incisors and canines), stored in a 0.1% thymol

solution, were randomly selected for the study from the department’s stock of

extracted teeth. Canal morphology was verified from radiographs (Kodak,

Rochester, NY, USA) (70 KV and 0.08 s), taken both buccolingually and

mesiodistally. The pulp chambers were opened and canal preparation at a working

length 1 mm from the apex was completed to a 35 size master apical file. A step-

back technique was used with stainless-steel K-files (Union Broach, New York, NY,

USA), Gates Glidden drills size 2 to 4 (Union Broach). Irrigation was performed

using 2.5% sodium hypochlorite and EDTA (Glyde File Prep, Dentsply Maillefer,

Ballaigues, Switzerland). The prepared teeth were obturated with thermoplasticized,

injectable gutta-percha (Obtura, Texceed Corp., Costa Mesa, CA, USA), and resin

sealer (AH-26, DeTrey, Zurich, Switzerland).

The root canal walls of each sample were enlarged and the gutta-percha removed

with the low-speed drills provided by the manufacturer (RTD, St. Egrève, France),

to a depth of 9 mm from the cementum-enamel junction. The samples were

randomly divided into four groups of ten specimens each (Table 1).

72

Table 1: Bonding-luting procedures

Group 1 - OS (control): The bonding system was light cured separately for 20 seconds.

Group 2 – OS 30: The bonding system was light cured together with the resin cement through the

translucent post for 30 seconds.

Group 3 – OS 60: The bonding system was light cured together with the resin cement through the

translucent post for 60 seconds.

Group 4 – OS 90: The bonding system was light cured together with the resin cement through the

translucent post for 90 seconds.

Group Bonding system Clinical steps Resin cement Clinical steps

1. OS a,b,c, Duo-Link d,e,f,g,h

2. OS - 30 a,b, Duo-Link d,e,f,g,h

3. OS - 60 a,b, Duo-Link d,e,f,g,h

4. OS – 90 a,b, Duo-Link d,e,f,g,h

a. Dentin conditioning with phosphoric acid b. Primer application with microbrush c. Light-curing d. Post treated with the Primer-adhesive solution e. Mixing resin cement f. Cement application into the root canal with a lentulo drill g. Removing resin excess h. Light-curing through the translucent fibre post

OS: One-Step (Bisco, Schaumburg, Il); Duo-Link (Bisco)

Group 1: The first ten specimens were treated with One Step bonding system (Bisco,

Schaumburg, IL, USA), following the manufacturer’s instructions (Ferrari et al

2000b). The root canal walls were etched with 32% phosphoric acid (Bisco) for 15 s,

washed with water by means of a syringe with a small endodontic needle, in order to

completely remove the acid, and then gently air-dried. Excess water was removed

from the post space using paper points. Four coats of primer-adhesive material were

placed in the root canals with a thin microbrush Plus (Microbrush Co., Greyton, WI,

USA) (Ferrari et al 2001b). The excess primer-adhesive solution was removed with

a paper point, gently air-dried, and then cured by applying the light tip at the canal

orifice, parallel to the long axis of the root for 20 s. For curing purposes, a VIP

curing device (Bisco) was used, with a light intensity of 600 mW/cm2. Duo-Link

(Bisco) resin cement, a dual cure resin cement, catalyst and base were mixed and

used following the manufacturer’s instructions. The resin cement was applied into

73

the root canal space with a lentulo drill, the fibre post was seated, and the excess

resin removed and each specimen light-cured for 20 s through the post.

Group 2: Ten root specimens were treated as Group 1 samples. The only difference

was that the primer/adhesive solution One Step (Bisco) was not cured immediately.

Rather, the dual-cure resin cement was applied with a lentulo drill, the post was

placed in the root canal preparation, and only at this time were the adhesive material

and the cement light-cured simultaneously through the post for 30 s.

Group 3: These roots were treated as described in Group 2. The simultaneous light-

curing was performed for 60 s

Group 4: These samples were treated as described in Group 2. The simultaneous

light-curing was performed for 90 s.

DT light posts (RTD, St Egrève, France) were used in the 40 samples (Boudrias et

al. 2001). Depending on the size and the shape of the root specimens, number 1 (tip

diameter = 90, taper 06) and 2 (tip diameter = 100, taper 08) DT posts were used.

The length of each post was controlled before the luting procedure, and the post was

sectioned to match the length to the root canal preparation.

After complete setting of the cement, crown build-ups were performed with the

proprietary resin composite (Biscore, Bisco) to eliminate the chance of

incompatibility between the luting cement and the core material.

The teeth were stored in water at room temperature for 1 week. The roots were then

sectioned parallel to the long axis of the tooth using a diamond saw (Isomet,

Buehler, Lake Bluff, NY, USA), at slow speed under water.

6.2.1 RDIZ observations

One section of each root was gently decalcified (32% phosphoric acid was applied

for 30 s; the sample was then washed and gently air-dried) and deproteinized (the

sample was immersed in a 2% sodium hypochlorite solution for 120 s), in order to

evaluate RDIZ formation.

After being extensively rinsed with water, the specimens were gently air-dried and

dehydrated with alcohol, sputter-coated with gold (Edwards Ltd, London, UK) and

observed under a scanning electron microscope (Philips 515, Philips Co.,

Amsterdam, The Netherlands) at x1010 magnification. The observations were made

74

by two operators, and repeated twice in order to ensure intra examiner consistency.

When a different score was given, the lower score was taken into account.

The following aspects were evaluated by scanning electron microscope:

1. The continuity of the RDIZ: this variable was assessed as the percentage ratio

between the length of the RDIZ and the total length of the adhesive interface using a

visual and computer aided examination and calculation. The differences among the

average ratios calculated for the four groups were tested for statistical significance.

The One-Way ANOVA and Newman-Keuls Multiple Comparisons Test were

applied, setting the level of significance at p=0.05.

2. The presence or absence of gaps: a. Inside the adhesive layer, b. Between the

adhesive and the resin cement layer, c. Inside the resin cement layer, d. Between the

adhesive and the post.

6.2.2 Evaluation of resin tag formation

The other section of each sample was stored in 30% HCl for 24 h and in 2% sodium

hypochlorite solution for 10 min, in order to completely dissolve the dental substrate

and to detect resin tags and adhesive lateral branch formation. The samples were

then processed for SEM observation as already described.

Serial SEM photomicrographs at x500 original magnification were taken of the

canal walls at the 1, 4.5 and 8 mm levels from the end of the post. The serial

photomicrographs were aligned to form a continuous horizontal examination strip at

the 3 levels. Irrespective of the number of photomicrographs needed to form a

complete strip, each strip was subdivided into eight “assessment units”. The density

and morphology of the resin tags were then assessed.

The density and morphology of resin tags present at x500 magnifications were

graded between 0 and 3. A score of 0 was assigned where resin tags were not

detectable, a score of 1 was recorded when few, short resin tags (resin plugs) were

visible. A score of 2 was recorded when uniform resin tags formation was seen but

with a few lateral branches. A score of 3 was recorded when long resin tags with

lateral branches were uniformly evident.

Higher standardized magnifications were taken in order to document resin tags and

adhesive lateral branches morphology.

75

The scores assigned to resin tags seen at the 1, 4.5, and 8 mm levels were analyzed

with the Kruskal Wallis test, in order to check for statistical significance of the

differences both within and among the groups. The level of significance was set at

p=0.05 level.

6.3 Results

The number of samples showing voids/bubbles within the resin cement or/and at the

interface between resin cement and root walls are summarized in Table 2. Table 2: Number of specimens in which the presence of gaps/voids/bubbles within resin

cements was noted.

Within resin cement Post/cement Adhesive/cement

Group 1 1 1 /

Group 2 2 1 5

Group 3 3 2 3

Group 4 2 2 2

Voids were present in the composite cement layers of all groups. The cement layer

was substantially similar in all groups. Between 10% (Group 1) and 30% (Group 3)

of samples showed bubbles/voids within the cement. The adhesive-composite

cement and composite cement-fibre post interfaces were substantially free of voids.

Half of the samples in Group 2 showed voids/bubbles in the adhesive/cement layer.

All groups with simultaneous curing of the adhesive and of the cement (Group 2, 3

and 4) showed a high number of voids in post/cement and adhesive/cement

interfaces.

6.3.1 RDIZ observations

The results obtained regarding the presence of RDIZ in the various groups under the

SEM microscope are shown in Table 3.

76

Table 3: Scanning electron microscope evaluation of the resin dentin interdiffusion zone (RDIZ). Groups

labelled with the same letter did not show any statistically significant difference.

Group Overall length of observed

interface (in mm)

Length of interface with RDIZ (in mm)

1 OS 25.5 22.7 (89%)a

2 OS 30 26.5 18.5 (60%)b

3 OS 60 27.0 18.5 (65%)b

4 OS 90 26.0 18.2 (70%)b

Group 1 - OS (control): The bonding system was light cured separately for 20 seconds. Group 2 – OS 30: The bonding system was light cured together with the resin cement through the translucent post for 30 seconds. Group 3 – OS 60: The bonding system was light cured together with the resin cement through the translucent post for 60 seconds. Group 4 – OS 90: The bonding system was light cured together with the resin cement through the translucent post for 90 seconds.

The ratio between the length of the RDIZ and the total length of the interface was

significantly higher in Group 1 than in the other two Groups (p<0.05). Group 1

samples had uniform RDIZ formation, while in the other groups RDIZ was less

represented, especially at the apical level. In some samples of Group 2, 3, and 4, a

discontinuous gap between the RDIZ and resin cement was observed. The RDIZ

formation of Group 1 samples was significantly more evident than in the other three

Groups (Group 2, 3 and 4). Group 4 showed a higher ratio than Group 3, which in

turn presented a higher ratio than Group 2, but no statistically significant differences

were found among these three Groups (p>0.05).

6.3.2 Evaluation of resin tag formation

The results obtained regarding morphology and density of resin tags are

summarized in Table 4.

In Group 1 resin tags and lateral branches formation was more uniform than in the

other Groups. Although the length of resin tags was more evident at the coronal

third, the morphology of the resin tags was similar in all three thirds. The surface of

resin tags reproducing de-mineralized tubular dentin was rough and depicted the

appearance of tubular dentin dissolved by the acid. In the apical third resin tags were

all approximately the same length, which was shorter than that seen in the coronal

and middle third.

77

Table 4: Median values of the resin tags formation scores recorded at 1-, 4.5-, and 8 mm

levels. (Groups labelled with the same letter did not show any statistically significant

difference).

Group 1mm level

(Coronal third)

4.5 mm level

(Middle third)

8 mm level

(Apical third)

1. OS 2.9a 2.9a 2.5a,b

2.OS 30 2.6a,b 2.4b 1.1d

3.OS 60 2.6a,b 2.5b 1.3c,d

4.OS 90 2.7a 2.5a,b 1.7c

Group 2, 3 and 4: The resin tags formed in the coronal and/or middle areas of the

roots were much longer than those in the apical areas. Also, the density of resin tags

was higher in the coronal and middle areas than in the apical areas. In the coronal

two thirds of the roots adhesive lateral branch formation was also observed. In the

coronal and middle third the resin tags had a characteristic reverse-cone shape, while

in the apical third this morphology could only occasionally be seen. In the apical

third resin tags were often seen to only plug the tubules or were completely absent.

In Group 2, 3, and 4, some ‘globuli’ were observed (Figs. 1-2). Resin tag formation

was statistically significant different (p<0.05) between Group 1 and the other three

groups.

6.4 Discussion

Recently, several studies have reported the quantitative evaluation of morphological

observations of root canals (Ferrari et al 2001a, Ferrari et al 2001b). In this study,

RDIZ formation was evaluated calculating the entire length of RDIZ formed along

the interface between conditioned dentin and adhesive resin. Also the incidence of

resin tags was recorded from horizontal bands around the post, 1-, 4.5- and 8- mm

from the apices of the root canal preparations. In this way it was possible to

statistically analyze the data obtained from SEM observations of the four different

groups. This evaluation was performed because formation of both resin tags and

RDIZ contribute to the mechanical bonding process to the etched dentin and

consequently to the sealing process (Nakabayashi & Pashley 1998, Vichi et al.

78

2002b). However, other issues have to be taken into account (Sano et al. 1995a, Tay

et al. 1995): the ‘overwet phenomenon’ plays an important role in the quality of the

RDIZ, and subsequently in the final bond strength of the adhesive system. In this

paper no TEM examination and no measurement of the bond strength were

performed (Sano et al 1995b, Tay et al 1996).

After light curing the bonding system from the coronal aspect of the canal (Group

1), the dentin bonding systems tested could form a RDIZ that did not interfere with

the post placement into the root canal. This is most likely due to the fact that the

‘one-step’ bonding system tested in this study created a low film thickness (Vichi et

al. 2002a) and the bonding system was light sensitive and could be polymerized by a

light source placed at the access to the root canal (Group 1). In Group 2, 3 and 4,

One Step (Bisco, Schaumburg, IL, USA) was not light cured before applying the

resin cement and the post, but adhesive materials were light-cured through the post

simultaneously, shortening the clinical procedure.

An important issue related to the clinical procedure is the care taken to remove

excess adhesive that, once cured, could interfere with the adaptation of the post to

the prepared dowel space. Even though all the samples were prepared by the same

operator, following the same procedure and using the same instruments, some

variability in the cement thickness was expected and actually observed as a result of

the naturally occurring variability in root canal shape.

It is always questionable whether an interfacial gap seen under the SEM is an

artefact due to specimen preparation. However, as most of these gaps were

consistently and locally concentrated in the apical third, the least accessible area of

the canal, it can be speculated that they were real gaps revealing an adhesion

mechanism of poor quality.

A different density and morphology of resin tags and adhesive lateral branches at the

three horizontal bands could be found in Group 1 as compared with Group 2, 3 and

4 samples. These three last Groups always had poorer results when compared to the

standardized technique for bonding fibre posts into root canals (Group 1). Even

when the exposure time to the light curing procedure was increased (Groups 2, 3 and

4, from 30 to 60 and 90 s respectively), the increase in the scores was not

statistically significant. Group 1 samples always had better results than samples

79

from the other three Groups. This may be due to a difference in the procedure, for

example, although it has been demonstrated that a proper light curing of resin

cement can be obtained in an experimental model (Boschian et al. 2001), it is

possible that light transmission through the post might not be sufficient to light-cure

the cement and the adhesive in the same step. The adhesive may be subjected to an

inadequate intensity of light and thus not be completely cured, thus leaving

‘unpolymerized’ adhesive resin. Even when increasing the light-exposure time, from

30 s (Group 2) to 60 s (Group 3) and to 90 s (group 4), uncured resin globuli were

still present. This could account for a reduction in resin tag formation and the poor

results presented in Table 4. This problem is supported by the finding of other

studies (Tay et al 1995).

Another factor affecting RDIZ and resin tag formation can be the viscosity of the

cement and its adaptation to prepared canal space. If the adhesive solution is not

light-cured before the application of the cement, a good adaptation to the root canal

walls is not achieved, and the RDIZ is not established adequately. Under these

conditions, when the cement is placed together with the post, the cement itself may

wash out the adhesive.

In all the four Groups a microbrush was used. The importance of this device in

reaching the narrowest and deepest portions of the root canal preparations has been

showed by recent findings (Ferrari et al 2001b, Vichi et al 2002b). The microbrush

is able to reach all the prepared root canal dentin, and to apply a certain pressure on

the adhesive solution, so as to maximize its penetration into the etched substrate.

This results in a deep diffusion of resin into the tubules and in the formation of

lateral branches (Chappel et al. 1994, Mjor & Nordhal 1996).

The absence of voids/bubbles at fibre post/resin cement interface could be related to

the good bond between the resin matrix of the post and that of the resin cement,

whereas the presence of voids/bubbles within the resin cement might be mainly due

to the viscosity of the resin cement and to the anatomy of the root samples. In fact,

anatomical variations of roots, the consequent variable amount of resin cement, and

its distribution into a prepared canal space could be other possible causes of void

formation. Discrepancies between root anatomy and post shape might account for

the clinical finding that the weakest point of fibre post/resin cement/adhesive

80

material/etched dentin system is the link between resin cement and the post (Ferrari

& Scotti 2002). The high percentage of voids/bubbles found in Group 2, 3 and 4

shows that several factors (light intensity, cement viscosity etc.) interfere with the

complete setting of the materials used, as compared with Group 1, where a

traditional technique was used and a lower number of voids were detected. No data

are available regarding a calculation of the percentage of light passing through the

post and reaching the apical area. However in order to improve the predictability of

the one-step technique, it would be desirable for the manufacturers to provide

translucent posts able to transmit a high intensity of light from coronal to apical

areas. Of course, the amount of light emitted by the light source is important, ideally

the light transmitted to the post should be such as to ensure an adequate degree of

polymerisation in the apical third, without resulting in an augmented polymerisation

shrinkage in the presence of unfavourable configuration factor that occurs in the root

canal (Feilzer 1987).

The microscopic observations in this study and their quantitative evaluations does

not provide information on the quality of RDIZ. It has been shown recently (Mason

2001) that collagen fibres can be denaturated in direct correlation with the time

passed after root canal treatment. In recently treated teeth a wide and dense collagen

fibre network could be noted. On the contrary, when the treatment had been

performed more than 5 years previously, the collagen fibres appeared shorter, and

their organization and uniformity was lost. This denaturation of collagen fibres can

be related to the loss of organic tissue turnover after root canal treatment.

6.5 Conclusions

The null-hypothesis tested in this study was not confirmed. The one-step (‘one-

shot’) technique, used for luting translucent fibre posts into root canal preparations

proved to be less effective than the traditional technique in forming resin tags,

adhesive lateral branches and RDIZ.

81

Fig. 1: Group 2 sample, apical third. Resin glubuli closely attached to the resin tags are noted

(original magnification x 2500).

Fig 2: Higher magnification, Group 4 sample (original magnification x 5000). These globuli,

probably formed by unpolymerized resin, can be due to an uncomplete curing of the adhesive

material when it is not light cured before the placement of the resin cement and the post.

82

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leakage within the hybrid layer. Oper Dent 1995b;20, 18-25.

ng KM, Wei SHY. Micromorphologic relationship of the

tine interface.

fibre posts under clinical conditions. Dent Mat 2002a;18,

-502.

root canal: a microscopic investigation. J Endod 2002b;28, 355-60.

months in vivo study. J Dent Res 2002;81. Special issue A, pag A-333 (Abstr 2656).

Mason PN. Bonding to root canal dentine. Transactions of Acad

Materials Meeting, Siena, 2001, pp. 65-9.

Mjor IA, Nordhal I (19

teeth. Arch Or Biol 41, 401-2.

Monticelli F, Grandini S, Goracci C, Ferrari M. Clinical behaviour of tra

fi sts and luting and restorative materials: a 2-year report. Int J Prosthod

2003;16,(6):593-6.

Nakabayashi N, Pashley DH. Hybridization of dental hard tissue. Berlin: Quint Co.

Pubbl 1998.

Sano H, Yoshiyama M, Ebisu S, Burrow MF, Takatsu T, Ciucchi B, Carvalho R,

Pashley DH. Comparative SEM and TEM observations of nanoleakage within the hybrid

layer. Oper Dent 19

Sano H, Takatsu T, Ciucchi B, Horner JA, Matthews WG, Pashley DH (1995b).

Nanoleakage:

Scotti S, Malferrari S, Monaco C. Clinical evaluation of quartz fibre posts: a 30

months results. J Dent Res 2002;81. Special issue A, pag A-333 (Abstr 2657).

Tay FR, Gwinnett AJ, Pa

resin-dentine interface following a total-etch technique in vivo using a dentinal bonding

system. Quint Int 1995;26, 63-70.

Tay FR, Gwinnett AJ, Wei SH. The overwet phenomenon: an optical,

micromorphological study of surface moisture in the acid-conditioned, resin-den

Am J Dent 1996;9, 43-8.

Vichi A, Grandini S, Davidson CL, Ferrari M. An SEM evaluation of several

adhesive systems used for bonding

495

Vichi A, Grandini S, Ferrari M. Comparison between two clinical procedures for

bonding fibre posts into a

84

C 7 Anatomic Post: an innovative approach

hapter

hrough rapid developments in the last few years. These changes

regarded essentially three main issues: materials, radiopacity and shape. Starting

from carbon fibers, glass and quartz fiber are now widely used, and the addition of

strontium to the resin components radiopaque fiber posts are now available. The

optical property of translucency has also been appreciated by clinicians, allowing the

use of dual-curing resin cements for luting purposes. Interestingly, starting from the

double-cylinder shape, endodontic shapes and then double tapered shapes were

presented, as the adhesive cementation now relies more on formation of resin dentin

interdiffusion zone and resin tags rather than on the good fitting and mechanical

retention of the post inside the root canal (Ferrari et al 2002). It is a clinical evidence

to encounter debondings, of the post or of the core, during temporary phase (Ferrari

et al 2000). An excess thickness of the cement, especially at the coronal level, can

generally be regarded as the main cause. As a matter of fact it is pretty common to

face root canals that are not perfectly round after endodontic instrumentation. This

chapter presents an in vitro and an in vivo study regarding the very last brand of

fiber post available (Anatomic Post’n Core, RTD, St Egrève, France), that is able to

reduce the cement thickness and to immediately restore the coronal portion in cases

where the root canal is not round and a huge loss of tooth structure is present.

7.1 SEM evaluation of the cement layer thickness after the luting procedures of

two different posts

The increasing popularity and wide-spreading use of fiber posts is inevitably

changing the procedure of reconstructing endodontically treated teeth. Since fiber

posts introduction in 1990 (Duret et al 1990), many investigations have confirmed

the good clinical performance of the system adhesive- resin cement- fiber post

(Ferrari et al 2000a, fredriksson et al 1998) due to its good retention value Asmussen

et al 1999, Drummond et al 1999) and low stressing behaviour (Rengo et al 1999).

The evolution of fiber posts has received an acceleration since Carbon and quartz

fiber posts have been replaced by glass fiber posts that are translucent and often

radiopaque. Also the shape of these posts have changed: from a double-cylinder,

Fibre posts went t

85

thus designed for retention purposes, cylindrical (Endopost) and conic profiles (DT

osts) have been developed, based on the good performances of the new bonding

is

asier than that of any kind of metallic posts (de Rijk et al 2000), thus offering the

ule effect’, or in the presence of a too thick layer of cement

p

p

procedures (Kurtz et al 2002).

The property of translucency reveals favourable for luting purposes, as the

transmission of light through the post allows the clinician to use also dual-cure

cements (Grandini et al 2003, Sawada et al 2002). Moreover, the wider choice of

available shapes permits to limit the amount of residual dentin that has to be

removed in order to achieve a satisfactory post adaptation.

Furthermore, the translucent fiber post has a modulus of elasticity similar to that of

dentin and of the other posts, and has indeed given proof of adequate mechanical

properties (Drummond et al 1999). The use of ‘one-bottle’ adhesive systems has

greatly simplified the procedure of bonding also into root canals, and has proved to

be clinically adequate (Ferrari et al 2001a and 2001b), especially when a

microbrush, in the place of a regular brush, is employed as a carrier of the adhesive

and the resin cement inside the root canal (Ferrari et al 2001b).

Clinical studies (Fredriksson et al 1998, Malferrari et al 2002, Scotti et al 2002) have

revealed that when using fiber posts, the most common cause of failure is not root

fracture, as it happens with metallic or cast posts, but debonding. Also endodontic

failure is an important issue (Tronstad et al 2000), and a reliable predictor of the

success rate of many kind of reconstructions; although the removal of a fiber post

e

clinician a chance of retreatment. Debonding is more likely to occur in the absence

of the desirable ‘fer

(Ferrari et al 2000a). In particular, if the post is not well fitting, especially at the

coronal level, the cement layer ends up being too thick, and bubbles are likely to be

present within it, all this predisposing to a debonding.

Clinically, when debonding occurs, the post often appears lined by cement still

adhering to it. In this case it is possible to lute again this cement-relined post, which

is now “anatomic”. This individual post, shaped to the root canal space ends u

having a better fit than any other prefabricated post (Ferrari et al 2000a).

This opportunity is particularly appreciated when dealing with root canals which

have an elliptic shape, such as canines, lower premolars etc. In these cases the

86

clinician is forced to adapt the residual root structure to the post shape, through the

removal of a further amount of dentin. On the contrary, it would be desirable that the

post adapt to the root canal anatomy as produced by the endodontic treatment. This

ini et al 2003). This way

ricated them with a

nesses were present when

analyzed

is indeed the rationale for the creation of an anatomic post (Boudrias et al 2001a and

2001b).

It goes back to two years ago the first documented attempt to make anatomic posts

by relining a quartz post with self-curing resin and a translucent post with light-

curing resin (Boudrias et al 2001a, Ferrari et al 2002, Grand

the authors were able to achieve a better adaptation of the post to the residual root

canal anatomy. Recently the Anatomic Post’n Core (RTD, St Egrève, France) has

been introduced (Ferrari et al 2002) . This new post is made by a DT post n. 1a that

is covered by a light-curing resin (Lumiglass, RTD, St Egrève, France).

The clinical procedure for the use of this post starts with the fitting of the Anatomic

post (post plus resin) into the root canal, after having eliminated with a drill all the

possibly present undercuts from the canal walls, and having lub

glycerine gel. When the anatomic post is introduced into the root canal, the resin

surrounding the post is able to reline the post itself, thus creating a new post whose

adaptation is expected to be better than that of any prefabricated post. A twenty-

second light-curing through the post allows the resin surrounding the post to set,

then the Anatomic post is removed and fully light cured for other twenty seconds.

Now the post has to be tried in, to make sure that no interference exists to its easy

placement. At this point the usual procedure for luting a translucent post can be

followed.

Aim of this study was indeed to evaluate the resin cement thickness after luting

anatomic posts and standardized fiber posts into root canal preparations.

The null hypothesis that similar resin cement thick

anatomic or standardized posts were used was evaluated.

In addition, the presence of voids and/or bubbles within the luting material or at the

interface between the cavity walls and the post was verified, and the uniformity and

morphologic characteristics of the resin-dentin interdiffusion zone were

under a scanning electron microscope, as parameters usually assessed when judging

87

the quality of the adhesion of the post inside the canal (Chappel et al 1994, Ferrari et

al 2001b, Mason et al 2001, Mjor et al 1996, Nakabayashi et al 1998).

7.1.1 Materials and Methods

Twenty upper anterior teeth, extracted for periodontal problems, were selected for

cturer. Excess primer-adhesive solution was removed with a paper point,

was used.

d into the root canal space

diameter, 08 % conicity; DT3, 90 tip diameter, 06 % conicity). The choice between

this study. The teeth were endodontically instrumented at a working length of 1 mm

from the apex to a #35 master apical file. A step-back technique was used with

stainless-steel K-files (Union Broach, New York, NY, USA), gates Glidden drills #2

to #4 (Union Broach, New York, NY, USA), and a 2.5% sodium hypochlorite

irrigation. The prepared teeth were obturated with thermoplasticized, injectable

gutta-percha (Obtura, Texceed Corp., Costa Mesa, CA, USA) and a resin sealer

(AH-26, DeTrey, Zurich, Switzerland).

The root canal walls of each specimen were enlarged with low-speed drills provided

by the manufacturer (RTD, St Egrève, France), and the depth of the post space

preparation was 9 mm from the cementum-enamel junction. The sample was

randomly divided into two groups of ten specimens each.

Group 1: The first ten specimens were treated with the One Step bonding system

(Bisco, Shaumburg, Il, USA), following manufacturer’s instructions. The root canal

walls were etched with 32% phosphoric acid (Bisco, Shaumburg, Il, USA) for 15

seconds, washed with a water syringe, and then gently air-dried. Excess water was

removed from the post space using paper points. Four to five coats of primer-

adhesive material were applied into the root canals with a microbrush provided by

the manufa

the remaining material was gently air-dried, and then light-cured for 20 seconds.

Duo-Link (Bisco, Shaumburg, Il, USA), a new dual-cure resin cement

The catalyst and base components of the material were mixed according to the

manufacturer’s instructions. The resin cement was applie

with a lentulo drill, and the fiber post was seated. The excess resin was removed and

the remaining material light-cured for 20 seconds through the post.

The DT translucent fiber posts (RTD, St Egrève, France) were used. They were

available in three different sizes (DT1, 120 tip diameter, 10% conicity; DT2, 100 tip

88

them was dictated by the size and the shape of the roots, the objective being the

achievement of a good fit of the post at the apical portion of the canal. The length of

ach post was controlled and the post was properly cut before luting.

ens were used for testing ‘experimental anatomic

h involved phosphoric acid etching of root

of the tooth, by means of

were aligned to

e

Group 2: The other ten specim

posts (RTD, St Egrève, France)’, following manufacturer’s instructions (Fig 1).

After lubricating the canal walls with a glycerin gel, the anatomic post was fitted

into the root preparation, and irradiated by the curing light for 20 seconds. Then the

post was removed and fully light-cured for other 20 seconds. The post was tried in

the root canal again, in order to check for its easy insertion, without any

interference. An abundant rinsing was performed to remove the excess of the

lubricant gel. Finally, the post was luted following the same technique already

described for Group 1 specimens, whic

canals, followed by the application of the One-Step adhesive system, and of the

Duo-Link resin cement.

The sample teeth were stored in a water solution at room temperature. A week later,

the root specimens were sectioned parallel to the long axis

a diamond saw (Isomet, Buhler, Lake Bluff, NY, USA).

7.1.1.1 Resin cement thickness

The sections were gently decalcified (32% phosphoric acid was applied for 30

seconds, then the sample was washed and gently air-dried) and deproteinized (the

sample was immersed in a 2% sodium hypochlorite solution for 120 seconds), in

order to clean the surface from any debris.

Specimens were at this point dehydrated with alcohol, sputter-coated with gold

(Edwards Ltd., London, UK), and observed under a scanning electron microscope

(Philips 515, Philips Co., Amsterdam, The Netherlands) at different standardized

magnifications (x250, x500, x2300 and x4580 for resin tags; x625 and x1310 for

resin dentin interdiffusion zone).

Serial SEM photomicrographs of the canal walls were taken at the 1-, 4.5- and 8-

mm levels (x500 magnification) (Fig. 2). The photomicrographs

form a continuous horizontal examination strip at the three levels. Irrespective of the

number of photomicrographs needed to form a complete strip, each strip was

89

subdivided into eight “assessment units”. In each assessment unit two distinct

operators in double blind evaluated the following aspects:

1. Resin cement thickness at the three different levels.

2. Presence or absence of gaps: a. Inside the resin cement, b. Between the dentinal

walls and resin cement, c. Between the resin cement and the post.

The differences in the cement layer thickness surrounding the two types of posts at

each of the three root canal levels were tested for statistical significance (t-Test,

p=0.05). Also, within the same group of samples and therefore for each type of post,

the differences among the cement layer thicknesses measured at the three checked

levels of the root canal were evaluated statistically (One-Way ANOVA, p=0.05).

Additionally, the Fisher’s Exact test was applied to check for statistical significance

of the differences in frequency of defects between the two experimental groups

(p>0.05).

7.1.2 Results

The cement thickness measured in microns in the two groups of specimens is

reported in Table I. Table I: Mean and standard deviation values of resin cement thickness (in µm) recorded at 1-,

4.5-, and 8 mm levels. The values labeled by the same letter were not significantly different.

Group 1mm level

(Coronal third)

4.5mm level

(Middle third)

8mm level

(Apical third)

1. control 610±67d 240±2 c b1.6 130±10.4

2. anatomic posts 20±2a 40±3.6a 100±8.2b

It can be noted that the resin cement thickness decreases from the apical to the

coronal level in the anatomic samples, while the opposite happens in the control

group (Figs. 3 and 4).

In Group 2 the highest thickness of cement (around 100 microns) was seen at the

margin between the coronal portion of the anatomic post and the resin composite

abutment (Fig. 5).

90

Statistically significant differences in cement thickness were found between the two

groups of specimens at the coronal and the middle level of the canal (p<0.05). Also,

the three different levels

t the coronal and

long the root canal preparation

Within resin cement Post/resin material Dentinal walls/cement

within the same group of specimens, cement thicknesses at

of observation were significantly different (p<0.05). Only in the presence of

anatomic posts, were similar thicknesses of cement measured a

middle third of the canal (Fig. 6) (Table I).

A good adaptation of the fiber post, relining material, luting material and residual

dentin could be noted (Fig. 7).

Often voids and bubbles were detected within the resin cement (Table II), as well as

within the abutment in both groups of specimens (Table III). Also, voids and

bubbles were noted between the fiber post and the resin material. Table II: Number of samples in which presence of gaps/voids/bubbles within resin cements

was noted a

Group 1 5 / 3

Group 2 1 1 /

Table III: Number of samples in which presence of gaps/voids/bubbles within the abutment

ed.

mate mater

was not

Within resin rial Post/resin ial

Group 1 8 3

Group 2 9 2

Occasionally, gaps of different extension were observed between the resin

composite relining material and the fiber post (Table II).

The differences in frequency of defects between the two experimental groups were

not statistically significant (p>0.05).

91

7.1.3 Discussion

SEM observations allow for a high resolution assessment of the conditions of

adhesion. The morphologic characteristics of the adhesive interface, as revealed by

scanning electron microscopy, can be evaluated through either a qualitative or a

quantitative analysis. The latter is usually preferable, as it provides a repeatable

method. For this reason, in the present study it was chosen to follow a recently

quency of structural discontinuities in the adhesive

i et al 1998, Vichi

dentin interdiffusion zone (Sano et al 1995,

Tay et al 1995). H S R y

to the qu ty of the adhesion, it eventually gives q ntitative information

on its uniform formation.

Th l steps eeded to create the anatomic post hav n described. The

que is relatively easy, and adding only few more actions to those required to

to considerably reduce the thickness of the cement layer, within which

the development of vo l

The expected advantages of this technique c be listed as follows: as a result of the

relining, the thickness of the cement layer is lower and constant; the formation of

bu oids, repr ing areas of weak ss within the material, is less likely in

thin and uniform layer of cement; the polymerization stress that develops within a

ent, being conic-shaped or

ing to adapt the root canal to the standardized

ost (Grandini et al 2003). Of course these advantages must be verified by further

udies as no statistically significant differences were evident between the two

roups.

proposed quantitative analysis (Ferrari et al 2001b), for the evaluation of cement

thickness, as well as of the fre

interface, such as bubbles, voids or gaps. This evaluation was performed because

formation of both resin tags and RDIZ contribute to creating a proper mechanical

bonding to etched dentin and consequently sealing it (Nakabayash

et al 2002a). TEM examination and measurement of the bond strength are the best

way to assess the quality of the resin-

owever, even if the EM evaluation of DIZ is not the best wa

measure ali ua

e clinica n e bee

techni

bond a regular translucent fiber post, allows to achieve a superior quality of the

fitting, and

ids or bubbles is less ikely.

an

bbles or v esent ne

a

low-thickness film of cement is minimal; furthermore, from a clinical point of view,

in a root canal that ends up, after the endodontic treatm

not perfectly round, the possibility of relining the Anatomic post is appreciated: the

post adapts to the canal instead of try

p

st

g

92

In comparison with metallic posts, the anatomic post offers the same advantages as

ity sufficient to induce polymerization (Boschian et al

ntific data that will answer the

all of the other fiber posts, including the fact that, in case endodontic retreatment is

needed, a fiber post is more quickly and easily removed than a metallic post

(Tronstad et al 2000). Also the considerations regarding chair-time and costs

required by the two compared procedures for restoring endodontically treated teeth

tend to tip the balance in favor of fiber posts, as the use of these, differently from

cast posts, allow to bond the post and build the core in only one visit, without any

laboratory phase and fee.

Whether a light-curing cement can be adequate for luting fiber posts or it is safer to

resort to a dual-cure material is still debated in the literature, the heart of the issue

being light transmission through the post. In other words, according to some Authors

the amount of light that, passing through the post, gets to the apical portion of the

post is not enough to adequately cure a light-activated resin cement (Rovatti et al

2001). Some other researchers, on the other hand, state that transmission through a

translucent post is efficient enough to allow also the apical portion of the post to be

reached by a light intens

2001).

As far as the anatomic post is concerned, the issue of light transmission through its

relining resin has still to be investigated. The question whether light absorption

through the relining resin may negatively affect the polymerization process of the

cement can in fact be raised. In the wait for scie

question, it remains safer and advisable to use a dual-curing resin cement for luting

anatomic posts.

Just like all of the resin-based materials, also the relining resin surrounding the

anatomic post shrinks as it cures. Although this aspect needs further evaluation,

however, it logically seems that the shrinkage should favor the extrusion of the

anatomic post from the canal after its relining.

The quality of the adhesion between the post and the relining resin appeared good in

all of the SEM views. This may be due to the compatibility between the two

materials, which have the same matrix components, as well as to the addition of a

coupling agent (silane) at the interface between the post and the relining resin.

93

Regarding the wider thickness of the resin cement layer found with the standardized

post, the references from the literature do not give a certain answer. Some clinical

works, perspective or retrospective studies (Ferrari et al 2000a, Fredriksson et al

1998, Malferrari et al 2002, Scotti et al 2002), show that debonding occurs when a

thicker cement layer is present. In this sense it can be assumed that a more precise

fitting obtained with the anatomic post can improve this aspect, even if a further

clinical control study is needed to confirm this aspect.

The null-hypothesis tested in the study was not confirmed. The resin cement

pe of fibers (from carbon to quartz, to glass), as well as the shape of

at variety of shapes (Asmussen et al

thickness was significantly lower in the ‘anatomic post’ group than in the control

group (standardized posts), except at the apical third of the canal, where there was

no statistically significant difference. Although there is no scientific evidence that a

thinner layer of cement can improve the quality of the luting procedure, a good

adaptation of anatomic posts was evident in all of the specimens, allowing the post

to stand still during the luting procedures .

The clinical procedure to make an anatomic post was effective and easy to perform.

7.2 Use of Anatomic Post’n Core for reconstructing an endodontically treated

tooth: a case report.

The introduction of fiber posts has had a great impact on the clinical procedures to

restore endodontically treated teeth. Since their début at the beginning of the 90’s

(Duret et al 1990), the research behind these products has continuously worked on

modifying the ty

the posts. The evolution in the technology has enabled the manufacturers to provide

today fiber posts that, beside offering superior esthetic and mechanical properties,

which had been the first qualities to be appreciated in comparison with metal or cast

posts, are also radiopaque and available in a gre

1999, Asmussen et al 1999, Fredriksson et al 1998). The growing popularity of fiber

posts witnesses their clinical success, and the results of longitudinal trials (Ferrari et

al 2000, Malferrari et al 2002, Scotti et al 2002, Fredriksson et al 1998) confirm

their reliability.

94

As regards in particular the shape of the posts, the evolution has gone from the

double-cylinder of the carbon posts, thus designed for retention purposes, to the

cylindrical or the conic profile of the Endoposts and DT posts respectively. These

latter designs are meant for a better adaptation of the post to the canal anatomy, thus

minimizing the amount of residual root structure that has to be sacrificed in order to

get the post to fit. Obviously, this trend toward more and more conservative root

preparations for post adaptation has been possible only thanks to the contemporary

ugh its insertion into the canal, with the

t al 2000, Ferrari et al 2002a). As a result of its precise adaptation to the root canal

ace, the relined post is going to be surrounded by a thin and uniform layer of resin

ividualizing’ the post through its relining, although advisable

n fracture with extensive pulp exposure on teeth 1.1 and 2.1, and

an enamel-dentinal fracture without pulp exposure on tooth 2.2. After clinical and

progress in the field of materials and techniques for bonding, that has made adhesion

to root canal walls safer and more predictable (Ferrari et al 2001a, 2001b and 2002b,

Mason 2001, Mjor et al 1996).

It is likely that a further significant improvement in fiber posts adaptation and

retention will be achieved with the so-called ‘anatomic post’. This is a translucent

fiber post covered by a layer of light-curing resin (Anatomic Post’n Core. RTD),

which allows for a relining of the post thro

aim of achieving a better fit than that possible with any prefabricated post (Grandini

e

sp

cement, which creates ideal conditions for post retention (Boudrias et al 2001).

The procedure of ‘ind

in all cases, appears to be particularly effective for the purpose of improving post

retention when dealing with canals of elliptic shape, or exhibiting a reduced amount

of residual root structure after endodontic treatment; this latter situation obviously

contraindicates a further removal of dentin to make the canal shape match the post

shape. The creation of an ‘anatomic post’, involving the opposite adaptation, that is

shaping the post to the root anatomy, is the procedure of choice in these clinical

situations, of which the described case is an example.

7.2.1 Case report

A nine-year old patient comes to the office two days after having hit his front teeth

as a result of falling down while playing in the school gym. The trauma caused a

complicated crow

95

x-ray examination, it was decided to endodontically treat teeth 1.1 and 2.1, and to

restore all the teeth with resin composites, waiting for the adequate time to perform

a prosthetic treatment. The root canal treatments were done, and tooth 1.1 was

restored with a direct resin composite restoration (Figs. 8 and 9). On tooth 2.1, the

root canal anatomy after endodontic treatment was such that no prefabricated post

could satisfactorily adapt to it (Fig. 10); on the other hand, the amount of residual

dentin on the canal walls was such as to contraindicate the further removal of tissue,

to make the canal shape adapt to that of the post. It was then decided to use for tooth

2.1 an ‘anatomic post’. The procedure started with removing by means of a drill any

undercut still possibly present on the canal walls, which were then lubricated with

was

ss of material removed before

ght-curing for 40 seconds through the post (Fig 14). Due to the young age of the

ded to avoid the immediate preparation for a prosthetic crown.

glycerine. At this point the anatomic post’n core was inserted (Fig 11) and light

cured for 20 seconds (Fig 12). Then the anatomic post was gently pulled out of the

canal, and an additional 20-second light curing was performed in order to

completely polymerize the relining resin (Fig 13). The anatomic post was tried in

again, in order to check for its easy insertion, without any interference. At this point

a luting procedure was performed similar to that recommended for a regular

translucent post. The root canal walls were etched with 32% phosphoric acid (Bisco)

for 15 seconds, washed with a water syringe and gently air-dried. Excess water

removed from the post space using paper points (Mynol). Four to five coats of the

One Step bonding system (Bisco) were applied into the root canals with a

microbrush provided by the manufacturer. The excess primer-adhesive solution was

removed with a paper point (Mynol), gently air-dried, and then light-cured for 20

seconds. Dual Link (Bisco), a new dual-cure resin cement was used for luting. The

catalyst and base components of the material were mixed and applied following

manufacturer’s instructions. The resin cement was carried into the root canal space

with a lentulo drill, the post was seated, and the exce

li

patient, it was deci

The anatomic post was therefore simply used as a base for a direct composite

restoration (Fig. 15). The prepared tooth was etched with 32 % phosphoric acid

(Bisco) (Fig. 16); then, the One step adhesive system (Bisco) was applied as

96

recommended by the manufacturer (Fig 17), and the restoration was completed with

a microhybrid resin composite material (Micronew, Bisco) (Figs. 18, 19 and 20).

7.2.2 Discussion

The observation of a residual root canal shape after endodontic treatment which is

not perfectly round is not so uncommon (Davis et al 1972, Walton et al 1996). This

case is a suitable situation for using the Anatomic post. In fact, in the attempt to

place a regular fiber post in a thus shaped canal, one would be forced to round up the

canal walls with burs, thus sacrificing a conspicuous amount of the residual tissue,

or would end up applying a thick layer of cement, to fill up the spaces between the

loosely fitting post and the canal walls. The latter is a predisposing situation to

failure of the adhesion and debonding of the post (Ferrari et al 2000). On the other

hand, a post relined to closely match the shape of the canal will be surrounded by a

thin and uniform film of cement, which represents an ideal situation for retention

purposes.

In addition, the technique of the anatomic post allows to perform a direct restoration

on an ‘individual’ post in only one visit and without the laboratory involvement,

whereas the classic post and core system, direct or indirect, requires at least two

visits and a laboratory phase. This opportunity is particularly appreciated in a case

like the one described, where the young age of the patient calls for a treatment to be

completed in few visits, each one as quick and easy as possible.

On the other hand, if a prosthetic restoration is planned for the endodontically

treated tooth, it is possible to immediately build up on the anatomic post a resin

composite core, which in the same visit can be prepared for prosthetic purposes.

From a clinical point of view, it appears that the step of creating an individual post

by letting the surrounding resin reline it according to the canal shape, adding only

five minutes of chair-time to the standard procedure for luting a translucent post, can

greatly improve post adaptation and retention. A study involving both an in vivo trial

and a SEM evaluation of the quality of adhesion is already available (Grandini et al

2004), with the aim of providing some more scientific support to the positive clinical

impression.

97

7.2.3 Conclusions

The clinical procedure of the Anatomic post can be used for reconstructing an

ndodontically treated tooth when the resulting anatomy of the root canal walls is

, and when there’s an important loss of substance at the coronal

e

not perfectly round

level. This way it is possible to obtain a superior fitting of the individual anatomic

post, as compared with any other prefabricated fiber post.

98

Fig 1: Shape of the Anatomic post in comparison with that of DT posts

of different sizes (DT1, 2, and 3).

Fig 2: picture showing the three levels of observations: apical,

medium and coronal level (original magnification x13).

99

Fig 3: Group 2 sample. Low magnification image showing the relining provided by the light-

activated resin surrounding the post (original magnification x 13).

100

Fig 4: Group 1 sample. An abundant amount of cement can be noted around

the fiber post (original magnification x 21).

FP: fiber post, D: Dentin, LC: luting cement

101

Fig 5: Group 2 sample. A thicker layer (arrows) of cement (C) is

visible at the interface between the abutment and the coronal dentin

(original magnification x 170).

102

Fig 6: Picture showing the presence of voids/bubbles within the resin material

(original magnification x 11).

103

Fig 7: High magnification picture showing the good quality of the adhesion

between relining material (RM), luting material (between arrows) and root canal

dentin (D) (original magnification x 356).

104

Fig 8: x-ray examination after having completed the endodontic treatment.

Fig 9: Endodontic treatment and a direct composite restoration were

performed on teeth 1.1 and 2.1.

Fig 10: After rubber dam placement, the wide and not perfectly

round residual root canal anatomy is visible on tooth 2.1.

105

Fig 11: The post surrounded by light-curing resin is inserted

into the root canal with the aim of relining it (Anatomic Post).

Fig 12: Light-curing through the post (20 seconds) to

allow for the setting of the surrounding resin.

Fig 13: The relined post as it appears after having completed

the light-curing out of the patient’s mouth.

106

Fig.14: The post after the luting procedures.

Fig 15: View of tooth 2.1 after preparation for a direct

resto r the

resin composite restoration.

ration. The anatomic post is used as a ‘base’ fo

Fi d. g 16: Etching procedure with phosphoric aci

107

Fig 17 ore of

the tooth and to obtain the proper effect of opacity or to

reproduce the natural opacity of the tooth.

: Opaque resin composite is used to build the c

Fig 18: The restoration is completed with a translucent

resin composite, used as ‘enamel’ material.

108

Fig 19: Post-operative x-ray examination. The anatomic post

has been luted into the root canal, and the restoration completed.

Fig 20: Facial view immediately after the removal of the rubber dam.

109

References

Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit, and strength of

newer types of endodontics posts. J Dent 1999; 27: 275-278.

Boschian L, Galimberti B, Fadini L. A new method to evaluate the conversion of a

composite resin into the root canal: HPLC. J Dent Res 2001; 80: (Abstr 1842) page 757.

Boudrias P, Sakkal S, Petrova Y. Anatomical post design applied to quartz

fiber/epoxy technology: a conservative approach. Oral Health, 2001a;11 9-16.

Boudrias P, Sakkal S, Petrova Y. Anatomical post design meets quartz fiber

technology: rationale and case report. Compendium. 22: 337-348, 2001b.

Chappel RP, Cobb CM, Spencer P. Dentinal tubule anastomosis: A potential factor

in adhesive bonding? J Prosthet Dent 1994; 72: 183-188.

Davis SR, Brayton SM, Goldman M. The morphology of the prepared root canal: a

study utilizing injectable silicone. Oral Surg 1972; 34: 642-8.

Drummond JL, Toepke RS, King TJ. Thermal and cy ing loading of endodontic

posts. Eur J Or

Du tution corono-

radiculaire: le composiposte (1). Chirurg Dent France 1990; 540: 131-141.

Ferrari M, Vichi A, Mannocci F, Mason PN. Retrospective study of clinical

behaviour of several types of fiber posts. Am J Dent 2000; 13: B15-B18.

Ferrari M, Vichi A, Grandini S, Goracci C. Efficacy of a Self-Curing

Adhesive/Resin Cement System on Luting Glass-Fiber Posts into Root Canals: An SEM

Investigation. Int J Prosthod 2001a; 14: 543-549.

Ferrari M, Vichi A, Grandini S. Influence of adhesive application technique on

efficacy of bonding to root canal walls: An SEM investigation. Dental Materials 2001b; 17:

422-429.

Ferrari M, Scotti R. Fiber posts: clinical and research aspects. Masson Ed, Milano

2002a.

F ep adhesive

systems used for bonding fiber posts into root canals under clinical conditions: an SEM

investigation. Dent Mat, 2002b.

Fredriksson M, Astback J, Pamenius M, Arvidson K. A retrospective study on 236

patients with teeth restored by carbon fiber-reinforced epoxy resin posts. J Prosthet Dent

1998; 80: 151-157.

Grandini S, Sapio S, Goracci C, Monticelli F, Ferrari M. ‘One-shot’ luting

procedure for lutingfiber posts: an SEM evaluation. Int Endod J 2004, in press.

cl

al Sci 1999; 107: 220-224.

ret B, Reynaud M, Duret F. Un nouveau concept de reconsti

errari M, Vichi A, Grandini S, Davidson C. ‘One-bottle’ and three st

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;5(3):243-7.

hes Dent 2004,

in press.

-out bong strengths

of toothco

ranslucent quartz fiber posts: a 20

ions of Academy of Dental

and branching of dentinal tubules in human teeth.

erlin:

n of stress in carbon

er pos

om endodontically treated teeth. American

ano H, Takatsu T, Ciucchi B, Horner JA, Matthews WG, Pashley DH.

anoleak

Sawada N, Hikage S, Sakaguci K. Shape of composite resins photopolymerized by

e transl

Special issue A, pag A-333 (Abstr 2657).

95; vol 26, n 1: 63-70.

Grandini S, Sapio S, Simonetti M. Use of anatomic post’n core for reconstructing an

endodontically treated tooth: a case report. J Adhes Dent 2003

Grandini S, Ferrari M. Una tecnica per rendere anatomici i perni in fibra. Il Dentista

Moderno. Anno XVIII, n° 5, May 2000.

Grandini S, Sapio S, Goracci C, Monticelli F, Ferrari M. SEM evaluation of the

cement layer thickness after the luting procedures of two different posts. J Ad

Kurtz JS, Bowles WR, Perdigao J, Geraldeli S, Hodges JS. Push

loured posts. J Dent Res 81 Special issue A, pag A78, # 0425; 2002.

Malferrari S, Baldissara P, Arcidiacono A. T

months in vivo study. J Dent Res, 2002, 81. Special issue A, pag. A-333 (Abstr 2656).

Mason PN. Bonding to root canal dentin. Transact

Materials Meeting, Siena, 2001, pp. 65-69.

Mjor IA, Nordhal I. The density

Archs Oral Biol 1996; 41: 401-412.

Nakabayashi N, Pashley DH. Hybridization of dental hard tissue. B

Quintessence Co. Publ., 1998.

Rengo S, Apicella A, Ausiello P, Davidson CL. The distributio

fib ts restorations: a preliminary study. Proceedings from the 3rd International

Symposium. 60-61, 1999.

de Rijk WG. Removal of fiber posts fr

Journal of dentistry. 13: 19B-21-B, 2000.

Rovatti L, Dallari A. Odontoiatria conservatrice. Hermes Ed. Milano, 2001.

S

N age: leakage within the hybrid layer. Oper Dent (1995) Jan-Feb;20(1):18-25.

th ucent post. J Dent Res IADR abstract # 2569; 2002.

Scotti S, Malferrari S, Monaco C. Clinical evaluation of quartz fiber posts: a 30

months results. J Dent Res, 2002, 81.

Tay FR, Gwinnett AJ, Pang KM, Wei SHY. Micromorphologic relationship of the

resin-dentin interface following a total-etch technique in vivo using a dentinal bonding

system. Quint Int 19

Tronstad L, Asbjornsen K, Doving L, Pedersen I, Eriksen HM. Influence of coronal

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restorations on the periapical health of endodontically treated teeth. Endod Dent Traumatol

2000 Oct

several

;16(5): 218-221.

Vichi A, Grandini S, Davidson CL, Ferrari M. An SEM evaluation of

adhesive systems used for bonding fiber posts under clinical conditions. Dent Mater. (2002)

Nov;18(7):495-502.

Walton R, Torabinejad M. Principles and practice of endodontics, 2nd edition, W.B.

Saunders Co., 1996: 212-14.

112

Chapter 8 Clinical aspects and future role of fiber posts in dentistry

In st 10 years the use of fiber posts for restoring root canal treated teeth has

increased in popularity. The major advantage is their similar elastic modulus to

entin, produ

the la

ions at the post-dentin interface (Pegoretti et al 2002).

ze this fact by calling “low modulus” restorations those made

with a fiber post, and “high modulus” those made with rigid posts (metal, alloys,

zirconium etc.) (Ferrari et al 2002). It has also been reported that using a “low

modulus” restoration could reduce the risk of root fractures (Isidor et al 1996,

Akkayan et al 2002). Clinical studies have also demonstrated high success rates

without the occurrence of root fractures (Ferrari et al 2000a and 2000b). Many

clinical studies are available regarding the use of fiber posts, a resin core and a

crown (Scotti et al 2002, Malferrari et al 2002, Ferrari et al 2000a and 2000b, Dallari

et al 1998, Monticelli et al 2002).

With the use of contemporary restorative techniques, it is possible to restore teeth

with direct composite procedures, with good functional and esthetic outcomes, and

in a way to save tooth structure. Indications for their use have expanded enormously

in recent years, and now include restoration of tooth structure and contour, changes

to tooth form and enhancement of esthetics, combination restorations (Hickel et al

2004).

This chapter analyzes a possible future use of fiber posts in combination with a

direct resin crown for the restoration of root canal treated teeth, according to the aim

of the minimal intervention philosophy (Mjor et al 2002).

8.1. Clinical evaluation of the use of fiber posts and direct resin restorations for

endodontically-treated teeth

The potential of utilizing fiber-reinforced materials in restorative dentistry has been

appreciated for some time (Bradley et al 1980). The introduction of carbon fiber

posts in 1990 (Duret et al 1990) provided the dental profession with an alternative to

cast or prefabricated metal posts for the restoration of endodontically-treated teeth,

as the elastic moduli of these fiber posts are closer to that of dentin when compared

d cing a stress field similar to that of natural teeth, whereas metal posts

exhibit high stress concentrat

Some authors emphasi

113

with the metal posts (Asmussen et al 1999). Although these earlier generations of

ber posts yielded promising results in clinical trials (Fredriksson et al 1998, Ferrari

ure when fiber posts are used for restoration of

overage has always been highly recommended (Fuss et al 2001). An

e or deflection of bonded

ber-reinforced composite posts demonstrated that they are protective of the

). Although retrospective studies reported good

fi

et al 2000a and 2000b), they suffered from the limitations of being radiolucent and

difficult to mask under all-ceramic or resin composite restorations (Vichi et al

2000).

Over the years, there has been a rapid development in fiber post technology. With

the more recent introduction of radiopaque and more aesthetic quartz and glass fiber

post systems, there is a continuing improvement in the acceptance of fiber posts by

the dental profession (Ferrari et al 2000a, Drummond et al 1999). Studies on the

adhesion of fiber posts to root dentin Nakabayashi et al 1998, Chappel et al 1994,

Mjor et al 1996), the different luting procedures (Ferrari et al 2000c, Vichi et al

2002) and the abutment build-up (Gateau et al 1999, Cohen et al 1996, Freedman

2001) demonstrated the quality performance of the new generations of fiber posts

(Dietschi et al 1997). These favorable results are also supported by clinical trials

showing the absence of tooth fract

endodontically-treated teeth (Monticelli et al 2003, Ferrari et al 2000a and 2000b).

The need for crown coverage after root canal treatment is still conjectural, and no

recent clinical study is available to confirm the indications given in the literature

(Sorensen et al 1984, Paul et al 1998). Post placement and root canal treatment are

usually considered the major etiological factors for root fractures. For this reason

crown c

association between crown placement and the survival of endodontically-treated

teeth was observed when the loss of tooth structure was remarkable (Aquilino et al

2002, Newman et al 2003). However, the mode of failur

fi

remaining tooth structures, and fracture usually comes about at loads that rarely

occur clinically (Paul et al 2001

clinical performances when a crown was used after tooth build-up (Monticelli et al

2003, Ferrari et al 2000a and 2000b), no clinical study was available to confirm the

performances of fiber posts when they are used in conjunction with direct resin

restorations. Thus, the aim of this study was to evaluate the results of a clinical

114

evaluation on root-treated teeth that were restored using fiber posts and direct resin

restorations without additional crown coverage.

8.2 Materials and Methods

Eighty-one patients who required endodontic treatment and restorations on 38

anterior teeth and 62 posterior teeth (33 premolars and 29 molars) were recruited for

s

walls were enlarged with a low-speed bur provided by the manufacturer. The depth

this study. Clinical and radiographic examination demonstrated the need for root

canal treatment in these 100 teeth. The treatment and recall protocol was approved

by the ethical committee from the University of Siena, Italy, and the patients’

informed consent was obtained before enrolment in the clinical evaluation. The

endodontic procedure was performed using a crown-down technique. A portable E-

Master (VDW GmbH, Munich , Germany) endodontic motor was used and speed

rotation and torque were adjusted according to manufacturer’s indications. A

chelating agent (FileCare EDTA, VDW GmbH) and 2.5% sodium hypochlorite

(NaOCl) were used to clean the pulp chamber at the beginning of the

instrumentation. In addition, 2 ml of NaOCl were delivered to the pulp chamber

after the use of each file. All teeth were instrumented with Flexmaster instrument

(VDW, Germany). These instruments’ philosophy is based on the crown down

approach, and they include an “introfile” for the enlargement of the coronal end, a

35.02 file and three different tapers (0.6, 0.4, 0.2) for 30, 25 and 20 files. The

working sequence, proposed by the manufacturer, is based on the degree of the

curvature: canals are divided in wide, medium and narrow canals. For all of them, a

guiding path for the insertion of a size 10 manual file to the working length was

created. Then the sequence was changed depending on the size of the canals.

- wide canals: intro file, 30.06, 25.06, 20.06, 30.04.

- medium canals: intro file, 25.06, 20.06, 30.04, 25,04 (then 25.02, 30.02 and

35.02 if needed).

- narrow canals: intro file, 20.06, 30.04, 25.04, 20.04 (then 20.02, 25.02, 30.02,

35.02 if needed).

The prepared canals were obturated with gutta-percha points (Mynol, Block Co,

Jersey City, NJ, USA) and an epoxy resin sealer (Pulp Canal Sealer, Kerr, Romulus,

Michigan, USA) using a warm vertical compaction technique. Then the root canal

115

of the post space preparation was 9-10 mm. The root canal walls were etched with

37% phosphoric acid (Bisco Inc., Schaumburg, Illinois, USA) for 15 seconds,

then gently air-dried. The excess water was removed

s were

ts were recalled before the

bruary 2004 for the third evaluation and before August 2004 to

vity of the restorations was performed with the following criteria:

washed with water spray and

from the post space using paper points (Mynol). Subsequently, One-Step (Bisco)

adhesive was applied with a microbrush in two consecutive coats, gently air-dried

and the pooled adhesive left in the post space was removed using a paper point

before light curing for 20 seconds. Then a dual-cure resin cement (DuoLink, Bisco)

was used to perform the luting procedure with translucent glass fiber posts (DT post,

RTD, St Egrève, Grenoble, France). According to the diameter of the canal, either

DT size 1, 2 or 3 was used. The cement was applied with a lentulo spiral into the

post space, and the post was inserted into the canal. Resin cement excess was

removed with a clean microbrush and then the cement was light-cured for 40

seconds. The restorative procedure was completed by building up the tooth with a

direct composite restoration (Gradia Direct, GC Corp., Tokyo, Japan) using the

appropriate shades. As far as anterior teeth were concerned, both opaque dentin,

enamel and translucent enamel shades were used with a layering technique in order

to achieve the aesthetic results of the restorations. Regarding posterior teeth, they

were included in the study when showing 2 or 3 remaining coronal walls. The

restorative procedure was carried out using a centripetal technique (Hassan et al

1987, Bichacho 1994), and layering procedure also included opaque dentin and

enamel shades.

The patients were recalled at 6, 12, 24 and 30 months for clinical and radiographic

evaluation of the endodontically-treated and restored teeth. All restoration

placed between January and February 2002. The patien

end of July 2002 for first evaluation, before February 2003 for the second

evaluation, before Fe

complete the final evaluation. During the recall appointments, an assessment of the

stability and longe

1. The presence or absence of periapical lesions; 2. Marginal leakage and integrity;

3. Color stability; 4. Surface staining; 5. Loss of retention due to fracture of the post

or fracture of the composite build-up material. The restorations were evaluated by

116

two operators who 1) were not involved with the restorations, and 2) who were not

revealed of the time of recall (single blind trial).

8.3 Results

Table 1 shows the recall data obtained after 1, 6, 12, 24 and 30 months. Table 1 Periapical lesions (n=100) A Absent B Present but without symptoms C Present - to be retreated Baseline 100 (100%) 1 month 100 (100%) 6 months recall 97 (97%) 3 (3%) 12 months recall 97 (97%) 3 (3%) 24 months recall 96 (96%) 3 (3%) 1(1%) 30 months recall 96 (96%) 3 (3%) 1(1%) Retention (n=100) Present A Partial loss B Complete loss C Baseline 100 (100%) 1 month 100 (100%) 6 months recall 97 (97%) 3 (3%) 12 months recall 96 (91%) 4 (9%) 24 months recall 95 (95%) 5 (5%) 30 months recall 95 (95%) 5 (5%) Marginal leakage (n=100) A B C Baseline 100 (100%) 1 month 100 (100%) 6 months recall 98 (98%) 2 (2%) 12 months recall 96 (96%) 4 (4%) 24 months recall 95 (95%) 5 (5%) 30 months recall 94 (95%) 6 (6%) Legends: A= excellent continuity at the restorative-tooth interface, no discoloration; B= Slight discoloration at the interface; C= Moderate discoloration at the at margins, and need

restorative-tooth interface measuring 1 mm or greater or recurrent decay for replacement.

30 months recall 92 (92%) 8 (8%) Legends: a) Absent; b) Present.

Color stability (n=100) A B C Baseline 100 (100 %) 1 month 100 (100 %) 6 months recall 100 (100%) 12 months recall 98 (98%) 2(2%) 24 months recall 97 (97%) 3(3%) 30 months recall 96 (96%) 4(4%) Legends: a) No mismatch; b) Slight discoloration not requiring replacement; c) Discoloration requiring replacement Surface staining (n=100) A B Baseline 100 (100 %) 1 month 100 (100 %) 6 months recall 97 (97%) 3 (3%) 12 months recall 94 (94%) 6 (6%) 24 months recall 93 (93%) 7 (7%)

117

At 1- or 2-year recall, endodontic retreatment was performed on those patients with

persisting periapical lesions, and/or clinical symptoms. Only 4 teeth exhibited

sions after 30 months of clinical service, and in one case retreatment

5 out of 100

loss of the restoration. This was manifested as “chipping” of

the hundred teeth examined exhibited

ssfully refurbished using the same

of clinical servic

t discoloration, not requiring replacement. Surface staining was

fter 2 years of clinical service. These teeth were

nst the following two clinical cases:

car accident (fig

m the enamel and dentin fracture, and was

tral incisor (tooth 11) had an

d. After root canal treatment, a

ber post was inserted (fig 1b). Then the restoration was completed with the same

to restore tooth 11 (fig 1c). During the recall

. The restorations were reburished with BisCover (Bisco), a

lt after 30 months

ed fo cute pain regarding tooth

molar was subsequently endodontically-treated (fig2a), and a direct resin

was placed after the bonding of a fiber post to the root-treated

as a treatment alternative to

tient decided to postpone the

aphic results of the

periapical le

was performed without replacing the direct restoration. After 30 months

teeth showed a partial

the resin composite. The restorations were repaired using the same resin composite

used for the initial restoration. Six out of

slight marginal staining. They were also succe

material used for the initial restoration. After 2 years e, only 4 teeth

showed a sligh

present in 8 out of 100 teeth a

finished and polished.

Representative results are demo rated with

CLINICAL CASE #1

This 21 years old patient was treated as an emergency case after a

1a). Tooth 11 was asymptomatic apart fro

restored with a direct resin restoration. The left cen

irreversible pulp injury and was endodontically-treate

fi

resin composite material used

appointment, the patient did not want to prepare tooth 11 for a full ceramic crown

for economic reason

composite surface sealant and the clinical and radiographic resu

are illustrated in fig. 1d and 1e.

CLINICAL CASE #2

This 53 years old patient was initially examin r an a

44. The pre

composite restoration

tooth (figs 2b,2c). An all ceramic crown was suggested

the patient. However, for economic reasons, the pa

indirect restoration. Figs 2d and 2e show the clinical and radiogr

composite restoration after 30 months.

118

8.4 Discussion

In the last decade, metallic posts have been widely used for restoring

endodontically-treated teeth. Metal posts (i.e., alloys or titanium) were most

commonly used because of their physical properties (Sorensen et al 1984): their high

stiffness and rigidity were highly appreciated. Because of their color, they cannot

meet the aesthetic demands of contemporary direct resin composite restorations. The

aesthetic requirements for posts and cores became even more demanding following

the introduction of more translucent, enamel-like all-porcelain restorations.

Some authors have emphasized the need to use endodontic posts made with

biomechanical properties similar to those of dentin. Fiber posts are the only

available materials that have this property (Ferrari et al 2002). This is because the

stresses that were distributed to the residual tooth structure by the presence of a

1997,

he important difference between using "stiff" metal posts and

d for bonding of fiber posts may be performed by

y of the resin-dentin interdiffusion zone (RDIZ), resin tags,

i et al 2002). The microbrush is also able to

metal post were much higher than when a fiber-post was used (Ausiello et al

Yamada et al 2004). T

flexible resin based posts is in the transfer of stress (energy) from restoration to

tooth. With flexible posts all stress is located at the top of the root (the root-crown

border area) while the stiff post can transfer stress down in the root canal.

The rapid influx of these new aesthetic fiber posts has imposed the need for a

systematic evaluation of their mechanical properties and clinical performances. For

that purpose, scanning electron microscopy (SEM) –with or without the use of a

tracer- (Ferrari et al 2001a, Tay et al 1995)), transmission electron microscopy

(TEM) and fatigue test (Baran et al 2001) can provide an indication of the type of

post that would perform better under clinical conditions. The evaluation of the

efficacy of adhesive systems use

observing the uniformit

and adhesive lateral branches (Drummond et al 1999), and by recording the presence

of voids/bubbles within the luting material or at the interface between the cavity

wall and the post (Ferrari et al 2001b).

In this clinical trial, microbrushes were used to carry the “one-bottle” adhesive

system inside the root canal. The importance of the microbrush in reaching the

narrowest and deepest portions of the root canal preparations has been shown by

recent findings (Ferrari et al 2001b, Vich

119

reach all the prepared root canal dentin, resulting in a deep diffusion of resin into the

ost and

omposites

of the resin material sometimes occurred,

tubules and in the formation of lateral branches (Nakabayashi et al 1998, Chappel et

al 1994).

The results of this clinical trial can be important in that direct resin restorations were

performed, whereas previous prospective and retrospectives studies evaluated fiber

post/resin restorations that were covered with either full porcelain or metal-ceramic

crowns (Fredriksson et al 1998, Ferrari et al 2000a and 2000b, Monticelli et al

2003). Thus, we were able to analyze the clinical performances of fiber p

resin restoration alone. Moreover, the preservation of tooth structure is regarded as

the most important aspect in increasing the survival rate of endodontically-treated

teeth (Lodval et al 1977, Trabert et al 1978, Sorensen 1988). When only adhesive

procedures and direct resin composites are used, all the tooth structure remaining

after caries removal and the root canal treatment is preserved. On the contrary, tooth

preparation for an indirect restoration would eliminate a substantial amount of sound

tooth structure. A 2.5 years period of observation is short, for this reason the

evaluation is being continued to have more significant clinical results.

After 30 months, good coronal seals were achieved with the direct resin c

and fiber post restorations, as the incidence of persistent periapical lesions did not

differ from those provided by other studies (Fredriksson et al 1998, Ferrari et al

2000a and 2000b, Monticelli et al 2003). In the only case that was endodontically

retreated, the procedure was performed without removing the direct restoration. The

composite material was partially removed until the fiber post was visible. Then the

removal of the post was performed using a “removal kit” provided by the

manufacturer (Removal Kit, RTD, France). After the completion of the new

endodontic procedure, a new post was inserted and the restoration completed with

resin composite. The whole procedure of the endodontic retreatment was easily

performed, according to recent data available in the literature (Gesi et al 2003).

Marginal discoloration, and “chipping”

and their repair with the same type of composite achieved acceptable clinical results

(Frankemberger et al 2003, Saunders 1990). In 8 out of 100 cases, slight

discoloration of the restorations were present after 30 months. Refurbishing and

polishing were performed, and these procedures appeared to have prevented further

120

discoloration or color mismatch problems. Undoubtedly, the resin composite

employed is inferior in terms of wear resistance (Yip et al 2004), when compared to

full ceramic or ceramometal crowns (Derand et al 1999). On the other hand,

mechanical

porcelain are susceptible to brittle failure, while ductile materials utilize their

plasticity to reduce stress concentrations along the crack tip (Derand et al 1999). The

use of a direct resin restoration is also more economical from the patient’s point of

view, as these restorations are much cheaper than any other indirect restorations.

The use of direct composite restorations also minimizes the amount of residual tooth

structure that has to be sacrificed for full crown coverage. They are also less time

consuming in their fabrication and no additional laboratory costs are required. The

ability to refurbish these fiber post-direct composite restorations is thus an important

alternative with the potential to save tooth structure and increase the longevity of

restorations at a lower cost (Hickel et al 2004, Mjor et al 2002) In cases with

questionable prognosis, it is also desirable to wait for a period of time before making

definitive indirect restorations.

It has recently been shown that if a quality fiber post with good

properties is used, it can resist up to two million cycles in fatigue testing (Grandini

S, Goracci C, Monticelli F, Tay FR, Ferrari M. Fatigue resistance and structural

characteristics of fiber posts: three-point bending test and SEM evaluation. Dent

Mater-in press). It is encouraging to observe that no post or root fracture occurred

after 30 months of clinical service, confirming the results of previous studies

(Fredriksson et al 1998, Ferrari et al 2000a and 2000b). Longer clinical trials should

be performed to validate the use of fiber posts and direct resin composites as a

simplified conservative approach to the rehabilitation of endodontically-treated

teeth.

8.5 Conclusions

After 30 months of clinical service, the root canal treated teeth restored with fiber

posts and direct resin composite restorations exhibited favourable clinical results.

121

fig 1a

fig 1b

fig 1c

122

fig 1d

fig1e

123

fig 2a

fig2b

fig 2c

124

fig 2d

fig 2e

125

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128

C 9 Summary and conclusions

hapter

has al

s. This

e select

reated tooth. Many changes can occur after root canal treatment in

rms of

vior. A vital tooth presents with a stiffer

ructure

hat can reduce tooth

04). Moreover,

th

nder str

ure incidence documented in maxillary

remola

ures, are responsible for a reduction

the fr

the qu

re and

7), as they

ficantly strengthen endodontically-treated teeth…” (Sorensen

1984a). The progress made in the technology of fiber-reinforced materials have

improved the structure, shape, and optical properties of contemporary fiber-

reinforced resin posts. This led to the development of materials which have

It ways been a big challenge for clinicians to restore endodontically-treated

teeth. Fiber posts acquired high importance in this field in the last 15 year

thesis contains a study about several different basic and clinical aspects related to

th ion and use of fiber posts.

There is scientific evidence showing that a healthy tooth is different from an

endodontically-t

te the physical, chemical and elastic properties of dentin, resistance to fatigue,

morphology and biomechanical beha

st (enamel) and a more compliant support underlying it (dentin). Caries and

tooth preparation for endodontic treatment are the first factors t

resistance. There is a decrease in moisture content (Helfer et al. 1972), an increased

ung’s mYo odulus (Huang et al. 1992), and a reduction in the percentage of collagen

fibrils in dentin (Mason 2001, Hashimoto et al. 2000, Ferrari et al. 20

changes also occur in the morphology and in the biomechanical behavior of tee

u ess (Grimaldi 1971, Tidmarsh 1976). The access preparation for endodontic

treatment causes the loss of both the roof of the pulp chamber and the marginal

ridges, influencing the relatively high fract

p rs (Ross et al. 1980, Salis et al. 1987). In general, removal of the roof of the

pulp chamber, together with endodontic proced

in acture resistance (Fuzzi 1993, Morgano et al. 1993, Trabert et al. 1978,

t et al. 199Milo 2).

It is also known that the likelihood of survival of a pulpless tooth is directly related

to antity and quality of remaining tooth structure (Assif et al. 1994, Guttman

1992, Cohen et al. 1996). Traditionally, a post was inserted to ensure retention of the

co to “reinforce” the tooth. To date, the eventual reinforcement provided by

metal posts is no longer considered as possible (Shillimburg HT 199

“…do not signi

129

overcome so of the limitations of metallic me posts (platinum, alloys or titanium),

oncerning esthetic appearance, mode of failure, and clinical performance. In terms

ts are concerned, it has been shown that metallic

number of residual walls, that were restored using resin

c

of esthetics, translucent fiber posts were introduced commercially to support anterior

restorations (Vichi et al. 2000a and 2000b, Ferrari et al. 2001a and 2001b, Ferrari et

al. 2002, Paul et al. 1998, Heydecke et al. 2002). As far as the mechanical behavior

and failure mechanisms of fiber pos

posts on failure tend to produce irreversible root fractures. Conversely, root fracture

that occur with the use of fiber posts are usually located more coronally and are

more easily retreatable (Akkayan et al. 2002, Cornier et al. 2001, Reagan et al. 1999,

Newman et al. 2003). This type of failure may be due to the greater amount of tooth

structure that must be removed when a metallic post is placed (Stankiewitz et al.

2002). In the event that endodontic re-treatment is necessary, fiber posts are more

easily removed than either metallic or ceramic ones (Gesi et al. 2003, Hauman et al.

2003). In conclusion, fiber posts function well as retention for resin composite cores.

When compared to metal or zirconia posts, they are able to preserve residual tooth

structure due to their mechanical behavior and the accompanying luting procedures.

Techniques has been described for restoring endodontically-treated teeth with the

use of resin composites to replace lost root dentin, with the possibility of

strengthening the root. Unfortunately these reports were published in non peer-

reviewed publications (Freedman et al. 1994, Godder et al. 1994, Martelli 2000,

Castellucci 2004). A recent study was performed comparing the fracture resistance

and failure patterns of endodontically-treated maxillary premolars with a

progressively reduced

composite materials with or without translucent glass fiber posts (Sorrentino et al.

2004). This study showed that the number of residual dental walls influenced the

mechanical resistance of endodontically-treated maxillary premolars. In specimens

with the same number of residual dental walls, higher fracture loads were recorded

in teeth restored with fiber posts. Moreover, restorable fractures were observed in

the specimens restored with fiber posts. If these data can be subsequently validated

with clinical studies, the concept of reinforcing root structures with the bonding of

fiber posts to root canals will be more firmly established.

130

A successful endodontic procedure is a key factor to ensure success in the

restoration of root-treated teeth. A well performed endodontic treatment is based on

the removal of debris and organic material inside the root canal (Castellucci 1993)

and on the mechanical preparation of the canal itself to receive an obturation

material (Ingle 1993). The influence of cements and irrigating solutions has been

extensively discussed in the literature. When evaluating the effect of different

irrigating regimes on the cleanliness of the root canals achieved after endodontic

treatment (Grandini et al. 2002b), it was found that none of the techniques used in

that study showed a perfect removal of the smear layer and debris. However, it was

noted that a combination of sodium hypochlorite and a chelating agent can help

reduce the amount of debris along root canal walls. The functions of root canal

filling are essentially to seal the root canal and to prevent further microleakage. In

this sense, post fabrication and placement can be considered as part of the

endodontic treatment if they contribute to the filling and sealing of the root canal

space (Trope 2004). Unfortunately, due to the high C-factors encountered in post

spaces (Morris et al., 2002; Bouillaguet et al., 2003; Goracci et al., 2004), substantial

difficulty was experienced with the luting of fiber posts to intraradicular dentin with

resin cements. It has been suggested that similar to the use of non-bonding cements,

a substantial part of the dislocation resistance of bonded fiber posts to root canals is

contributed by sliding friction (Goracci et al., 2005).

The popularity with the use of fiber posts for restoration of the endodontically-

treated teeth has imposed the need for a systematic evaluation of the different brands

and types of fiber posts available commercially. Some criteria are usually employed,

such as the composition and shape of the post, cost and luting procedures, based on

basic and experimental evaluations. A study comparing the fatigue resistance and

the structural characteristics of different types of fiber posts has been described

(Grandini et al. 2004a). Some brands of fiber posts can resist up to 2.000.000 cycles

of fatigue testing without affecting their general quality. In particular the quality of

the bonding between the two components of a fiber post (the fibers and the epoxy

resin matrix) can influence the quality of the post itself. As a matter of fact, static

impact and fatigue properties are proportional to the strength of the filler/resin

interface in fiber-reinforced composite systems (Zhao et al. 2000, Kessler et al.

131

2000, Keusch et al. 1999). A recent study confirmed that increasing the strength of

the bond between the fillers and matrix will result in improvements in the

mechanical properties of fiber-reinforced composites (Debnath et al. 2004).

Luting procedures are extremely important as far as fiber posts are concerned. The

recommended procedure has already been described in the literature (Ferrari et al.

2001a and 2001b, Vichi et al. 2002a). Acid etching, the use of a fourth or fifth

generation adhesive, and of a dual-curing resin cement provides the best clinical

results. Leaving the adhesive solution unpolymerized before placing the cement

(one-step procedure), in order to reduce the time for the cementation procedure,

produces unfavourable results both from the clinical and experimental standpoint

(Grandini et al. 2004b). If a crown is placed, the post can be adjusted after the core

restoration. In case a direct restoration is placed, it is better to adjust the length of

the post before the luting procedures. The adjustment should be performed with a

carborundum disk or a diamond bur (Grandini et al. 2002a). This way, it is possible

to cover the cut end of the post with resin composite, a material much more able

than a fiber post to resist tooth-to-tooth and tooth-to-food wear. If a post is good

enough, cutting procedures will not affect its structural integrity.

Much development occurred concerning the materials used for the fabrication of

posts: carbon was the first material employed; glass, quartz and silica have

subsequently been used, taking advantage of their translucent optical properties.

Interesting development was also seen in the modification of the design of these

posts, from the original double-cylinder, endodontic shapes, to the more recently

introduced double-tapered shapes, as adhesive cementation now relies more on the

formation of the resin-dentin interdiffusion zone and resin tags rather than on the

good fitting and mechanical retention of the post inside the root canal (Ferrari et al.

2002). Moreover, a wider selection of sizes permits conservation of the amount of

residual dentin that has to be removed in order to achieve a satisfactory post

adaptation. Debonding is more likely to occur in the absence of the desirable ‘ferrule

effect’, or in the presence of an overly thick layer of cement wherein the entrapment

of bubbles is conducive to debonding (Ferrari et al. 2000a). The idea of having a

custom-fabricated post that fits individual post space is appealing, especially when

dealing with root canals that have elliptical shapes, such as those observed in

132

canines and lower premolars. In these cases, the clinician is forced to adapt the

residual root structure to the post shape, through the removal of a further amount of

dentin. On the contrary, it would be desirable that the post adapt to the root canal

ct resin composite

anatomy as produced by the endodontic treatment. This is indeed the rationale for

the creation of an anatomic post (Grandini et al 2000, Boudrias et al. 2001a and

2001b). Recently the Anatomic Post’n Core (RTD, St Egrève, France) has been

introduced (Ferrari et al. 2002). This new post is made by a DT post n. 1 that is

covered by a light-curing resin (Lumiglass, RTD, St Egrève, France). The relining

resin is able, once introduced in the root canal, to produce a good fitting thus

reducing the amount of cement to be used and stabilizing the post during the luting

procedures.

The final test for a clinical procedure is always the clinical evaluation. Many studies

reported on the use of fiber post to restore endodontically-treated teeth (Malferrari et

al. 2003, Ferrari et al. 2000a and 2000b, Fredriksson et al. 1998, Monticelli et al.

2003, Dallari et al. 1998, Scotti et al. 2002). The majority of them combines the use

of fiber post restorations with ceramic or ceramometal crowns. The last few years

have seen an enormous expansion in the indications for dire

restorations (Hickel et al. 2004). Thus, it is interesting to evaluate the performances

of fiber posts when they were used in conjunction with direct resin restorations,

without additional crown coverage. After 30 months of clinical service, root-treated

teeth restored with fiber posts and direct resin composite restorations exhibited no

root fractures and favourable clinical results.

Conclusions and recommendations

The following conclusions and recommendations may be drawn from our basic and

clinical evaluations on the use of fiber posts in dentistry:

1) Fiber posts exhibit good overall mechanical properties and the related failure

modes are usually more conservative and favorable when compared to metallic

posts.

2) Endodontic procedures can influence the final result of the post restoration. Great

attention should be placed in the removal of bacteria, debris and other materials

inside the root canal before the filling is completed.

133

3) Fiber posts contribute to the filling sealing of the root canal space with the help of

adhesive cementation. For this reason they can be considered as part of the

endodontic treatment.

4) There are several brands of fiber posts. The quality of the bonding between the

fibers and the resin may influence the final quality of the whole post, and this should

be taken into account when selecting a fiber post together with composition, desired

shape, basic and experimental evaluation.

5) As far as luting procedures are concerned, a reliable bonding between the fiber

post-resin cement unit and the root canal can be reasonably well achieved with the

use of acid etching, that has to removed meticulously from the root canal with a

syringe and an endodontic needle.

6) A fourth or fifth generation adhesive system, inserted in the canal with the help of

a microbrush, and a dual-curing resin cement can be recommended when using

translucent fiber posts.

7) An individual post (Anatomic Post’n Core) can be of great help in a clinical

situation where there is a great loss of coronal structure and root canals after

endodontic treatment end up in a non-rounded shape.

8) Fiber posts can be safely used in combination with ceramic or ceramo-metal

crowns. Indications for their use are rapidly expanding, and recent clinical studies

indicated that they can be safely used as a foundation for direct resin composite

crowns. With the use of this technique, the restoration of the endodontically treated

teeth can be easier and less costly.

134

Riassunto e conclusioni

Il restauro del dente trattato endodonticamente ha da sempre rappresentato una

te trattato endodonticamente differisce da

più cedevole all’interno (la dentina). La carie e la

72), un aumento del modulo di Young (Huang et al. 1992),

io-meccanico del dente sotto

generale, la rimozione del tetto della camera

ulpare, insieme alle procedure endodontiche, è responsabile di una riduzione

complessiva della resistenza alla frattura (Fuzzi 1993, Morgano et al. 1993, Trabert

et al. 1978, Milot et al. 1992).

La possibilità di sopravvivenza nel cavo orale di un dente trattato endodonticamente

è direttamente proporzionale alla qualità ed alla quantità della struttura dentale

residua (Assif et al. 1994, Guttman 1992, Cohen et al. 1996). Tradizionalmente,

veniva inserito un perno per assicurare ritenzione alla ricostruzione coronale e per

“rinforzare” il dente. Attualmente, l’eventuale rinforzo determinato da un perno

metallico non può più essere considerato possibile (Shillimburg HT 1997), poichè

esso “…non rinforza significativamente il dente trattato endodonticamente…”

grossa sfida, e negli ultimi 15 anni i perni in fibra hanno acquisito una grossa

importanza in questo campo. Questa tesi contiene uno studio riguardante diversi

aspetti scientifici di base e clinici in relazione all’uso dei perni in fibra.

La letteratura scientifica mostra che un den

un dente sano. Molti cambiamenti avvengono in termini di proprietà chimiche,

fisiche ed elastiche della dentina, di resistenza alla fatica, morfologia e

comportamento bio-meccanico. Un dente vitale presenta una struttura più rigida (lo

smalto) all’esterno ed un supporto

preparazione per il trattamento endodontico sono i primi fattori che possono ridurre

la resistenza complessiva del dente. Vi è inoltre un decremento nel contenuto di

umidità (Helfer et al. 19

ed una riduzione nella percentuale di fibrille collageniche nella dentina (Mason

2001, Hashimoto et al. 2000, Ferrari et al. 2004). Altri cambiamenti avvengono

anche riguardo la morfologia ed il comportamento b

stress (Grimaldi 1971, Tidmarsh 1976). La preparazione della cavità di accesso per

il trattamento endodontico provoca la perdita sia del tetto della camera pulpare che

del collegamento fra le creste marginali, ed è considerata una delle possibili cause

che portano all’elevata incidenza di fratture documentata nei premolari superiori

(Ross et al. 1980, Salis et al. 1987). In

p

135

(Sorensen 1984a). I progressi fatti nel campo della tecnologia dei materiali rinforzati

on fibra hanno migliorato la struttura, le proprietà di trasmissione della luce e la

ti sono stati

unatamente questi reports sono stati pubblicati su

c

forma dei perni in fibra attualmente disponibili sul mercato. Questo ha portato allo

sviluppo di materiali che hanno superato alcune delle limitazioni dei perni metallici

(platino, leghe o titanio) riguardanti le proprietà estetiche, la modalità di fallimento

ed i risultati clinici. In termini di estetica, i perni in fibra translucen

introdotti in commercio per supportare restauri anteriori estetici (Vichi et al. 2000a

and 2000b, Ferrari et al. 2001a and 2001b, Ferrari et al. 2002, Paul et al. 1998,

Heydecke et al. 2002). Per quanto riguarda il comportamento bio-meccanico e la

modalità di fallimento, è stato dimostrato che i perni metallici tendono a produrre

fratture irreversibili. All’opposto, le fratture che avvengono con i perni in fibra sono

generalmente posizionate più coronalmente e sono più facili da ritrattare (Akkayan

et al. 2002, Cornier et al. 2001, Reagan et al. 1999, Newman et al. 2003). Questo

tipo di fallimento può essere dovuto alla maggior quantità di struttura dentale che

deve essere rimossa per il posizionamento di un perno metallico (Stankiewitz et al.

2002). Nel caso in cui sia necessario eseguire un ritrattamento endodontico, i perni

in fibra possono essere rimossi più facilmente dei perni metallici e dei perni

ceramici (Gesi et al. 2003, Hauman et al. 2003). In conclusione, i perni in fibra

possono essere adoperati allo scopo di ritenere i restauri coronali in denti trattati

endodonticamente; se comparati ai perni metallici o in zirconio sono in grado di

preservare una maggiore quantità di struttura dentale residua grazie al loro

comportamento bio-meccanico ed alle relative procedure di cementazione.

Sono state riportate tecniche cliniche per il restauro del dente trattato

endodonticamente con resine composite per ripristinare la struttura dentale residua e

per rinforzare la radice. Sfort

riviste prive di revisione da parte di esperti (Freedman et al. 1994, Godder et al.

1994, Martelli 2000, Castellucci 2004).

Uno studio recente ha comparato la resistenza alla frattura e le modalità di

fallimento di premolari superiori trattati endodonticamente con un numero

progressivo sempre minore di pareti residue, che sono state ricostruite usando resine

composite con o senza perni in fibra translucenti (Sorrentino et al. 2004). Questo

modello di studio ha mostrato che il numero di pareti residue influenza la resistenza

136

meccanica dei denti sottoposti a carico: in campioni con lo stesso numero di pareti

residue sono state registrati valori più elevati di resistenza alla frattura nei denti

“rinforzati” con perni in fibra. Inoltre, nei campioni ricostruiti con i perni in fibra le

fratture osservate erano “favorevoli”, quindi fratture facilmente riparabili in quanto

avvenute al di sopra della cresta ossea. Se questi dati dovessero essere confermati da

studi clinici, il concetto di “rinforzare” le strutture radicolari con l’adesione al canale

di perni in fibra sarà indiscutibilmente rafforzato.

Un trattamento endodontico efficace risulta essere un fattore chiave nell’ambito del

restauro del dente trattato endodonticamente. Di basilare importanza risultano la

rimozione di detriti e materiale organico dall’interno del canale (Castellucci 1993) e

la preparazione meccanica del canale stesso per ricevere un materiale da otturazione

(Ingle 1993). L’influenza dei cementi e delle soluzioni irriganti è stata discussa

ampiamente in letteratura. Valutando l’effetto di diverse soluzioni irriganti

nell’ottenere un canale libero da impurità dopo il trattamento endodontico (Grandini

et al. 2002b), si è verificato che nessuna delle tecniche usate nello studio in oggetto

si è dimostrata perfettamente efficace nel rimuovere completamente fango dentinale

e detriti. Ad ogni modo, una combinazione di ipoclorito di sodio e di un agente

chelante possono efficacemente rimuovere gran parte dei detriti dal canale. Gli scopi

dell’otturazione canalare sono essenzialmente quelli di sigillare il canale radicolare e

prevenire l’ulteriore eventuale microinfiltrazione. In questo senso, il posizionamento

di un perno in fibra può aiutare a fornire un sigillo efficace contro l’infiltrazione

batterica coronale (Trope 2004). Sfortunatamente, a causa dell’elevato fattore C

desivamente sia data dal contributo della

presente nei canali radicolari (Morris et al., 2002; Bouillaguet et al., 2003; Goracci

et al., 2004), sono state registrate difficoltà nella cementazione dei perni in fibra alla

dentina intra-radicolare con i cementi resinosi. Si è speculato che, come per l’uso di

cementi non adesivi, una elevata quota parte della resistenza alla dislocazione

incontrata nei perni in fibra cementati a

frizione da contatto del perno stesso e del cemento resinoso all’interno del canale

radicolare (Goracci et al., 2005).

La sempre maggiore popolarità incontrata dai restauri con perni in fibra ha imposto

la necessità di una valutazione sistematica dei diversi tipi e qualità dei perni in fibra

ad oggi presenti sul mercato. I criteri di scelta sono generalmente basati sulla

137

composizione e forma dei perni, costo, procedure di cementazioni adesive,

valutazioni sperimentali in vivo e in vitro. Uno studio ha comparato la resistenza alla

fatica e le caratteristiche strutturali di diversi tipi di perni in fibra (Grandini et al.

2004a). Alcuni tipi di perni in fibra possono facilmente resistere fino a 2.000.000 di

cicli di fatica senza cambiamenti alla loro struttura. In particolare, la qualità

dell’adesione e del legame fra le due componenti del perno in fibra (le fibre e la

matrice di resina epossidica) può influenzare la qualità del perno stesso. Infatti,

perno con resina composita, un materiale cioè

l’impatto statico e la resistenza alla fatica sono proporzionali alla forza di adesione

dell’interfaccia riempitivo/resina nei sistemi compositi rinforzati con fibre (Zhao et

al. 2000, Kessler et al. 2000, Keusch et al. 1999). Uno studio recente ha confermato

che all’aumentare della forza di adesione tra il riempitivo e la matrice si ottiene un

incremento delle proprietà meccaniche dei compositi rinforzati con fibre (Debnath et

al. 2004).

Le procedure di cementazione sono un fattore estremamente importante nell’ambito

del restauro con perni in fibra, e sono da tempo state descritte nella letteratura

internazionale (Ferrari et al. 2001a and 2001b, Vichi et al. 2002a). La mordenzatura

acida, l’uso di adesivi di quarta o quinta generazione, e di un cemento resinoso duale

porta a risultati clinici ottimali. Il fatto di lasciare la soluzione adesiva non

polimerizzata prima del posizionamento del cemento (one-step procedure), allo

scopo di ridurre il tempo necessario per la cementazione, produce risultati clinici

sfavorevoli sia dal punto di vista clinico che sperimentale (Grandini et al. 2004b).

Nel caso si scelga di eseguire una corona dopo il posizionamento del perno in fibra,

il perno stesso può essere aggiustato in lunghezza dopo il restauro del core. Invece,

nel caso in cui si scelga un restauro conservativo, è preferibile aggiustare la

lunghezza del perno prima di procedere alla cementazione, in modo da poter

eseguire al contempo cementazione del perno e ricostruzione adesiva avvalendosi di

un’unica fase di mordenzatura ed adesione. Il taglio del perno può avvenire con un

disco di carborundum o con una fresa diamantata (Grandini et al. 2002a). In questo

modo è possibile ricoprire la testa del

maggiormente capace di resistere alle sollecitazioni dell’usura dente contro dente e

dente contro cibo. Se siamo di fronte ad un perno di buona qualità, la procedura di

taglio non modificherà l’integrità strutturale del perno stesso.

138

Negli anni molti cambiamenti hanno riguardato i materiali impiegati per la

fabbricazione dei perni in fibra: il carbonio è stato il primo materiale impiegato;

quindi il vetro, il quarzo e la silice, con particolare riguardo alle capacità di

trasmissione della luce. Interessanti sviluppi hanno inoltre riguardato la forma dei

perni stessi, partendo dal doppio cilindro originale, fino alle forme endodontiche ed

ai più recenti perni a doppia conicità. Infatti la cementazione adesiva permette di

affidarsi alla formazione di zaffi resinosi e strato ibrido piuttosto che alla forma

ritentiva, alla ritenzione meccanica ed al perfetto adattamento del perno all’interno

delle pareti canalari (Ferrari et al. 2002). Inoltre, nel conseguire l’adattamento del

perno, una maggiore varietà di perni disponibili sul mercato permette all’operatore

di selezionare quello più appropriato allo scopo di risparmiare la maggior quantità di

struttura dentale residua. La decementazione avviene più facilmente in assenza

dell’auspicabile “effetto ferula”, o in presenza di un elevato spessore di cemento nel

a

n fibra per il restauro

quale è più verosimile che si verifichi l’intrappolamento di bolle d’aria che può

portare appunto alla decementazione (Ferrari et al. 2000a). L’idea di avere un perno

individuale, che si adatti perfettamente al singolo spazio canalare è decisamente

attraente per l’operatore, specialmente quando si tratti di canali con forma ellittica

così come i canini ed i premolari. In questi casi il clinico è costretto ad adattare la

struttura dentale residua al perno attraverso la rimozione di un’ulteriore quantità di

dentina, o a cementare un perno affidandosi ad una maggiore quantità e spessore di

cemento. Al contrario, sarebbe desiderabile che il perno si adattasse all’anatomi

canalare prodotta dal trattamento endodontico. Questo è infatti il fondamento logico

alla base della creazione del perno anatomico (Grandini et al 2000, Boudrias et al.

2001a and 2001b). Recentemente è stato introdotto l’ Anatomic Post’n Core (RTD,

St Egrève, France) (Ferrari et al. 2002). Questo nuovo perno è composto da un perno

a doppia conicità (DT) numero 1, ricoperto da una resina foto-polimerizzabile

(Lumiglass, RTD, St Egrève, France). La resina ribasante è in grado, una volta

introdotta nel canale, di produrre un buon fitting fra perno ribassato e pareti canalari,

riducendo la quantità di cemento e stabilizzando il perno durante le procedure di

cementazione.

Ma il test decisivo e finale per una procedura è sempre la valutazione clinica. Molti

studi presenti in letteratura hanno riguardato l’uso dei perni i

139

del dente trattato endodonticamente (Malferrari et al. 2003, Ferrari et al. 2000a and

2000b, Fredriksson et al. 1998, Monticelli et al. 2003, Dallari et al. 1998, Scotti et

al. 2002). La maggior parte di essi combina l’uso di restauri con perni in fibra e

corone in ceramica o metallo-ceramica. Negli ultimi anni abbiamo assistito ad una

enorme espansione delle indicazioni per i restauri diretti in resina composita (Hickel

et al. 2004). Perciò è interessante valutare i risultati dei perni in fibra in

combinazione con restauri diretti in resina composita, senza copertura protesica.

Dopo 30 mesi di servizio clinico, i denti trattati endodonticamente ricostruiti con

perni in fibra e restauri diretti in resina composita hanno mostrato risultati clinici

favorevoli senza fratture radicolari.

Conclusioni e raccomandazioni

Sulla base delle valutazioni cliniche e sperimentali possiamo trarre le seguenti

conclusioni e raccomandazioni riguardo l’uso dei perni in fibra in odontoiatria.

1) I perni in fibra hanno mostrato buone proprietà meccaniche ed il relativo modo di

fallimento è generalmente più conservativo e favorevole di quello mostrato dai perni

metallici.

2) Le procedure endodontiche possono influenzare il risultato finale del restauro con

perno. Deve essere posta grande attenzione nella rimozione di batteri, detriti ed altri

materiali dall’interno del canale prima di procedere all’otturazione canalare.

3) I perni in fibra possono contribuire al sigillo dello spazio canalare con l’aiuto

della cementazione adesiva. Per questa ragione possono essere considerati come

parte del trattamento endodontico.

4) Ci sono diversi tipi di perni in fibra. La qualità del legame tra le fibre e la matrice

può influenzare la qualità globale del perno, e questo dovrebbe essere preso in

considerazione al momento della scelta del perno, insieme alla composizione, alla

forma, ed alla valutazione di base e clinica.

5) Per quanto riguarda le procedure di cementazione, un legame affidabile fra perno

in fibra, cemento, sistema adesivo e canale radicolare può essere raggiunto con la

mordenzatura acida. Il mordenzante deve essere accuratamente rimosso dal canale

radicolare con una siringa contenente acqua ed un ago endodontico.

140

6) Un sistema adesivo di quarta o di quinta generazione, veicolato nel canale con

l’aiuto di un microbrush, ed un cemento resinoso duale possono essere adoperati con

i perni in fibra translucenti.

7) Un perno individuale (Anatomic Post’n Core) può essere di grande aiuto in

situazioni cliniche dove si abbia grossa perdita di struttura coronale ed un canale che

risulta non circolare dopo il trattamento endodontico.

8) I perni in fibra possono essere adoperati con sicurezza in combinazione con

restauri protesici in ceramica o in metallo-ceramica. Le indicazioni per il loro uso

sono in rapida espansione, e studi clinici recenti indicano che possono essere

adoperati anche come base per un restauro diretto in resina composita. Con questa

cnica, il restauro del dente trattato endodonticamente può essere più semplice e più te

economico.

141

Résumé et conclusions

Depuis longtemps la restauration de la dent traitée endodontiquement représente un

ploi des tenons en fibres.

réparation pour le traitement endodontique sont les premiers facteurs

ui peuvent réduire la résistance globale de la dent. Il y a aussi une diminution de

umidité contenue dans la dentine (Helfer et al. 1972), une augmentation du module

e Young (Huang et al. 1992), et une réduction du pourcentage de fibrilles de

collagène dans la dentine (Mason 2001, Hashimoto et al. 2000, Ferrari et al. 2004).

D’autres changements surviennent aussi dans la morphologie et le comportement

biomécanique de la dente soumise à des contraintes (Grimaldi 1971, Tidmarsh

1976). La préparation de la cavité d’accès pour le traitement endodontique provoque

la perte du toit de la chambre pulpaire et aussi de la liaison entre les crêtes

marginales, et elle est considérée comme une des causes possibles entraînant le taux

important de fractures que l’on rencontre dans les prémolaires supérieures (Ross et

al. 1980, Salis et al. 1987). En général, le déplacement du toit de la chambre

pulpaire, avec les procédures endodontiques, est responsable d’une réduction

globale de la résistance à la fracture (Fuzzi 1993, Morgano et al. 1993, Trabert et al.

1978, Milot et al. 1992).

La possibilité de survie dans la cavité orale d’une dent traitée endodontiquement est

directement proportionnelle à la qualité et à la quantité de la structure dentaire

restante (Assif et al. 1994, Guttman 1992, Cohen et al. 1996). Traditionnellement,

un tenon était mis en place pour assurer la rétention à la reconstruction coronaire et

pour renforcer la dent. Actuellement, l’éventuelle consolidation déterminée par un

tenon métallique ne peut plus être considérée possible (Shillimburg HT 1997),

grand défi, et durant les 15 dernières années les tenons en fibre ont acquis une

énorme importance dans ce domaine. Cette thèse est une étude sur les différents

aspects scientifiques de base et cliniques relatifs à l’em

La littérature scientifique démontre qu’une dent traitée diffère d’une dente saine.

Plusieurs changements se produisent en termes de propriétés chimiques, physiques

et élastiques de la dentine, de résistance à la fatigue, de la morphologie et du

comportement biomécanique. Une dente vital présente une structure plus rigide

(l’email) à l’extérieur et un support plus malléable à l’intérieure (la dentine). Les

caries et la p

q

h

d

142

puisqu’il “…ne fortifie pas de façon significative la dent traitée

ndodontiquement… ” (Sorensen 1984a). Les progrès faits dans le domaine de la

ont

s résines composites au fin de rétablir la structure dentaire

e

technologie des matériaux renforcés avec de la fibre ont amélioré la structure du

tenon, la propriété de transmission de la lumière et la forme des tenons en fibres

actuellement disponible sur le marché. Ces progrès concernant les propriétés

esthétiques, les modalités d’échec et les résultats cliniques des tenons fibrés

permis de dépasser quelques unes des limitations des tenons métalliques (platine,

titane ou alliages). En termes d’esthétique, les tenons fibrés translucides ont été

introduits sur le marché pour soutenir les restaurations antérieures esthétiques (Vichi

et al. 2000a and 2000b, Ferrari et al. 2001a and 2001b, Ferrari et al. 2002, Paul et al.

1998, Heydecke et al. 2002). En ce qui concerne le comportement biomécanique et

le mode d’échec, il a été démontré que les tenons métalliques tendent à produire des

fractures irréversibles. A l’inverse, les fractures qui se produisent avec les tenons en

fibres sont en général en position plus coronaire et sont plus faciles à retraiter

(Akkayan et al. 2002, Cornier et al. 2001, Reagan et al. 1999, Newman et al. 2003).

Ce type d’échec peut être dû à la plus grande quantité de structure dentaire qui doit

être déplacée pour placer les tenons métalliques (Stankiewitz et al. 2002). Au cas où

il serait nécessaire d’effectuer le retraitement endodontique, les tenons en fibres sont

plus faciles à déposer que les tenons métalliques et les tenons céramiques (Gesi et al.

2003, Hauman et al. 2003). En conclusion, les tenons en fibres peuvent être

employés dans le but de retenir les restaurations coronaires dans les dents traitées

endodontiquement ; si on les compare aux tenons métalliques ou en zirconium, ils

sont à même de préserver une plus grande quantité de structure dentaire restante

grâce à leur comportement biomécanique et aux procédures associées de scellement.

La littérature décrit des techniques cliniques pour la restauration de la dent traitée

endodontiquement avec de

restante et pour renforcer la racine. Malheureusement ces rapports ont été publiés sur

des revues sans aucune révision des experts (Freedman et al. 1994, Godder et al.

1994, Martelli 2000, Castellucci 2004).

Une étude récente a comparé la résistance à la fracture et les modalités de faillite de

prémolaires supérieures traitées endodontiquement avec un nombre progressif

toujours plus petite de parois restantes, qui ont été reconstruites avec des résines

143

composites avec ou sans tenons en fibres translucides (Sorrentino et al. 2004). Ce

modèle d’étude a démontré que le nombre de parois restantes influence directement

la résistance mécaniques des dents soumises à une charge. Des échantillons avec le

même nombre de parois restantes ont permis d’enregistrer des valeurs plus élevées

de résistance à la fracture dans les dents « renforcées » avec des tenons en fibres. De

plus, dans les échantillons reconstruits avec les tenons en fibres, les fractures

observées étaient « favorables », c'est-à-dire des fractures facilement réparables car

elles s’étaient produites au dessus de la crête osseuse. Si ces données peuvent être

confirmées par des études cliniques, l’idée de « renforcer » les structures radiculaires

avec le collage canalaire des tenons en fibres sera sans aucun doute renforcé.

Un traitement endodontique efficace se révèle être un facteur clef dans les limites de

la restauration de la dent traitée endodontiquement. Un traitement performant est

basé sur l’enlèvement de débris et de matière organique de l’intérieure du canal

(Castellucci 1993) et la préparation mécanique de ce canal pour recevoir un matériau

d’obturation (Ingle 1993). L’influence des ciments et des solutions irrigantes a été

amplement discutée en littérature. D’après l’évaluation de l’effet de différentes

solutions irrigantes dans le but d’obtenir un canal exempt d’impuretés après le

traitement endodontique (Grandini et al. 2002b), il a été vérifié qu’aucune des

techniques employées dans l’étude ne s’est montrée parfaitement efficace pour

enlever complètement la boue et les détritus. Cependant, une combinaison

d’hypochlorite de sodium et d’un agent chélatant peut efficacement enlever une

grande partie des détritus du canal. Les fonctions de l’obturation canalaire sont

essentiellement de sceller le canal radiculaire et de prévenir une éventuelle micro

infiltration ultérieure. Dans ce sens, le placement d’un tenon en fibres peut aider à

fournir un sceau efficace contre l’infiltration bactérienne coronaire (Trope 2004).

Malheureusement, à cause de « facteur C » élevé présente dans les canaux

radiculaires (Morris et al., 2002; Bouillaguet et al., 2003; Goracci et al., 2004), on a

enregistré des difficultés dans le scellement des tenons en fibres à la dentine intra

radiculaire avec les ciments résineux. On croit que, comme pour l’emploi de ciments

non adhésifs, une résistance au dé-scellement rencontré dans les tenons en fibres

cimentés adhésivement est donnée par la friction du contact tenon-ciment résineux à

l’intérieur du canal radiculaire (Goracci et al., 2005).

144

La popularité toujours croissante rencontrée par les restaurations avec les tenons en

fibres a imposé la nécessité d’une évaluation systématique des différents types et de

la qualité des tenons en fibre aujourd’hui présents sur le marché. Les critères de

choix en général sont fondés sur la composition et la forme des tenons, les coûts, sur

les procédures de scellement adhésif, les évaluations expérimentales in vivo et in

vitro. Une étude a comparé la résistance à la fatigue et les caractéristiques

structurales de différents types de tenons en fibre (Grandini et al. 2004a). Quelques

types de tenons en fibres peuvent facilement résister jusqu’à 2.000.000 de cycles de

fatigue sans aucune conséquence à leur qualité générale. En particulier, la qualité de

l’adhésion et du lien entre les deux composants du tenon en fibre (les fibres et la

n adhésive en se servant d’une

matrice de résine époxydique) peut influencer la qualité du tenon lui-même. En

effet, la résistance à la charge statique et la résistance à la fatigue, sont

proportionnelles à la force d’adhésion de l’interface charges-résine, dans les

systèmes composites renforcés avec des fibres (Zhao et al. 2000, Kessler et al. 2000,

Keusch et al. 1999). Une étude récente a confirmé que l’augmentation de la force de

adhésion entre les charges (fibres) et la matrice conduit à un accroissement des

propriétés mécaniques des composites renforcés avec des fibres (Debnath et al.

2004).

Les procédures de collage/scellement sont un facteur extrêmement important dans le

domaine de la restauration avec des tenons en fibres, et elles ont été depuis

longtemps décrites dans la littérature internationale (Ferrari et al. 2001a and 2001b,

Vichi et al. 2002a). Le mordançage acide, l’emploi d’ adhésifs de quatrième ou

cinquième génération et d’un ciment résineux dual conduit à des résultats cliniques

optimales. Le fait de laisser la solution adhésive non polymérisée avant le placement

du ciment (« One-Step procédure ») afin de réduire le temps nécessaire pour le

scellement, conduit à des résultats cliniques défavorables tant du point de vue

clinique qu’expérimental (Grandini et al. 2004b).

Le tenon peut être ajusté à la longueur adéquate après la restauration du faux-

moignon dans le cas où une couronne recouvre l’ensemble. Dans le cas contraire, au

cas où l’on choisit une restauration conservative, il est préférable d’ajuster la

longueur du tenon avant de procéder au scellement de manière à pouvoir exécuter en

même temps le scellement du tenon et la reconstructio

145

phase unique de mordançage et de collage. La section tenon peut s’effectuer à l’aide

d’un disque de carborundum ou une fraise diamantée (Grandini et al. 2002a). De

cette façon il est possible de recouvrir la tête du tenon avec de la résine composite,

c'est-à-dire un matériau capable de supporter les contraintes dent contre dent ou des

contraintes masticatoires. Si l’on est en face d’un tenon de bonne qualité, la

procédure de coupure ne modifiera pas l’intégrité de la structure du tenon.

Pendant des années beaucoup de changements ont concerné les matériaux employés

pour la fabrication des tenons en fibres : les fibres de carbone ont été la première

fibre employée ; après la fibre de verre, de quartz et de silice, avec une attention

particulière aux capacités de transmission de la lumière. Des développements

intéressants ont eu lieu sur la forme des tenons, partant du double cylindre original,

jusqu’aux formes endodontiques et aux plus récents tenons à double conicité. En

effet la cimentation adhésive permet de se confier à la formation de « resin tags » et

à la couche hybride plutôt qu’à la rétention mécanique et à la parfait ajustement du

tenon (Ferrari et al. 2002). De plus, pour obtenir l’adaptation du tenon, une plus

grande variété de tenons disponibles sur le marché permet au clinicien de

sélectionner le tenon le plus approprié afin d’économiser la plus grande quantité de

structure dentaire restante. Le descellement survient plus facilement en l’absence du

le que le tenon s’adapte à

souhaitable « Ferrule effect» ou en présence d’une épaisseur élevée de ciment dans

laquelle vraisemblablement des bulles d’air se sont formées conduisant au

descellement (Ferrari et al. 2000a). L’idée d’avoir un tenon sur-mesure, qui s’ajuste

parfaitement à chaque espace du canal est décidément attrayant pour le praticien,

surtout quand il s’agit de canaux à forme elliptique telle que les dents canines et les

prémolaires. Dans ces cas le clinicien est obligé d’adapter la structure dentaire

restante au tenon à travers l’enlèvement d’une quantité ultérieure de dentine, ou à

sceller un tenon plus petit, par conséquent d’avoir une plus grande épaisseur de

ciment. Dans le cas contraire , il serait souhaitab

l’anatomie du canal produite par le traitement endodontique. En effet c’est le

fondement logique à la création du tenon anatomique (Grandini et al 2000, Boudrias

et al. 2001a and 2001b). Récemment le tenon Anatomic Post’n Core (RTD, St

Egrève, France) (Ferrari et al. 2002) a été introduit. Ce nouveau tenon est composé

d’un tenon à double conicité (DT) numéro 1 recouvert par un résine photo-

146

polymérisable (Lumiglass, RTD, St Egrève, France). La résine qui environne le

tenon est à même, une fois introduite dans le canal, de produire un bon ajustement

entre le tenon et le parois du canal, en réduisant la quantité de ciment et en

stabilisant le tenon pendant les procédures de scellement.

De toute façon le test décisif pour une procédure clinique est toujours l’évaluation

clinique. Beaucoup d’études publiées se sont concentrées sur l’emploi des tenons

fibrés pour la restauration de la dent traitée endodontiquement (Malferrari et al.

2003, Ferrari et al. 2000a and 2000b, Fredriksson et al. 1998, Monticelli et al. 2003,

Dallari et al. 1998, Scotti et al. 2002). La plus grande partie d’entre eux combine

l’emploi des restaurations avec des tenons fibrés et des couronnes en céramique ou

métallo-céramique. Une énorme expansion des indications pour les restaurations

directes en résine composite s’est produite pendant ces dernières années(Hickel et al.

2004). Pour cela il est intéressant d’évaluer les performances des tenons fibrés en

combinaison avec des restaurations directes en résine composite, sans être

recouverts par une prothèse dentaire. Après 30 mois de service clinique, les dents

traitées endodontiquement reconstruites avec des tenons en fibres et des

restaurations directes en résine composite ont démontré des résultats cliniques

favorables sans fractures radiculaires.

Conclusions et recommandations

En ce qui concerne l’emploi des tenons en fibres en dentisterie, selon les résultats

issus de nos évaluations cliniques et expérimentales, les conclusions et

recommandations suivantes peuvent être comme suit :

1) Les tenons fibrés ont montré de bonnes propriétés mécaniques et le mode d’échec

est en général plus favorable et conservateur que celui des tenons métalliques.

2) Les procédures endodontiques peuvent influencer le résultat final de la

restauration avec le tenon. Une grande attention doit être portée à l’enlèvement de

bactéries, de débris et d’autres matériaux à l’intérieur du canal avant d’obturer le

canal.

3) Les tenons en fibres peuvent contribuer au seau de l’espace canalaire avec l’aide

du scellement adhésif Pour cela ils peuvent être considérées comme une partie

intégrante du traitement endodontique.

147

4) Plusieurs marques de tenons existent. La qualité de la liaison entre les fibres et la

matrice peut influencer sur la qualité finale du tenon, et ceci devrait être pris en

considération au moment du choix du tenon, en même temps que la composition, la

forme, et l’évaluation de base et clinique.

5) En ce qui concerne les procédures de scellement, un lien fiable entre tenon fibré,

le système adhésif et le canal radiculaire peut être atteint avec l’emploi du

mordançage acide. L’acide de mordançage doit être enlevé soigneusement avec une

seringue et une aiguille endodontique.

6) Un système adhésif de quatrième ou de cinquième génération, inséré dans le canal

à l’aide d’un applicateur Microbrush®, et un ciment résineux duale peuvent être

employé avec les tenons en fibre translucides.

7) Un tenons sur-mesure (Anatomic Post’n Core®) peut être d’une grande aide dans

une situation clinique où une perte importante de substance coronaire et canalaire a

conduit à une forme non circulaire après le traitement endodontique.

8) Les tenons en fibre peuvent être employés en toute sécurité en combinaison avec

des restaurations prothétiques en céramique ou métallo-céramique. Les indications

pour leur usage sont en constante progression, et des études cliniques récentes ont

démontré qu’ils peuvent être employées aussi comme élément de base pour une

stauration directe en résine composite. Avec cette technique, la restauration de la

tre plus simple et plus économique.

re

dent traitée endodontiquement peut ê

148

Schlußfolgerung

Schon immer war die Restauration endodontisch behandelter Zähne eine

Herausforderung für den Zahnarzt. Im Laufe der letzten 15 Jahre haben Faserstifte

einer Wurzelkanalbehandlung können viele

ail) und eine darunter liegende

odulus erhöht

ßt, die in

berkiefer-Prämolaren angetroffen werden (Ross et al. 1980, Salis et al. 1987). Im

Allgemeinen ist die Entfernung der Pulpakammerdecke, zusammen mit der

endodontischen Behandlung verantwortlich für eine Verringerung der

Frakturresistenz (Fuzzi 1993, Morgano et al. 1993, Trabert et al. 1978 , Milot et al.

1992)

Bekanntlich hängt das Überleben von pulpalosen Zähnen direkt von Menge und

Qualität der verbliebenen Zahnstruktur ab (Assif et al. 1994, Guttman 1992, Cohen

et al. 1996).

Bisher wurde ein Stift eingesetzt, um den Kern zu befestigen und den Zahn zu

“verstärken”. Heute ist die Verstärkung der Zahnwurzelstruktur durch Metallstifte

widerlegt (Shillimburg HT 199), denn sie „...verstärken endodontisch behandelte

Zähne nicht signifikant..“ (Sorensen 1984a). Im Zuge des technischen Fortschritts in

an Bedeutung gewonnen. Die vorliegende Arbeit untersucht mehrere grundsätzliche

und klinische Aspekte zu Wahl und Anwendung von Faserstiften. Es ist

wissenschaftlich bewiesen, dass sich ein gesunder Zahn von einem endodontisch

behandelten Zahn unterscheidet. Nach

Veränderungen auftreten bezüglich physischer, chemischer und elastischer

Eigenschaften, Ermüdungsresistenz, Morphologie und biomechanischem Verhalten.

Ein vitaler Zahn hat eine steifere Struktur (Em

nachgiebige und unterstützende Schicht (Dentin). Karies und endodontische

Zahnaufbereitung sind die ersten Faktoren, die den Zahn schwächen können. Der

Feuchtigkeitsgehalt verringert sich (Helfer et al. 1972), Young’s M

sich (Huang et al. 1992), die Anzahl der Kollagenfibrillen im Dentin nimmt ab

(Mason 2001, Hashimoto et al. 2000, Ferrari et al. 2004). Weiterhin können sich

unter Stress Veränderungen in der Morphologie und im biomechanischen Verhalten

der Zähne ergeben (Grimaldi 1971, Tidmarsh 1976). Die Zugangsaufbereitung für

eine endodontische Behandlung führt zum Verlust der Pulpakammerdecke und der

Randleisten, was die relativ hohe Anzahl von Frakturen beeinflu

O

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faserverstärkten Materialien wurden Struktur, Form und optische Eigenschaften

serverstärkter Harzstifte verbessert, und trugen zur Entwicklung von Materialien

Frakturwiderstand und Fehlermuster endodontisch behandelter Oberkiefer-

al. 2004). Diese Studie zeigt, dass die Menge der Kanalwandreste den

fa

bei, die über die Grenzen der Metallstifte (Platin, Legierungen oder Titan)

hinausgehen, insbesondere in Bezug auf ihre ästhetische Erscheinung, ihre

Fehlermechanismen und klinische Leistung. Wegen der Ästhetik und zur

Unterstützung bei Frontzahn-Revisionen wurden transluzente Faserstifte eingeführt

(Vichi et al. 2000a und 2000b, Ferrari et al. 20002, Paul et al. 1998, Heydecke et al.

2002). Was das mechanische Verhalten und die Fehlermechanismen der Faserstifte

angeht, wurde festgestellt, dass Versagen von Metallstiften zu irreversiblen

Wurzelfrakturen tendieren. Jedoch entstehen Wurzelfrakturen bei Faserstiften eher

im koronaren Bereich, und sie sind leichter zu behandeln (Akkayan et al. 2002,

Cornier et al. 2001, Reagan et al. 1999, Newman et al. 2003). Der Grund für das

Versagen könnte darin liegen, dass für einen Metallstift eine größere Menge

Zahnstruktur entfernt werden muss (Staniewitz et al. 2002). Im Fall einer

endodontischen Revision, können Faserstifte leichter als Metall- oder Keramikstifte

entfernt werden (Geisi et al. 2003, Hauman et al. 2003). Abschließend: Faserstifte

eignen sich gut für die Retention von Harz-Komposit-Kernen. Im Vergleich zu

Metall- oder Zirkonstiften, sind sie dank ihres mechanischen Verhaltens und der

Zementierungstechniken, fähig, die verbleibende Wurzelstruktur zu bewahren.

Einige Restaurationstechniken endodontisch behandelter Zähne mit Harz-

Kompositen, die verloren gegangenes Wurzeldentin ersetzen und möglicherweise

die Wurzel stärken sollten, wurden beschrieben. Leider wurden diese Berichte ohne

wissenschaftliche Überprüfung veröffentlicht (Freedman et al. 1994, Godder et al.

1994, Martelli 2000, Castellucci 2004). In einer kürzlich durchgeführten Studie

wurden

Prämolaren mit zunehmend reduzierten Kanalwandresten untersucht, die mit Harz-

Komposit und mit oder ohne durchsichtige Glasfaserstifte restauriert wurden

(Sorrentino et

mechanischen Widerstand endodontisch behandelter Oberkiefer-Prämolaren

beeinflusst. Die mit Fasterstiften versorgten Exemplare zeigten, bei gleicher

Restwandmenge, höhere Bruchbelastungsgrenzen auf. Weiterhin wurden

restaurierbare Frakturen in mit Faserstiften restaurierten Exemplaren beobachtet.

150

Wenn diese Daten durch klinische Studien überprüft würden, könnte die Annahme

bestätigt werden, dass Wurzelkanalwände durch den Verbund mit Faserstiften

verstärkt werden.

Schlüsselfaktor für eine gelungene Restauration ist eine erfolgreiche endodontische

Aufbereitung. Für eine gut ausgeführte endodontische Behandlung müssen Debris

und organisches Material aus dem Wurzelkanal entfernt (Castellucci 1993), und der

Kanal zur Aufnahme des Obturationsmaterials mechanisch aufbereitet sein (Ingle

1993). Der Einfluss von Zementen und Irrigationslösungen wurde in der Literatur

ausführlich diskutiert. In einer Untersuchung über die Wirkung verschiedener

Irrigationsmethoden auf die Sauberkeit des Wurzelkanals nach endodontischer

Behandlung (Grandini et al. 2002b), wurde festgestellt, dass keine der in der Studie

benutzten Techniken einwandfreie Entfernung von Smear Layer und Debris

erreichte. Jedoch, wurde ebenfalls festgestellt, dass die Kombination von Natrium

Hypochlorit und einem Chelator helfen kann, die Debrismenge an den

Wurzelkanalwänden zu verringern. Die Hauptaufgabe der Wurzelkanalfüllung ist es,

den Wurzelkanal abzudichten und Undichtigkeit; Microleakage, zu verhindern. In

diesem Sinne kann die Herstellung und das Setzen eines Stiftes, wenn sie dazu

beitragen, den Raum im Wurzelkanal zu füllen und abzudichten, als Teil der

endodontischen Behandlung angesehen werden (Trope 2004). Wegen des hohen C-

Faktors, in den Stiftzwischenräumen (Morris et al., 2002, Bouillaguet et al., 2003,

Goracci et al., 2004), treten große Adhäsionsprobleme zwischen intra-radikularem

Dentin und Faserstift mit Hrz-Zementen auf. Man nimmt an, dass, ähnlich wie bei

nicht bindenden Zementen, auch bei den Faserstiften die Gleitfriktion im

Wurzelkanal zum großen Teil dazu führt, dass der Stift sich nicht löst (Goracci et

al., 2005). Da Restaurationen mit Faserstiften große Nachfrage finden, ist es

notwendig, die verschiedenen Marken und Typen auf dem Markt systematisch zu

untersuchen. Hierfür werden üblicherweise einige auf grundlegenden und

experimentellen Untersuchungen basierende Kriterien angewandt, wie z.B.

Komposition und Form des Stiftes, Kosten und Zementierungstechnik. Es gibt eine

Studie die Ermüdungswiderstand und Struktureigenschaften verschiedener

Faserstifte vergleicht (Grandine et al. 2004a). Einige Faserstiftmarken widerstehen

ohne Qualitätsbeeinträchtigung bis zu 2.000.000 Ermüdungs-Test-Zyklen.

151

Insbesondere die Verbundqualität zwischen zwei Komponenten eines Faserstiftes

(die Faser und die Harz Matrix) können die Qualität des Stiftes beeinflussen. In

faserverstärkten Komposit-Systemen verhalten sich statischer Druck und

Ermüdungseigenschaft proportional zur Stärke der Kontaktstelle von Füllung und

Harz (Zhao et al. 2000, Kessler et al. 2000, Keusch et al. 1999). Eine kürzlich

erschienene Studie bestätigt, dass die Anhebung der Verbundstärke zwischen

Füllmaterial und Matrix zur Verbesserung der mechanischen Eigenschaften

faserverstärkter Komposite führt (Debnath et al. 2004).

Bei Faserstiften sind die Verbundprozesse von großer Bedeutung. Die Technik

wurde bereits in der Literatur behandelt (Ferrari et al. 2001a und 2001b, Vichi et al.

2002a). Das Ätzen sowie die Verwendung von Adhäsiven der 4. und 5. Generation

und eines dual härtenden Zement-Harzes erzielen die besten klinischen Resultate.

Wenn die Adhäsiv-Lösung vor Anwendung des Zements nicht polymerisiert wird

(Einstufen-Prozedur), um die Zeit für die Zementierung zu verringern, ergibt das

ungünstige Resultate vom klinischen sowie experimentellen Standpunkt (Grandinie

et al. 2004b). Wenn eine Krone gesetzt wird, kann der Stift nach Restauration des

Kerns angepasst werden. Handelt es sich um eine direkte Restauration, wird

empfohlen, die Länge des Stiftes vor dem Verkleben anzupassen. Der Stift sollte mit

einer Korundscheibe oder einem Diamantbohrer geschnitten werden (Grandini et al.

2002a). So kann das abgeschnittene Stiftende mit Epoxyd-Komposit beschichtet

werden, ein Material, das fähiger als Faserstifte ist, der Zahn zu Zahn und Zahn zu

Essen Abnutzung zu widerstehen. Ein Stift von guter Qualität wird seine strukturelle

Integrität durch das Abschneiden nicht verändern.

Was das Material der Stifte betrifft, gibt es viele Neuentwicklungen: Karbon wurde

als erstes als Stiftmaterial verwendet, dann kamen Stifte aus Glas, Quarz und

Silizium wegen ihrer transluzenten Eigenschaften. Im Design gab es ebenfalls

interessante Entwicklungen, vom Original-Doppel-Zylinder, über endodontische

Formen bis hin zu den jüngeren Double-Taper-Stiften. Hier beruht die Adhäsiv-

Zementierung mehr auf die Verbindung der Harz-Marker mit dem Dentins als auf

gute Passform und mechanische Verankerung des Stiftes im Kanal (Ferrari et al.

2002). Weiterhin wird durch eine erweiterte Größenauswahl der Stifte mehr

Zahnsubstanz bewahrt, die für eine zufrieden stellende Stiftanpassung abgetragen

152

werden muss. Der Stift wird sich eher lösen, wenn der gewünschte „ferrule-effect“

nicht vorhanden ist, oder wenn eine zu dicke Zementschicht mit Blasenbildung

vorliegt (Ferrari et al. 2000a). Die Idee, individuell geformte, dem Kanal angepasste

Stifte, herzustellen, besonders bei elliptisch geformten Wurzelkanälen, die in

Eckzähnen und unteren Prämolaren vorkommen, ist interessant. In diesen Fällen

muss der Zahnarzt die Wurzelstruktur durch Entfernung von noch mehr Dentin an

die Stiftform anpassen. Jedoch wäre es wünschenswert, dass sich der Stift an die

Anatomie des Wurzelkanals nach erfolgter endodontischer Behandlung anpasst. Das

interessant, die Leistungen der

ist die Grundlage für die Entwickluung eines anatomischen Stiftes (Grandini et al.

2000, Boudrias et al. 2001a und 2001b). Kürzlich wurde der Anatomic Post’n Core

eingeführt (RTD, St. Egrève, Frankreich), (Ferrari et al. 2002). Dieser neue Stift

wird aus einem DT Post Nr.1 mit lichthärtendem Harz (Lumoglass, RTD, St.

Egrève, Frankreich) hergestellt. Dieser (relining) Harzbelag stellt, nach Einführung

in den Wurzelkanal, eine gute Passform her, und erlaubt es, die Zementmenge zu

reduzieren, die zum Stabilisieren des Stiftes während des Verbunds nötig ist.

Der endgültige Test eines Verfahrens besteht immer aus seiner klinischen

Beurteilung. Viele Studien berichten über die Anwendung von Faserstiften für die

Restauration von endodontisch behandelten Zähnen (Malferrari et al. 2003, Ferrari

et al. 2000a und 2000b, Fredriksson et al. 1998, Monticelli et al. 2003, Dallari et al.

1998, Scotti et al. 2002). Die meisten Studien verbinden die Anwendung von

Faserstift-Restaurationen mit Kronen aus Keramik- oder Keramo-Metall. Während

der letzten Jahre haben Direkt-Restaurationen mit Harz-Kompositen zugenommen

(Hickel et al. 2004). Aus diesem Grund ist es

Faserstifte im Zusammenhang mit Direkt-Restaurationen aus Harz-Kompositen

ohne Kronenabeckung zu untersuchen. Nach 30 Monaten klinischen Einsatz

wurzelbehandelter Zähne gab es keine Wurzelfrakturen. (und zeigten positive

Ergebnisse.)

Fazit und Empfehlungen

Aufgrund unserer grundlegenden und klinischen Untersuchungen über die

Anwendung von Faserstiften in der Zahnheilkunde können wir folgende

Schlussbetrachtungen und Empfehlungen geben:

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1) Im Vergleich zu Metallstiften zeigen Faserstifte allgemein positive mechanische

Eigenschaften und besseres Fehlerverhalten.

2) Vorangegangene endodontische Behandlungen können das Endresultat einer

Stiftrestauration beeinflussen. Vor Abschluss der Füllung muss der Entfernung von

Bakterien, Debris und anderen Materialien aus dem Wurzelkanal größte Beachtung

beigemessen werden.

3) Die Adhäsivtechnik mit Faserstiften verhilft zur kompletten Füllung und

Abdichtung des Wurzelkanals. Aus diesem Grund kann sie durchaus als Teil der

endodontischen Behandlung angesehen werden.

4) Es gibt mehrere Faserstiftmarken. Die Verbundqualität zwischen Faser und Harz

kann die endgültige Qualität des Stiftes beeinflussen. Dies sollte, ebenso wie die

Zusammensetzung, die gewünschte Form, und die grundlegenden Überlegungen bei

der Wahl des Faserstiftes beachtet werden.

5) Ein zuverlässiger Verbund zwischen Faserstift-Harz-Zement und dem

Wurzelkanal kann relativ leicht mit einem Ätzmittel erreicht werden, wenn dieses

nen verwendet werden können. Durch diese Technik wird die

estauration von endodontisch behandelten Zähnen leichter und kostengünstiger.

mit Hilfe einer Spritze und einem Wurzelkanalinstrument gründlich aus dem

Wurzelkanal entfernt wird.

6) Für transluzente Stifte wird empfohlen, den Kanal mit einem Adhäsiv-System der

4. oder 5. Generation, zusammen mit einem dual-härtenden Harz-Zement und mit

Hilfe einer Microbrush zu beschicken.

7) Ein individueller Stift (Anatomic Post’n Core) kann sehr hilfreich sein, wenn ein

großer Verlust koronaler Struktur vorliegt, und wenn der Wurzelkanal nach

endodontischer Behandlung eine nicht-runde Form aufweist.

8) Faserstifte können zusammen mit Keramik oder Keramo-Metall-Kronen

eingesetzt werden. Ihre Verbreitung nimmt schnell zu, und neue klinische Studien

zeigen, dass sie ohne Risiko als Grundlage für Direkt-Restaurationen mit Harz-

Komposit-Kro

R

154

Resumen y conclusiones

Siempre ha sido un desafío grande para los clínicos el restaurar dientes

endodonticamente tratados. Los postes de fibra han adquierido una importancia en

este campo en los últimos 15 años. Esta tesis contiene un estudio acerca de varios

aspectos diferentes, básicos y clínicos relacionando la selección y el uso de postes de

físicos, químicos morfologicos y

eros factores que pueden reducir la

ri et al. 2004). Además, los cambios ocurren también en

lpa y las aristas marginales, influyendo en la

, son responsables de

un

poste se introducia para asegurar la retención a la recostrución y para “reforzar” el

diente. Hoy en día el refuerzo determinado por postes de metal no se puede

considerar posible (Shillimburg HT 1997) porque “…no refuerza apreciablemente

dientes tratados endodonticamente…” (Sorensen 1984a). El progreso hecho en la

fibra. Existe la evidencia cientifica de que la actuacion de un diente sano es diferente

a la de un diente endodonticamente tratado. Muchos cambios pueden ocurrir después

del tratamiento del canal de la raíz en términos

bioquímico y de las propiedades elásticas de la dentina, la resistencia para la fatiga,.

Un diente vital presenta una estructura (esmalte) más rigida y un apoyo

fundamentalmente más blando (dentina). La caries y la preparación del diente para

el tratamiento endodóntico son los prim

resistencia de un diente. Hay una disminución en el contenido de la humedad (Helfer

et al. 1972), un incremento del modulo de Young (Huang et al. 1992), y una

reducción en el porcentaje de fibras de colágeno en la dentina (Mason 2001,

Hashimoto et al. 2000, Ferra

la morfología y en la conducta biomecanica de dientes bajo el estrés (Grimaldi 1971,

Tidmarsh 1976). La preparación del acceso para el tratamiento endodóntico causa la

pérdida del techo de la cámara de la pu

incidencia relativamente alta de fracturas documentadas en premolares maxilares

(Ross et al. 1980, Salis et al. 1987). En general, la eliminación del techo de la

cámara de la pulpa, juntos con procedimientos endodónticos

una reducción en la resistencia a la fractura (Fuzzi 1993, Morgano et al. 1993,

Trabert et al. 1978, Milot et al. 1992).

También es sabido que la probabilidad de sobrevivencia de un diente sin pulpa es

relacionada directamente con la cantidad y la calidad de la estructura restante del

diente (Assif et al. 1994, Guttman 1992, Cohen et al. 1996). Tradicionalmente,

155

tecnología de materiales de fibra-reforzada ha mejorado la estructura, la forma, y las

ropiedades ópticas de postes de fibra-reforzados de resina. Esto llevó al desarrollo

ara expertos (Freedman et al. 1994, Godder et

p

de materiales que vencen algunas de las limitaciones de postes metálicos (platino,

aleaciones o titanio), con respecto a la apariencia estética, el modo del fracaso y el

desempeño clínico. En términos de la estética, los postes translúcidos de fibra se

introdujeron para sostener comercialmente las restauraciones anteriores (Vichi et al.

2000a y 2000b, Ferrari et al. 2001a y 2001b, Ferrari et al. 2002, Paul et al. 1998,

Heydecke et al. 2002). Por lo que concierne a el comportamiento bio-mecánicos y el

fracaso, se ha demostrado que los postes metálicos tienden a producir fracturas

irrevocables de la raíz. Opuestamente, una fractura de la raíz que ocurre con el uso

de postes de fibra se localiza generalmente más coronalmente y es más fácilmente

retratable (Akkayan et al. 2002, Cornier et al. 2001, Reagan et al. 1999, Newman et

al. 2003). Este tipo de fracaso puede estar debido a la mayor cantidad de estructura

del diente que se debe quitar cuando se coloca un poste metálico (Stankiewitz et al.

2002). En el caso en que sea necesario un re-tratamiento endodóntico, los postes de

fibra son más fácilmente removibles de los metálico o los cerámicos (Gesi et al.

2003, Hauman et al. 2003). En conclusion, los postes de fibra funcionan bien como

retenciones para los cementos de resinas compuestas en dientes tratados

endodonticamente. Cuando se compararon con postes de metal o circonios, ellos son

capaces de preservar la estructura residual del diente gracias a su conducta mecánica

y a los procedimientos de cementación que los acompañan.

Se han descrito técnicas para restaurar dientes endodonticamente tratados con el uso

de resinas compuestas para remplazar la dentina perdida de la raiz, con la

posibilidad del refuerzo de esta. Desgraciadamente, estos informes se publicaron en

publicaciones que no estan revisadas p

al. 1994, Martelli 2000, Castellucci 2004). Recientemente se realizó un estudio

comparando la resistencia de fractura y las pautas de fracaso de premolares

maxilares endodonticamente tratados con un número progresivamente reducido de

paredes residuales, estos se restauraron utilizando un material de resinas compuestas

con o sin postes traslúcidos de fibra de vidrio (Sorrentino et al. 2004). Este estudio

mostró que el número de paredes dentales residuales influyó en la resistencia

mecánica de los premolares maxilares endodonticamente tratados. En especímenes

156

con el mismo número de paredes dentales residuales, las cargas más altas de fractura

se registraron en dientes restaurados con postes de fibra. Además, en los

especímenes restaurados con postes de fibra se observaron fracturas sencillamente

restaurables. Si estos datos se pueden validar con estudios clínicos, el concepto de

reforzar las estructuras radiculares con el cementado de postes de fibra se

establecerá más firmemente.

Un exitoso procedimiento endodóntico es un factor clave de asegurar el éxito en la

restauración de dientes con las raices tratadas. Un tratamiento endodóntico bien

realizado se basa en la eliminación de detritus y material orgánico que hay dentro

del canal de la raíz (Castellucci 1993) y en la preparación mecánica del canal para

recibir un material de obturación (Ingle 1993). La influencia de cementos y de las

soluciones irrigadoras se han discutido extensamente en la literatura. Cuando se

evaluó el efecto de diferentes regímenes de irrigación en la limpieza de los canales

de la raíz que se lograron después del tratamiento endodóntico (Grandini et al.

2002b), se encontró que ninguna de las técnicas utilizadas en ese estudio mostró una

eliminación perfecta de la capa de barrillo dentinario y de los detritus. Sin embargo,

se notó que una combinación de hipoclorito sódico y un agente quelante puede

ayudar a reducir la cantidad de detritus por las paredes del canal. Las funciones de

relleno del canal de la raíz deberán sellar esencialmente el canal y prevenir futuras

microfiltraciones. En este sentido, la fabricación del poste y su colocación se pueden

considerar como partes del tratamiento endodóntico si ellos contribuyen al relleno y

al sellado del espacio de canal (Trope 2004). Desgraciadamente, debido a los

factores-C altos que hay en los canales radiculares (Morris et al., 2002; Bouillaguet

et al., 2003; Goracci et al., 2004), se encontraron dificultades en la cementacion de

postes de fibra a la dentina intraradicular con cementos de resina. Se ha sugerido que

semejante al uso de cementos no-adhesivos, la fricción de deslizamiento contribuje

por una parte substancial a la resistencia a la dislocación de postes cementados en

los canales radiculares (Goracci et al., 2005).

La popularidad siempre mas grande que tiene el uso de postes de fibra para la

restauración de los dientes endodonticamente tratados ha impuesto la necesidad de

una evaluación sistemática de las marcas y tipos diferentes de postes de fibra

disponibles comercialmente. Algunos criterios se emplean generalmente, tal como la

157

composición y la forma del poste, el costo y los procedimientos de cementacion,

basado en evaluaciones básicas y experimentales. Un estudio ha comparado la

resistencia a la fatiga y las características estructurales de tipos diferentes de postes

de fibra (Grandini et al. 2004a). Algunas marcas de postes de fibra pueden resistir

hasta 2.000.000 de ciclos de fatiga sin afectar su calidad general. En particular la

calidad de la adhesión entre los dos componentes de un poste de fibra (las fibras y la

rocedimientos de corte no afectarán a

matriz de resina de epoxi) puede influir en la calidad del poste mismo. De hecho, las

propiedades de fatiga y los impactos estaticos son proporcionales a la fuerza de la

interfase relleno/resina en sistemas de composite reforzados con fibra (Zhao et al.

2000, Kessler et al. 2000, Keusch et al. 1999). Un reciente estudio confirmó que

aumentando la fuerza de adhesion entre el relleno y la matriz se obtiene como

resultado un aumento de las propiedades mecánicas de composites reforzados con

fibras (Debnath et al. 2004).

Los procedimientos de cementado son muy importantes en las restauraciones con

postes de fibra. El procedimiento recomendado ya se ha descrito en la literatura

(Ferrari et al. 2001a y 2001b, Vichi et al. 2002a). El grabado ácido, el uso de un

adhesivo de cuarta o quinta generación, y el uso de un cemento de resina de doble-

curado proporciona los mejores resultados clínicos. Dejando la solución adhesiva

no-polimerizada antes de colocar el cemento (one step procedure), para reducir el

tiempo del procedimiento de cementación, se producen resultados desfavorables

desde el punto de vista clínico y experimental (Grandini et al. 2004b). Si se coloca

una corona, el poste se puede cortar después de la restauración del “core” (muñon).

En caso de que se haga una restauración conservadora es preferible ajustar la

longitud del poste antes del cementado. El ajuste se debe realizar con un disco de

carborundum o una fresa de diamante (Grandini et al. 2002a).De esta manera, es

posible cubrir el fin del corte del poste con composite de resina, un material más

capaz de resistir que un poste de fibra a el desgasto diente-diente y diente-alimento.

Si un poste es lo suficientemente bueno, los p

su integridad estructural.

Un gran desarrollo ocurrió con respecto a los materiales utilizados para la

fabricación de postes: el carbono era la primera materia empleada; vidrio, cuarzo y

sílice se han utilizado despues, aprovechándose de sus propiedades ópticas

158

traslúcidas. Un desarrollo interesante fue también la modificación del diseño de

estos postes, desde el doble-cilíndro original, a las formas “endodontica”, y por fin a

las formas más recientemente introducidas de la doble-conicidad. De echo la

cementación adhesiva ahora confía más en la formación de la zona de interdifusión

de resina-dentina y tags de resina que en la retención mecánica del poste dentro del

canal (Ferrari et al. 2002). Además, un amplio surtido de tamaños permite la

conservación de la dentina residual que se tiene que quitar para lograr una

adaptación satisfactoria del poste. El despegamiento es más probable que ocurra en

ausencia del deseable ‘ferrule effect’, o a la presencia de una capa excesivamente

gruesa de cemento en donde la incitación de burbujas conduce al despegamiento

(Ferrari et al. 2000a). La idea de tener un poste anatomico que quede bien en el

espacio individual del canal, especialmente con canales de raíz tratados que tienen

las formas elípticas, tal como fueron observados en caninos y premolares, seria una

onticelli et al. 2003, Dallari et al. 1998, Scotti et al. 2002).

situacion muy agradable por el clinico. En estos casos, el clínico es forzado a

adaptar la estructura dental residua a la forma del poste, mediante la eliminación de

una cantidad adicional de dentina o mediante una major cantidad y grosor de la capa

de cemento. Al contrario, sería deseable que el poste se adaptese a la anatomía del

canal de la raíz producida por el tratamiento endodóntico. Esto es verdaderamente

la base para la creación de un poste anatómico (Grandini et al 2000, Boudrias et al.

2001a y 2001b). Recientemente el Poste anatómico cementado (RTD, San Egrève,

Francia) ha sido introducido (Ferrari et al. 2002). Este nuevo poste es hecho por un

poste de DT n.1 que es cubierto por una resina de fotocurado (Lumiglass, RTD, San

Egrève, Francia). La resina es capaz, una vez que es introducido en el canal de la

raíz, de producir un adecuada forma, reduciendo la cantidad de cemento que debe

ser utilizada y estabilizando el poste durante los procedimientos de cementado.

La prueba final para un procedimiento clínico es siempre la evaluación clínica.

Muchos estudios informaron sobre el uso del poste de fibra para restaurar dientes

endodónticamente tratados (Malferrari et al. 2003, Ferrari et al. 2000a y 2000b,

Fredriksson et al. 1998, M

La mayoría de ellos combinan el uso de restauraciones de poste de fibra con

cerámico o coronas de ceramometal. En los ultimos años se ha podido observar una

enorme expansión en las indicaciones para las restauraciones directas con resina

159

(Hickel et al. 2004). Así, es interesante evaluar la actuación de postes de fibra

cuando ellos fueron utilizados en conjunción con restauraciones directas de resina,

sin el cubrimiento adicional de corona. Después de 30 meses de servicio clínico,

dientes con raices tratadas con postes de fibra y restauraciones de composite de

resina directa exhibieron unos resultados clínicos favorables y no ocurriron fracturas

de raíces.

Conclusiones y recomendaciones

Las conclusiones y recomendaciones siguientes se pueden deducir de nuestras

evaluaciones básicas y clínicas en el uso de postes de fibra en odontología:

1) Los postes de fibra exhiben unas propiedades mecánicas generales buenas y los

tipos de fracaso son generalmente más conservadores y favorables que cuando son

comparado con postes metálicos.

2) Los procedimientos endodónticos pueden influir en el resultado final de la

restauración con el poste. Se debe prestar gran atención en la eliminación de

bacterias, detritus y otros materiales que queden dentro del canal de la raíz antes que

el relleno sea completado.

3) Los postes de fibra contribuyen al relleno que sella el espacio de canal de la raíz

con la ayuda de la cementación adhesiva. Es por esta razón que ellos se pueden

considerar como parte del tratamiento endodóntico.

4) Existen varias marcas de postes de fibra. La calidad de la adhesión entre las fibras

y la resina puede influir en la calidad final del poste entero, y esto debe ser tenido en

cuenta al escoger un poste de fibra junto con la evaluación de la composición, la

forma deseada, la evaluación básica y clínica.

5) Por lo que conciernan a los procedimientos de cementado, una adhesión segura

entre la unitad cemento-poste de fibra y el canal de la raíz puede ser razonablemente

conseguido con el uso del grabado ácido, que ha sido meticulosamente removido del

canal de la raíz con una jeringa y un aguja endodóntica.

6) Un adhesivo de cuarta o quinta generación, metido en el canal con la ayuda de un

micropincel, y de un cemento de resina de doble-curado puede ser recomendado

cuando se utilizan postes de fibra traslúcidas.

160

7) Un poste individual (Anatomic Post’n Core) puede ser de gran ayuda en una

situación clínica donde hay una falta de estructura coronal y canales de raíz en una

forma no-redondeado despues el tratamiento endodontico.

8) Los postes de fibra se pueden utilizar con seguridad en combinación con cerámica

o coronas de ceramo-metal. Las indicaciones para su uso han sido rapidamente

extendidas, y los estudios clínicos recientes indicaron que ellos pueden ser utilizados

guramente como una base para las restauracion directa de resina. Con el uso de

e tratado endodónticamente puede ser más fácil

se

esta técnica, la restauración del dient

y meno costosa.

161

Sumário e conclusões

A restauração de dentes tratados endodonticamente permanence ainda como um

dente endodonticamente tratado. Diversas alterações podem

correr apόs o tratamento do complexo radicular no que concerne as propriedades

físicas, químicas e elásticas da dentina, além de alterações quanto a resistência a

fadiga, morfologia e comportamento biomecânico. Um dente vital, por sua vez,

apresenta uma estrutura mais rígida (esmalte) e um suporte com relativa

complascência abaixo (dentina). A presença de cáries e o preparo mecânico para o

tratamento endodôntico são os fatores iniciais que levam a uma queda da resistência

dental. Observa-se um decréscimo na umidade intrínseca da estrutura dental (Helfer

et al. 1972), um aumento do mόdulo de Young (Huang et al. 1992), e uma redução

na porcentagem de fibrilas colágenas na dentina (Mason 2001, Hashimoto et al.

2000, Ferrari et al. 2004). Além disso, alterações ocorrem também na morfologia e

no comportamento mecânico da estrutura dental mediante esforços (Grimaldi 1971,

Tidmarsh 1976). O acesso para o preparo endodôntico leva a perda de tanto o teto da

câmara pulpar quanto das cristas marginais, influenciando a incidência de fraturas

documentadas em pré-molares superiores (Ross et al. 1980, Salis et al. 1987). De

uma forma geral, a remoção do teto da câmara pulpar, aliado a terapia endodôntica,

são grandes responsáveis pela redução da resistência a fratura dental (Fuzzi 1993,

Morgano et al. 1993, Trabert et al. 1978, Milot et al. 1992).

Sabe-se também que a taxa de “sobrevivência” de um dente despolpado está

diretamente relacionado com a quantidade e a qualidade da estrutura dental

remanescente (Assif et al. 1994, Guttman 1992, Cohen et al. 1996).

Tradicionalmente, um pino era indicado para aumentar a retenção do material de

preenchimento, bem como “reforçar” o remanescente dental. Atualmente, o eventual

“reforço” promovido por pinos metálicos não é mais considerado possível

grande desafio para a grande maioria dos clínicos. Dentro deste campo da

Odontologia, os pinos de fibra de vidro ganharam muita importância nos últimos 15

anos. Esta tese contêm um estudo sobre diferentes aspectos básicos e clínicos

relacionados com a seleção e a utilização destes tipos de pinos.

Há evidências clínicas que mostram que um dente hígido apresenta características

diferentes de um

o

162

(Shillimburg HT 1997), uma vez que estes “…não reforçam significativamente os

entes tratados endodonticamente …” (Sorensen 1984a). O progresso tecnolόgico

estética, os pinos de

d

no campo de materiais reforçados por fibras melhoraram a estrutura, a forma, e as

propriedades όpticas dos pinos reforçados por fibra contemporâneos. Tal progresso

levou ao desenvolvimento de materiais que puderam se sobrepor às limitações dos

pinos metálicos (platina, ligas ou de titânio), no que diz respeito a sua aparência

estética, modo de fratura e performance clínica. Em termos de

fibra translúcidos foram introduzidos no mercado buscando dar maior suporte às

restaurações de dentes anteriores (Vichi et al. 2000a e 2000b, Ferrari et al. 2001a e

2001b, Ferrari et al. 2002, Paul et al. 1998, Heydecke et al. 2002). O conhecimento

do comportamento mecânico e o mecanismo de falha dos pinos de fibra é de suma

importância, e é demonstrado que os pinos metálicos, quando submetidos a testes de

fadiga, tendem a produzir fraturas radiculares irreversíveis. Adicionalmente, as

fraturas radiculares que ocorrem quando da utilização de pinos de fibra se localizam

em uma porção mais coronária da raiz, além de serem mais facilmente retratadas e

reparadas (Akkayan et al. 2002, Cornier et al. 2001, Reagan et al. 1999, Newman et

al. 2003). Tal tipo de fratura pode se dar em função da grande quantidade de

estrutura dental que deve ser removida quando da inserção de um pino metálico

(Stankiewitz et al. 2002). Em casos em que se faz necessário um retratamento

endodôntico, pinos de fibra são mais facilmente removidos, quando comparado com

pinos metálicos ou cerâmicos (Gesi et al. 2003, Hauman et al. 2003). Como

conclusão, pinos de fibra funcionam de maneira efetiva como “ancoragem” para

núcleos de resina composta. Quando comparados com pinos metálicos ou de

zircônia, pinos de fibra mostram-se capazes de preservar a estrutura dental

remanescente em função de seu comportamento mecânico, bem como em função de

seu método de cimentação adesivo.

Ultimamente, técnicas restauradoras com resinas compostas em dentes tratados

endodonticamente têm sido descritas, buscando repor a dentina perdida, e

possivelmente reforçar a estrutura radicular. Infelizmente, tais artigos foram

publicados em publicações que não são acuradamente revisadas (Freedman et al.

1994, Godder et al. 1994, Martelli 2000, Castellucci 2004). Um recente estudo

buscou comparar a resistência e o padrão de fratura de pré-molares superiores

163

tratados endodonticamente, com diferentes quantidades de paredes remanescentes,

que foram restaurados com compósitos; associados ou não a utilização de pinos de

fibra de vidro translúcidos (Sorrentino et al. 2004). Este estudo mostrou que o

número de paredes dentais remanescentes influenciou significativamente a

resistência mecânica de tais dentes tratados endodonticamente. Em dentes com o

mesmo número de paredes remanescentes, observou-se uma maior resistência a

fratura quando da utilização dos pinos de fibra de vidro. Adicionalmente, fraturas

com prognóstico mais favoráveis foram observadas nos dentes restaurados com

pinos de fibra. Se tais observações puderem ser validadas em estudos clínicos, o

conceito de reforço das estruturas radiculares através da adesão de pinos de fibra

estará definitivamente muito melhor embasada.

Um tratamento endodôntico bem realizado é um fator chave para se obter sucesso

longitudinal na restauração de dentes tratados endodonticamente. Um tratamento

endodôntico bem realizado está baseado na remoção total de debris e materiais

orgânicos internamente à porção radicular (Castellucci, 1993) bem como no preparo

mecânico propriamente dito, para que seja possível o perfeito acomodamento do

material obturador (Ingle 1993). A influência de cimentos e soluções irrigantes têm

sido extensivamente discutidas na literatura. Quando da avaliação de diferentes

soluções irrigantes na efetividade da limpeza das paredes radiculares após o

tratamento endodôntico (Grandini et al. 2002b), pode-se observar que nenhuma das

técnicas avaliadas em tal estudo mostrou uma remoção perfeita da camada de

“smear layer” e de debris. No entanto, notou-se que a combinação de hipoclorito de

sódio e um agente quelante reduz a quantidade de debris ao longo das paredes

radiculares. As funções primordiais de um material obturador são essencialmente

selar o canal radicular e prevenir uma futura microinfiltração. Neste sentido, a

confecção e a colocação de pinos intraradiculares podem ser consideradas parte do

tratamento endodôntico, uma vez que contribuem para o preenchimento e o

selamento do espaço radicular (Trope 2004). Infelizmente, em função de um alto

fator C encontrado nesta região (Morris et al., 2002; Bouillaguet et al., 2003;

Goracci et al., 2004), dificuldades substanciais são comumente encontradas quando

da cimentação de pinos de fibra à dentina intraradicular com o auxilio de cimentos

resinosos. Postula-se que similarmente aos cimentos não-adesivos, uma parte

164

substancial da resistência ao deslocamento de pinos de fibra aderidos às paredes

radiculares está ligada a forças friccionais (Goracci et al., 2005).

A popularização do uso de pinos de fibra para a restauração de dentes tratados

endodonticamente impuseram uma necessidade de avaliação sistemática dos mais

diferentes tipos de pinos disponíveis no mercado. Alguns critérios são usualmente

empregados, tais como a composição e o formato do pino, o custo e os

procedimentos de cimentação, sempre baseados em avaliações básicas e

experimentais. Um estudo comparando a resistência a fadiga e as características

estruturais dos mais diferentes tipos de pinos de fibra foi desenvolvido (Grandini et

al. 2004a). Algumas variedades de pinos de fibra podem resistir a mais de 2.000.000

ciclos de fadiga in vitro, sem que haja efeitos em sua integridade. Particularmente, a

qualidade adesiva entre os dois componentes inerentes a um pino de fibra (as fibras

e a matriz de resina epóxica) pode influenciar a qualidade do pino propriamente dita.

Como via de regra, as propriedades de impacto estático e de fadiga são

proporcionais a resistência da interface carga/resina nos sistemas de compósito

reforçado por fibras (Zhao et al. 2000, Kessler et al. 2000, Keusch et al. 1999). Um

recente estudo confirmou que aumentando a força de união entre as partículas de

carga e a matriz, obtêm-se melhoras significativas nas propriedades mecânicas dos

compósitos reforçados por fibras (Debnath et al. 2004).

Em se tratando de pinos de fibra, os procedimentos de cimentação apresentam

extrema importância. Os procedimentos recomendados encontram-se amplamente

descritos na literatura (Ferrari et al. 2001a e 2001b, Vichi et al. 2002a). As etapas de

condicionamento ácido, a utilização de um sistema adesivo de quarta ou quinta

geração, aliado a um cimento resinoso de polimerização dual, possibilitam os

melhores resultados clínicos. A tentativa de deixar o sistema adesivo sem ser

polimerizado antes da colocação do cimento (procedimento em passo único),

buscando reduzir o tempo clínico de cimentação, produz resultados desfavoráveis,

tanto do ponto de vista experimental quanto do ponto de vista clínico (Grandini et al.

2004b). Se uma coroa será posteriormente efetuada, o pino pode ser ajustado após a

confecção de um núcleo de preenchimento. Em casos de restaurações diretas, deve-

se ajustar o comprimento do pino anteriormente ao procedimento de cimentação. Tal

ajuste pode ser feito com um disco de carborundum ou com uma ponta diamantada

165

(Grandini et al. 2002a). Desta maneira, é possível recobrir a porção mais coronal do

pino com resina composta, um material que apresenta maior resistência ao desgaste

iva (Ferrari et al. 2000a). A

que os pinos de fibra de vidro. Partindo do principio que se está trabalhando em um

pino de boa qualidade, os procedimentos de corte não virão a afetar a sua integridade

estrutural.

Muitos avanços nos materiais utilizados para a fabricação de pinos foram obtidos

nos últimos tempos: o carbono foi o primeiro material utilizado; vidro, quartzo e

sílica foram em seguida aplicados, buscando tirar vantagem de suas propriedades

ópticas translucentes. Alterações interessantes foram também empreendidas no

“design” de tais pinos, o originalmente duplo cilíndro, com formato endodôntico,

para os mais recentes de “double-tapered”, ja que a cimentação adesiva esta

principalmente baseada na formaçao da zona de interdifusão resina-dentina e na

formação de “tags” de resina, em detrimento de uma maior adaptação e de retenção

mecânica do pino dentro do canal radicular (Ferrari et al. 2002). Além disso, a

variedade de tamanhos permite uma maior conservação da dentina radicular que

provavelmente teria que ser removida para buscar uma melhor adaptação do pino. A

quebra da adesão (debonding) esta mais propensa a acontecer na ausência de um

efeito férula, ou na presença de uma camada de cimento muito espessa, onde uma

maior quantidade bolhas incorporadas levam a falha ades

idéia de se ter um pino individualizado que se encaixa justamente no canal radicular

é extremamente interessante, especialmente quando lida-se com canais radiculares

que apresentam formato elíptico, comumente observados em caninos e pré-molares

inferiores. Nestes casos, o clínico é forçado a adaptar a estrutura radicular residual

ao formato do pino, através da remoção de uma determinada quantidade de dentina.

Contrariamente, o ideal seria que o pino se adaptasse à anatomia do canal radicular

produzida após o tratamento endodôntico. Sem dúvida, tal problemática levou ao

desenvolvimento de pinos anatômicos (Boudrias et al. 2001a e 2001b).

Recentemente, o sistema Anatomic Post’n Core (RTD, St Egrève, France) foi

introduzido no mercado (Ferrari et al. 2002). Este novo pino é feito por um DT n. 1

que em seguida é coberto por uma resina fotopolimerizável (Lumiglass, RTD, St

Egrève, France). Tal resina de reembasamento, uma vez introduzida no canal

radicular, permite uma boa adaptação às paredes radiculares, além de reduzir a

166

quantidade de cimento a ser utilizada e estabilizando melhor o pino durante os

procedimentos de cimentação.

O teste final para um procedimento clínico cai sempre em uma minuciosa avaliação

clínica. Muitos estudos relatam o uso de pinos de fibra de vidro para restaurar dentes

tratados endodonticamente (Malferrari et al. 2003, Ferrari et al. 2000a e 2000b,

Fredriksson et al. 1998, Monticelli et al. 2003, Dallari et al. 1998, Scotti et al. 2002).

A grande maioria deles associa o uso de pinos de fibra com a colocação de coroas

metaloceramicas ou em cerâmica pura. Nos últimos anos pode-se observar uma

enorme expansão na indicação de restaurações diretas em resina composta (Hickel et

al. 2004). Adicionalmente, é de grande relevância avaliar a performance de pinos de

fibra quando utilizados em conjunto com restaurações diretas em compósito, sem

cobertura adicional de próteses unitárias. Após 30 meses de avaliação clínica, dentes

tratados endodonticamente, que foram restaurados diretamente com pinos de fibra

de vidro e resina composta não exibiram fraturas radiculares, com resultados

clínicos bastante favoráveis.

Conclusões e recomendações

As seguintes conclusões e recomendações podem ser extraidas a partir de nossas

avaliações clínicas e laboratoriais, quanto a utilização de pinos de fibra em

Odontologia:

1) Pinos de fibra apresentam ótimas propriedades mecânicas, com padrões de fratura

mais conservadores e favoráveis, quando comparados com pinos metálicos.

2) Os procedimentos endodônticos podem influenciar o resultado final da

restauração com pinos. Extremo cuidado deve ser tomado quanto à remoção de

bactérias, debris e outros materiais dentro do canal radicular previamente ao

fechamento completo da estrutura.

3) Pinos de fibra contribuem para o selamento do espaço radicular adjuntamente

com a cimentação adesiva. Por tal razão, tal etapa operatória pode ser considerada

como parte do tratamento endodôntico.

4) Existem diversos tipos de pinos de fibra. A qualidade da adesão entre as fibras e a

resina influenciam a qualidade final de todo o pino, e tal fato deve ser levado em

167

conta quando da seleção de um pino de fibra, juntamente com a composição e o

formato, além das avaliações básicas e experimentais.

ica pura. Suas indicações estão se expandindo

pidamente, e estudos clínicos recentes indicam que podem ser utilizados como

s em resina composta. Através do uso desta técnica,

5) No que concerne aos procedimentos de cimentação, a obtenção de uma adesão

confiável entre o pino de fibra de vidro e o cimento resinoso pode ser conseguida

através da técnica do condicionamento ácido, que deve ser enxaguado com água do

canal radicular meticulosamente, com auxílio de uma agulha endodôntica.

6) Um sistema adesivo de quarta ou quinta geração, aplicado ao canal com auxílio

de um “microbrush”, e um cimento resinoso de polimerização dual são

recomendados quando da utilização de um pino de fibra translúcido.

7) Um pino indvidualizado (Anatomic Post’n Core) pode ser de grande valia em

situações clínicas de grande perda de estrutura coronária, bem como após

tratamentos endodônticos onde nao é possível obter os canais com formato

cilíndrico.

8) Pinos de fibra podem ser seguramente utilizados em conjunto com coroas

metalocerâmicas ou em cerâm

ra

alicerce para restaurações direta

a restauração de dentes tratados endodonticamente pode ser facilitada, e muito

menos custosa.

168

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bonding area. J Dent Res 1993;72: 1434-42.

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masking of various types of opaque posts. J Prosthet

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Adhes Dent 2001; 3: 353-359.

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Amsterdam 2002.

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adhesive systems used for bonding fib

4

Vichi A, Grandini S, Ferrari M. Comparison betw

bonding fibre posts into a root canal: a microscopic investigation. J Endod 2002b;28, 355-60.

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182

A ledgements

cknow

is the

, University of Siena,

nce, and to Prof Marco Ferrari, Pro-Rector for

international affairs and President of Dental School, University of Siena.

I want to express my heartfelt appreciation to Prof Bertelli. He gave me the

possibility to start my adventure in Siena, and always supported my uncertain steps

in my new University.

My sincere gratitude to my promoter Prof Marco Ferrari. He patiently and

continuously reviewed my work, and shared his knowledge with generosity. He has

been my promoter, my professor, my friend. “Give a man a fish, and he survives for

a day. Teach the man to fish, and he will feed himself for life”, he always say, and I

thank him for the fishes and for the fishing!

My deepest thanks to Prof Franklin Tay, my co-promoter. Not only he shared his

awareness with me, but he also “lighted the fire” of research! His knowledge and

friendship have been so precious to me. I find it hard to express my gratitude to him.

I would also like to express my sincere appreciation to the whole Committee, Prof

Carel Davidson, Prof Michel Goldberg, Prof Manuel Toledano, Prof Piero Balleri,

for spending time on reviewing this piece of work and for their precious suggestions,

stimulation and encouragement.

Let me also thank the friends who shared this challenge with me and helped me in so

many ways that they cannot even imagine. Dr Marco Simonetti, my very dear

friend; Dr PierFrancesco Porciani (the wizard of computers!) for unwearyingly

solving all the problems with my laptop, and listening to my other problems as a real

friend; Dr Cecilia Goracci (the queen of statistics!) and all the other PhD candidates

and PhD students that shared this way and worked with me during this period.

A great thank you to Dr Bianca Angelotti, for the secretarial support, and to the

people who helped me with the translation: my mother Vanda (french), Mrs Pamela

Marklew and Mrs Barbara Johnson (german), Dr Maria Carolina Erhardt

(portuguese), Mrs Ornella Raffaelli and Dr Alberto Albalalejo Martinez (spanish).

Th sis is respectfully submitted to Prof Piero Tosi, Rector of the University of

Siena, to Prof Alberto Auteri, Dean of the Faculty of Medicine

to Prof Egidio Bertelli, vice-Dean of the Faculty of Medicine and Director of the

Department of Dental Scie

183

Last but not least I would like to thank my family at large. They supported me

uring this busy period and had to bear my unpredictable humour in the house: I

y life. A

d

love them forever, and I am probably incapable to show how much. My father

Romano (The Professor!): I probably did all I did because I wanted to try to imitate

him, poor me, he is not imitable. He’s a superb clinician, a warm and generous

teacher in the University, and most important of all a respected and honest man. My

mother Vanda: she’s the best mum one could have, and a milestone in m

kiss to my sisters Ilaria and Valentina.

There are too many other people I’d like to thank, who will, I hope, understand my

forgetfulness.

184

CURRICULUM VITAE

Dr. Simone Grandini

Office Via Poliziano, 3

50127 Florence.

Home: Via Guelfa 86

Phones Tel: 055-472895 (office) Fax: 055-474520

055-489789 (home)

e-mail: grandini@unisi.it

simogr@tiscalinet.it

Date and place of birth: Florence, Italy, 22 February 1970

Professional positions

Chair of Restorative Dentistry III, School of Dentistry, University of Siena.

Professional Organizations membership

2004- Academy of Dental Materials

2001 and 2003 International Association for Dental Research

1993- Società Italiana di Odontoiatria Conservatrice (Italian Society of

Restorative Dentistry)

1993- Società Italiana di Odontoiatria e Chirurgia Maxillo-Facciale (SIOCMF)

50129 Florence, Italy

185

List of papers part of this thesis

randini S, Balleri P, Ferrari M. valuation of Glyde File Prep in combination with sodium hypochlorite as root anal irrigant: a scanning electron microscopic study. ournal of Endodontics 2002 Apr;28(4):300-3.

n , Balleri P, Fe M. g lectron microscopic inve rface of post after cutting.

-2.

se of Anatomic post’n for dontically treated tooth: a ase report. ournal of Adhesive Dentistry 2003, vol 5, num. 3, pag. 243-247

cedures of two

randini S, Sapio S, Goracci C, Monticelli F, Ferrari M. l

Monticelli F, Tay F, Ferrari M. tructural characteristics of fiber posts: three-point bending

ental Materials 2004, in press.

, Grandini R, Ferrari M. posts and direct resin crowns for restoring

re

GEcJ Grandi i S rrariScannin e stigation of the suJournal of Endodontics 2002 Aug;28(8):610 Grandini S, Sapio S, Simonetti M. U core reconstructing an endocJ Grandini S, Sapio S, Goracci C, Monticelli F, Ferrari M. SEM evaluation of the cement layer thickness after the luting prodifferent posts. Journal of Adhesive Dentistry 2004, in press. GA one step procedure for uting glass fibre posts: an SEM evaluation International Endodontic Journal 2004, Oct;37(10):679-86. Grandini S, Goracci C, Fatigue resistance and stest and SEM evaluation. D Grandini S, Goracci C, Monticelli F, Tay FClinical evaluation of the use of fiber endodontically-treated teeth. International Journal of Prosthodontics, in press, 2004. Grandini S. The Anatomic post’n coFrom the book: “Fiber posts” Scotti R, Ferrari M. Masson Ed, Milano 2002

186

List of abstracts part of this thesis

F, Ferrari M.

randini S, Ferrari M, Goracci G, Bertelli E. morphology in root canals after shaping and

002, #52, pag B238

chi A.

resin cement. 2

Ferrari M.

any, June 5-8, 2003

ri M. Posts

, B-192

82 (Special Issue B) 2003, #2935, B-376

randini S, Vichi A, Borracchini A, Ferrari M.

Grandini S, Narducci P, Porciani PSEM investigation of the surface of fiber posts after cutting procedures. ADM transactions, 232, vol 15, 2001 GQuantitative evaluation of dentinirrigation of the endodontic space. Journal of Dental Research 81 (special issue B) 2 Grandini S, Ferrari M, Balleri P, ViClinical trial of fiber posts luted with self-curing Excite in combination with an experimentalJournal of Dental Research 81 (special issue A) 2002, #198, pag A5 Grandini S, Balleri P, Goracci C, Monticelli F, Bertelli E,Scanning Electron Microscopic Evaluation of two different techniques for luting glass fiber post Abstract from Conseuro meeting, Munich, Germ Grandini S, Borracchini A, Goracci C, Monticelli F, FerraSEM Study to Compare the Luting Procedures of Two Different FiberJournal of Dental Research 82 (Special Issue B) 2003, #1442 Grandini S, Goracci C, Monticelli F, Tay FR, Ferrari M.Fatigue Resistance of Different Kinds of Fiber Posts Journal of Dental Research GDirect resin restorations with a fiber post: a case report Accepted for IADR meeting, Istambul 2004

187

Complete list of papers Ferrari M, Grandini S. Use of enamel dentinal adhesives systems: clinical implications. (Les adhésifs

) ealités Cliniques 2000.; 11:419-429

iques on bonding to root canal walls: An SEM

ental Materials 2001 Sep;17(5):422-9.

glass-fiber posts.

an SEM investigation.

as root

ournal of Endodontics 2002 Apr;28(4):300-3.

sts into a root anal: a microscopic investigation.

reatment of crown fractures. (Traitement des fractures coronaires) Réalités Cliniques 2002, vol 13, n.1, 17-26. Grandini S, Balleri P, Ferrari M. Scanning electron microscopic investigation of the surface of post after cutting. Journal of Endodontics 2002 Aug;28(8):610-2. Ferrari M, Grandini S, Simonetti M, Monticelli F, Goracci C. Influence of a microbrush on bonding fiber posts into root canals under clinical conditions. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics 2002; 94: 627-631.

amélo-dentinaires: implications pratiquesR Ferrari M, Vichi A, Grandini S. Efficacy of different adhesive technevaluation. D Vichi A, Grandini S, Ferrari M. Clinical procedure for luting Journal of Adhesive Dentistry 2001 Winter;3(4):353-9. Ferrari M, Vichi A, Grandini S, Goracci C. Efficacy of a self-curing adhesive resin cement system on luting glass-fiber posts into root canals:International Journal of Prosthodontics 2001 Nov-Dec;14(6):543-9. Grandini S, Balleri P, Ferrari M. Evaluation of Glyde File Prep in combination with sodium hypochlorite canal irrigant: a scanning electron microscopic study. J Vichi A, Grandini S, Ferrari M. Comparison between two clinical procedures for bonding fiber pocJournal of Endodontics 2002 May;28(5):355-60. Grandini S, Sapio S, Ferrari M. T

188

Vichi A, Grandini S, Davidson CL, Ferrari M. n SEM evaluation of several adhesive systems used for bonding fiber posts under

i S. fluence of microbrush on efficacy of bonding into root canals

Aug;15(4):227-31.

Sapio S, Simonetti M. ucting an endodontically treated tooth: a

ase report. 3, vol 5, num. 3, pag. 243-247

linical behavior of translucent fiber posts and luting and restorative materials: a 2-

Six-Week Study to Evaluate the AnticalculusEfficacy of a Chewing Gum olyphosphate”

nticalculus Efficacy of a Chewing Gum with Polyphosphates in a Twelve-Week

rari M. EM evaluation of the cement layer thickness after the luting procedures of two

oracci C, Ferrari M, Grandini S, Monticelli F, Tay FR. ment to dental hard tissues

onticelli F, Goracci C, Grandini S, Garcìa-Godoy F, Ferrari M. re units built up with

publication in the American Journal of Dentistry 2003

Goracci C, Monticelli F, Ferrari M. one step procedure for luting glass fibre posts: an SEM evaluation ternational Endodontic Journal 2004, Oct;37(10):679-86.

Aclinical conditions. Dental Materials 2002 Nov;18(7):495-502. Ferrari M, Vichi A, Grandini S, GeppInAmerican Journal of Dentistry 2002 Grandini S, Use of Anatomic post’n core for reconstrcJournal of Adhesive Dentistry 200 Monticelli F, Grandini S, Goracci C, Ferrari M. Cyear report. International Journal of Prosthodontics 2003, volume 16, number 6, pag. 593-596 Porciani PF, Grandini S. AContaining Pyrophosphate and TripJournal of Clinical Dentistry 14:11-13, 2003 Porciani PF, Grandini S. ASingle-Blind Trial Journal of Clinical Dentistry 14: 2003 Grandini S, Sapio S, Goracci C, Monticelli F, FerSdifferent posts. Accepted in the Journal of Adhesive Dentistry 2003. GBonding of a self-adhesive resin ceAccepted in the Journal of Adhesive Dentistry 2003 MScanning electron microscopic evaluation of fiber post-resin codifferent resin composite materials Accepted for Grandini S, Sapio S, AIn

189

Grandini S, Goracci C, Monticelli F, Tay F, Ferrari M.

tion. 2004

C, Monticelli F, Yiu C, Huang C, Prati

ives ournal of Dental Research 2004; 83: 459-464.

Fatigue resistance and structural characteristics of fiber posts: three-point bending test and SEM evaluaAccepted for publication in Dental Materials Chersoni S, Suppa P, Grandini S, GoracciC, Breschi L, Ferrari M, Pashley DH, Tay FR. In vivo and in vitro permeability of 1-step self-etch adhesJ

190

Complete list of abstracts Grandini S, Magheri P, De Marco M.

EA. 3 endodontic world congress. Rome, 1995

central incisor. ental trauma. Florence, Italy, 1996.

ag 76 Porciani PF, Magheri P, Grandini S. Multidisciplinary approach to endodontic retreatments. Abstracts from 8th biennial congress european society of endodontology. Goteborg 1997 Porciani PF, Magheri P, Grandini S. Multi-disciplinary management of endodontic retreatments. Abstracts from IFEA fourth endodontic world congress. Jerusalem 1998, pag.1 Fabianelli A, Vichi A, Grandini S, Ferrari M, Davidson CL. Influence of self-etching priming bonding systems on sealing ability of class II restorations: leakage and SEM evaluation. Atti del congresso delle Società Europee di Conservativa (Conseuro 2000), pag 26 Ferrari M, Grandini S, Vichi A, Mannocci F, Lopes B, Fuzzi M. One-bottle and three steps adesive systems used for bonding fiber posts into root canals under clinical conditions: a SEM investigation. Atti del congresso delle Società Europee di Conservativa (Conseuro 2000), pag 27 Porciani PF, Grandini S. Clinical evaluation of a new endo-system: The A.E.T. IFEA, fifth endodontic world congress. Madrid 2001. Porciani PF, Grandini S. A new endodontic system: the A.E.T. A suggested flow chart. The 10th Biennial Congress of the European Society of Endodontology, 4-6 October 2001, Munich Fuzzi M, Grandini S. Clinical application of ceramic bonded restorations. ADM transactions, 51, vol 15, 2001 Lima Mourao R, Reis Hannas A, Grandini S, Ferrari M. Microleakage evaluation of the marginal adaptation of different restorative-adhesive combinations in class II composite restorations. ADM transactions. 167, vol. 15. 2001

The utilization of a new dental dam for endodontics. rdIF

Bertini F, Grandini S, Magheri P. Multidisciplinary aproach in a case of complicated fracture of aAbstract book. IADT. VIIth world congress on dP

191

Fabianelli A, Ferrari M, Dagostin A, Grandini S. perator variability influence on marginal seal of class II resin restorations.

EM investigation of the surface of fiber posts after cutting procedures.

tive evaluation of dentin morphology in root canals after shaping and rigation of the endodontic space.

issue B) 2002, #52, pag B238

study on the efficacy of a self-activating adhesive system used for bonding ber posts into root canal. Journal of Dental Research 81 (special issue B) 2002,

linical trial of Gradia indirect restorations. ag A333

elli E, Dolci G.

urnal of Dental Research 81 (special issue A) 2002, #3486, pag A429

ink luting materials.

Pyrophosphate: a six week

urnal of Dental Research 81 (special issue A) 2002, #2155, pag A276

sin cement. urnal of Dental Research 81 (special issue A) 2002, #198, pag A52

lli E, Ferrari M. of two different techniques for luting

lass fiber post June 2003

OADM transactions, 213, vol 15, 2001 Grandini S, Narducci P, Porciani PF, Ferrari M. SADM transactions, 232, vol 15, 2001 Grandini S, Ferrari M, Goracci G, Bertelli E. QuantitairJournal of Dental Research 81 (special Ferrari M, Grandini S, Fabianelli A, Vichi A. SEM fi#420, pag B282 Fabianelli A, Grandini S, Bertelli E, Ferrari M. CJournal of Dental Research 81 (special issue A) 2002, #2654, p Ferrari M, Cagidiaco MC, Grandini S, BertEffect of concentration on tooth whitening in a highly stained population. Jo Borracchini A, Fabianelli A, Grandini S, Ferrari M. Clinical trial of Empress II, selfcuring Excite and MultilJournal of Dental Research 81 (special issue A) 2002, #2634, pag A331 Porciani PF, Grandini S. Anticalculus efficacy of a chewing-gum containing study. Jo Grandini S, Ferrari M, Balleri P, Vichi A. Clinical trial of fiber posts luted with self-curing Excite in combination with an experimental reJo Grandini S, Balleri P, Goracci C, Monticelli F, BerteScanning Electron Microscopic Evaluation gProceedings of Conseuro meeting, Munich (Germany), 5-8

192

Monticelli F, Goracci C, Balleri P, Grandini S, Ferrari M. Clinical behavior of translucent fiber posts and luting restorative materials: a 2-year

port. ny), 5-8 June 2003

laque accumulation in One day with Four Chewing-gums in the absence of Oral

ransmission Electron Microscopic Evaluation of a Self-adhesive Material Luted to

racchini A, Goracci C, Monticelli F, Ferrari M. EM Study to Compare the Luting Procedures of Two Different Fiber Posts

003, #1442, B-192

ne-year Clinical Trial of Gradia Direct Class II Restorations , B-196

canning Electron Microscopic Evaluation of Fiber Post-Resin Core Unit , #1953, B-254 Journal of

randini S, Goracci C, Monticelli F, Tay FR, Ferrari M. rent Kinds of Fiber Posts

omposite inlays (Les inlays composites) e 169-171

errari M, Grandini S, Pashley DH, Prati C, Tay FR.

DR meeting, Honolulu 2004, Paper #46694

tric observations about the chromatic correspondence of some shade

ccepted for IADR meeting, Istambul 2004

reProceedings of Conseuro meeting, Munich (Germa Porciani PF, Grandini S, Sapio S. PHygiene Journal of Dental Research 82 (Special Issue B) 2003, #1056, B-144 Monticelli F, Grandini S, Goracci C. Ferrari M, Tay FR. TDifferent Dental Substrates. Journal of Dental Research 82 (Special Issue B) 2003, #1439, B-192 Grandini S, BorSJournal of Dental Research 82 (Special Issue B) 2 Fabianelli A, Grandini S, Goracci C, Ferrari M. OJournal of Dental Research 82 (Special Issue B) 2003, #1472 Monticelli F, Goracci C, Grandini S, Bertelli E, Balleri P, Ferrari M. SJournal of Dental Research 82 (Special Issue B) 2003dental Research 82 (Special Issue B) 2003, #1056, B-144 GFatigue Resistance of DiffeJournal of Dental Research 82 (Special Issue B) 2003, #2935, B-376 Ferrari M, Grandini S, Colon P. CAtti del Congresso ADF, Parigi, 2003. pagin Chersoni S, Acquaviva GL, FIn vivo fluid movement through adhesive in post space IA Borracchini A, Vichi A, Grandini S, Goracci C, Ferrari M. Spectrophotomeguides A

193

Goracci C, Sadek F, Grandini S, Vichi A, Borracchini A, Tay FR, Ferrari M.

d for IADR meeting, Istambul 2004

randini S, Vichi A, Borracchini A, Ferrari M. a case report

olor correspondence between Vita Shade guide and three different composite

Push-out bond strength and TEM evaluation of luted fiber posts Accepte GDirect resin restorations with a fiber post: Accepted for IADR meeting, Istambul 2004 Vichi A, Grandini S, Borracchini A, Ferrari M CAccepted for IADR meeting, Istambul 2004

194