UNIVERSITY OF SIENA SCHOOL OF DENTAL MEDICINE

PHD PROGRAM:

“DENTAL MATERIALS AND THEIR CLINICAL APPLICATIONS”

PhD THESIS OF: Michele Vano TITLE A study into the mechanical properties and clinical aspects of fiber posts

Academic Year 2007/08 12 April 2008 Siena, Italy Committee: Promoter Prof. Marco Ferrari

Co-Promoter Dr. Cecilia Goracci

Prof. Piero Balleri

Prof. Lorenzo Breschi

Prof. Carel Davidson

Prof. Raquel Osorio Ruiz

Prof. Manuel Toledano Perez

Dr. Grandini Simone

TITLE A study into the mechanical properties and clinical aspects of fiber posts CANDIDATE Michele Vano

2

CONTENTS Chapter 1 1.1 General Introduction 6 1.2 Fiber post in dentistry: background information 9 1.3 Principles for post placement 11

References

1.4 Superficial treatments: a way to improve bond strength to fiber posts 20

References

1.5 The adhesion between fiber posts and composite resin cores: the evaluation of

microtensile bond strength following various post-surface chemical treatments to

posts 25

References

Chapter 2

2.1 Timing of post space preparation and cementation 49

References

2.2 The effect of immediate versus delayed cementation on the retention of

different types of fiber post in canals obturated using a eugenol sealer 53

References

2.3 Retention of fiber posts cemented at different time intervals in canals obturated

using an epoxy resin sealer 65

3

References

2.4 Endodontic sealer: eugenol versus non-eugenol sealers 84

References

Chapter 3

3.1 Water detrimental effect on fiber-reinforced composite and dental resins 86

References

3.2 Flexural strength of fiber post: the influence of storage condition

and duration 89

References

3.3 The effect of different storage conditions and duration on the fracture strength

of three types of translucent fiber posts 92

References

3.4 The influence of storage condition and duration on the resistance to fracture of

different fiber posts systems 114

References

Chapter 4

4.1 Effects of wear on fiber post morphology 134

References

4.2 Effects of oral environment and occlusal wear on FRC-posts integrity in

clinical service for 5 years 137

4

References

Chapter 5 5.1 Summary 153 5.2 Conclusions 155 5.3 Riassunto e conclusioni 156 5.4 Resumen, conclusiones 160 5.5 Resumé, conclusions 165 5.6 Zusammenfassung, schlussfolgerungen 168 5.7 Sumário, conclusões 171 References Complete list of references 177 Curriculum Vitae 199 Acknowledgements 207

5

Chapter 1

1.1. General Introduction Patients and dentists have been making increasing demands on the aesthetics of

dental restorations used in recent years. Industry has reacted by introducing several

innovative post-and-core systems for restoring nonvital teeth. Endodontically

treated teeth with insufficient coronal tooth structure generally require radicular

posts to assist in restoring the tooth to function (Goodacre and Spolnik, 1994). First

introduced in 1990 (Duret et al., 1990), fiber posts were rapidly accepted by

clinicians (Ferrari et al., 2000 a, b), and provided a viable alternative to cast metal

posts for the restoration of root filled teeth. The major advantage of fiber posts is

their similar elastic modulus to dentine, producing a stress field similar to that of

natural teeth, whereas metal posts exhibit high stress concentrations at the post

dentine interface (Stankiewicz and Wilson, 2002). Clinical studies have

demonstrated high success rates without the occurrence of root fractures (Ferrari et

al., 2000 a,b). Moreover fiber posts are ready to use whereas the construction of a

cast post and core is more time consuming and demands extra clinic and laboratory

time (DeSort,1983).

In order to improve the fracture resistance of endodontically treated teeth restored

with a post-and-core system, research has focused on post materials (Ferrari et al.,

2000), (Sorensen and Engelman, 1990), post designs and luting agents (Ferrari et

al., 2006), (Grandini et al., 2004), (Ferrari et al., 2001). However recently it has

been shown that other factors such as storage condition (Mannocci et al., 2001) and

duration (Chai et al., 2004) may influence the fracture resistance of fiber posts.

Aging in water or aqueous fluids is known to decrease the fracture resistance of

fiber reinforced composites (FRC) materials as a result of water absorption by the

resin matrix and hydrolisis of filler matrix interfaces (Ferracane et al., 2006),

6

(Santos et al., 2002), (Lassila et al., 2002), (Miettinen et al., 1999). In vitro tests

reported that water storage negatively affects the flexural properties of fiber posts

when directly immersed in water (Lassila et al., 2004). The inflow predominantly

occurs in the resinous matrix and depends on the nature of the resin and the amount

of this phase within the material (Fan et al., 1985). This process is generally time

dependent and increases with time until the material is saturated and hydrolytically

stable (Takahashi et al., 2006).

In clinical conditions endodontic posts are cemented into the root canal and their

coronal part is immersed into the composite resin core, therefore fiber posts are

protected from the oral environment and from any water or saliva uptake.

However a recent study reported the presence of water into root canals after

endodontic and prosthodontic procedures (Chersoni et al., 2005). Chersoni et al.,

showed blistering formation on the surface of simplified adhesives when applied on

intra-radicular dentin. The authors speculated that droplets formation occurred due

to residual dentin water that was osmotically soaked by the etching and adhesives

and then retrieved on the adhesive surface due the intrinsic permeability of the

polymerized bonded surface. More recently Ferrari et al., (Ferrrari et al., 2007),

repeated a similar in vivo protocol, the results showed that after etching of the

intra-radicular dentin no water droplets formation occurred on the dentin surface.

The authors concluded that the adhesives themselves are responsible for the

droplets formation, probably due to residual un-evaporated solvent (Van Landuyt et

al., 2005). Therefore once fiber posts are cemented into the root canal of

endodontically treated teeth and their coronal part is immersed into the composite

resin core, no water uptake or outflow is expected from radicular dentin.

However observation of exposed post on a direct restoration is a common finding

(Fredriksson et al., 1998). It is not clear yet whether post exposition to the oral

environment may influence its morphological and mechanical properties.

7

This thesis contains a study into different aspects related to fiber posts, with the

purpose of identifying factors affecting the bond strength between the post, the

resin cement, and radicular dentin as well as selecting the procedures for enhancing

post retention.

In addition this thesis aimed to evaluate in vitro the effects of water aging on the

resistance to fracture of different fiber posts systems and to assess in vivo whether

the exposure to the oral environment and occlusal wear during function affects the

morphological integrity of luted endocanalar fiber posts retaining a direct

composite restoration.

Microtensile bond strength test and push-out test were used to perform mechanical

trials. Stereo and scanning electron microscopy (SEM) were essential to understand

and to show the results obtained. An overview of the literature was provided in

order to present the background information existing on fiber posts.

The first study aimed at evaluating the influence of post-surface treatments on the

microtensile bond strength between fiber posts and different composite resins for

core build-up.

The second study evaluated the effect of immediate versus delayed post

cementation on the retention of different types of fiber post systems in canals

obturated with a eugenol sealer or with an epoxy resin sealer.

In the final part of this thesis two investigations assesed the flexural strength of

different types of fiber posts stored under different conditions including water

aging. Finally an in vivo study provived interesting results on the clinical behaviour

of fiber posts exposed to the oral environment and occlusal function.

8

1.2. Fiber post in dentistry: background information Fiber posts were first introduced by Duret at the beginning of the 90s (Duret et al.,

1990). Fiber posts can be considered as composite reinforced materials in which

the fibers are embedded in a matrix of epoxy-resin or methacrylate-resin, and an

interfacial agent such as silane is used to optimize the link between the two

components. The post is fabricated through a semi-automated industrial process

called pultrusion (Grandini, 2004). The diameter and density of the fibers as well as

the adhesion between them and the matrix, strictly influence the quality of the post

and its mechanical properties. The resinous matrix (epoxy or methacrylate) is

injected into the pre-tensioned fiber bundle to completely fill the spaces between

fibers. As alternative, fibers are simply immersed in a resin bath. Differences in

manufacturing are strictly related to the quality, mechanical and clinical behaviour

of posts (Grandini et al., 2005).

Fiber posts main advantage is the variability of their modulus of elasticity

depending on loading direction: in particular, when considering a transversal

loading, the modulus of elasticity has a value close to sound dentin (Ferrari and

Scotti, 2002). This property reduces stress transmission to root canal walls and thus

the risk of vertical fractures (Asmussen et al., 1999). On the contrary the highly

rigid metal post would transfer lateral forces without distortion to the less rigid

dentin and lead to a higher chance of root fracture (Bateman et al., 2003). In the

event of failure when restored with fiber reinforced posts, teeth are more likely to

be restorable (Cormier et al., 2001, Akkayan et al., 2002).

The failure rate for metal post and fiber posts is different. Studies demonstrated that

metal posts reported a higher failure rate when compared to fiber posts (Ferrari et

al., 2000). The most common failure that can occur with a fiber post, is 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. In the presence of a fiber post, if a root fracture occurs, is usually

located more coronally and is more easily retreatable (Reagan et al., 1999, Ukon et

9

al., 2000, Cormier et al., 2001). On the contary, metallic posts tend to produce an

irreversible root fracture. This type of failure may be due to the wider amount of

tooth structure that must be sacrificed when a metallic post is placed (Stankiewicz

et al., 2002). This concept is valid 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 (Heydecke et al., 2002).

Many commercially available prefabricated posts exist. For example, the axial form

is either tapered or parallel, and the surface can be smooth, serrated with or without

vents, or threaded using taps or self-threading. Caputo and Standlee 1987,

categorize these different design features into three basic combinations: 1) tapered,

serrated or smoothsided, cemented into a post space prepared with a matched-size

post drill; 2) parallel-sided, serrated or smooth-sided, cemented into matched

cylindrical channels prepared by a postdrill; 3) parallel-sided, threaded and inserted

into pretapped channels.

Stainless steel, titanium and titanium alloys, goldplated brass, ceramic and fiber

reinforced polymers have been used as materials for prefabricated posts. However

the carbon fibers were first used for manufacturing posts, representing the first true

alternative to cast metal posts and cores. The ideal post and core material should

have physical properties such as modulus of elasticity, flexural strength and

coefficient of thermal expansion that are similar to those of dentin.

The increased demand for newer products influenced research on posts with the

purpose of saving tooth structure modifying their shape and improving aesthetics.

Translucent quartz and glass fiber post systems recently were introduced as an

alternative to achieve optimal esthetics. These types of posts allow the light to pass

through the post and they can be light-polymerized during cementation (Vichi et

al., 2000) (Ferrari et al., 2001).

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1.3. Principles for post placement

The restoration of endodontically treated teeth frequently poses a challenge for the

clinician. Apart from substantial tissue loss which can be considered as one of the

major obstacles, endodontically treated teeth are assumed to be more prone to

fracture because of desiccation or premature loss of moisture supplied by a vital

pulp (Carter et al., 1983). In cases of severe hard tissue loss, posts are frequently

used as reinforcing elements in the prosthodontic restoration of endodontically

treated teeth. Previously posts were believed to reinforce tooth structure and

strengthen weakened endodontically treated teeth against intraoral forces by

distributing torquing forces within the radicular dentin to supporting tissue along

their roots. Currently, posts are not believed to function as a reinforcing component

of prosthodontic treatment but rather as an element supporting a core foundation

(Lloyd et al., 1993), (Sorensen et al., 1990), (Morgano et al., 1996), (Abou-Rass,

1992). Due to substantial loss of coronal tooth structure, corono-radicular

stabilization is often required, especially in anterior teeth to provide retention and

resistance form for the restoration. Ideal posts should impart minimal stress to the

tooth, provide adequate retention to the core, and be easily removed to permit

endodontic retreatment. Preservation of sound tooth structure is regarded as one of

the the most important aspect in increasing the survival rate of endodontically

treated teeth (Assif et al., 1994), (Guttman, 1992), (Cohen et al., 1996). 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 and Whang, 1985). Many factors affect the fracture resistance and the

failure modes of post-core restorations (Morgano et al.,1999). Among these the

type of tooth and its position in the dental arch. In retrospective clinical reports,

(Tamse A et al., 1999) premolars were found to be the most frequently fractured

teeth.

Many authors have offered guidelines for determining the desired post length. The

longer the post in the canal, the more retentive it is. However, increased post length

11

also increases risk of fracture and perforation of the remaining root (Leary et al.,

1987). It is generally accepted that the apical 3 to 6 mm of guttapercha must be

preserved to maintain the apical seal (Zillich et al., 1984).

The post diameter makes little difference in the retention of the post. An increase in

the post’s width, on the other hand, will increase the risk of root fracture (Caputo

and Standlee, 1987).

In general, the post width should not exceed one-third of the root width at its

narrowest dimension. A minimum of 1 mm of sound dentin should be maintained

circumferentially, especially in the apical area where the root surface usually

becomes narrower and functional stresses are concentrated.

Anterior teeth with a minimal loss of tooth structure can be restored conservatively

(Sorensen and Martinoff, 1984), but if the tooth is planned to receive a crown, a

post is often required. Single-rooted teeth are loaded non-axially and in most cases

the remaining tooth structure is not able to provide adequate resistance and

retention for a crown without a post (Peters et al., 1983). Molars should receive a

cuspal coverage after endodontic treatment but sometimes cast post is not

necessary if the pulp chamber may provide an adequate retention for a core build-

up (Kane and Burgess, 1991). Premolars require post more often than molars:

functional demands and the amount of remaining tooth structure are, once again,

key factors for treatment planning. These aspects were recently confirmed by a 5

years follow-up prospective clinical study, in which the survival rate of cast versus

direct post and core restoration was evaluated revealing that the amount of

remaining dentin height after preparation influenced the longevity of the restoration

(Creugers et al., 2005).

Several investigations reported that fixed prosthodontics continues to be performed

in significant quantities as the final restoration of structurally compromised

endodontically treated teeth. However the possibility of using fiber posts in

12

conjunction with direct composite restorations (without additional crown coverage)

is becoming a reliable alternative, ensuring long-term service (Grandini, 2004).

References 1.1, 1.2, 1.3

Abou-Rass M. Post and core restoration of endodontically treated teeth. Curr Opin

Dent1992;2:99-107.

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

restored with different post systems. J Prosthet Dent 2002;87:431-7.

Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit and strength of

newer types of endodontics posts. J Dent 1999;27:275-78.

Assif D, Gorfil C. Biomechanical considerations in restoring endodontically treated

teeth. J Prosthet Dent 1994;71:565-7.

Bateman G, Ricketts DN, Saunders WP. Fibre-based post systems: a review. Brit

Dent J 2003;195:43-8.

Caputo AA, Standlee JP. Restoration of endodontically involved teeth. In:

Biomechanics in clinical dentistry. Chicago: Quintessence;1987:185-203.

Carter JM, Sorensen SE, Johnson RR, Tietelbaum RL, Levine MS. Punch shear

testing of extracted

vital and endodontically treated teeth. J Biomech 1983;16(10):841-848.

13

Chai J, Takahashi Y, Hisama K, Shimizu H. Water sorption and dimensional

stability of three glass fiber-reinforced-composites. Int J Prosthodont 2004;17:195-

9.

Chersoni S, Acquaviva GL, Prati C, Ferrari M, Pashley DH, Tay FR. In vivo fluid

movement through dentin adhesives in endodontically treated teeth. J Dent Res

2005;84:223-7.

Cohen BI, Pagnillo MK, Condos S, Deutsch AS. Four materials measured for

fracture strength in combination with five designs of endodontic posts. J Prosthet

Dent1996;76:487-95.

Cormier CJ, Burns DR, Moon P. In vitro comparison of the fracture resistances and

failure mode of fiber, ceramic and conventional post systems at various stages of

restoration. J Prosthod 2001;10:26-36.

Creugers NH, Mentink AG, Fokkinga WA, Kreulen CM. 5-year follow-up of a

prospective clinical study on various types of core restorations. Int J Prosthod

2005;18:34-9.

Duret B, Reynaud M, Duret F. Un noveau concept de reconstitution

coronoradiculaire : le Composipost 1º. Le Chir Dent de France 1990a ;540:131-41.

Fan PL, Edahl A, Leung RL, Stanford JW. Alternative interpretations of water

sorption values of composite resins. J Dent Res 1985;64:78–80.

Ferracane L. Hygroscopic and hydrolytic effects in dental polymer networks. Dent

Mater 2006;22:211-222.

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Ferrari M, Coniglio I, Magni E, Cagidiaco MC, Gallina G, Prati C, Breschi L. How

can droplets formation occur in endodontically treated teeth during bonding

procedures? J Adhes Dent, In press.

Ferrari M, Goracci C, Sadek FT, Monticelli F, Tay FR. An investigation of the

interfacial strengths of methacrylate resin-based glass fiber post-core buildups. J

Adhes Dent 2006;8:239-45.

Ferrari M, Scotti R. Fiber post: Characteristics and clinical applications. Masson

Ed, Milano, 2002.

Ferrari M, Vichi A, Garcia-Godoy F. Clinical evaluation of fiber reinforced epoxy

resin posts and cast post and cores. Am J Dent 2000;13:8B-15B.

Ferrari M, Vichi A, Grandini S. Efficacy of different adhesive techniques on

bonding to root canal walls: an SEM investigation. Dent Mater 2001;17:422-9.

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: an SEM investigation.

Int J Prosthodont 2001;14:543-9.

Fredriksson M, Astback J, Pamenius M. A retrospective study on 236 patients with

teeth restored by carbon fiber-reinforced epoxy resin posts. J Prosthet Dent

1998;80:151-7.

Grandini S. Basic and clinical aspects of selection and application of fiber posts.

PhD Thesis 2004: pp 16-8.

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

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

Mater 2005;21(2):75-82.

Grandini S, Sapio S, Goracci C, Monticelli F, Ferrari M. A one step procedure for

luting glass fibre posts: an SEM evaluation. Int Endod J 2004;37:679-86.

Goodacre CJ, Spolnik KJ. The prosthodontic management of endodontically

treated teeth: a literature review. Part I. Success and failure data, treatment

concepts. J Prosthod 1994;3:243-50.

Gutmann JL. The dentin-root complex: anatomic and biologic considerations in

restoring endodontically treated teeth. J Prosthet Dent 1992;67:458-67.

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, Peters MC. The restoration of endodontically treated, single-rooted

teeth with cast or direct posts and cores: A systematic review. J Prosthet Dent

2002;87:380-6.

Kane JJ, Burgess JO. Modification of the resistance form of amalgam coronal-

radicular restorations. J Prosthet Dent 1991;65:470-4.

Lassila LV, Nohrstrom T, Vallittu PK. The influence of short-term water storage

on the flexural properties of unidirectional glass fiber-reinforced composites.

Biomaterials 2002;23:2221–9.

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Lassila LVJ, Tanner J, Le Bell AM, Narva K, Vallittu PK. Flexural properties of

fiber reinforced root canal posts. Dent Mater 2004;20:29-36.

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

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

Lloyd PM, Palik JF. The philosophies of dowel diameter preparation: a literature

review. J Prosthet Dent 1993;69:32-6.

Mannocci F, Sherriff M, Watson TF. Three-point bending test of fiber posts. J

Endod 2001;27:758-61.

Mattison GD. Photoelastic stress analysis of cast-gold endodontic posts. J Prosthet

Dent 1982;48:407-11.

Miettinen VM, Narva KK, Vallittu PK. Water sorption, solubility and effect of

post-curing of glass fibre reinforced polymers. Biomaterials 1999;20:1187–1194.

Morgano SM. Restoration of pulpless teeth: application of traditional principles in

present and future contexts. J Prosthet Dent 1996;75:375-80.

Morgano SM, Brackett SE. Foundation restorations in fixed prosthodontics: current

knowledge and future needs. J Prosthet Dent 1999;82: 643-57.

Peters MC, Poort HV, Farah JW, Craig RG. Stress analysis of a tooth restored with

a post and core. J Dent Res 1983;62:760-3.

Pilo R, Corcino G, Tamse A. Residual dentin thickness in mandibular premolars

prepared with hand and rotary instruments. J Endod 1998; 24: 401-4.

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Pilo R, Tamse A. Residual dentin thickness in mandibular premolars prepared with

gates glidden and ParaPost drills. J Prosthet Dent 2000; 8: 617-23.

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.

Santos C, Clarke RL, Braden M, Guitian F, Davy KWM. Water absorption

characteristics of dental composites incorporating hydroxyapatite filler.

Biomaterials 2002;23:1897–1904.

Sorensen JA, Engelman MJ. Effect of post adaptation on fracture resistance of

endodontically treated teeth. J Prosthet Dent 1990;64:419-24.

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

study of endodontically treated teeth. J Prosthet Dent 1984; 51:780-4.

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

2002; 35:575-81.

Takahashi Y, Chai J, Tan SC. Effect of water storage on the impact strength of

three glass fiber-reinforced composites. Dent Mater 2006;22:291-7.

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

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

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.

18

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.

Van Landuyt KL, De Munck J, Snauwaer J, Coutinho E, Poitevin A, Yoshida Y,

Inoue S, Peumans M, Suzuki K, Lambrecths P, Van Meerbeek B. Monomer-

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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.

Zillich RM, Corcoran JF. Average maximum post lengths in endodontically treated

teeth. J Prosthet Dent 1984;52:489-91.

19

1.4. Superficial treatments: a way to improve bond strength to fiber posts

The quality of the bond between the post and the dentin both at the coronal and

radicular level is of uttermost importance for post retention (Ferrari et al., 2001)

(Ngoh et al., 2001) (Ari et al., 2003). Since the introduction of fiber posts, a

continuous effort has been made to improve bonding inside the root canal, however

radicular dentin still offers less favourable conditions for bonding than coronal

dentin (Ferrari et al., 2002) (O’Keefe and Powers, 2001).

The most frequent cause of adhesive failure is debonding of post restoration at the

resin cement/dentin interface (Ferrari et al., 2000a) (Ferrari et al., 2000b). The

weakest point of the restoration, is represented by the adhesion into the root canal.

Nonetheless also the post/composite adhesion has to be considered, in fact, the

restoration has to resist to the stresses transmitted during core trimming to adapt the

provisional crown (Goracci et al., 2005).

At the post-core interfacial level, only the chemical interaction between the fiber

post surface and the resin composite may ensure the bond of the core material

around the post.

Surface treatments are common methods to improve the general adhesion

properties of a material, by facilitating chemical and micromechanical retention

between different constituents. Surface conditioning techniques are used for natural

substrates (i.e. dentine) (Nakabayashi, 1982) (Nakabayashi et al., 1991) and

restorative materials (i.e. ceramics) (Horn, 1983). In fact the use of acids to

condition the surfaces or to partially dissolve the substrate generate a rough surface

that enhance adhesion (Hayakawa et al., 1992).

With respect to post/core restorations, most studies were designed to improve the

performances of these restorations acting on the mechanical properties of the

composite core build-up materials (Combe et al., 1999) (Chutian et al., 2004). In

20

other scientific fields many chemical treatment techniques have been introduced to

improve the adhesion between the components of fiber reinforced resin composites

(Cheng et al., 1993) (Crasa et al., 1999) (Roizard et al., 2002). A similar approach

may be applied in dentistry for surface pre-treatment of fiber posts to increase their

post-core bond strength. Hydrofluoric acid in combination with a silane coupling

agent is often employed to enhance the bond strength between composite resins

and feldspathic ceramics (Aida et al., 1995), (Chen et al., 1998), (Ozcan and

Vallitu, 2003). Silanes are also used for coupling the glass filler particles or the

glass fibers with the embedding matrix in composite and fibre-reinforced resins

respectively (Ishida, 1985), (Iglesias et al., 2002). Silane coupling agents are able

to chemically bridge resins and OH-covered inorganic substrates (Plueddemann,

1991). Although the clear benefit of silane coating in enhancing post-core bond

strength, it still remains a weak bond. Treating the post surface with a silane

coupling agent is advisable for enhancing adhesion (Aksornmuang et al., 2004)

(Goracci et al., 2005).

Post surface pre-treatment with hydrogen peroxide has been shown to significantly

increase the bond strength between fiber posts and flowable materials used for core

build-up (Monticelli et al., 2005). Recently other investigations showed that

retentive post bond strengths were significantly enhanced with hydrofluoric acid or

hydrogen peroxide post surface pretreatments (D’acangelo et al., 2006) (Yenisey

and Kulunk, 2008).

The following study aimed at evaluating the influence of post surface treatment

with hydrofluoric acid or hydrogen peroxide on the microtensile bond strength

between glass fiber posts containing methacrylate resin and different composite

resins for core build-up.

21

References 1.4.

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Aida M, Hayakawa T, Mizukawa K Adhesion of composite to porcelain with

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Ari H, Yasar E, Belli S. Effects of NaOCl on bond strength of resin cement to root

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Chen JH, Matsumura H, Atsuta M (Effect of etchant, etching period and silane

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Cheng TH, Jones FR, Wang D. Effect of fibre conditioning on the interfacial shear

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Chutian S, Platt JA, Cochran MA, More BK. Volumetric dimensional changes of

six direct core materials. Dent Mater 2004;20:345-51.

Combe EC, Shaglouf A-MS, Watts DC, Wilson NHF. Mechanical properties of

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Crasa JJ, Rowe-Tattib CA, Nivensb DA, Ligler FS. Comparison of chemical

cleaning methods of glass preparation for silanization. Bios Bioelectr 1999;14:683-

8.

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D'Arcangelo C, D'Amario M, Prosperi GD, Cinelli M, Giannoni M, Caputi S.

Effect of surface treatments on tensile bond strength and on morphology of quartz-

fiber posts. J Prosthet Dent 2006;95(3):218-23.

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

Surg, Oral Med, Oral Path, Oral Rad and Endod 2002;94:627-31.

Ferrari M, Mannocci F, Vichi A, Cagidiaco MC, Mjör IA. Bonding to root canal:

structural characteristics of the substrate. Am J Dent 2000;13:255-60.

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:

9B-13B.

Ferrari M, Vichi A, Grandini S. Efficacy of different adhesive techniques on

bonding to root canal walls: an SEM investigation. Dent Mater 2001;17:422-9.

Ferrari M, Vichi A, Mannocci F, Mason PN. Retrospective study of clinical

behaviour of several types of fiber posts. Am J Dent 2000b; 13:14B-19B.

Goracci C, Raffaelli O, Monticelli F, Balleri P, Bertelli E, Ferrari M. The Adhesion

between fiber posts and composite resin cores: microtensile bond strength with and

without post silanization. Dent Mater 2005;12:437-44.

Hayakawa T, Horie K, Aida M, Kanaya H, Kobayashi T, Murata Y. The influence

of surface conditions and silane agents on the bond of resin to dental porcelain.

Dent Mater 1992;8:238-40.

23

Horn HR. Porcelain laminate veneers bonded to etched enamel. In; Phillips RW,

editor. Symposium on Dental Materials. Dent Clin of North Amer 1983;27:671-84.

Monticelli F, Toledano M, Tay FR, Cury AH, Goracci C, Ferrari M.

Post surface conditioning improves interfacial adhesion in post/core restorations.

Dent Mater 2006;22(7):602-9.

Nakabayashi N. Resin reinforced dentin due to infiltration of monomers into

dentine at the adhesive interface. Jpn J Dent Mater 1982;1:78-81.

Ngoh EC, Pashley DH, Loushine RJ, Weller N, Kimbrough F. Effect of eugenol on

resin bond strengths to root canal dentin. J Endod 2001;27:411-4.

O’Keefe KL, Powers JM. Adhesion of resin composite core materials to dentin. Int

J Prosthod 2001; 14:451-6.

Ozcan M, Vallitu PK Effect of surface conditioning methods on the bond strength

of luting cement to ceramics. Dent Mater 2003;19:725-31.

Roizard X, Wery M, Kirmann J. Effects of alkaline etching on the surface

roughness of a fibre-reinforced epoxy composite. Comp Struct 2002;56:223-8.

Plueddemann EP. Silane coupling agents. New York: Plenum Press; 1991.

Yenisey M, Kulunk S. Effects of chemical surface treatments of quartz and glass

fiber posts on the retention of a composite resin. J Prosthet Dent 2008;99(1):38-45.

24

1.5. The adhesion between fibre posts and composite resin cores: the

evaluation of microtensile bond strength following various post-surface

chemical treatments to posts

Michele Vano, Cecilia Goracci, Francesca Monticelli, Francesco Tognini, Mario

Gabriele, Franklin R. Tay, Marco Ferrari. International Endodontic Journal

2006;39(1):31-9.

Introduction

The restoration of root filled teeth often requires the placement of a post to ensure

adequate retention of the core (Gutmann 1992). First introduced in 1990 (Duret et

al. 1990), fibre posts were rapidly accepted by clinicians (Ferrari et al. 2000), and

provided a viable alternative to cast metal posts for the restoration of root filled

teeth. The major advantage of fibre posts is their similar elastic modulus to dentin,

producing a stress field similar to that of natural teeth, whereas metal posts exhibit

high stress concentrations at the post-dentin interface (Pegoretti et al. 2002).

Clinical studies have demonstrated high success rates without the occurence of root

fractures (Ferrari et al. 2000). Moreover fibre posts are ready to use whereas the

construction of a post core casting is more time consuming and demands extra

clinic and laboratory time (DeSort 1983).

In vivo data have shown that the establishment of reliable bonds at the root-post-

core interfaces are critical for the clinical success of a post-retained restoration

(Monticelli et al. 2003). It has also been demonstrated that parameters such as post

length, shape, and post surface characteristics influence post retention (Schwartz &

Robbins 2004).

25

In order to improve the bond strength between the post and the resin cement, many

surface pre-treatment procedures for posts have been investigated that involve the

use of mechanical (Kern & Thompson 1994, Sahafi et al. 2003) or chemical agents

(Kern & Wegner 1998, Yangida et al. 2001). Chemical treatment is aimed at

roughening the post surface, thus enhancing the mechanical interlocking between

post and resin cement (Wolf et al. 1993). In a recent in vitro study, post surface

pre-treatment with hydrogen peroxide has been shown to significantly increase the

bond strength between fibre posts and flowable materials used for core build-up

(Monticelli et al. 2005).

Hydrofluoric acid in combination with a silane coupling agent is often employed to

enhance the bond strength between composite resins and feldspathic ceramics

(Hayakawa et al. 1992, Aida et al. 1995, Chen et al. 1998, Ozcan & Vallitu 2003).

Silanes are also used for coupling the glass filler particles or the glass fibres with

the embedding matrix in composite and fibre-reinforced resins respectively (Ishida

1985, Iglesias et al. 2002). Silane coupling agents are able to chemically bridge

resins and OH-covered inorganic substrates. At the fibre post-composite core

interface, chemical coupling is only possible between the resin of the core material

and the exposed glass fibres of the post (Ferrari & Scotti 2002, Aksornmuang et al.

2004, Goracci et al. 2005). Due to the difference in chemistry, no bonding is

expected to occur between the methacrylate based resin of the core and the epoxy

resin of the fibre post matrix (Monticelli et al. 2005).

Several materials have been used for core build-ups that differ in their mechanical

properties, viscosities and setting reactions (Combe et al. 1999). In a recent

microscopic study (Monticelli et al. 2005), flowable composites achieved structural

homogeneity and continuity with the post surface that were superior to hybrid

composites. However, the latter materials are expected to provide higher

mechanical properties than the lightly filled flowable composites. Also, several

composite resins specifically formulated for abutment build-up are currently

available in the market.

26

Previous studies (Goracci et al. 2005, Monticelli et al. 2005) have shown that

hydrogen peroxide is able to dissolve the epoxy resin matrix, breaking epoxy resin

bonds and exposing the fibres surface to silanisation. This method of pre-treatment

was found to be effective for enhancing the retention between epoxy resin-based,

conventional fibre post systems and core materials (Monticelli et al. 2005).

However, little is known of the physical and chemical effects of hydrogen peroxide

on methacrylate-based resin fibre post systems.

The present study was aimed at evaluating the influence of post surface treatment

with hydrofluoric acid or hydrogen peroxide on the microtensile bond strength

between glass fibre posts containing methacrylate resin and different composite

resins for core build-up. The changes in post surface characteristics following the

different pre-treatments were also observed using scanning electron microscopy

(SEM). The tested null hypotheses were: 1) the microscopic aspect of the post

surface and the post-core strength are not affected by different post surface pre-

treatments; 2) the type of resin composite used for core build-up has no influence

on the post-core interfacial strength.

Materials and methods

One hundred and ten translucent glass fibre posts (GC Corporation, Tokyo, Japan)

with a maximum diameter of 1.6 mm were used in the study. They are made of

unidirectional glass fibres (77% vol) bound in a methacrylate resin matrix (23%

vol). Posts were randomly picked from their boxes and divided into five groups of

22 each, depending on the post surface pre-treatment to be performed. These pre-

treatments include: immersion in 24% hydrogen peroxide for 10 min at room

temperature and silanisation for 60 s (Group 1); immersion in 10% hydrogen

peroxide for 20 min at room temperature and silanisation for 60 s (Group 2);

immersion in 4% hydrofluoric acid gel (Porcelain Etchant, Bisco, Schaumburg, IL,

USA) for 60 s and silanisation for 60 s (Group 3); silanisation of the post surface

for 60 s and application of the bonding agent G-Bond (GC Corp.) (Group 4);

27

silanisation of the post surface for 60 s only (Group 5, control group). After the

application of hydrogen peroxide or hydrofluoric acid, all the posts were rinsed

with water and air-dried. The silane coupling agent (Monobond-S, Ivoclar-

Vivadent, Schaan, Liechtenstein) was applied in a single layer with a brush on the

post surface, and left to air-dry for 60 s at room temperature. The chemical

composition and batch numbers of the tested materials are reported in Table 1.

SEM Analysis

Two posts were randomly selected with the flip of a coin from each group for SEM

examination of the superficial aspect of the post following surface pre-treatment. In

each group one post was observed longitudinally, while the other one was cross-

sectioned by means of a water-cooled diamond blade (Isomet 1000, Buehler, Lake

Bluff, IL, USA). All the posts were sonicated for 5 min in deionised water (CP104,

CEIA Int., Rassy CDG, France), immersed in 96% ethanol, and gently air-dried.

Each post was mounted on a metallic stub, gold-sputtered (Polaron Range SC7620,

Quorum Technology, Newhaven, UK), and observed under a JSM 6060 LV

microscope (JEOL, Tokyo, Japan) at different magnifications (200X, 1000X).

Core build-up and microtensile test procedures

The materials used for core build-up were: two flowable composites UniFil Flow

(subgroup A) and UniFil Lo Flo Plus (subgroup B), the hybrid composite Gradia

Direct (subgroup C), and the core material UniFil Core (subgroup D). These

materials were handled according to the instructions supplied by the manufacturer

(GC Corp.).

For the core build-up procedure, each post was positioned upright on a glass slab,

and secured with a drop of sticky wax. A cylindrical plastic matrix was then placed

around the post and adjusted so that the post would be exactly in the middle. The

matrix was 10 mm in diameter and the length was equal to the non-tapered portion

of the post. For an easier calculation of the bonding surface in microtensile

28

specimens, it is desirable that the post diameter be constant throughout the post

length (Goracci et al. 2005).

The light-activated composites were applied to the post in 1-2 mm thick

increments. Each increment was carefully placed onto the post surface, and light-

cured separately for 40 secs according to the manufacturer’s instructions, using a

halogen light curing unit with an output of 600 mW/cm2 (VIP, Bisco, Schaumburg,

IL, USA). The composite was always irradiated directly from the open upper side

of the matrix and through the post. Irradiation was never performed through the

plastic matrix. Once the matrix was completely filled, the composite cylinder was

detached from the glass slab. An additional 40 s irradiation was then performed

from the bottom of the cylinder prior to the removal of the matrix, to ensure

optimal polymerisation of the core material.

The sectioning and loading of the specimens began on completion of the core

build-up procedure, in order to simulate the clinical situation of immediate loading

following core build-ups. Each composite cylinder was secured on an Isomet

cutting machine for sectioning (Buehler). Two longitudinal cuts were initially made

with the water cooled diamond blade along the two opposite sides of the post at its

outermost periphery. This sectioning produced a rectangular slab of uniform

thickness, with the post in the centre and the core build-up composite on either

side. Each slab was subsequently sectioned into 1-mm thick sticks for microtensile

bond testing (Fig.1).

Each stick was secured with cyanoacrylate adhesive (Zapit, Dental Ventures of

America, CA, USA) to the two free sliding components of a jig, that was mounted

on a universal testing machine (Controls, Milan, Italy). The stick was loaded in

tension at a cross-head speed of 0.5 mm/min,

until failure occurred at either side of the post-composite interface. Bond strength

was expressed in MegaPascals (MPa), by dividing the load at failure by the

bonding surface area. As the bonded interface was curved, its area was calculated

using a mathematical formula previously applied by Bouillaguet et al. (2003).

29

Statistical analysis of the microtensile bond strength data

After analysing the bond strength data for the normality of data distribution

(Kolmogorov-Smirnov test) and homogeneity in variances (Levene’s test), a two-

way ANOVA was applied with bond strength as the dependent variable, and the

types of surface pre-treatment and core material as factors. The Tukey test was

used for post-hoc multiple comparisons of surface pre-treatments and core

materials. In all the tests, the level of significance was set at α=0.05, and

calculations were handled by the SPSS 11.0 software (SPSS Inc, Chicago, IL,

USA).

Results

Microtensile bond strength test

The means and standard deviations of the bond strengths for the five experimental

and control groups are shown in Table 2. Statistical analysis revealed that both the

post-surface treatment procedure and the type of composite resin used for core

build-up had significant influence on microtensile bond strength (p<0.05). More

precisely, the post-core strengths achieved following the two variants of hydrogen

peroxide pre-treatment (Groups 1 and 2) were comparable and significantly higher

than those of Groups 3, 4 and 5 in which the post surface had been treated with 4%

hydrofluoric acid/silane, silane/bonding agent and silane (control group)

respectively. In the control group (Group 5), the lowest post-core strength was

achieved, and the difference was statistically significant (p<0.05).

In Groups 1 and 2, the post-core bond strengths were similar regardless of the

composite resin used for the core build-up (Table 2). Conversely, core material was

a significant factor in Groups 3, 4 and 5 with UniFil Core recording the highest

bond strengths (p<0.05). In addition the difference between Gradia and UniFil

Flow was significant (p<0.05) in Groups 4 and 5 (Table 2).

30

SEM Analysis

SEM evaluation revealed that the post surface morphology was modified following

treatment with hydrogen peroxide and hydrofluoric acid. The two variants of

treatment with hydrogen peroxide produced similar changes in the ultrastructure of

the post surface. At a lower magnification (Fig. 2a, 3a), a uniform distribution of

micro-spaces was evident among the exposed fibres. As a result, a rough surface

along the whole post length was created. Exposed fibres did not appear to be

damaged by the action of hydrogen peroxide and no defects or fractures were

evident on their surfaces (Fig. 2b, 3b). The cross-sections revealed a significant

exposure of the superficial fibres due to resin matrix removal, especially following

24% hydrogen peroxide-10 min treatment (Fig. 2c, 3c). However, the resin matrix

was retained in the spaces among the inner fibres.

Treatment with 4% hydrofluoric acid had a greater impact on the post structure.

The resin matrix was removed more extensively and to a greater depth (Fig. 4a).

Some fibres appeared to be thinner (Fig. 4a, 4c), and damaged (Fig. 4b). Cross-

sections of the posts revealed that the outermost glass fibres were deprived of their

resin embedding to a greater extent (Fig. 4c).

Discussion

The bond strengths of different composite resins to translucent glass fibre posts

were affected by both the core material and by the type of post surface pre-

treatment. Moreover, SEM revealed that the post pre-treatments under investigation

had an impact on post surface characteristics. Thus, the null hypotheses tested in

this study can be rejected.

Hydrogen peroxide was found to be the most effective treatment with respect to

post-core bond strength. In fact, either concentration of hydrogen peroxide

significantly enhanced the interfacial bond strength between fibre posts and core

materials (p<0.05). These data are in agreement with the results of previous

microtensile tests by Monticelli et al. (2005). In particular, post-core bond strengths

31

in Group 1 and 2 were very similar, regardless of the material used for core build-

up (Table 2).

Interestingly, the flowable composites groups benefited the most from post surface

pre-treatment with hydrogen peroxide. It can be speculate that because of their low

viscosity, the flowable composites were able to penetrate optimally within the post

surface irregularities, taking the greatest advantage of the increase in surface area

available for bonding following post surface pre-treatment. This enabled the

flowable composites to achieve a bond with the post that was as solid as that

established by intrinsically stronger composites, such as Gradia Direct and UniFil

Core (Graph 1).

The depths of the resin removed from the matrices of the fibre posts were similar

for the two concentrations of hydrogen peroxide (Fig 2c, 3c). Post-core bond

strengths were also increased as a result of post treatment with 4% hydrofluoric

acid, though to a lesser extent than following post immersion in hydrogen peroxide.

One conceivable explanation for these results could be that hydrofluoric acid

selectively dissolves the glass component of the fibre post, producing an irregular

pattern of microspaces on the post surface (Fig. 4a, 4b). This may increase the

surface area and facilitate the penetration of the composite, especially the flowable

resins, into the microretention of the etched post surface. Hydrofluoric acid etching

has been found to improve the bond strength between resin and conventional

silicate-based ceramics (Stangel et al. 1987, Wolf et al. 1993). However, this study,

in agreement with a previous report (Dallari & Mason 2004), showed that

hydrofluoric acid alters the post structure more radically. Conversely, for hydrogen

peroxide pre-treatment, SEM analysis revealed a differential removal of the resin

matrix instead of the glass fibre component, leaving denuded, intact fibres that

appeared undamaged.

This study also evaluated the use of a single-component silane coupling agent with

and without a bonding agent. The results clearly showed that in the absence of

surface modification of the post surface, the adjunctive use of an adhesive only

32

produced limited improvement in the coupling of resin composites to even

methacrylate resin-based fibre posts. Silane coupling agents mainly exert their

function by bonding chemically to the posts and core material and improving

surface wettability (Plueddemann 1991). Following the manufacturer’s

specifications, the silane was applied in a single layer. According to the results of a

recent in vitro study, the formation of a multi-layer structure may result in a

reduction of the effectiveness of silane coupling, since the number of free

methacrylate groups is reduced, and cohesive failure within the silane coating may

occur (Debnath et al. 2003). The low bond strength values obtained for Group 4

and 5 may be due to the absence of free radicals in the pre-polymerised post that is

performed under heat and vacuum by the manufacturer. As an oxygen inhibition

layer is absent, the bonding is poor.

The method utilised for bond strength testing was the microtensile bond test that

has been reported to be suitable for the evaluation of interfacial bond strengths on

areas below 1 mm2 (Pashley et al. 1999). In particular, the non-trimming variant of

the technique was adopted to reduce the number of premature failures during

specimen preparation, in comparison with the “more aggressive” trimming variant

of the microtensile bond test (Goracci et al. 2004).

However this experimental technique has some limitations: The data of this in vitro

study does not give an exact prediction whether the in vitro performance of the

fibre posts is the same as the performance in vivo. Only one type of fibre post was

tested in this study. It would be of interest to analyse other types of posts and to

compare their performances. In this in vitro study the pre-treatment of the post was

immediately followed by the application of the resin composite for the core build-

up. Further in vitro and in vivo studies are necessary to evaluate whether the

positive effect on post-core bond strength is still retained by pre-treating the post

surface well in advance of the clinical use. Evaluation of such a strategy will enable

manufacturers to supply pretreated fibre posts in pre-sealed sachets, as well as

saving clinicians valuable chair-time.

33

Conclusions

Surface treatment of post with hydrogen peroxide and silane application or

hydrofluoric acid and silane application significantly enhances the interfacial bond

strength between fibre posts and core materials. Post pre-treatment with 24%

hydrogen peroxide for 10 min appears to be as an easy, effective and inexpensive

method that can improve the clinical performance of methacrylate resin-based glass

fibre posts.

34

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39

Table 1. List of investigated materials

Material Batch

number Composition Manufacturer

Post GC fibre post

100602061 Glass fibres (77% vol), methacrylate resin matrix (23% vol)

GC Corporation, Tokyo, Japan

Core material

UniFil Flow

0309101 Di-2-Methacryloyloxyethyl, 2,2,4-trimethylhexamethylene dicarbamate, Triethylene glycol dimethacrylate, Fluoro-alumino silicate glass (50- 60%), Silica powder 10-15%

GC Corporation, Tokyo, Japan

UniFil Lo Flo Plus

0405131 Urethane dimethacrylate, Triethylene glycol dimethacrylate, Fluoro-alumino silicate glass (30-40%), Silica powder 5-10% , Camphorquinone

GC Corporation, Tokyo, Japan

Gradia Direct

0305151 Urethane dimethacrylate, Dimethacrylate comonomers, silica, Prepolymerised filler, pigments, catalysts

GC Corporation, Tokyo, Japan

UniFil Core

0310162 Urethane dimethacrylate, Dimethacrylate, photo/chemical initiator, Fluoro-amino silicate glass

GC Corporation, Tokyo, Japan

Surface treatment

Monobond S

E26882 1% wt 3-methacryloxypropyltrimethoxysilane (3-MPS), ethanol/water-based solvent

Ivoclar-Vivadent, Schaan, Liechtenstein

Porcelain Etchant

0300012353 4% Hydrofluoric acid gel Bisco, Schaumburg, IL, USA

Hydrogen peroxide

073196 24% Hydrogen peroxide Sella, Schio, Italy

40

Material Batch number

Composition Manufacturer

24% Hydrogen peroxide 10%

12 10% Hydrogen peroxide Nova Argentia, Milano, Italy

G-Bond

0411221

4-methacryloyl-oxyethyl trimelliate Monomer, Phosphoric Acid Ester Monomer

GC Corporation, Tokyo, Japan

41

Table 2. Mean and standard deviation (in parenthesis) of post-core strength

calculated for all the experimental groups.

Post surface treatment (MPa) Core

material Silane

for 60

seconds

Silane for

60 seconds

+

G-Bond

24% H2O2

for 10

minutes

+ Silane

for 60

seconds

10% H2O2

for 20

minutes

+ Silane

for 60

seconds

4%

Hydrofluoric

acid gel for 60

seconds +

Silane for 60

seconds

UniFil

Flow

5.02

(0.95)

6.04

(2.06)

13.75

(3.20)

13.44

(2.26)

8.55

(3.26)

UniFil Lo

Flo Plus

5.88

(1.13)

6.37

(2.01)

14.93

(3.03)

13.82

(3.32)

9.66

(2.94)

Gradia Direct

7.07 (1.2)

7.48 (2.41)

14.54 (3.36)

13.62 (3.38)

10.96 (3.21)

UniFil Core

8.29 (1.79)

8.53 (2.95)

15.35 (3.37)

14.49 (3.22)

12.78 (2.63)

42

Legends to Figures.

Fig 1. A schematic of the sectioning procedure. One mm thick sticks were serially

cut from the slab (C=core, P=post).

Fig 2. SEM images of the post surface after treatment with 24% hydrogen peroxide

for 10 min (Fig. 2a) (200X bar = 100 µm), (Fig. 2b) (1000X, bar = 10 µm). Cross

section of the post (Fig. 2c) (1000X, bar = 10 µm).

43

44

Fig 3. Representative SEM micrographs of the post surface treated with 10%

hydrogen peroxide for 20 min: (Fig. 3a) (200X, bar =100 µm), (Fig. 3b) (1000X,

bar = 10 µm). Cross-section of the post (Fig. 3c) (1000X, bar = 10 µm).

45

46

Fig 4. SEM images of the post surface after treatment with 4% hydrofluoric acid

gel for 60 s: (Fig. 4a) (200X bar = 100 µm), (Fig. 4b) (1000X, bar = 10 µm). Cross

section of the post (Fig. 4c) (1000X, bar = 10 µm).

47

48

Chapter 2

2.1. Timing of post space preparation and cementation

Many factors can possibly interfere with the development of high bond strength

values between an endodontic post and root canal dentin. Among these the timing

of post preparation and cementation plays an important role (Ewart and Saunders,

1990). There is no consensus on the time interval between the endodontic treatment

and the post preparation. Posts can be placed immediately after completion of the

endodontic treatment or at a later stage after full setting of the sealer. Immediate

post space preparation and cementation is less time consuming (Galen and Mueller,

1998) (Saunders et al.,1991). In addition dye leakage studies reported less apical

leakage when immediate post space preparation was performed (Solano et al.,

2005).

To properly cement a fiber post, is necessary to remove the sealer impregnated

dentin from the canal walls during post space preparation. Then paper points are

required for drying the canal and a microbrush (Ferrari et al., 2001) is required for

placing the primer and the adhesive in the post space. However, both the paper

points and the microbrush can be contaminated by the unset sealer when

performing an immediate post space preparation. This may jeopardize the

cementation procedure as the unset sealer may be transported from the apical to the

coronal portion of the canal before post insertion. Contamination of the post space

with the sealer may impede the set of the luting resin cement during post

cementation (Rosenstiel et al., 1998).

An ideal endodontic sealer should, in part, adhere firmly both to dentin and to

gutta-percha. Differences in the adhesive properties of endodontic sealers may be

expected, because their interaction with either dentin or gutta-percha may vary with

49

their chemical composition. No specific interaction either with dentin or

guttapercha is expected from the setting reaction of the epoxy-based sealers. In

contrast, the zinc oxide-eugenol sealer should firmly bond to dentin and

guttapercha. The setting reaction of the zinc oxide-eugenol mixtures is a chelation

reaction occurring with the zinc ion of the zinc oxide (Lee et al. 2002). In addition,

eugenol is a solvent of gutta-percha that may soften it during the setting reaction

and increase bonding of sealer to gutta-percha.

The effect of eugenol and noneugenol sealers on the retention of resin-cemented

posts has been studied with conflicting results. There have been several

investigations into the effects of endodontic sealers or their constituents on post

retention. Tjan and Nemetz 1992, reported substantial loss of retention of resin

retained posts when they contaminated canals with eugenol before cementation.

Other authors (Wu et al., 1994), (Rohde et al., 1996), (De Almeida et al., 2000),

(Miletic et al., 2002) found lower leakage with the use of epoxy resin sealants

compared with zinc oxide-eugenol sealers. On the other hands other investigations

(Schwartz et al., 1998), (Karapanou et al., 1996) reported that zinc oxide-eugenol

and epoxy resin sealers had similar behaviours.

In the following studies an evaluation of the effect of immediate versus delayed

post cementation on the retention of different types of fiber posts in canals

obturated with a eugenol sealer or with an epoxy resin sealer was conducted.

50

References 2.1.

De Almeida WA, Leonardo MR, Tanomaru Filho M, Silva LA. Evaluation of

apical sealing of three endodontic sealers. Int Endod J 2000;33(1):25-7.

Ewart A, Saunders WP. Investigation into the apical leakage of root-filled teeth

prepared for a post crown. Int Endod J 1990;23(5):239-44.

Ferrari M, Vichi A, Grandini S. Influence of adhesive application technique on

efficacy of bonding to root canal walls: an SEM investigation. Dent Mater

2001;17:422-9.

Galen WW, Mueller KI. Restoration of the endodontically treated tooth. In: Cohen

S, Burns RS, editors. Pathways of the pulp. 7th ed. St. Louis: Mosby; 1998. p.691-

717.

Karapanou V, Vera J, Cabrera P, White RR, Goldman M. Effect of immediate and

delayed post preparation on apical dye leakage using two different sealers. J Endod

1996;22(11):583-5.

Lee KW, Williams MC, Camps JJ, Pashley DH. Adhesion of endodontic sealers to

dentin and gutta-percha. J Endod 2002;28(10):684-8.

Miletic I, Ribaric SP, Karlovic Z, Jukic S, Bosnjak A, Anic I. Apical leakage of

five root canal sealers after one year of storage. J Endod 2002;28(6):431-2.

Rosenstiel SF, Gegauff AG. Effect of provisional cementing agents on provisional

resins. J Prosthet Dent 1988;59:29-33.

51

Rohde TR, Bramwell JD, Hutter JW, Roahen JO. An in vitro evaluation of

microleakage of a new root canal sealer. J Endod 1996;22(7):365-8.

Saunders EM, Saunders WP, Rashid MY. The effect of post preparation on the

apical seal of root fillings using chemically adhesive materials. Int Endod J

1991;24:51-7.

Schwartz RS, Murchison DF, Walker WA. Effects of eugenol and noneugenol

endodontic sealer cements on post retention. J Endod 1998; 24:564-7.

Solano F, Hartwell G, Appelstein C. Comparison of Apical Leakage Between

Immediate Versus Delayed Post Space Preparation Using AH Plus Sealer. J Endod

2005; 31:752-4.

Tjan A, Nemetz H. Effect of eugenol-containing endodontic sealer on retention of

prefabricated posts luted with an adhesive composite resin cement. Quintessence

Int 1992;22:839-44.

Wu MK, De Gee AJ, Wesselink PR. Leakage of four root canal sealers at different

thickness. Int Endod J 1994;27(6):304-8.

52

2.2. The effect of immediate versus delayed cementation on the retention of

different types of fiber post in canals obturated using a eugenol sealer

Michele Vano , Alvaro Cury, Cecilia Goracci , Nicoletta Chieffi, Mario Gabriele,

Franklin R Tay, Marco Ferrari. Journal of Endodontics. 2006;32(9):882-5.

Introduction

When restoring endodontically treated teeth with posts and cores, meticulous

attention to details during post cementation is crucial for post retention (1). Posts

may be placed immediately after completion of the endodontic treatment or at a

later stage after full setting of the sealer. Although cementation of a post

immediately after a root filling has been considered safe and less time consuming

(2), there are significant disadvantages. Post space preparation is performed when

the remaining apical 4-5 mm of sealer and gutta-percha are not fully set. Thus,

paper points and microbrushes that are used to apply the dentin adhesives and

luting composites may be contaminated with the unset sealer, jeopardizing their

polymerization and stability. Immediate post space preparation may also disrupt the

apical seal (3). Eugenol-containing root canal sealers represent the gold standard of

sealers in endodontics (4,5). The effect of eugenol and non eugenol sealers on the

retention of resin-cemented posts has been studied with conflicting results. The

presence of eugenol on the canal walls appeared to have an adverse effect on post

retention (6,7). However, others reported no difference between the use of a

eugenol and a noneugenol sealer on post retention (8). Clinically, the ideal time

needed for the sealers to set should be neither too fast nor too slow (9). Depending

on the type of sealer and the experimental technique, a wide range of setting times

has been recorded (10,11). A variable setting time ranging from a few minutes to

one day has been reported for Pulp Canal Sealer (Sybron-Kerr Romulus, MI) (12).

Controversial results exist on the manifestation of leakage after post placement.

53

While some authors demonstrated there was no difference in leakage between

immediate and delayed post space preparation (13-15), others reported that

immediate removal of gutta-percha resulted in less leakage when compared to

delayed removal (16-18). Recently, the effects of the sequence of post space

preparations and cementation using eugenol and resin-based sealers have been

examined (19). Post spaces prepared prior to obturation exhibited lower post

retention strength than preparation after root canal obturation.

The aim of this study was to evaluate the effect of immediate versus delayed post

cementation on the retention of different types of fiber posts in canals obturated

with a eugenol sealer. The null hypothesis tested was that there are no differences

in the interfcaial strengths derived from posts cemented immediately, 24 h or 1

week after completion of the root canal fillings.

Material and Methods

Sixty caries-free, recently extracted single-root human teeth with straight root

canals were used in this study. They were stored in 0.5% chloramines T until use.

All root canals were prepared by one trained operator with nickel titanium rotary

instruments M-two (Sweden & Martina, Due Carrare, Padova, Italy) and Profiles

(Dentsply Maillefer, Ballaigues, Switzerland) that were mounted in a 16:1 gear

reduction handpiece and driven by an electric motor (Endo IT professional,

Aseptico Inc., Woodinville, WA).

Specimen Preparation

Each tooth was decoronated below the cementoenamel junction and

perpendicularly to the longitudinal axis with a diamond blade under copious water

cooling. The working length was obtained at 1 mm above the radiographic apex.

The roots canals were endodontically instrumented using stainless steel instruments

K-files (#08-10-15; Dentsply Maillefer) and rotary Ni-Ti instruments M-two (#10-

54

15-20-25) and Profiles .06 taper (#30-35-40). Instrumentation was performed under

an operating microscope (OPMI pico, Carl Zeiss Surgical, Inc., Thornwood, NY)

at 12.5X magnification. The root canal was irrigated in between instrumentation

with 3 mL of 5.25% sodium hypochlorite using a long 27 gauge needle. Deionized

water was employed as the final rinse and patency of the canals was maintained

with a #10 K-file. The canals were dried with multiple paper points.

Warm Vertical Compaction of Gutta-Percha

A nonstandardized gutta-percha master cone (Hygienic, Coltène/Whaledent,

Mahwah, NJ) was fitted with tug-back to the working length of each root canal.

Pulp Canal Sealer was placed in the canal and spread with a #45 K-file with a

counterclockwise motion. The master gutta-percha cone was coated with the sealer

and seated in the canal 1 mm short of the working length. The gutta-percha was

compacted using the continuous wave technique up to 4 to 5 mm from the apex

with a System B heat source (Analytic Technology, Redwood). Backfilling of

gutta-percha was performed using thermoplastic gutta-percha and an Obtura II unit

(Obtura Corp., Fenton, MO) at 185°C. The filled teeth were divided into four

experimental groups (N=15) according to the different times of post space

preparation and cementation:

Group 1: The post space was prepared immediately after obturation, with part of

the filling material was removed with burs. The canal walls of each specimen were

enlarged with low-speed post drills provided by the manufacturer. To preserve the

apical seal, at least 5 mm of the root filling was retained at the apical level (20).

Prior to post cementation, each specimen was examined with the operating

microscope to observe any irregularities in the post space preparation.

Group 2: The teeth were stored in saline at 37°C for 24 h after obturation and the

post spaces were prepared in the same manner as in Group 1.

Group 3: The teeth were stored in saline at 37°C for 1 week after obturation and

the post spaces were prepared in the same manner as in Group 1.

55

Group 4: The roots were cleaned and shaped as in the other groups but no filling

was performed (positive control). Post spaces were then created in the same

manner as in Group 1.

After post space preparation, the access cavities of the teeth from all groups were

restored with a non-eugenol temporary filling material (Coltosol,

Coltène/Whaledent). The teeth were kept moist in deionized water prior to the

luting procedures.

Each group was further divided into three subgroups of 5 teeth each, according to

the type of post and the materials used for luting the posts (Table 1). Prior to

cementation, each post was cleaned with 95% ethanol. A microbrush was used to

introduce the primer and the adhesive into each canal (21). A gentle stream of air

was directed over the canal orifice for 2 s. The cement was then placed on the post

and into the canal space. The post was inserted as close to the center of the post

space as possible to mantain a circumferential layer of sealer between the post and

the intraradicular dentin. The materials were used according to the manufacturers’

instructions (Table 1).

Push-out Test

A push-out test was performed to evaluate the post-intraradicular dentin interfacial

strength (22-24). The portion of each root that contained the fiber post was

sectioned into five to six 1 mm thick slices with a water-cooled diamond blade

(Labcut 1010, Extec Corp., Enfield, CT). A compressive load was applied to the

apical aspect of the slice via a cylindrical plunger of 0.65 mm diameter that was

mounted on a universal testing machine (Controls S.P.A., Milano. Italy). A plunger

tip size was selected and positioned to contact only the post, without stressing the

surrounding root canal walls (22). The load was applied to the apical aspect of the

root slice and in an apical-coronal direction, so as to push the post toward the larger

part of the root slice, thus avoiding any limitation to the post movement. Care was

also taken to ensure that the contact between the punch tip and the post section

56

occurred over the most extended area, to avoid notching of the punch tip into the

post surface. Loading was performed at a crosshead speed of 0.5 mm/min until

bond failure occurred. Bond failure was manifested by the extrusion of the post

from the root section. Interfacial strength (in megaPascal) was calculated by

dividing the load at debonding (Newtons) by the area (mm2). The area (SL) was

estimated by using the formula for calculating the lateral surface area of a truncated

cone: SL = π(R+r)[(h2 + (R-r)2]0.5, where R represents the coronal post radius, r

the apical post radius, and h the thickness of the slice.

Statistical Analysis

As bond strength data were normally distributed (Kolmogorov-Smirnov test) and

homogeneous in variances (Levene’s test), a two-way ANOVA was performed to

examine the effect of the type of post and timing of post space preparation on

interfacial strength. Post-hoc multiple comparisons were performed using the

Tukey test, with the significance level set at α=0.05.

Results

Statistical analysis revealed that both the type of post used and the timing of post

space preparation significant affected the interfacial strength between the post and

intraradicular dentin (p<0.05). The interaction between these two factors was not

significant (p>0.05). For the factor "post type', interfacial strength of the FRC

Postec post (Ivoclar Vivadent, Liechtenstein, Germany) was significantly higher

than the ENA posts (GDF, Rosbach, Germany) (p<0.05). Interfacial strengths of

the DT Light Post (Dentsply DeTrey, Konstanz, Germany) were higher than the

ENA Post but lower than the FRC Postec post; however the differences were not

statistically significant (Table 2).

For the factor "timing of post space preparation", interfacial strength achieved with

immediate post preparation (Group 1) was significantly lower than those achieved

when post preparations were performed after 24 h (Group 2) and at 1 week (Group

57

3) (p<0.05). There was no difference in interfacial strengths measured at 24 h and 1

week (p>0.05). Regardless of the post type, the control group (Group 4) showed

the highest interfacial strengths. These values were significantly higher that those

in Group 1 (p<0.05), but were similar to those in Groups 2 and 3 (p>0.05). A

summary of interfacial strength data is depicted in Table 2.

Discussion

The results of this study indicated that irrespective of post type, immediate post

space preparation and post cementation resulted in inferior post retention, as

manifested by the lower interfacial strengths between the bonded post and

intraradicular dentin. Conversely, better post retention was achieved, as manifested

by the higher interfacial strengths, when the post space preparation and post

cementation were performed 24 h or one week after the canals with filled with

gutta-percha and a eugenol sealer. Thus, the null hypothesis that there are no

differences in the interfacial strengths derived from posts cemented immediately,

24 h or 1 week after completion of the root canal fillings has to be rejected.

Mechanical removal of the sealer-impregnated dentin from the canal walls during

post space preparation is considered to be critical to achieve ideal post retention

using adhesive techniques (19). A disadvantage of the immediate technique is that

post space preparation and cementation are perfomed when the sealer in the apical

part of the canal is not fully set yet. To properly cement a fiber post, paper points

are required for drying the canal and a microbrush (21) is required for placing the

primer and the adhesive in the post space. However, both the paper points and the

microbrush may be contaminated by the unset sealer. This may jeopardize the

cementation procedure as the unset sealer may be transported from the apical to the

coronal portion of the canal before post insertion. Contamination of the post spaces

with the eugenol-containing sealer may impede the set of the luting resin cement

during post cementation (25). Interestingly, bond strengths in the 24 h and 7-day

groups (i.e. Groups 2 and 3) were similar (Table 2). A possible explanation is that

58

contamination of the post spaces is minimized when the sealer is allowed to set

completely before post space preparation. Indeed, the highest interfacial strength

values were recorded from the control group that was only clean and shaped but

without being filled. Clearly the adhesive procedure benefited the most from a

perfect clean root surface which was not contaminated with the eugenol-containing

sealer. Apart from the timing of post space preparation, interfacial strength was

also significantly affected by the type of post employed. In particular the FRC

Postec posts achieved the highest interfacial strengths in all the tested groups than

the DT Light Posts and the ENA posts. Presumably, the methacrylate resin matrix

of the FRC Postec posts allows better bonding with the methacrylate-based

adhesives and resin cements (26, 27). Conversely, apart from silanization of the

glass fibers, there is no chemical interaction between the epoxy resin matrices of

the DT Light Posts and ENA posts with the methacrylate-based adhesives and resin

cements. Within the limits of this study, it may be concluded that clinicians should

be cautious about performing post space preparation and cementation of fiber posts

immediately after filling of the root canals with a zinc oxide eugenol root canal

sealer, as delayed preparation and cementation shows higher interfacial strengths

irrespective of the type of fiber post employed.

59

References

1. Standlee JP, Caputo AA, Hanson EC. Retention of endodontic dowels: effect of

cement, dowel length, diameter, and design. J Prosthet Dent 1978; 39:401-5.

2. Galen WW, Mueller KI. Restoration of the endodontically treated tooth. In:

Cohen S, Burns RS, eds. Pathways of the pulp. 7th ed. St. Louis: Mosby, 1998;

691-717.

3. Saunders EM, Saunders WP, Rashid MY. The effect of post preparation on the

apical seal of root fillings using chemically adhesive materials. Int Endod J 1991;

24:51-7.

4. Hagge MS, Wong RD, Lindemuth JS. Retention of posts luted with phosphate

monomer-based composite cement in canals obturated using a eugenol sealer. Am J

Dent 2002; 15:378-82.

5. Mickel AK, Wright ER. Growth inhibition of Strreptococcus anginosus (milleri)

by three calcium hydroxide sealers and one zinc oxide-eugenol sealer. J Endod

1999; 25:34-7.

6. Tjan A, Nemetz H. Effect of eugenol-containing endodontic sealer on retention

of prefabricatedposts luted with an adhesive composite resin cement. Quintessence

Int 1992; 22:839-44.

7. Ngoh EC, Pashley DH, Loushine RJ, Weller RN, Kimbrough WF. Effects of

eugenol on resin bond strengths to root canal dentin. J Endod 2001; 27:411-4.

8. Schwartz RS, Murchison DF, Walker WA. Effects of eugenol and noneugenol

endodontic sealer cements on post retention. J Endod 1998; 24:564-7.

9. Allan NA, Walton RC, Schaeffer MA. Setting times for endodontic sealers under

clinical usage and in vitro conditions. J Endod 2001; 27:421-3.

10. McComb D, Smith D. Comparison of physical properties of polycarboxylate-

based and conventional root canal sealers. J Endod 1976; 2:228–34.

11. Ørstavik D, Nordahl I, Tibballs J. E. Dimensional change following setting of

root canal sealer materials. Dent Mater 2001; 17:512-19.

60

12. Caicedo R, von Fraunhofer J. The properties of endodontic sealer cements. J

Endod 1988; 14: 527–33.

13. Bourgeois RS, Lemon RR. Dowel space preparation and apical leakage. J

Endod 1981;7:66–9.

14. Madison S, Zakariasen KL. Linear and volumetric analysis of apical leakage in

teeth prepared for posts. J Endod 1984;10:422–7.

15. Abramovitz I, Tagger M, Tamse A, Metzger Z. The effect of immediate vs.

delayed post space preparation on the apical seal of a root canal filling: a study in

an increased-sensitivity pressuredriven system. J Endod 2000; 26:435–9.

16. Kwan EH, Harrington GW. The effect of immediate post preparation on apical

seal. J Endod 1981; 7:325–9.

17. Fan B, Wu MK, Wesselink PR. Coronal leakage along apical root fillings after

immediate and delayed post space preparation. Endod Dent Traumatol 1999;

15:124–6.

18. Solano F, Hartwell G, Appelstein C. Comparison of Apical Leakage Between

Immediate Versus Delayed Post Space Preparation Using AH Plus Sealer. J Endod

2005; 31:752-4.

19. Boone KJ, Murchison DF, Schindler WG, Walker WA. Post retention: the

effect of sequence of post-space preparation, cementation time and different

sealers. J Endod 2001; 27:768-71.

20. Abramovitz L, Lev R, Fuss Z, Metzger Z. The unpredictability of seal after post

space preparation: a fluid transport study. J Endod 2001; 27:292–5.

21. Ferrari M, Vichi A, Grandini S. Influence of adhesive application technique on

efficacy of bonding to root canal walls: an SEM investigation. Dent Mater

2001;17:422 9.

22. Goracci C, Tavares AU, Fabianelli A, Monticelli F, Raffaelli O, Cardoso PC,

Tay F, Ferrari M The adhesion between fiber posts and root canal walls:

comparison between microtensile and pushout bond strength measurements. Eur J

Oral Sci 2004;112:353-61.

61

23. Goracci C, Fabianelli A, Sadek FT, Papacchini F, Tay FR, Ferrari M. The

contribution of friction to the dislocation resistance of bonded fiber posts. J Endod

2005; 31:608-12.

24. Gesi A, Raffaelli O, Goracci C, Pashley DH, Tay FR, Ferrari M. Interfacial

strength of Resilon and gutta-percha to intraradicular dentin. J Endod 2005;

31:909-13.

25. Rosenstiel SF, Gegauff AG. Effect of provisional cementing agents on

provisional resins. J Prosthet Dent 1988;59(1):29-33.

26. Monticelli F, Osorio R, Albaladejo A, Aguilera FS, Ferrari M, Tay FR,

Toledano M. Effects of adhesive systems and luting agents on bonding of fiber post

to root canal dentin. J Biomed Mater Res B Appl Biomater 2005; 21:[Epub ahead

of print].

27. Vano M, Goracci C, Monticelli F, Tognini F, Gabriele M, Tay FR, Ferrari M.

The adhesion between fibre post and composite resin cores: the evaluation of

microtensile bond strength following various post surface chemical treatments to

posts. Int Endod J 2006;39(1):31-9.

62

TABLE 1. Summary of the “step-by-step” procedures employed for fiber post cementation, according to the manufacturer’s instructions

Dentsply DeTrey Konstanz, Germany (Post type: DT Light Post)

Ivoclar-Vivadent Schaan, Liechtenstein (Post type:

FRC Postec)

GDF Gesellschaft für Dental Forschung und

Innovationen, Rosbach, Germany (Post type: ENA

Post) Acid-etch post space with Conditioner

Acid-etch post space with Total Etch

Acid-etch post space with ENA-Etch

36 Gel for 15 s for 15 s for 60 s

Water/Rinse without desiccation Water/Rinse without desiccation

Water/Rinse without desiccation

Mix Prime&Bond NT + Dual Cure Mix Primer A � B (1:1) for5sand

Mix ENA Bond � Catalyst (1:1) for

catalyst for 2 s and apply for 20 s in

apply to the root canal for 15 s 5 s and apply to the root canal

the root canal and on the DT Light for 20 sec and on the ENA post

Post (0,90/1,50)* surface (0,95/1,45)* surface

Gently air dry for 5 s Gently air dry for 5 s Gently air dry for 5 s

Apply Monobond S (silane) to the

FRC Postec post (0,85/1,45)* surface for 60 s and gently air

dry

for5s Apply Calibra Esthetic Resin Cement

Apply MultiLink resin cement on Apply ENA Cem cement on the

on the post and place the post the post and place the post inside

post and place the post inside

inside the root canal the root canal the root canal

Light-cure with minimum output Light-cure with minimum output Light-cure with minimum output

intensity of 600 mw/cm2 for 40 s intensity of 600 mw/cm2 for 40 s

intensity of 600 mw/cm2 for 40 s

*Minimum/maximum cross-section post diameter in mm.

63

Table 2. Effect of immediate versus delayed post space preparation on post retention

Post type Group 1 Immediate

Group 2 24 hours

Group 3 7 days

Group 4 Control

DT Light Post 6.0 ± 3.60 (49)a 6.6 ± 3.6 (47)b 7.1 ± 3.1 (47)b 7.5 ± 3.5 (48)b

Ena Post 5.2 ± 2.0 (47)a 6.4 ± 3.3 (47)b 5.8 ± 3.2 (48)b 6.1 ± 2.7 (57)b

FRC Postec 5.8 ± 5.8 (59)a 7.6 ± 3.1 (51)b 7.7 ± 3.2 (54)b 8.1 ± 4.4 (58)b

Values are mean ± standard deviation in MPa. The number in parenthesis represents the number of specimens tested. Symbols represent significant differences with regard to the factor “time of post insertion” (P < 0.05). Lower case letters represent significant differences among the post systems (P<0.05).

64

2.3. Retention of fiber posts cemented at different time intervals in canals

obturated using an epoxy resin sealer

Michele Vano, Alvaro H. Cury, Cecilia Goracci, Nicoletta Chieffi , Mario

Gabriele, Franklin. R. Tay, Marco Ferrari. Journal of Dentistry, Submitted

Introduction

Many factors can possibly interfere with the development of high bond strength

values between an endodontic post and root canal dentin. Among these the timing

of post space preparation and cementation plays an important role.1 There is no

consensus on the time interval between the endodontic treatment and the post space

preparation.2 Posts can be placed immediately after completion of the endodontic

treatment or at a later stage after full setting of the sealer. Dye leakage studies

reported less apical leakage when immediate post space preparation was

performed.3 In addition immediate post space preparation and cementation is less

time consuming.4,5 However concerns on the immediate procedure were arousen

because of the possible negative effect of the unset sealer on post retention. The

removal of the sealer impregnated dentin from the canal walls during post space

preparation represents an important factor for post retention.6 To properly cement a

fiber post, paper points are required for drying the canal and a microbrush is

required for placing the primer and the adhesive in the post space.7 However, both

the paper points and the microbrush can be contaminated by the unset sealer. This

may jeopardize the cementation procedure as the unset sealer may be transported

from the apical to the coronal portion of the canal before post insertion.

Contamination of the post space with the sealer may impede the set of the luting

resin cement during post cementation.8 A recent study recorded low bond strength

values between the post and root dentin when immediate post space preparation

and cementation with an eugenol sealer were performed.9

65

The effect of eugenol sealers on the retention of resin-cemented posts has been

studied with conflicting results.10,11 The presence of eugenol on the canal walls

appeared to have an adverse effect on post retention.12 To avoid this problem epoxy

resin root canal sealers have been recomended.13 AH Plus (Dentsply, De Trey,

Konstanz, Germany) is an epoxy-amine resin sealer that has gained recent

popularity among clinicians.

The aim of this study was to evaluate the effect of immediate versus delayed post

space preparation and cementation on the retention of different types of fiber post

systems in canals obturated with an epoxy resin sealer. Post space characteristics

following immediate versus delayed post cementation were also observed using

scanning electron microscopy (SEM)

The null hypothesis tested was that there are no differences in the retentive

strengths derived from post systems cemented immediately, 24 hours or 1 week

after completion of the root canal fillings.

Material and Methods

Sixty-eight caries-free, recently extracted single-root human teeth with straight root

canals were used in this study. They were stored in 0.5% chloramines T until use.

Each tooth was decoronated below the cementoenamel junction and

perpendicularly to the longitudinal axis with a diamond blade under copious water

cooling.

All root canals were prepared by one trained operator. The roots canals were

endodontically instrumented using stainless steel instruments K-files (#08-10-15;

Dentsply Maillefer Ballaigues, Switzerland) and rotary Ni-Ti instruments M-two

(#10-15-20-25; Sweden & Martina, Due Carrare, Padova, Italy) and Profiles .06

taper (#30-35-40; Dentsply Maillefer) that were mounted in a 16:1 gear reduction

handpiece, driven by an electric motor (Endo IT professional, Aseptico Inc.,

Woodinville, WA). The working length was obtained at 1 mm above the

66

radiographic apex. Instrumentation was performed under an operating microscope

(OPMI pico, Carl Zeiss Surgical, Inc., Thornwood, NY) at 12.5X magnification.

The root canal was irrigated in between instrumentation with 3 mL of 5.25%

sodium hypochlorite using a long 27 gauge needle. Deionized water was employed

as the final rinse and patency of the canals was maintained with a #10 K-file. The

canals were dried with multiple paper points. A nonstandardized gutta-percha

master cone (Hygienic, Coltène/Whaledent, Mahwah, NJ) was fitted with tug-back

to the working length of each root canal. AH Plus sealer (Dentsply, De Trey,

Konstanz, Germany) was placed in the canal and spread with a #45 K-file with a

counterclockwise motion. The gutta-percha was compacted using the continuous

wave technique up to 4 to 5 mm from the apex with a System B heat source

(Analytic Technology, Redwood). Backfilling of gutta-percha was performed using

thermoplastic gutta-percha and an Obtura II unit (Obtura Corp., Fenton, MO) at

185°C. After the root filling, the access cavities of the teeth from all groups were

restored with a non-eugenol temporary filling material (Coltosol,

Coltène/Whaledent). The teeth were kept moist in saline solution at 37° before the

luting procedures. The filled teeth were divided into three experimental groups

according to the different times of post space preparation and cementation. A

control group was included.

Group 1: The post space was prepared immediately after obturation and part of the

filling material was removed with an heated instrument (System B Spreader)

(Analytic Technology, Redwood) inserted into the canal to the desired length. The

canal walls of each specimen were enlarged with low-speed post drills provided by

the manufacturer. To preserve the apical seal, at least 5 mm of the root filling was

retained at the apical level.14 Before post cementation, each specimen was

examined with the operating microscope to observe any irregularities in the post

space preparation.

67

Group 2: The teeth were stored for 24 h after obturation. Then the post spaces

were prepared in the same manner as in group 1.

Group 3: The teeth were stored for 1 week after obturation. Then the post spaces

were prepared in the same manner as in group 1.

Group 4: The roots were cleaned and shaped as in the other groups but no filling

was performed (control group). Post spaces were then prepared in the same manner

as in group 1.

Each group was furtherly divided into three subgroups of five teeth each (n=5),

according to the type of post and the materials used for luting the posts (Table 1).

Before cementation, each post was cleaned with 95% ethanol. A microbrush was

used to introduce the primer and the adhesive into each canal.7 A gentle stream of

air was directed over the canal orifice for 2 s. The cement was then placed on the

post and into the canal space. The materials were used according to the

manufacturers’ instructions (Table 1).

SEM analysis

Two teeth were randomly selected from each group for SEM examination of the

post space. In order to assess qualitatively the cleanliness of the post space just

before post insertion the luting procedure were performed without cementing the

post in the canal. The specimen was then sectioned longitudinally. Each specimen

was mounted on a metallic stub, gold-sputtered (Polaron Range SC7620, Quorum

Technology, Newhaven, UK), and observed under a JSM 6060LV microscope

(JEOL, Tokyo, Japan) at different magnifications.

Push-out Test

A push-out test was performed to evaluate the post-intraradicular dentin interfacial

strength.15,16 The portion of each root that contained the fiber post was sectioned

into five to six 1 mm-thick slices with a water-cooled diamond blade (Labcut 1010,

68

Extec Corp., Enfield, CT). A compressive load was applied to the apical aspect of

the slice via a cylindrical plunger of 0.65 mm-diameter that was mounted on a

universal testing machine (Controls S.P.A., Milano. Italy). A plunger tip size was

selected and positioned to contact only the post, without stressing the surrounding

root canal walls.15 The load was applied to the apical aspect of the root slice and in

an apical-coronal direction, so as to push the post toward the larger part of the root

slice, thus avoiding any limitation to the post movement. Care was also taken to

ensure that the contact between the punch tip and the post section occurred over the

most extended area, to avoid notching of the punch tip into the post surface.

Loading was performed at a crosshead speed of 0.5 mm/min until bond failure

occurred. Bond failure was manifested by the extrusion of the post from the root

section. Interfacial strength (in megaPascal) was calculated by dividing the load at

debonding (Newtons) by the area (mm2). The area (SL) was estimated by using the

formula for calculating the lateral surface area of a truncated cone: SL = π(R+r)[(h2

+ (R-r)2]0.5, where R represents the coronal post radius, r the apical post radius, and

h the thickness of the slice.

Statistical Analysis

After having checked that bond strength data were normally distributed

(Kolmogorov-Smirnov test), that group variances were homogeneous (Levene’s

test), and that the root of origin of the slices was not a significant factor for bond

strength (Regression analysis), root slices were considered as statistical units and a

two-way ANOVA was performed to examine the effect of the type of post and

timing of post space preparation on interfacial strength. Post-hoc multiple

comparisons were performed using the Tukey test, with the significance level set at

α=0.05.

69

Results

Statistical analysis revealed that both the type of post system used and the timing of

post space preparation and cementation significantly affected the interfacial

strength between the post and intraradicular dentin (p<0.05). The interaction

between these two factors was not significant (p>0.05). For the factor post type,

interfacial strength values of the FRC Postec posts (Ivoclar Vivadent,

Liechtenstein, Germany) and DT Light Post posts (Dentsply DeTrey, Konstanz,

Germany) were significantly higher than those achieved with ENA Post posts

(GDF, Rosbach, Germany) (p<0.05). (Table 2).

For the factor timing of post space preparation, interfacial strength values achieved

with immediate post preparation (group 1) were significantly lower (p<0.05) than

those achieved when post preparation and cementation were performed 24 h (group

2) and/or 1 week (group 3) after the root canal filling. There was no difference in

interfacial strength values measured at 24 h and 1 week (p>0.05) after root canal

fillings. Regardless of the post type, the control group (group 4) showed the highest

interfacial strength values. These values were significantly higher than those in

group 1 (p<0.05), but comparable to those in groups 2 and 3 (p>0.05). A summary

of interfacial strength data is depicted in Table 2.

SEM investigation

SEM examination revealed a higher presence of sealer remnants along the post

space walls of the specimens in group 1 (immediate post space preparation and

cementation) when compared to those in group 2 (post space preparation and

cementation performed 24 h after the root canal filling) and 3 (post space

preparation and cementation performed 1 week after the root canal filling)

independently of the type of luting materials used (Fig.1A-B). The aumont of

sealer remnants along the post space walls observed in group 2 (Fig. 2A-B), and 3

(Fig. 3A-B) was similar.

70

Discussion

There was a significant increase in retention when the post space preparation and

post cementation were performed 24 h and/or one week after the canals were filled

with gutta-percha and AH Plus sealer (Dentsply DeTrey, Konstanz, Germany).

Conversely, immediate post space preparation and cementation resulted in low

interfacial strength values between the bonded post and radicular dentin (Table 2).

Thus, the null hypothesis that there are no differences in the interfacial strengths

derived from posts cemented immediately, 24 h or 1 week after completion of the

root canal filling has to be rejected.

SEM micrographs revealed that specimens in group 1 showed more remnants of

sealer and gutta-percha than specimens in group 2 and 3 (Fig. 1A-B, 2A-B, 3A-B).

These findings lead the authors to speculate that there could be a correlation

between post retention and the cleanliness of the post space walls. The data of the

present study are in accordance with those obtained in a recent report 9 in which the

canals were obturated with an eugenol sealer (Pulp Canal Sealer) (Sybron-Kerr

Romulus, MI,USA).

Both AH Plus (Dentsply, De Trey, Konstanz, Germany) and Pulp Canal Sealer

have a similar setting time (6-8 h) therefore when immediate post space preparation

and cementation are perfomed the sealer in the apical part of the canal is not fully

set yet.17,18 As a consequence both the paper points and the microbrush used in the

luting procedure contaminate the post space with the unset sealer just before post

insertion. On the contrary a delayed post space preparation and cementation allows

the sealer to set properly thus the contamination of the post space is avoided.

Apart from the timing of post space preparation, the interfacial strength was also

significantly affected by the type of post employed. In particular the FRC Postec

achieved the highest interfacial strengths when compared to DT Light Post and the

ENA Post. Presumably, the methacrylate resin matrix of the FRC Postec allows

better bonding with the methacrylate-based adhesives and resin cements.19,20

Conversely, apart from silanization of the glass fibers, there is no chemical

71

interaction between the epoxy resin matrices of the DT Light Post and ENA Post

with the methacrylate-based adhesives and resin cements.

Conclusions

Within the limits of this study, it may be concluded that clinicians should be

cautious about performing post space preparation and cementation of fiber posts

immediately after filling of the root canals, as delayed preparation and cementation

shows higher interfacial strengths irrespectively of the type of fiber post employed.

72

References

1. Ewart A, Saunders WP. Investigation into the apical leakage of root-filled teeth

prepared for a post crown. International Endodontic Journal 1990;23:239-44.

2. Karapanou V, Vera J, Cabrera P, White RR, Goldman M. Effect of immediate

and delayed post preparation on apical dye leakage using two different sealers.

Journal of Endodontics 1996;22:583-5.

3. Solano F, Hartwell G, Appelstein C. Comparison of Apical Leakage Between

Immediate Versus Delayed Post Space Preparation Using AH Plus Sealer. Journal

of Endodontics 2005; 31:752-4.

4. Galen WW, Mueller KI. Restoration of the endodontically treated tooth. In:

Cohen S, Burns RS, editors. Pathways of the pulp. 7th ed. St. Louis: Mosby; 1998.

p.691-717.

5. Saunders EM, Saunders WP, Rashid MY. The effect of post preparation on the

apical seal of root fillings using chemically adhesive materials. International

Endodontic Journal 1991;24:51-7.

6. Boone KJ, Murchison DF, Schindler WG, Walker WA. Post retention: the effect

of sequence of post-space preparation, cementation time and different sealers.

Journal of Endodontics 2001;27:768-71.

7. Ferrari M, Vichi A, Grandini S. Influence of adhesive application technique on

efficacy of bonding to root canal walls: an SEM investigation. Dental Materials

2001;17:422 9.

73

8. Rosenstiel SF, Gegauff AG. Effect of provisional cementing agents on

provisional resins. Journal of Prosthetic Dentistry 1988;59:29-33.

9. Vano M, Cury AH, Goracci C, Chieffi N, Gabriele M, Tay FR, Ferrari M. The

effect of immediate versus delayed cementation on the retention of different types

of fibre post in canals obturated using a eugenol sealer. Journal of Endodontics

2006;3:882-5.

10. Tjan A, Nemetz H. Effect of eugenol-containing endodontic sealer on retention

of prefabricated posts luted with an adhesive composite resin cement. Quintessence

International 1992;22:839-44.

11. Schwartz RS, Murchison DF, Walker WA. Effects of eugenol and noneugenol

endodontic sealer cements on post retention. Journal of Endodontics 1998; 24:564-

7.

12. Ngoh EC, Pashley DH, Loushine RJ, Weller RN, Kimbrough WF. Effects of

eugenol on resin bond strengths to root canal dentin. Journal of Endodontics

2001;27:411-4.

13. Cohen BI, Volovich Y, Musikant BL, Deutsch AS. The effects of eugenol and

epoxy-resin on the strength of a hybrid composite resin. Journal of Endodontics

2002;28:79-82.

14. Abramovitz I, Tagger M, Tamse A, Metzger Z. The effect of immediate vs.

delayed post space preparation on the apical seal of a root canal filling: a study in

an increased-sensitivity pressure-driven system. Journal of Endodontics

2000;26:435–9.

74

15. Goracci C, Tavares AU, Fabianelli A, Monticelli F, Raffaelli O, Cardoso PC,

Tay F, Ferrari M. The adhesion between fiber posts and root canal walls:

comparison between microtensile and push-out bond strength measurements.

European Journal of Oral Science 2004;112:353-61.

16. Goracci C, Fabianelli A, Sadek FT, Papacchini F, Tay FR, Ferrari M. The

contribution of friction to the dislocation resistance of bonded fiber posts. Journal

of Endodontics 2005;31:608-12.

17. Allan NA, Walton RC, Schaeffer MA. Setting times for endodontic sealers

under clinical usage and in vitro conditions. Journal of Endodontics 2001;27:421-3.

18. McMichen FRS, Pearson G, Rahbaran S, Gulabivala K. A comparative study of

selected physical properties of five root-canal sealers. International Endodontic

Journal 2003;36:629-35.

19. Monticelli F, Osorio R, Albaladejo A, Aguilera FS, Ferrari M, Tay FR,

Toledano M. Effects of adhesive systems and luting agents on bonding of fiber post

to root canal dentin. Journal of Biomedical Materials Research Part B: Applied

Biomaterials 2006;77:195-200.

20. Vano M, Goracci C, Monticelli F, Tognini F, Gabriele M, Tay FR, Ferrari M.

The adhesion between fibre post and composite resin cores: the evaluation of

microtensile bond strength following various post surface chemical treatments to

posts. International Endodontic Journal 2006;39:31-9.

75

Table 1 Summary of the “step-by-step” procedures employed for fiber post

cementation, according to the manufacturer’s instructions

Dentsply DeTrey Konstanz, Germany (Post type: DT Light

Post)

Ivoclar-Vivadent Schaan, Liechtenstein

(Post type: FRC Postec)

GDF Gesellschaft für

Dental Forschung und Innovationen,

Rosbach, Germany (Post type: ENA Post)

Acid-etch post space with Conditioner 36 Gel for 15 s

Acid-etch post space with Total Etch for 15 s

Acid-etch post space with ENA-Etch for 60 s

Water/Rinse without desiccation

Water/Rinse without desiccation

Water/Rinse without desiccation

Mix Prime&Bond NT + Dual Cure catalyst for 2 s and apply for 20 s in the root canal and on the DT Light Post (0,90/1,45)* surface

Mix Primer A+B (1:1) for 5 s and apply to the root canal for 15 s

Mix ENA Bond + Catalyst (1:1) for 5 s and apply to the root canal for 20 sec and on the ENA Post (0,95/1,45)* surface

Gently air dry for 5 s Gently air dry for 5 s Gently air dry for 5 s Apply Monobond S

(silane) to the FRC Postec post (0,90/1,45)* surface for 60 s and gently air dry for 5 s

Apply Calibra Esthetic Resin Cement on the post and place the post inside the root canal

Apply MultiLink resin cement on the post and place the post inside the root canal

Apply ENA Cem cement on the post and place the post inside the root canal

Light-cure with minimum output intensity of 600mw/cm2 for 40 s

Light-cure with minimum output intensity of 600mw/cm2 for 40 s

Light-cure with minimum output intensity of 600mw/cm2 for 40 s

* minimum / maximum cross-section post diameter in mm.

76

Table 2. Effect of immediate versus delayed post space preparation and cementation on post retention

Post type Group 1 Immediate

Group 2 24 hours

Group 3 1 week

Group 4

Control

DT Light Post* 5.9 ± 2.2 (51)a 7.3 ± 2.3 (49)b 7.0 ± 2.8 (48)b 7.5 ± 3.5 (48)b

ENA Post§ 5.0 ± 2.1 (50)a 6.5 ± 2.6(46)b 6.8 ± 2.5 (47)b 6.1 ± 2.7 (57)b

FRC Postec* 6.3 ± 2.7 (57)a 7.9 ± 2.8 (49)b 7.4 ± 2.3 (55)b 8.1 ± 4.4 (58)b

Values are mean ± standard deviation in MPa. The number in parenthesis represents the number of specimens tested Symbols represent significant differences with regard to the factor “post type” (p < 0.05) Lower case letters represent significant differences with regard to the factor “timing of post space preparation and cemenattion” (p < 0.05)

77

Figure 1A. SEM photomicrographs of the post space in Group 1. Sealer and gutta-

percha remnants are visible all along the post canal walls (original

magnification×20, bar=1 mm).

78

Figure 1B. Higher magnification of the post space (original magnification×500,

bar=50 µm).

79

Figure 2A. SEM photomicrographs of the post space in Group 2. Small areas of

sealer and guttapercha remnants are present along the post canal walls (original

magnification×20, bar=1 mm).

80

Figure 2B. Higher magnification of the post space. The surface of the post space is

clean with only few areas of sealer and gutta-percha remnants (original

magnification×500, bar=1 µm).

81

Figure 3A. SEM photomicrographs of the post space in Group 3. The surface of the

post space is clean with only few areas of sealer and gutta-percha remnants

(original magnification×22, bar=1 mm).

82

Figure 3B. Higher magnification of figure 3A (original magnification×500, bar=50

µm).

83

2.4. Endodontic sealer: eugenol versus non-eugenol sealers

Retention is of high importance for the success of intracanal posts in

endodontically treated teeth. The effect of eugenol and noneugenol sealers on the

retention of resin-cemented posts has been studied with conflicting results. There

have been several investigations into the effects of endodontic sealers or their

constituents on post retention. Tjan and Nemetz 1992, reported substantial loss of

retention of resin retained posts when they contaminated canals with eugenol

before cementation. Other authors (Wu et al., 1994), (Rohde et al., 1996), (De

Almeida et al., 2000), (Miletic et al., 2002) found lower leakage with the use of

epoxy resin sealants compared with zinc oxide-eugenol sealers. On the other hands

other investigations (Schwartz et al., 1998), (Karapanou et al., 1996) reported that

zinc oxide-eugenol and epoxy resin sealers had similar behaviours. In agreement

with these investigations, the studies described in sections 2.2. and 2.3. of this

thesis, found no differences in terms of post retention when an eugenol or an epoxy

resin based sealer were used as endodontic sealers.

84

References 2.4

De Almeida WA, Leonardo MR, Tanomaru Filho M, Silva LA. Evaluation of

apical sealing of three endodontic sealers. Int Endod J 2000;33(1):25-7.

Karapanou V, Vera J, Cabrera P, White RR, Goldman M. Effect of immediate and

delayed post preparation on apical dye leakage using two different sealers. J Endod

1996;22(11):583-5.

Miletic I, Ribaric SP, Karlovic Z, Jukic S, Bosnjak A, Anic I. Apical leakage of

five root canal sealers after one year of storage. J Endod 2002;28(6):431-2.

Rohde TR, Bramwell JD, Hutter JW, Roahen JO. An in vitro evaluation of

microleakage of a new root canal sealer. J Endod 1996;22(7):365-8.

Schwartz RS, Murchison DF, Walker WA. Effects of eugenol and noneugenol

endodontic sealer cements on post retention. J Endod 1998;24:564-7.

Tjan A, Nemetz H. Effect of eugenol-containing endodontic sealer on retention of

prefabricated posts luted with an adhesive composite resin cement. Quintessence

Int 1992;22:839-44.

Wu MK, De Gee AJ, Wesselink PR. Leakage of four root canal sealers at different

thickness. Int Endod J 1994;27(6):304-8.

85

Chapter 3

3.1. Water detrimental effect on fiber -reinforced composite and dental resins

The exposure of polymeric restorative materials such as fiber-reinforced

composites (FRC) and restorative resins to the aqueous oral environment

immediately draws one to the attention of the potentially detrimental effect of water

sorption on these materials. There is concern that the effects of solvent uptake and

hydrolytic degradation may lead to a shortened service life of dental resins. In fact

water ingress into dental composites in the oral cavity can, with time, lead to

deterioration of the physical/mechanical properties, mainly due to a hydrolytic

breakdown of the bond between silane and filler particles, filler–matrix debonding

or even hydrolytic degradation of the fillers (Soderholm et al., 1984) (Ferracane,

2006) (Takahashi et al., 1998) (Takahashi et al., 1999). Negative effects caused by

water exposure in composite materials have been reported as a reduction in their

physical properties, like tensile strength (Söderholm et al., 1996), flexural strength,

modulus of elasticity (Öysaed et al.,1986) and wear resistance (Scarret et al., 1991)

(Miettinen et al., 1999). Water is absorbed into the FRC by diffusion. The inflow

predominantly occurs in the resinous matrix and depends on the nature of the resin

and the amount of this phase within the material (Fan et al., 1985) (Santos et al.,

2002). This process is generally time dependent and increases with time (Chai et

al., 2004) (Behr et al.,2000).

FRC materials differ for the amount of water sorption, but show a similar

dimensional stability, after water storage (Chai et al., 2004). Among the reasons

used to explain the variation were the difference in the amount of water sorption,

fiber content and voids present within the matrix and at the fiber-matrix interface

(Chai et al., 2006). The sorbed water which is molecularly dispersed into the

polymer matrix acts as plasticizer, causing the swelling of polymer. The quantity of

water uptake depends on the available equilibrium hole-free volume, the

86

physicochemical affinity of polymer groups to water, and the resistance of polymer

chains to a swelling deformation stress (Ping et al., 2001) (Patil et al., 2000).

References 3.1 Behr M, Rosentritt M, Lang R, Handel G. Flexural properties of fiber reinforced

composite using a vacuum/pressure or a manual adaptation manufacturing process.

J Dent 2000;28:509–514.

Chai J, Takahashi Y, Hisama K, Shimizu H. Water sorption and dimensional

stability of three glass fiber-reinforced-composites. Int J Prosthodont 2004;17:195-

9.

Chai J, Takahashi Y, Hisama K, Shimizu H. Effect of water storage on the flexural

properties of three glass fiberreinforced-composites. Dent Mater 2006;22(3):291-7.

Fan PL, Edahl A, Leung RL, Stanford JW. Alternative interpretations of water

sorption values of composite resins. J Dent Res 1985;64:78–80.

Ferracane L. Hygroscopic and hydrolytic effects in dental polymer networks. Dent

Mater 2006;22:211-222.

Miettinen VM, Narva KK, Vallittu PK. Water sorption, solubility and effect of

post-curing of glass fibre reinforced polymers. Biomaterials 1999;20:1187–1194.

Öysaed H, Ruyter I. Composites for use in posterior teeth: mechanical properties

tested under dry and wet conditions. J Biomed Mater Res 1986;20:261-271.

Patil RD, Mark JE,.Apostolov A, Vassileva E, Fakirov S. Crystallization of water

in some crosslinked gelatins. Eur Polym J 2000;36:1055–1061.

87

Ping ZH, Nguyen QT, Chen SM, Zhou JQ, Ding YD. States of water in different

hydrophilic polymers-DSC and FTIR studies. Polymer 2001; 42:8461–8467.

Santos C, Clarke RL, Braden M, Guitian F, Davy KWM. Water absorption

characteristics of dental composites incorporating hydroxyapatite filler.

Biomaterials 2002;23:1897–1904.

Scarret DC, Söderholm KJM, Ybatich CD. Water and abrasive effects on three-

body wear of composites. J Dent Res 1991;70:1074-1081.

Söderholm K, Mukherjee R, Longmate J. Filler leachability of composites stored in

distilled water or artificial saliva. J Dent Res 1996;75:1692–1699.

Soderholm K-JM, Zigan M, Ragan M, Fischlschweiger W, Bergman M. Hydrolytic

degradation of dental composites. J Dent Res 1984;63:1248–1254.

Takahashi Y, Chai J, Kawaguchi M. Effect of water sorption on the resistance to

plastic deformation of a denture base material relined with four different denture

reline materials. Int J Prosthodont 1998;11:49–54.

Takahashi Y, Chai J, Kawaguchi M. Equilibrium strengths of denture polymers

subjected to long-term water immersion. Int J Prosthodont 1999;12:348–352.

88

89

3.2. Flexural strength of fiber post: the influence of storage condition and

duration

Thanks to a rapid evolution, several types of fiber posts are currently available, and

their mechanical properties must be taken into account when making a clinical

decision. Evaluation of strength related properties of experimental and

commercially available posts have been investigated utilising fatigue resistance

(Grandini et al., 2005) (Sahafi et al., 2005) and flexural strength tests (Asmussen et

al., 1999) (Seefeld et al., 2007) (Plotino et al., 2007). The quality of the support of

the coronal restoration can be reflected by the stiffness of the post, being related to

loss of retention of a crown (Sahafi et al., 2004). The flexural modulus parameter

defines the flexibility of a sample and higher values indicate more stiffness, while

lower values indicate more flexibility. The flexural strength parameter determines

the resistance to fracture of a sample. Higher values indicate that a sample is more

resistant to fracture, lower values that it is less so. The flexural strength is

determined by the highest load a sample can withstand and depends on the

specimen configuration. A linear correlation between the diameter of posts and

their resistance to fracture load was shown in an investigation involving 17

different FRC-posts (Lassila et al., 2004). It is still not clear how the structural

properties of FRC-posts influence their flexural strengths. To investigate the

relationship between flexural strength and the structural characteristics of FRC-

posts the combination of scanning electron microscopy (SEM) and fracture testing

can be used. SEM observations can provide the information to assess the fiber/resin

matrix ratio and the fiber diameter and look at the interface between the fibers and

the matrix.

A previous study (Mannocci et al., 2001) showed that storage of posts in bovine

teeth immersed in water resulted in similar flexural strength values of posts that

were dry-stored. In order to reproduce a clinical situation, in the following studies

extracted human canines teeth were selected as one of the storage condition to be

tested.

89

90

References 3.2

Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit, and strength of

newer types of endodontic posts. J Dent 1999;27(4):275-8.

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 2005;21(2):75-82.

Lassila LV, Tanner J, Le Bell AM, Narva K, Vallittu PK. Flexural properties of

fiber reinforced root canal posts. Dent Mater 2004;20:29–36.

Mannocci F, Sherriff M, Watson TF. Three-point bending test of fiber posts. J

Endod 2001;27:758-61.

Ferracane JL, Berge HX, Condon JR. In vitro aging of dental composites in water-

effect of degree of conversion, filler volume, and filler/matrix coupling. JBiomed

Mater Res 1998;42:465-72.

Plotino G, Grande NM, Bedini R, Pameijer CH, Somma F. Flexural properties of

endodontic posts and human root dentin. Dent Mater 2007;23(9):1129-35.

Sahafi A, Peutzfeldt A, Asmussen E, Gotfredsen K. Retention and failure

morphology of prefabricated posts. Int J Prosthodont 2004;17:307-12.

Sahafi A, Peutzfeldt A, Ravnholt G, Asmussen E, Gotfredsen K. Resistance to

cyclic loading of teeth restored with posts. Clin Oral Investig 2005;9(2):84-90.

90

91

Seefeld F, Wenz HJ, Ludwig K, Kern M. Resistance to fracture and structural

characteristics of different fiber reinforced post systems. Dent Mater

2007;23(3):265-71.

91

92

3.3. The effect of different storage conditions and duration on the fracture

strength of three types of translucent fiber posts.

Alessandro Vichi, Michele Vano, Marco Ferrari. Dental Materials 2007, In press.

Introduction

Water degradation is a phenomenon that can cause several alterations in dental

resins, from physical changes, such as plasticization and softening, to chemical

ones (i.e oxidation or hydrolysis) [1-3]. Negative effects caused by water exposure

in composite materials have been reported as a reduction in their physical

properties, like tensile strength [4], flexural strength, modulus of elasticity [5] and

wear resistance [6]. Fiber reinforced composites (FRC) materials may be affected

by the detrimental effect of water uptake [7]. Water is absorbed into the FRC by

diffusion. The inflow predominantly occurs in the resinous matrix and depends on

the nature of the resin and the amount of this phase within the material [8,9]. This

process is generally time dependent and increases with time [10,11].

It is known that water storage negatively affects the flexural properties of fiber

posts [12,13]. Methacrylate-based posts have been recently introduced as an

alternative to epoxy resin-based translucent fiber posts [14]. Both methacrylate and

epoxy dental resins exhibit a tendency to water uptake due to their hydrophilicity

[15-18].

In a previous study Mannocci et al., [13] showed that storage of posts in bovine

teeth immersed in water resulted in similar flexural strength values of posts that

were dry-stored. In order to reproduce a clinical situation, in this study extracted

human canines teeth were selected as one of the storage condition to be tested.

Moreover storage in mineral oil was selected as a control group to avoid the effects

of water storage [19].

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Endodontic posts are cemented into the root canal of endodontically treated teeth,

and their coronal part is immersed into the composite resin core. Therefore in

clinical conditions the coronal restoration prevent fiber posts to be contaminated by

the oral environment and from any water or saliva uptake [13].

Thus, the aims of the study were: a) To evaluate the effects of storage duration and

condition on the flexural strength of different translucent fiber posts; b) To

morphologically evaluate the post structure before and after different storage

conditions. The null hypotheses tested were that the storage duration and condition

had no effect on the flexural strength and surface morphology of fiber post and the

post type (methacrylate or epoxy resin-based) did not affect the flexural strength in

each storage condition.

Materials and Methods

Three types of translucent fiber posts were investigated in the study: DT Light

Post, (RTD, St. Egreve, France), GC Post (GC Corporation, Tokyo Japan) and FRC

Postec Plus (Ivoclar-Vivadent, Schaan, Liechtenstein) (Table 1). The posts were

divided in 36 groups (n=14 posts each group) according to the aging protocol

performed in terms of storage duration (1, 6, 12 months) and condition: 1. Dry

storage at 37° C. 2. Storage in saline water at 37° C. 3. Storage in mineral oil

(Rhodorsil Huile 47 V 20 bacth no. 3053002, Franceschi, Pisa, Italy) at 37° C. 4.

Storage in root canal immersed in saline water at 37° C. In groups restored

according to condition 4, human canine teeth extracted for periodontal disease were

used. The teeth were endodontically treated. All root canals were treated by one

trained operator using stainless steel instruments K-files (#08-10-15; Dentsply

Maillefer Ballaigues, Switzerland), M-two instruments (#10-15-20-25; Sweden &

Martina, Due Carrare, Padova, Italy), and Profiles .06 taper (#30-35-40; Dentsply

Maillefer) mounted in a 16:1 gear reduction handpiece, driven by an electric motor

(Endo IT professional, Aseptico Inc., Woodinville, WA). The working length was

obtained at 1 mm above the radiographic apex. Instrumentation was performed

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under an operating microscope (OPMI pico, Carl Zeiss Surgical, Inc., Thornwood,

NY) at 12.5X magnification. The root canal was irrigated in between

instrumentations with 3 mL of 5.25% sodium hypochlorite using a long 27 gauge

needle. Deionized water was employed as the final rinse, and patency of the canals

was maintained with a #10 K-file. The canals were dried with multiple paper

points. AH Plus sealer (Dentsply, De Trey, Konstanz, Germany) was placed in the

canal and spread with a #45 K-file with a counterclockwise motion. The gutta-

percha was condensed using the continuous wave technique up to 4 to 5 mm from

the apex with a System B heat source (Analytic Technology, Redwood, USA).

Backfilling of the root canal was performed using thermoplastic gutta-percha and

an Obtura II unit (Obtura Corp., Fenton, MO) at 185°C.

Then the post space was prepared with low-speed post drills provided the

manufacturer to achieve diameters corresponding to those to the posts. The depth

of each canal was adjusted in such a manner that the post could be completely

inserted inside the root. The posts were not luted into the roots. After that, the

access cavity was sealed with adhesive system (Scotchbond Multi-Purpose

Adhesive, 3M/ESPE, St. Paul, MN, USA) and composite resin (Filtek Supreme

XT, 3M/ESPE, St. Paul, MN, USA shade A3). The root surface was painted with

two consecutive coats of nail varnish. Then the tooth were stored in water at 37°

for the reported time. After storage, the composite seal was removed, and the posts

were taken out from the root.

Flexural strength measurements

Artificial root canals were drilled in acrylic resin blocks (1x1x3 cm) (Endo-

Training-Bloc, Dentsply Maillefer, Ballaigues, Switzerland). The artificial canals

were enlarged with low-speed calibrated drills provided by the same manufacturer

in order to have a correspondence with the post diameter. The depth of each canal

was adjusted leaving 4.8 mm of the post extending above the resin blocks,

according to the experimental procedure previously described by Asmussen et al.,

[20]. The posts were then cemented into the artificial canals with a dual-cured

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luting cement (Calibra, Batch no. 050811-0501102, Dentsply Caulk, Milford, DE,

USA).

After the complete setting of the luting cement, the specimens were loaded in a

universal testing machine (Triaxial Tester T400 Digital, Controls S.P.A., Milano,

Italy) with a compressive load applied on the end of the post at a 45° angle to the

long axis using a crosshead speed of 1 mm/min until specimen failure (Fig. 1). The

fracture strength (S) in Newton was converted into MPa with the following

equation: S=32/π•Fl/d3 where F is the fracture load (N), l is the length of the post

(4.8 mm), and d is the diameter of the post (mm).

SEM investigation

Two posts from each group were observed longitudinally and in cross-section

before and after the storage to qualitatively evaluate their morphology. The

specimens were fixed on metallic stubs and sputtered with gold in an ion-sputtering

device (Polaron Range SC7620, Quorum Technology, Newhaven, UK). The visual

examination of the surfaces was performed with a scanning electron microscope

(SEM JSM-6060 LV, JEOL, Tokyo, Japan) at different magnifications.

Statistical Analysis

Having checked that flexural strength data were normally distributed

(Kolmogorov-Smirnov test) and group variances were homogeneous (Levene’s

test), a three-way ANOVA and Tukey's test were used to compare the effect of the

experimental factors (storage duration, storage condition, type of fiber post) on the

fracture strength (α=.05).

Results

The mean flexural strength values and standard deviations of the tested post are

presented in Table 2.

Statistical analysis revealed that the type of post and storage condition, had a

significant effect on flexural strength (p<0,001). The interaction between the two

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factors was also significant (p<0,05). Storage duration did not affect flexural

strength (p>0,05). GC Post showed the highest flexural strength (p<0,05). Water

storage significantly decreased the mean flexural strength, regardless of the post

type and the storage duration (Table 2). Posts stored into human roots immersed in

water, showed similar strength values to those stored in dry and in mineral oil.

SEM results

SEM-micrographs revealed a higher amount of voids and discontinuities between

the fibers and the resinous matrix after water storage for each post type (Fig. 2a).

All the tested posts showed a similar amount of defects in which the detachment of

the complex fiber-resin matrix was observed as the predominant degradation

pattern (Fig. 2b). No major differences were found between the three different

types of posts. However, qualitatively, FRC Postec Plus showed at 12 months of

water immersion a more pronounced delamination of the complex fiber-resin

matrix (Fig.3a). For all the post type the delamination of the fibers from the

adjacent resin matrix could be identified only along the periphery of the fiber post

(Fig. 3b). No significant alterations were recorded when posts were stored in dry,

in oil and in root dentin regardless of the post type (Fig. 4a, 4b, 4c).

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Discussion

The results of this study indicated that storage of fiber posts in human root

immersed in water resulted in similar flexural strengths values to those obtained in

dry and oil storage. Water storage had a detrimental effect on the mechanical and

morphological properties of the tested fiber posts. Thus, the null hypothesis that

there is no effect of storage conditions on the flexural strength and on the

morphology of fiber post has to be rejected. With respect to post type GC Post

showed the highest fracture strength values. Thus, also the null hypothesis that

there is no effect of post type on the flexural strength was rejected. Storage

duration did not influence fracture strengths values. Therefore the null hypothesis

that there is no effect of storage duration on the flexural strength was accepted.

The results of this study confirm the absence of any detrimental water effect on

post inserted into root canal. Previous studies clarified that droplets formation is

evident on the surfaces of replicas of deep vital dentin in the presence of positive

pulpal pressure [21-24]. Conversely as intra-radicular dentin is characterized by

absence of pulpal pressure, minor water should spontaneously emanates from the

surface. It was also previously revealed that after proper endodontic

instrumentation no increased radicular dentin permeability is evident in the

presence of intact cementum on the root surface [25] thus suggesting that the

outward fluid coming from the intra-radicular dentin is negligible in presence of at

least 1.5 mm residual dentin [26]. This hypothesis was confirmed by the analysis of

replicas showing no spontaneous droplets formation after post space preparation

[27]. The absence of water after root canal space preparation can also be due to

residual gutta-percha fragments, endodontic cement, smear layer and smear plugs

which reduce dentin permeability. Moreover unbound water is around 11% of the

entire water amount contained into a tooth and therefore hydraulic pressure and/or

osmotic gradient can unlikely attract water toward the surface of the endodontic

post space [28,29]. It should be also considered that adhesive and luting materials

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are interposed between the root dentin and a luted post therefore, even in case of a

small residual amount of water left after etching and rinsing, no water contact is

foreseen.

These results showing a reduction in the mechanical properties of fiber posts after

acqueos storage are in agreement with several reports [12,13]. The effects of water

immersion on post structure are both physical and chemical. The resinous matrix

may undergo a process of plasticization and softening, with the result of a

reduction in hardness and in wear resistance [30]. The process of water uptake is

generally time dependent and material dependent. Thus, the amount of water

absorbed into the fiber post is expected to increase with time until the material is

saturated and hydrolytically stable [31]. However in this study the storage duration

did not influence the flxural strengths values. One possible explanation is that the

water immersion time difference between the groups is relatively short or that the

water immersion time for each duration (1, 6, 12 months) was long enough to

saturate the material.

SEM-micrographs revealed a higher amount of voids and discontinuities between

the fibers and the resinous matrix after water storage. It has been described that

these voids can negatively influence the mechanical properties of posts [32]. Under

functional loading, these defects could act as starting points for microcracks

propagation, eventually leading to post fracture (Fig. 2a). Indeed under the

experimental condition of direct water immersion, a complete hydrolyzation of the

silane coupling agent which is normally used to promote adhesion between fibers

and polymer matrix may occur. As a result, fibers may detach from the matrix that

may account for the reduction in flexural strength [33,34]. In fact all the tested

posts showed a similar amount of defects in which the detachment of the complex

fiber-resin matrix was observed as the predominant degradation pattern (Fig. 3a).

No significant alterations were recorded when posts were stored in dry, in oil and

in root dentin regardless of the post type (Fig. 4a, 4b, 4c).

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The fiber posts investigated in this study differed for the nature of the resinous

matrix and the fibers. This diversity could explain the different flexural strength

values recorded between the three post types [35]. It has been shown that water has

a detrimental effect both on epoxy and methacrylate-based resinous matrixes [36].

Methacrylate and epoxy resin matrixes exhibit a high susceptibility to water

sorption and undergo a variable extent of hydrolysis over time [37,38].

Specimens exposure to water for up to 12 months resulted in partial delamination

of the quartz fibers from the epoxy resin matrix along the periphery of the DT

Light Posts (Fig. 2a). Although quartz fibers are basically inert to water sorption,

these defects may be the consequence of hydrolysis of the silane employed in

manufacturing and/or swelling of the epoxy resin matrix after water sorption [39].

A similar delamination pattern was observed also for FRC Postec and GC Post

posts, in which the glass fibers were detached from the methacrylate matrix

especially in the peripheric portions of the post.

All post types showed a reduction of flexural strength after direct water storage.

Therefore, under clinical conditions, it is advisable that fiber posts should not be

exposed to the oral environment. On the other hand the storage in human

endodontically treated teeth (group 4) which is very similar to that of a clinical

situation, was effective in avoiding the flexural-strength reduction due to contact of

posts with water. Therefore in a clinical scenario, if the fiber post is protected from

contact with water by the root canal filling and by resin composite materials, its

flexural strength will remain intact.

Further in vivo researches should be conducted to assess the clinical effect of water

on fiber posts exposed to the oral environment.

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Conclusion

Within the limitations of the study, the following conclusions can be drawn:

1. Fiber posts placed inside human root canals immersed in water showed to be

effectively preserved from water degradation effect.

2. Fiber posts stored in direct contact with water showed significant lower flexural

strength values and morphological changes regardless the post type tested.

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systems. J Appl Polymer Sci 1999;71:787-98.

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Table 1. Chemical composition and diameters of the fiber posts investigated in the study Post Brand and (batch number)

Composition Post diameter (Min / Max cross-section in mm)

Manufacturer

DT Light Post (batch n. 0401A)

Quartz fibers (60 vol%) Epoxy resin matrix (40 vol %)

1/2 RTD, St. Egreve, France

Gc Post (batch n. N4409005)

Glass Fibers (77 vol %), Methacrylate resin matrix (23 vol %),

1/2

GC Corporation, Tokyo Japan

Frc Postec Plus (batch n. H31059)

Glass fibers (70 vol %), Dimethacrylate resin matrix (21 vol %) Ytterbium fluoride (9 vol%)

1/2

Ivoclar-Vivadent Schaan, Liechtenstein

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Table 2 Mean flexural strength and standard deviation of the tested posts

Post type and store conditions 1 month 6 months

12 months

DT Light Post

Dry stored at 37°

939,33 (85,48) a 963,61 (121,94) a 1012,96 (102,89) a

Stored in saline water at 37° 654,82 (45,08) b 593,9 (61,77) b 562 (97,98) b

Stored in oil 37°

904,64 (87,64) a 837,96 (86,81) a 917,52 (114,97) a

Stored in root dentin and

immersed in water at 37°

906,33 (65,31) a 901,09 (86,11) a 926,29 (88,42) a

GC Post

Dry stored at 37° 1144,5 (189,19) c 1121,38 (112,84) 1179,86 (159,61) c

Stored in saline water at 37° 829,28 (103,93) d 716,1 (101,39) d 675,55 (124,46) d

Stored in oil at 37° 1079,18 (183,9) c 1035,5 (132,86) c 1079,18 (130,4) c

Stored in root dentin and

immersed in water at 37°

1128,02 (122,65) c 1118,5(66,18) c 1166,38( 130,95) c

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FRC Postec Plus

Dry stored at 37° 870,37(72,02) a 930,82 (99,07) a 917,9 (84,98) a

Stored in saline water at 37° 596,09 (25,98) b 547,3 (57,43) b 532,9 (41,1) b

Stored in oil 37° 822,05 (100,38) a 859,63 (101,49) a 895,1 (54,36) a

Stored in root dentin and

immersed in water at 37°

908,47 (85,29) a 884,08 (86,19) a 917,14 (84,79) a

Values are mean and standard deviation in MPa. Values with the same lower case letters are not significantly different (p > 0.05)

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FIGURE LEGENDS

Fig. 1 Schematic drawing of the setup for ultimate fracture strength testing of the

post

Fig. 2 (a) Representative SEM micrograph of DT Light Post after 12 months of

water storage condition (1500x; bar=10 µm). Lack of bonding between the fibers

and the resinous matrix is evident. (b) Representative SEM micrograph of GC Post

after 12 months of storage in water (250x; bar=100 µm). The fibers appear denuded

of the resinous matrix.

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Fig. 3 (a) Representative SEM micrograph of FRC Postec Plus after 12 months of

water storage condition (1500x; bar=10 µm). The complex fiber-resin matrix

appears disrupted.

(b) Representative SEM micrograph of a cross section showing the delamination of

the glass fibers (GC Post) from the adjacent methacrylate resin matrix along the

periphery of the fiber post after 12 months of water storage (70x; bar=200 µm).

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Fig. 4 (a) Representative SEM micrograph of DT Light Post after 12 months of

storage in root immersed in water (500x; bar=50 µm) showing a compact matrix

without porosities. (b) Representative SEM micrograph of GC Post after 12 months

of storage in root canal immersed in water showing the integrity of the post

structure (500x; bar=50 µm). (c) Representative SEM micrograph of FRC Postec

Plus after 12 months of storage in root canal immersed in water showing an intact

post structure (500x; bar=50µm).

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3.4. The influence of storage condition and duration on the resistance to

fracture of different fiber posts systems

Michele Vano, Carlos Carvalho, Maurizio Sedda, Mario Gabriele, F Garcia-Godoy,

Marco Ferrari. American Journal of Dentistry; Accepted 2007.

Introduction

In order to improve the fracture resistance of endodontically treated teeth restored

with a post-and-core system, research has focused on post materials,1,2 post designs

and luting agents.3-7 However recently it has been shown that other factors such as

storage condition 8 and duration 9 may influence the fracture resistance of fiber

posts.

Aging in water or aqueous fluids is known to decrease the fracture resistance of

fiber reinforced composites (FRC) materials as a result of water absorption by the

resin matrix and hydrolisis of filler matrix interfaces.10-13 In vitro tests reported that

water storage negatively affects the flexural properties of fiber posts when directly

immersed in water. 14 The inflow predominantly occurs in the resinous matrix and

depends on the nature of the resin and the amount of this phase within the material.

15 This process is generally time dependent and increases with time until the

material is saturated and hydrolytically stable. 16

In clinical conditions endodontic posts are cemented into the root canal of

endodontically treated teeth and their coronal part is immersed into the composite

resin core, therefore fiber posts are protected from the oral environment and from

any water or saliva uptake.

However a recent study reported the presence of water into root canals after

endodontic and prosthodontic procedures.17 Chersoni et al., 17 showed blistering

formation on the surface of simplified adhesives when applied on intra-radicular

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dentin. The authors speculated that droplets formation occurred due to residual

dentin water that was osmotically soaked by the etching and adhesives and then

retrieved on the adhesive surface due the intrinsic permeability of the polymerized

bonded surface. More recently Ferrari et al., 18 repeated a similar in vivo protocol,

the results showed that after etching of the intra-radicular dentin no water droplets

formation occurred on the dentin surface. The authors concluded that the adhesives

themselves are responsible for the droplets formation, probably due to residual un-

evaporated solvent.19 In order to reproduce a similar clinical situation, in this study

extracted canines were selected as one of the storage condition to be tested.

Thus, the aims of the study were: a) To evaluate the effects of storage condition

and duration on the resistance to fracture of different translucent fiber posts; b) To

morphologically evaluate the post structure before and after different storage

conditions. The null hypotheses tested were that the post type, the storage condition

and duration had no effect on the resistance to fracture and on the surface

morphology.

Materials and Methods

Three types of translucent fiber posts of small size were investigated in the study:

DT Light Post, (RTD, St. Egreve, France), GC Post (GC Corporation, Tokyo

Japan) and FRC Postec Plus (Ivoclar-Vivadent, Schaan, Liechtenstein) (Table 1).

Four different test groups were evaluated and for each of these 3 post types and 2

storage duration were evaluated. Thus a total of 24 individual groups, each

consisting of 12 posts were evaluated, ten of them, randomly chosen, were used for

the three-point bending test and two were used for SEM evaluation without being

fractured.

The groups were divided according to the aging protocol performed in terms of

storage duration (6, 12 months) and storage condition: 1. Dry storage at 37° C. 2.

Storage soaked in saline water at 37° C. 3. Storage soaked in mineral oil (Rhodorsil

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Huile 47 V 20 bacth no. 3053002, Franceschi, Pisa, Italy) at 37° C. 4. Storage

inside the root canal immersed in saline water at 37° C. Storage in mineral oil was

selected as a control group 20. In groups restored according to condition 4, human

canine teeth extracted for periodontal disease were used. The teeth were

endodontically treated. All root canals were treated by one previously calibrated

operator using stainless steel instruments K-files (#08-10-15; Dentsply Maillefer

Ballaigues, Switzerland), M-two instruments (#10-15-20-25; Sweden & Martina,

Due Carrare, Padova, Italy), and Profiles .06 taper (#30-35-40; Dentsply Maillefer)

mounted in a 16:1 gear reduction handpiece, driven by an electric motor (Endo IT

professional, Aseptico Inc., Woodinville, WA). The working length was obtained

at 1 mm above the radiographic apex. Instrumentation was performed under an

operating microscope (OPMI pico, Carl Zeiss Surgical, Inc., Thornwood, NY) at

12.5X magnification. The dowel space was irrigated in between instrumentations

with 3 mL of 5.25% sodium hypochlorite using a syringe with and endodontic

needle. Deionized water was employed as the final rinse, and patency of the canals

was maintained with a #10 K-file. The canals were dried with multiple paper points

until moisture was not detected. AH Plus sealer (Dentsply, De Trey, Konstanz,

Germany) was placed in the canal and spread with a #45 K-file with a

counterclockwise motion. The gutta-percha was condensed using the continuous

wave technique up to 4 to 5 mm from the apex with a System B heat source

(Analytic Technology, Redwood, USA). Backfilling of the root canal was

performed using thermoplastic gutta-percha and an Obtura II unit (Obtura Corp.,

Fenton, MO) at 185°C.

Then the post space was prepared with low-speed post drills provided the

manufacturer in order to have diameters corresponding to those to the posts. The

depth of each canal was adjusted in such a manner that the post could be

completely inserted inside the root. The posts were not luted into the roots. After

that, the access cavity was sealed with adhesive system (Scotchbond Multi-Purpose

Adhesive, 3M/ESPE, St. Paul, MN, USA) and resin composite (Filtek Supreme

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XT, 3M/ESPE, St. Paul, MN, USA shade A3). The root surface was sealed with

two consecutive coats of nail varnish. Then the roots were maintained soaked in

water at 37° C for the reported storage time. After storage, the composite seal was

removed, and the posts were carefully dislocated from the root.

Three-point bending test

The three-point bending method was conducted according to the DIN-EN 843-1 in

a universal testing machine (Triaxial Tester T400 Digital, Controls S.P.A., Milano,

Italy). The load was applied to the posts with a loading angle of 90° and a

crosshead speed of 0.5 mm/min until fracture. The two supports and the central

loading anvil had a 2-mm cross-sectional diameter and the distance between the

two supports was 8 mm. In order to eliminate the influence of the conical end of

some of the posts, a short span length (8 mm) was used to get support for the post

within the cylindrical part of the post. The parallel-sided cylindrical part of the post

was considered to be the specimen. Fracture loads were recorded and the flexural

strength was calculated using the formula: 38dFl

πσ =

where F is the applied load (N) at which the sample fractured, l (mm) is the span

length, d (mm)is the diameter of the specimens.

Scanning Electron Microscopy (SEM) evaluation

Two posts randomly selected from each group were observed longitudinally and in

cross-section before and after the storage to qualitatively evaluate their

morphology. The specimens were cleaned with ethanol, fixed on metallic stubs and

sputtered with gold in an ion-sputtering device (Polaron Range SC7620, Quorum

Technology, Newhaven, UK). The visual examination of the surfaces was

performed with a scanning electron microscope (SEM JSM-6060 LV, JEOL,

Tokyo, Japan) at different magnifications.

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Statistical Analysis

Having checked that flexural strength data were normally distributed

(Kolmogorov-Smirnov test) and group variances were homogeneous distributed

(Levene’s test), a three-way ANOVA and Tukey's test were used to compare the

effect of the experimental factors (storage condition, storage duration, type of fiber

post) on the flexural strength (α=0.05).

Results

The flexural strength of tested specimens is presented in Table 2.

Statistical analysis revealed that the type of post and storage condition, had a

significant effect on flexural strength (p<0.05). The interaction between the two

factors was also significant (p<0.05). Storage duration did not affect flexural

strength (p>0.05). GC Post and DT Light Post showed the highest flexural strength

(p<0.05). Water storage significantly decreased the mean flexural strength,

regardless of the post type and the storage duration (Table 2). Posts stored inside

human roots immersed in water, showed similar flexural strength values to those

stored in dry and in mineral oil.

SEM analysis

SEM-micrographs revealed a high quantity of voids and discontinuities between

the fibers and the resinous matrix after water storage for each post type (Fig. 1

a,b,c). All the tested posts showed a similar quantity of defects in which the

detachment of the complex fiber-resin matrix was observed as the predominant

degradation pattern. No major differences were found among the three different

types of posts. However, qualitatively, FRC Postec Plus showed at 12 months

immersed inside water more pronounced delamination of the complex fiber-resin

matrix (Fig. 1c). For all the post type the delamination of the fibers from the

adjacent resin matrix could be identified only along the periphery of the fiber post

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(Fig. 1b). No significant alterations were recorded when posts were stored in dry,

in oil and inside root dentin regardless of the post type (Fig. 2 a,b,c).

Discussion

The results of this study indicated that storage of fiber posts in human roots

immersed in water resulted in similar flexural strengths values to those obtained in

dry and oil storage. On the other hand the storage of fiber posts in water, showed

the lowest fracture loading values. Moreover water storage affected the

morphological properties of the tested fiber posts. Thus, the null hypothesis that

there is no effect of storage conditions on the fracture resistance and on the

morphology of fiber post has to be rejected. Regarding the storage duration no

significant difference was observed. Thus, the null hypothesis that there is no effect

of storage duration on the fracture resistance of fiber post has to be accepted. The

highest flexural strength values were achieved by GC Post and DT Light Post.

Thus, the null hypothesis that there is no effect of post type on the flexural strength

was rejected.

The results of this study confirm the absence of any detrimental water effect on

post inserted in root canal. Indeed the statistics showed that after storage in human

teeth all posts had flexural strength values that were not significantly different from

posts that were dry-stored or oil stored. On the contrary, fiber posts immersed

directly in water showed a reduction in the flexural strength values. The effects of

water immersion on post structure are both physical and chemical. The resinous

matrix may undergo a process of plasticization and softening, with the result of a

reduction in hardness and in wear resistance.21 The process of water uptake is

generally time dependent and material dependent.9 Thus, the amount of water

absorbed into the fiber post is expected to increase with time until the material is

saturated and hydrolytically stable.22 Conversely, in this study the storage duration

did not influence the flexural strengths values. One possible explanation is that the

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water immersion time difference among the groups is relatively short or the tested

storage duration (6, 12 months) was long enough to saturate the material.

SEM-micrographs revealed a higher quantity of voids and discontinuities between

the fibers and the resinous matrix after water storage. It has been described that

these voids can negatively influence the mechanical properties of posts.23 Under

functional loading, these defects could act as starting points for microcracks

propagation, eventually leading to post fracture (Fig. 1a). Indeed under the

experimental condition of direct water immersion, a complete hydrolyzation of the

silane coupling agent which is normally used to promote adhesion between fibers

and polymer matrix may occurs. As a result, fibers may detach from the matrix that

may account for the reduction in flexural strength values.24,25 In fact, all the tested

posts showed a similar amount of defects in which the detachment of the complex

fiber-resin matrix was observed as the predominant degradation pattern (Fig. 1b).

No significant alterations were recorded when posts were stored in dry, in oil and

in root dentin regardless of the post type (Fig. 3 a,b,c).

Explanations of the difference of flexural strengths among the tested posts could

include the differences in matrix, fiber nature, the number of flaws, and porosities

at the fiber–matrix junction.26 It has been shown that water has a detrimental effect

both on epoxy and methacrylate-based resinous matrixes.27 Methacrylate and epoxy

resin matrixes exhibit a high susceptibility to water sorption and undergo a variable

extent of hydrolysis over time.28,29 Specimens exposure to water for up to 12

months resulted in partial delamination of the quartz fibers from the epoxy resin

matrix along the periphery of the DT Light Post (Fig. 1a). Although quartz fibers

are basically inert to water sorption, these defects may be the consequence of

hydrolysis of the silane employed in manufacturing and/or swelling of the epoxy

resin matrix after water sorption.30 A similar delamination pattern was observed

also for GC Post (Fig. 1b) and FRC Postec Plus (Fig. 1c), in which the glass fibers

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were detached from the methacrylate matrix especially in the peripheric portions of

the post.

All post types showed a reduction of fracture load after direct water storage.

Therefore, under clinical conditions, it is advisable that fiber posts should not be

exposed to the oral environment. On the other hand the storage in human

endodontically treated teeth which is very similar to that of a clinical situation was

effective in avoiding the fracture-load reduction due to contact of posts with water.

Within the limitations of the study, the following conclusions can be drawn:

1. Fiber posts placed inside human root canals immersed in water are not affected

by water detrimental effect.

2. Fiber posts stored in direct contact with water showed significant lower flexural

strength values and morphological changes regardless the post type.

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REFERENCES

1. Ferrari M, Vichi A, Garcia-Godoy F. Clinical evaluation of fiber reinforced

epoxy resin posts and cast post and cores. Am J Dent 2000;13:8B-15B.

2. Sorensen JA, Engelman MJ. Effect of post adaptation on fracture resistance of

endodontically treated teeth. J Prosthet Dent 1990;64:419-24.

3. Ferrari M, Goracci C, Sadek FT, Monticelli F, Tay FR. An investigation of the

interfacial strengths of methacrylate resin-based glass fiber post-core buildups. J

Adhes Dent 2006;8:239-45.

4. Vano M, Cury AH, Goracci C, Chieffi N, Gabriele M, Tay FR, Ferrari M. The

effect of immediate versus delayed cementation on the retention of different types

of fiber post in canals obturated using a eugenol sealer. J Endod 2006;32:882-5.

5. Grandini S, Sapio S, Goracci C, Monticelli F, Ferrari M. A one step procedure

for luting glass fibre posts: an SEM evaluation. Int Endod J 2004;37:679-86.

6. 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 Prosthodont 2001;14:543-9.

7. Ferrari M, Vichi A, Grandini S. Efficacy of different adhesive techniques on

bonding to root canal walls: an SEM investigation. Dent Mater 2001;17:422-9.

8. Mannocci F, Sherriff M, Watson TF. Three-point bending test of fiber posts. J

Endod 2001;27:758-61.

9. Chai J, Takahashi Y, Hisama K, Shimizu H. Water sorption and dimensional

stability of three glass fiber-reinforced-composites. Int J Prosthodont 2004;17:195-

9.

10. Ferracane L. Hygroscopic and hydrolytic effects in dental polymer networks.

Dent Mater 2006;22:211-222.

11. Miettinen VM, Narva KK, Vallittu PK. Water sorption, solubility and effect of

post-curing of glass fibre reinforced polymers. Biomaterials 1999;20:1187–1194.

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12. Santos C, Clarke RL, Braden M, Guitian F, Davy KWM. Water absorption

characteristics of dental composites incorporating hydroxyapatite filler.

Biomaterials 2002;23:1897–1904.

13. Lassila LV, Nohrstrom T, Vallittu PK. The influence of short-term water

storage on the flexural properties of unidirectional glass fiber-reinforced

composites. Biomaterials 2002;23:2221–9.

14. Lassila LVJ, Tanner J, Le Bell AM, Narva K, Vallittu PK. Flexural properties

of fiber reinforced root canal posts. Dent Mater 2004;20:29-36.

15. Fan PL, Edahl A, Leung RL, Stanford JW. Alternative interpretations of water

sorption values of composite resins. J Dent Res 1985;64:78–80.

16. Takahashi Y, Chai J, Tan SC. Effect of water storage on the impact strength of

three glass fiber-reinforced composites. Dent Mater 2006;22:291-7.

17. Chersoni S, Acquaviva GL, Prati C, Ferrari M, Pashley DH, Tay FR. In vivo

fluid movement through dentin adhesives in endodontically treated teeth. J Dent

Res 2005;84:223-7.

18. Ferrari M, Coniglio I, Magni E, Cagidiaco MC, Gallina G, Prati C, Breschi L.

How can droplets formation occur in endodontically treated teeth during bonding

procedures? J Adhes Dent, In press.

19. Van Landuyt KL, De Munck J, Snauwaer J, Coutinho E, Poitevin A, Yoshida

Y, Inoue S, Peumans M, Suzuki K, Lambrecths P, Van Meerbeek B. Monomer-

solvent phase separation in one-step self-etc adhesives. J Dent Res 2005;84:183-8.

20. Carrilho MR, Tay FR, Pashley DH, Tjaderhane L, Carvalho RM. Mechanical

stability of resin-dentin bond components. Dent Mater 2005;21:232-41.

21. Ferracane L, Berge HX, Condon JR. In vitro aging of dental composites in

water–effect of degree of conversion, filler volume, and filler/matrix coupling. J

Biomed Mater Res 1998;42:465–47.

22. Nishiyama N, Komatsu K, Fukai K, Nemoto K. Influence of absorption

characteristics of silane on the hydrolytic stability of silane at the silica-matrix

interface. Composites 1995;26:309-313.

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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 Mater 2005;21:75–82.

24. Söderholm KJM, Roberts MJ. Influence of water exposure on the tensile

strength of composites. J Dent Res 1990;69:1812-6.

25. Meyer M, Friedman R, Del Schutte H, Latour R. Long-term durability of the

interface in FRP composites after exposure to simulated physiologic saline

environments. J Biomed Mater Res 1994;28:1221–1231.

26. Drummond JL, Mahenda SB. Static and cyclic loading of fiber-reinforced

dental resin. Dent Mater 2003;19:226–31.

27 Venz S, Dickens B. NIR-spectroscopic investigation of water sorption

characteristics of dental resins and composites. J Biomed Mater Res 1991;25:1231–

1248.

28. Miyata N, Matsuura W, Kokubo T. Mechanical behaviour of bioactive

composite cements consisting of resin and glass-ceramic powder in a simulated

body fluid: Effect of silane coupling agent. J Mater Sci 2004;15:1013-1020.

29. Harper EJ, Braden M, Bonfield W. Mechanical properties of hydroxyapatite

reinforced poly(ethylmethacrylate) bone cement after immersion in a physiological

solution: influence of silane coupling agent. J Mater Sci 2000;11:491-497.

30. Van Landingham MR, Eduljee RF, Gillespie JW. Moisture diffusion in epoxy

systems. J Applied Polymer Sci 1999;71:787-98.

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Table 1. Chemical composition and diameters of the fiber posts investigated in the study. Post Brand and Manufacturer

Composition Mean Post diameter (mm)

Post Design

DT Light Post, RTD, St. Egreve, France

Quartz fibers (60 vol%) Epoxy resin matrix (40 vol %)

1.22 Cylindrical-conical

Gc Post, GC Corporation, Tokyo Japan

Glass Fibers (77 vol %), Methacrylate resin matrix (23 vol %),

1.15

Cylindrical

Frc Postec Plus, Ivoclar-Vivadent Schaan, Liechtenstein

Glass fibers (70 vol %), Dimethacrylate resin matrix (21 vol %) Ytterbium fluoride (9 vol%)

1.35

Cylindrical-conical

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Table 2. Mean flexural strength of the tested post systems

Post type and store media 6 months

12 months

DT Light Post

Dry stored at 37°

940,22 (95,75) a 946,7 (68,62) a

Stored in saline water at 37° 553,39 (52,92) b 503,32 (122,45) b

Stored in oil 37°

896,9 (64,77) a 899,47 (55,56) a

Stored in root dentin and

immersed in water at 37°

922,55 (42,9) a 903,61 (64,34) a

GC Post

Dry stored at 37° 985,02 (91,72) a 921,14 (92,66) a

Stored in saline water at 37° 490,04 (56,54) b 458, 67(72,9) b

Stored in oil at 37° 919,4 (98,01) a 902,46 (76,92) a

Stored in root dentin and

immersed in water at 37°

935,72(103,13) a 922,67( 83,79) a

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FRC Postec Plus

Dry stored at 37° 816,56 (83,47) c 824,46 (96,42) c

Stored in saline water at 37° 473,25 (88,17) d 426,53 (45,69) d

Stored in oil 37° 809,81 (91,59) c 819,36 (77,58) c

Stored in root dentin and

immersed in water at 37°

824,11 (105,99) c 817,28 (62,57) c

Values are mean and standard deviation in Mpa.

Values with the same lower case letters are not significantly different (p >0.05)

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FIGURE LEGENDS

Fig. 1 (a) Representative SEM micrograph of DT Light Post after 12 months of

water storage condition (250x; bar=100 µm). Lack of bonding between the fibers

and the resinous matrix is evident.

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(b) Representative SEM micrograph of GC Post after 12 months of storage in water

(500x; bar=50 µm). The fibers appear denuded of the resinous matrix.

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(c) Representative SEM micrograph of FRC Postec Plus after 12 months of storage

in water (1500x; bar=10 µm). The fibers appear denuded of the resinous matrix

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Fig. 2 (a) Representative SEM micrograph of DT Light Post after 12 months of

storage in root immersed in water (1000x; bar=10 µm) showing a compact matrix

without porosities.

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(b) Representative SEM micrograph of GC Post after 12 months of storage in root

canal immersed in water showing the integrity of the post structure (500x; bar=50

µm).

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(c) Representative SEM micrograph of FRC Postec Plus after 12 months of storage

in root canal immersed in water showing an intact post structure (500x; bar=50µm)

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Chapter 4

4.1. Effects of wear on fiber post morphology

The wear resistance of dental composites is of great consideration in the case of

dental restorations, as significant loss of restored surface due to wear can

jeopardize its clinical longevity (Venhoven et al., 1996). This loss of substance in

the dental context can be due to erosive, abrasive, corrosive and other types of

wear. The wear behavior of dental materials is an important research topic and

must be investigated when developing materials for dental applications. Based on a

literature survey, there is minimal data available on the mechanical behavior and

wear characteristics of fiber posts. The fiber-reinforced radicular posts have been

produced by incorporating various fibers into the resin matrix (Fortin et al., 2000).

Wear of composites is known to depend on filler particle-related features,

particularly on the concentration and size of the filler reinforcement (Turssi et al.,

2003). While many dental composites may contain a high percentage of filler

particles (some up to 90% by weight), FRCs are limited to a much smaller filler

ratio, for proper homogenous mixing. From the available compatible fibers, glass

fibers have drawn the most attention due to their esthetic qualities and easy

manipulation (Karacaer et al., 2002).

In vitro studies showed that fiber volume fraction and the water sorption of the

polymer matrix had a significant effect on the flexural properties of FRCs (Lassila

et al., 2002, 2004). A decrease of flexural properties after water immersion was

considered to be mainly caused by plasticizing effect of water.

Endodontic posts are cemented into the root canal of endodontically treated teeth,

and their coronal part is immersed into the composite resin core. Therefore in

clinical conditions the coronal restoration prevent fiber posts to be contaminated by

the oral environment and from any water, saliva uptake or wear effect (Mannocci et

al., 2001). However observation of exposed post on a direct restoration is a

common finding (Fredriksson et al., 1998). Therefore is it of interest to evaluate

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whether the exposure to the oral environment and occlusal function affects the

morphological integrity of luted intracanalar translucent fiber posts.

References 4.1.

Fortin D, Vargas MA. The spectrum of composites: new techniques and materials.

J Am Dent Assoc 2000;131:26–30.

Fredriksson M, Astbäck J, Pamenius M, Arvidson K. A retrospective study of 236

patients with teeth restored by carbon fiber-reinforced epoxy resin posts. J Prosthet

Dent 1998;80:151-7.

Lassila LV, Nohrstrom T, Vallittu PK. The influence of short-term water storage

on the flexural properties of unidirectional glass fiber-reinforced composites.

Biomaterials 2002;23:2221–9.

Lassila LV, Tanner J, Le Bell AM, Narva K, Vallittu PK. Flexural properties of

fiber reinforced root canal posts. Dent Mater 2004;20:29-36.

Mannocci F, Sherriff M, Watson TF. Three-point bending test of fiber posts. J

Endod 2001;27:758-61.13

Karacaer O, Dogan A, Dogan OM, Usanmaz A. Dynamic mechanical properties of

dental base material reinforced with glass fiber. J Appl Polymer Sci 2002;85:1683–

97.

Turssi CP, Purquerio BM, Serra MC. Wear of dental resin composites: insights into

underlying processes and assessment methods-a review. J Biomed Mater Res

2003;65B:280–5.

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Venhoven BA, De Gee AJ, Werner A, Davidson CL. Influence of filler parameters

on the mechanical coherence of dental restorative resin composites. Biomaterials

1996;17:735–40.

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4.2. Effects of oral environment and occlusal wear on FRC-posts integrity in

clinical service for 5 years

Michele Vano, Franklin Garcia-Godoy, Cecilia Goracci, Alessandro Vichi, Marco

Ferrari. Journal of Adhesive Dentistry, Submitted.

Introduction

Fiber posts can be used for restoring endodontically treated teeth with both direct

and indirect restorations.8 The primary purpose of a post is to connect the root with

the build-up material placed on the coronal portion and to provide retention to the

coronal restoration.10 Fiber post are made in several standardised lengths in order to

be adaptable to different roots. Each post must be tried in and then cut at the

adequate length to remain within the abutment and/or the direct restoration .11

Coronally the post surface should be completely covered by a composite resin layer

of at least 1.5 mm in thickness, in order to mask the post surface color shade,22 and

to protect the post itself from microfractures that may occur to the restoration

or/and the abutment.12 Visibility of the exposed post on a direct restoration is a

common finding,9 however it is not clear yet whether the exposure of the post to

the oral environment may lead to clinical failure of the restoration .

In vitro studies reported that the exposed post may undergo structural alterations

due to wear and water degradation that may influence its mechanical properties.13A

valid method to qualitatively evaluate the detrimental effect of water on post

morphology is scanning electron microscopy (SEM).21,23 Clinical evaluation is the

most widely accepted method to measure the wear resistance of a dental material.

2,4 Unfortunately, the complex and variable conditions in a human mouth makes

wear difficult, if not impossible to reproduce in a laboratory. Limited information

is available on the mechanical behavior and wear characteristics of dental FRCs.

Among the parameters for measuring wear, SEM analysis is commonly used as it

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allows to evaluate wear patterns and characteristics.3 Ideally, the wear of a dental

material should be similar to that of enamel. To date, however, this property may

only be found in ceramic materials and some metal alloys.1,6

Although significant improvements have been achieved, composite resins still

exhibit considerable in vivo wear in the long run.24 However, in vivo wear

measurements are generally scarce and differ from study to study, in relation to

differences in wear analyzing methods and sample selection.19 No data are

available on fiber posts wear under in vivo and in vitro conditions.

The aim of this study was to evaluate whether the exposure to the oral environment

and occlusal function affects the morphological integrity of luted intracanalar fiber

posts retaining a direct composite restoration or a composite resin crown abutment.

Material and Methods

Participants in the study were recruited from patients visiting the Department of

Fixed Prosthodontics and Dental Materials, University of Siena, Italy. The study

was approved by the Ethical Committee of the University. All patients signed an

informed consent form. Criteria for excluding patients from the study were being

under the age of 18 years or incapable of signing a contract (mentally disabled or

disordered patients, unable to give freewill statements), pregnancy or lactation,

unacceptable oral hygiene status, clenching or grinding of teeth, known allergic

reaction to the materials used (all evaluated from answers to specific questions by

the examiner). The study group consisted of 20 subjects (13 females and 7 males),

aged between 22 and 58 years, with a mean age of 40 years. All subjects had

comparable oral hygiene status. It was required that the teeth had opposing tooth

contacts. One tooth of each subject included in the study underwent a standardized

endodontic treatment. All root canals were treated by one trained operator using the

following instruments: K-files #08-10-15 (Dentsply Maillefer Ballaigues,

Switzerland), M-two instruments #10-15-20-25 (Sweden & Martina, Due Carrare,

Padova, Italy), Profiles .06 taper #30-35-40 (Dentsply Maillefer), mounted in a

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16:1 gear reduction handpiece driven by an electric motor (Endo IT professional,

Aseptico Inc., Woodinville, WA). The working length was obtained at 1 mm above

the radiographic apex. The root canal was irrigated in between instrumentation with

3 mL of 5.25% sodium hypochlorite using a long 27 gauge needle. Deionized water

was employed as the final rinse, and patency of the canals was maintained with a

#10 K-file. The canals were dried with multiple paper points. Endodontic sealer

(AH Plus, Dentsply, De Trey, Konstanz, Germany) was placed in the canal and

spread with a #45 K-file with a counterclockwise motion. The gutta-percha was

condensed using the continuous wave technique up to 4 to 5 mm from the apex

(System B heat source, Analytic Technology, Redwood, USA). Backfilling of the

root canal was performed using thermoplastic gutta-percha and an Obtura II unit

(Obtura Corp., Fenton, MO) at 185°C.

Then the post space was prepared with low-speed post drills provided by the

manufacturer (RTD, St. Egreve, France) in order to have diameters corresponding

to those to the DT Light Post posts (RTD, St. Egreve, France). Posts were luted

with Calibra Esthetic Resin Cement (Dentsply DeTrey Konstanz, Germany).

In ten teeth (Group 1) the post head remained exposed on the occlusal surface of a

direct resin composite restoration (Scotchbond Multi-Purpose Adhesive and Filtek

Supreme XT, 3M/ESPE, St. Paul, MN, USA) (Fig. 1), that was polished with

carbide burs (Diatech, Diatech Dental AC, Heerbrugg Switzerland) and extra thin

contouring and polishing discs (Sof-Lex, 3M Dental Products, St Paul, MN, USA).

In the other ten teeth (Group 2) (control group) the post head remained exposed on

the occlusal surface of a resin composite abutment (Filtek Supreme XT, 3M/ESPE,

St. Paul, MN, USA), to be covered with a porcelain fused to metal crown.

One experienced prosthodontist performed all tooth preparations in a standardized

manner with an occlusal reduction of 2.0 mm, axial reduction of 1.2–1.5 mm, a

total convergence angle of 6◦, and rounded line angles. The finish line was a 1.2

mm internally rounded circumferential shoulder.

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The crowns were finished and inspected with a microscope (OPMI pico, Carl Zeiss

Surgical, Inc., Thornwood, NY) at 12.5X magnification. All crowns were

fabricated by one dental laboratory technician. The fit of the crowns was assessed

on the respective teeth visually and tactually with a dental explorer. The fit of each

crown was repeatedly assessed, before and after the cementation procedures.

Crowns were cemented with a provisional cement (Temp Bond, Kerr, Romulus,

MI). All patients received oral hygiene instructions after cementation. For baseline

evaluation, polyether impressions (Permadyne, 3M ESPE Seefeld, Germany) were

taken of the restorations occlusal surfaces immediately after polishing in Group 1

and of the abutments before crown luting in Group 2 (Fig. 2). After a 5-year period

of clinical service, polyether impressions were taken again for the directly restored

teeth and the abutments.

SEM investigation

All the impressions were poured in epoxy resin (Buehler, Lake Bluff, IL, USA).

The specimens were fixed on metallic stubs, sputtered with gold in an ion-

sputtering device (Polaron Range SC7620, Quorum Technology, Newhaven, UK),

and observed under a scanning electron microscope (SEM JSM-6060 LV, JEOL,

Tokyo, Japan) at different magnifications, in order to assess whether the post

surface underwent structural changes due to water uptake and/or occlusal wear

during clinical function.

Results

No remarkable differences were seen between baseline (Fig. 3a) and after 5 years

(Fig. 3b) for either group. Neither group exhibited after the 5-year clinical service

microscopic signs of post surface degradation due to water uptake. In group 1

specimens, the exposed post exhibited some signs of wear, that appeared to be

more pronounced for the fiber-reinforced composite post than for the particle-filled

composite of the coronal restoration (Fig. 4).

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Discussion

No signs of degradation of post surface due to water uptake were seen for group 1

and group 2 specimens. In group 1 a limited amount of wear rate probably due to

the 5 years period of clinical service was detected. Therefore the null hypothesis

that the exposure to the oral environment has no effect on the morphological

integrity of fiber posts retaining a direct composite restoration must be accepted.

Aging in water or aqueous fluids is known to decrease the fracture resistance of

fiber reinforced composites (FRC) as a result of water absorption by the resin

matrix and hydrolisis of filler matrix interfaces 7,18. In vitro tests reported that water

storage negatively affects the flexural properties of fiber posts when directly

immersed in water 14. However in clinical conditions endodontic posts are

cemented into the root canal of endodontically treated teeth and their coronal part is

immersed into the composite resin core, therefore fiber posts are protected from the

oral environment and from any water or saliva uptake. Nonetheless observation of

exposed post on a direct restoration is a common finding.9 Therefore in the present

study the post was positioned in order to have its coronal portion exposed to the

oral environment in order to mimic those clinical situations. In addition having the

post head exposed was the only method to evaluate any morphological changes of

the post by polyether impressions.

Abutments under porcelain fused metal crowns were chosen as control group,

because represent the standard of care for indirect restorations thanks to their high

wear and occlusal loading resistance.16 Another advantage of metal ceramic crown

was that it could be removed when luted with a provisional cement. That allowed

taking several polyether impressions for SEM analysis.

The homogeneity of the bonding interface between the post and the core material

can play an important role on the longevity of the final restoration of the

endodontically treated tooth. The presence of voids/bubbles within the post surface

and the development of gaps along the interface with the resin core or abutment

may increase the risk of fracture under functional loading. 17 In the present study no

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voids or bubbles within the post and no gaps between the post and the restoration

were detected. Recent studies have showed that water storage of fiber post resulted

in a reduction of the mechanical properties.23 On the other hand when fiber posts

were placed inside human root canals immersed in water no detrimental effect was

observed.21 Specimens in group 1 are surrounded by a direct resin restoration,

which may impede any water effect. This could be a possible explanation for the

absence of any morphological alteration for tested posts.

When measuring wear, both the material of interest and the opposing material must

be considered, especially if the opposing substrate is enamel. All the samples tested

had enamel as opposing substrate, therefore a high rate of wear was expected .5 On

the contrary SEM observations both in group 1 and 2 revealed after 5 years of

clinical service respectively few and no wear signs. In particular the fibers

appeared well bonded to the matrix material with an uniform distribution pattern

(Fig.5). Interestingly in group 1 the resin matrix of the fiber post, after 5 years of

clinical service, abraded more than the resin matrix of the composite restoration

(Fig. 4). Wear of composites is known to depend on filler particle-related features,

particularly on the concentration and size of the filler reinforcement. 20 The

composition of DT Light Post posts (RTD, St. Egreve, France) differs from the

resin composite used for the direct restoration (Filtek Supreme XT, 3M/ESPE, St.

Paul, MN, USA). In fact the resin matrix of the composite restoration has a higher

filler content, that may enhance its wear resistance. 15

SEM observation of the surface of group 2 specimens after a 5 years period showed

no wear signs. This was rather expected, once the abutment is covered with a

prosthetic crown it can be assumed that the occlusal surface will remain intact.

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Conclusion

In conclusion, within the limitations of this 5-year study, the fiber post surface

exposed in direct resin restoration did not show evidence of morphological changes

related to water degradation, although it exhibited a limited loss of structure due to

occlusal wear. When the fiber post surface was exposed on the top of the abutment,

the seal provided by the crown effectively protected the fiber post against

deterioration.

Clinical relevance: Exposition of a fiber post in a direct restoration does not lead

to clinical failure. Over a 5-year period, the post surface exposed in a direct resin

restoration did not show morphological changes related to water degradation

although it exhibited a limited loss of structure due to occlusal wear.

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References

1. Anusavice KJ. Degradability of dental ceramics. Adv Dent Res 1992;6:82–9.

2. Barkmeier WW, Latta MA, Erickson RL, Lambrechts P.Comparison of

laboratory and clinical wear rates of resin composites. Quintessence Int

2004;35:269–74.

3. Callaghan DJ, Vaziri A, Hashemi HN. Effect of fiber volume fraction and length

wear characteristics of glass fiber-reinforced dental composites. Dent Mater

2006;22:84–93.

4. Condon JR, Ferracane JL. In vitro wear of composite with varied cure, filler

level, and filler treatment. J Dent Res1997;76:1405–11.

5. DeLong R. Intra-oral restorative materials wear: Rethinking the current

approaches: How to measure wear. Dent Mater 2006;22:702–711.

6. Ekfeldt A, Fransson B, Soderlund B, Oilo G. Wear resistance of some

prosthodontic materials in vivo. Acta Odontol Scand 1992;51:99–107.

7. Ferracane L. Hygroscopic and hydrolytic effects in dental polymer networks.

Dent Mater 2006;22:211-222.

8. Ferrari M, Cagidiaco MC, Grandini S, De Sanctis M, Goracci C. Post placement

affects survival of endodontically treated premolars. J Dent Res 2007;86:729-34.

9. Fredriksson M, Astbäck J, Pamenius M, Arvidson K. A retrospective study of

236 patients with teeth restored by carbon fiber-reinforced epoxy resin posts. J

Prosthet Dent 1998;80:151-7.

10. Goodacre CJ, Spolnik KJ. The prosthodontic management of endodontically

treated teeth: a literature review. Part I. Success and failure data, treatment

concepts. J Prosthodont 1994;3:243-50.

11. Grandini S, Balleri P, Ferrari M. Scanning electron microscopic investigation

of the surface of fiber posts after cutting. J Endod 2002;28:610-2.

12. Grandini S, Goracci C, Tay FR, Grandini R, Ferrari M. Clinical evaluation of

the use of fiber posts and direct resin restorations for endodontically treated teeth.

Int J Prosthodont 2005;18:399-404.

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13. Lassila LV, Nohrstrom T, Vallittu PK. The influence of short-term water

storage on the flexural properties of unidirectional glass fiber-reinforced

composites. Biomaterials 2002;23:2221–9.

14. Lassila LVJ, Tanner J, Le Bell AM, Narva K, Vallittu PK. Flexural properties

of fiber reinforced root canal posts. Dent Mater 2004;20:29-36.

15. Lim BS, Ferracane JL, Condon JR, Adey JD. Effect of filler fraction and filler

surface treatment on wear of microfilled composites. Dent Mater 2002;18:1–11.

16. Limkangwalmongkol P, Chiche GJ, Blatz MB. Precision of Fit of Two Margin

Designs for Metal-Ceramic Crowns. J Prosthodont 2007;16:233-237.

17. Monticelli F, Osorio R, Albaladejo A, Aguilera FS, Ferrari M, Tay FR,

Toledano M.

Effects of adhesive systems and luting agents on bonding of fiber posts to root

canal dentin. J Biomed Mater Res B Appl Biomater 2006;77:195-200.

18. Santos C, Clarke RL, Braden M, Guitian F, Davy KWM. Water absorption

characteristics of dental composites incorporating hydroxyapatite filler.

Biomaterials 2002;23:1897–1904.

19. Soderholm KJ, Lambrechts P, Sarrett D, Abe Y, Yang MC, Labella R. Clinical

wear performance of eight experimental dental composites over three years

determined by two measuring methods. Eur J Oral Sci 2001;109:273–81.

20. Turssi CP, Purquerio BM, Serra MC. Wear of dental resin composites: insights

into underlying processes and assessment methods—a review. J Biomed Mater Res

2003;65B:280–5.

21. Vano M, Carvalho C, Sedda M, Gabriele M, Ferrari M. The influence of

storage condition and duration on the resistance to fracture of different fiber posts

systems. Am J Dent 2007, in press.

22. Vichi A, Fraioli A, Davidson CL, Ferrari M. Influence of thickness on color in

multi-layering technique. Dent Mater 2007; Sep 6; ahead of print.

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23. Vichi A, Vano M, Ferrari M. The effect of different storage conditions and

duration on the fracture strength of three types of translucent fiber posts. Dent

Mater 2007, in press.

24. Willems G, Lambrechts P, Braem M, Vanherle G. Three-year follow-up of five

posterior composites: in vivo wear. J Dent 1993;21:74–8.

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Fig 1 Fiber post head exposed on the occlusal surface of a direct resin composite

restoration (Group 1).

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Fig 2 Polyether impressions of the abutment were taken at baseline and after 5

years of clinical service in group 2 samples.

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Fig 3a Representative SEM micrograph of DT Light Post at baseline.

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(b) Representative SEM micrograph of DT Light Post after 5 years of clinical service.

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Fig 4 Higher magnification of Fig 3b. No volume loss at the border between the

direct resin material and the fiber post was noted.

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Fig 5 SEM micrograph showing a good bonding between the fibers and the matrix

after 5 years of clinical service.

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Chapter 5

5.1. Summary Retention is one of the main aspect for the clinical success of fiber intracanal posts.

Thanks to research endodontics and adhesive dentistry improved the quality and

the longevity of the complex fiber post-dentin-core material (Akkayan and

Gulmetz, 2002) (Newman et al., 2003).

However the interfacial strength between composite core and fiber post is still

relatively weak, mainly due to chemical incompatibility among different

components (Aksornmuang et al., 2004) (Goracci et al., 2005).

In order to improve adhesion between fiber post and core build up, the first study

(Chapter 1) aimed at evaluating the influence of post surface treatment with

hydrogen peroxide or hydrofluoric acid. The results validated the effectiveness of

the surface treatment with hydrogen peroxide and silane application or hydrofluoric

acid and silane application as a method for enhancing bond strength. In addition

regarding the type of core build-up, the study demonstrated that flowable

composites exhibited the best adaptation to the post surface.

The timing of post space preparation and cementation also influences the retention

of the complex post-core (Ewart and Saunders, 1990). Posts can be placed

immediately after completion of the endodontic treatment or at a later stage after

full setting of the endodontic sealer (Galen and Mueller, 1998) (Saunders et

al.,1991).

In Chapter 2 the effect of immediate versus delayed post cementation on the

retention of different types of fiber posts in canals obturated with a eugenol sealer

or with an epoxy resin sealer was evaluated. Indipendently from the type of

endodontic sealer (eugenol or epoxy based sealer), immediate post space

preparation and post cementation resulted in lower interfacial strengths between the

bonded post and intraradicular dentin. Conversely, a significant increase in

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retention was recorded when the post space preparation and post cementation were

performed 24 hours and one week after the canals were filled with gutta-percha. In

agreement with previous investigations (Schwartz et al., 1998), (Karapanou et al.,

1996), the results of the studies in Chapter 2, showed no differences in terms of

post retention when an eugenol or an epoxy resin based sealer were used as

endodontic sealers.

It is important that the clinician considers the mechanical properties of fiber posts

when designing or using a post restoration in an endodontically treated tooth. In

fact the quality of the support of the coronal restoration can be reflected by the

stiffness of the post, being related to loss of retention of a crown (Sahafi et al.,

2004). The mechanical properties of fiber posts are negatively affected by water

exposure. In particular a reduction of flexural strength (Lassila et al., 2004)

(Mannocci et al., 2001) was reported after water storage. In Chapter 3 the water

detrimental effect on the flexural strength of different translucent fiber posts was

tested. In order to mimic a clinical situation extracted human canines teeth were

selected as one of the storage condition to be tested. The results of these studies

indicated that storage of fiber posts in human root immersed in water resulted in

similar flexural strengths values to those obtained in dry and oil storage, therefore

no detrimental effect was recorded. Conversely, a reduction in the mechanical

properties of fiber posts after water storage was observed in those groups in which

the fiber posts were soaked in water.

The results of the studies in Chapter 3 showed that once an endodontic post is

cemented into the root canal, and the coronal part is immersed into the composite

resin core, it can be considered free from any water detrimental effect. However

observation of exposed post on a direct restoration is a common finding

(Fredriksson et al., 1998). Therefore it was of interest to evaluate clinically whether

the exposure to the oral environment and occlusal function affected the

morphological integrity of luted intracanalar translucent fiber posts retaining a

direct composite restoration (Chapter 4). The results showed that after 5 years of

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clinical service no microscopic signs of post surface degradation due to water

uptake were seen. Only a limited amount of wear rate due to the 5 years period of

clinical service was detected for the exposed posts.

5.2. Conclusions

The following conclusions may be drawn from our evaluation of the factors

affecting fiber posts retention and mechanical properties:

1) Surface treatment of post with hydrogen peroxide and silane application or

hydrofluoric acid and silane application significantly enhances the interfacial bond

strength between fiber posts and core materials. Post pre-treatment with 24%

hydrogen peroxide for 10 min appears to be as an easy, effective and inexpensive

method that can improve the clinical performance of methacrylate resin-based glass

fiber posts.

2) Indipendently from the type of endodontic sealer (eugenol or epoxy based

sealer), immediate post space preparation and post cementation resulted in lower

interfacial strengths between the bonded post and intraradicular dentin. Conversely,

a significant increase in retention was recorded when the post space preparation

and post cementation were performed 24 hours and one week after the canals were

filled with gutta-percha.

3) Fiber posts placed inside human root canals immersed in water showed to be

effectively preserved from water degradation effect. Fiber posts stored in direct

contact with water showed significant lower flexural strength values and

morphological changes regardless the post type tested.

4) Exposition of a fiber post in a direct restoration does not lead to clinical failure.

Over a 5-year period, the post surface exposed in a direct resin restoration did not

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show morphological changes related to water degradation although it exhibited a

limited loss of structure due to occlusal function.

5.3. Riassunto e conclusioni

La ritenzione rappresenta un aspetto fondamentale per il successo clinico dei perni

in fibra intracanalari. La ricerca nel campo endodontico e conservativo ha permesso

di migliorare la qualità e la longevità del complesso perno endodontico-dentina-

materiale da ricostruzione (Akkayan and Gulmetz, 2002) (Newman et al., 2003).

Tuttavia la forza di adesione tra il materiale da ricostruzione e il perno in fibra è

ancora relativamente debole a causa della scarsa affinità chimica tra i componenti

(Aksornmuang et al., 2004) (Goracci et al., 2005).

Al fine di aumentare l’adesione tra il perno in fibra ed il materiale da ricostruzione,

il primo studio (capitolo 1) ha valutato l’influenza del trattamento di superficie del

perno applicando acido idrofluoridrico o perossido d’idrogeno. I risultati hanno

dimostrato l’effettiva capacità dell’acido idrofluoridrico con silano e del perossido

d’idrogeno con silano di aumentare la forza di adesione tra perno e materiale da

ricostruzione. Inoltre lo studio ha evidenziato un migliore adattamento dei

compositi di tipo flowable alla superficie del perno.

La tempistica nella preparazione del sito per il perno e la sua cementazione

influenza la ritenzione del complesso perno-materiale da ricostruzione (Ewart and

Saunders, 1990). Il perno infatti può essere posizionato subito dopo il trattamento

endodontico o in una fase successiva quando il cemento radicolare ha raggiunto la

stabilità ed è indurito (Galen and Mueller, 1998) (Saunders et al.,1991). Nel

Capitolo 2 è stata valutato l’effetto della cementazione immediata o ritardata sulla

ritenzione di differenti tipologie di perni in fibra in canali otturati con un cemento a

base di eugenolo o a base di resina epossidica. Indipendentemente dal tipo di

cemento utilizzato (eugenolo o epossidico), la preparazione immediata del sito per

il perno con susseguente cementazione ha prodotto i più bassi valori di adesione tra

perno e dentina radicolare. Al contrario un significativo aumento in termini di

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ritenzione fu riscontrato nei gruppi dove la preparazione del sito per il perno e la

cementazione erano effettuate 24 ore o una settimana dopo l’otturazione canalare

con cemento canalare e guttaperca. In accordo con altri studi (Schwartz et al.,

1998), (Karapanou et al., 1996), i risultati presentati nel capitolo 2, non

evidenziano alcuna differenza in termini di ritenzione del perno tra l’uso di un

cemento a base di eugenolo o di resina epossidica per la chiusura del canale

radicolare.

Prima di effettuare una riabilitazione di un dente trattato endodonticamente, il

clinico deve scegliere il tipo di perno in fibra tenendo conto delle sue proprietà

meccaniche. La qualità del supporto del restauro a livello coronale può essere

condizionata dalla rigidità del perno (Sahafi et al., 2004). I perni in fibra subiscono

una riduzione delle loro caratteristiche meccaniche ed in particolare della resistenza

alla flessione dopo lo ‘storage’ in acqua (Lassila et al., 2004) (Mannocci et al.,

2001). Nel terzo capitolo sono stati valutati gli effetti di alcune tipologie di

‘storage’ sulla resistenza alla flessione di differenti perni in fibra. I risultati di

questi studi indicano che lo ‘storage’ dei perni in fibra, in canali di denti umani

estratti, otturati coronalmente e immersi in acqua, non produce alcuna riduzione

delle loro proprietà meccaniche. I dati provenienti dai gruppi sopradescritti sono

comparabili con i dati ottenuti da perni in ‘storage’ in olio e a condizioni ambiente.

Al contrario i perni immersi in acqua (senza essere posizionati dentro le radici

dentarie) hanno mostrato valori di resistenza alla flessione significativamente

inferiori se paragonati agli altri gruppi.

I risultati presentati nel capitolo terzo dimostrano che il perno in fibra, dopo la

cementazione nel canale radicolare e la ricostruzione della porzione coronale con

materiale composito, non subisce alcun effetto negativo da parte dell’acqua o dei

fluidi orali. Tuttavia l’esposizione di una parte del perno nell’ambiente orale a

causa di un fallimento del restauro coronale rappresenta una situazione clinica

abbastanza comune (Fredriksson et al., 1998). Di conseguenza era di grande

interesse valutare clinicamente se l’esposizione del perno all’ambiente orale

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potesse compromettere la sua integrità morfologica (Capitolo 4). Dopo 5 anni di

servizio clinico nessun segno microscopico di degrado della superficie del perno

dovuto all’azione dell’acqua o dei fluidi orali è stato registrato. E’stato osservato

solo un lieve grado di usura delle superfici dei perni esposti in seguito ai 5 anni di

funzione masticatoria.

Conclusioni

Alla luce della valutazione dei fattori che influenzano la ritenzione dei perni e le

loro proprietà meccaniche è possibile trarre le seguenti conclusioni:

1) L’applicazione di perossido d’idrogeno e silano o l’applicazione di acido

idrofluoridrico e silano come trattamenti di superficie del perno, hanno la capacità

di aumentare la ritenzione tra perno in fibra e materiale composito. In particolare il

trattamento di superficie del perno con perossido d’idrogeno al 24% per 10 minuti

rappresenta una metodica semplice, efficace e poco costosa con la quale è possibile

migliorare la prestazione clinica dei perni in fibra di vetro a base di resina

contenente metacrilati.

2) Indipendentemente dal tipo di cemento radicolare utilizzato (a base di eugenolo

o di resine epossidiche) la preparazione del sito per il perno e la sua cementazione

subito dopo la chiusura del canale radicolare produce bassi valori di adesione tra il

perno e la dentina radicolare. E’ raccomandabile quindi ritardare la preparazione

del sito del perno e la sua cementazione di almeno 24 ore.

3) I perni in fibra immersi liberamente in acqua per lunghi periodi (6 mesi)

subiscono una riduzione delle loro proprietà meccaniche. Al contrario i perni in

fibra dentro i canali radicolari, otturati coronalmente, non subiscono alcuna

riduzione.

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4) L’esposizione di una porzione di un perno in fibra nella cavità orale non

pregiudica necessariamente la sopravvivenza clinica del restauro. Dopo 5 anni di

servizio clinico, i perni aventi la superficie coronale esposta all’ambiente orale non

mostravano alcun segno di degrado morfologico dovuto all’azione dell’acqua o dei

fluidi orali. Un lieve grado di usura è stato osservato a livello della superficie del

perno, in relazione a 5 anni di funzione occlusale.

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5.4. Resumen

La buena retención intrarradicular de un poste de fibra representa

una de las características más importantes para alcanzar un éxito

clínico. La calidad y la durabilidad de las restauraciones de los

dientes endodonciados se han mejorado por efecto del continuo

perfeccionamiento de la endodóncia y de la odontología adhesiva

(Akkayan and Gulmetz, 2002) (Newman et al., 2003).

De toda forma, la fuerza de adhesión establecida por el muňon de

resina compuesta -poste de fibra-dentina es aún relativamente

débil, principalmente debido a la incompatibilidad química entre

los distintos componentes (Aksornmuang et al, 2004) (Goracci et

al., 2005).

En la parte inicial de esta tesis doctoral (Capítulo 1) se realizó

una evaluación de diferentes metodos de grabado superficial de la

superficie de los postes por peroxido de hidrogeno y acido

hidrofluorico con el objetivo de mejorar la fuerza de adhesión con

el muňon de resina compuesta. Este enfoque validó con suceso el

grabado con peroxido de hidrogeno junto a la aplicación de silano

como agente de acoplamiento y el grabado con acido

hidrofluorico y aplicación de silano para aumentar la fuerza de

adhesión. Con respecto a la restauración en resina compuesta, el

estudio demostró que los composites de tipo fluido mostraron una

mejor adaptación a la superficie del poste.

El tiempo, que transcurre desde el fin del tratamiento endodóntico

hasta la preparación del espacio para el poste, y la cementación

del mismo en el canal radicular son dos factores que pueden

influenciar la retención final del complejo poste-muňon (Ewart

and Saunders, 1990). Tál y como sugerido en la literatura, el

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poste de fibra puede ser colocado en el conducto radicular

inmediatamente a fin del tratamiento endodóntico o bien después

del completo endurecimiento del cemento sellador (Galen and

Mueller, 1998) (Saunders et al, 1991).

En el Capitulo 2 se realizó una comparación entre dos distintas

tecnicas de cementación del poste, inmediata y postergada, y el

efecto que estas tuvieron sobre la retención intrarradicular de

varios tipos de postes de fibra cementados en canales radiculares

obturados por cemento óxido de zinc eugenol o cemento en resina

epóxida. A pesar del tipo de cemento endodóntico utilizado

(eugenol y epóxido), la preparación del espacio para el poste y su

cementación inmediata resultó en una reducida fuerza de

adhesión entre el poste cementado y la dentina intrarradicular.

Contrariamente, se lograron resultados mejores cuando la

preparación y cementación del perno de fibra fueron performadas

24 horas y 1 semana después de acabar la obturación del canal

radicular con gutapercha. De acuerdo con otras investigaciones

(Schwartz et al., 1998) (Karapanou et al., 1996), los resultados

conseguidos en el estudio (Capitulo 2) enseňaron que ní el

cemento de zinc eugenol ní aquello a base de resina epóxica

utilizados para el sellado endodontico influenciaron las

características retentivas intracanalares de los postes de fibra.

Es muy importante para el clínico considerar las propriedades

mecanicas de los postes de fibra cuando proyectan de utilizarlos

para restaurar los dientes desvitalizados. De hecho, la calidad del

soporte corónale de la restauración se vé influenciada por la

rigidez del poste, ya que está relacionada con la pérdida de

retención de la corona (Sahafi et al., 2004). Las propriedades

mecanicas de los postes de fibra se ven negativamente

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influenciadas cuando expuestos a medio acuoso. Sobretodo, una

reducción de las fuerzas flexurales (Lassila et al., 2004)

(Mannocci et al., 2001) ha sido reportada después de conservar el

especimen en agua. En el Capitulo 3 se valoró la fuerza de

flexión de diferentes tipos de postes de fibra translucidos

guardados en medio acuoso y el efecto perjudicial que resultó.

Así como para simular la verdadera situación clínica, se

seleccionaron caninos humanos extraidos representantes una de

las condiciones experimentales. La conservación de raices

endodociandas restauradas por postes de fibra en medio acuoso

mostró resultados parecidos, en termino de fuerza flexural, de

aquellos logrados por raices mantenidas en medios secos o en

aceite, aunque si no aparecieron defectos deletéreos. Sin

embargo, al mantener los postes de fibra completamente

inmergidos en agua, se asistió a una disminución de las

propriedades mecanicas.

A partir de los resultados del Capitulo 3, se deduce que, una vez

que el poste de fibra haya sido cementado en el canal radicular, y

que suya porción coronal haya sido completamente recubierta de

la resina compuesta, no hay posibilidad de que el agua pueda

perjudicar las propriedades del poste. Todavía ocasionalmente se

nota la exposición del poste através de la restauración corónal en

composite (Fredriksson et al., 1998). Además, se puso necesaria

una evalución clínica de como la exposición a los fluidos orales

hasta la función oclusal puedan afectar a la integridad

morfologíca de los postes de fibra traslucidos cementados nel

canal radicular y detenientes una restauración directa en

composite (Capitulo 4). El estudio clínico se desarrolló durante 5

aňos, al final de los cuales no se detectaron signos de degradación

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microscópica de la superficie de los postes de fibra por el efecto

de agua. Durante todos los 5 aňos se registrió solamente un

pequeňo porcentaje de infiltración de los postes expuestos.

Conclusiones

Las conclusiones siguientes se pueden deducir de las

evaluaciones de laboratorio y clínicas de los factores que pueden

influenciar la retención intracanal de los postes de fibra y sus

propriedades mecanicas:

1) Dos tratamientos de superficie de los postes llevaron a una

mejoría de la fuerza de adhesion del complejo poste-muňon:

grabado por peroxido de hidrogeno conjunto a la aplicación

de silano y tratamiento con acido hidrofluorico seguido de

silano. En particular, el utilizo de peroxido de hidrogeno 24%

por 10 minutos parece una práctica fácil, efectiva y

económica para mejorar el comportamento clínico de los

postes de fibra de vidrio a base de metacrilato.

2) A pesar del tipo de cemento sellador utilizado (eugenol o

epóxido), la preparación inmediata del espacio para poste y su

cementación revelaron una fuerza menor a nivel de la

interfase poste-dentina intrarradicular. Sin embargo, se asistió

a un aumento significativo de la retención cuando la

preparación y la cementación del poste se cumplieron 24

horas y 1 semana después de acabar la obturación canalar con

gutapercha.

3) Los postes de fibra utilizados para la restauración de dientes

endodonciados inmergidos en agua mostraron de ser lo

sufficientemente eficaz como para resistir a la acción

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degradante del agua. Mientras que los postes de fibra

completamente hundidos en medio acuoso desvelaron una

inferior fuerza flexural y modificaciones morfologicas de

superficie según el tipo de poste empleado.

4) La exposición del poste de fibra desde una restauración

directa no nos lleva necesariamente a un fracaso clínico.

Durante los 5 aňos de investigación clínica, la pieza del poste

sobresaliente a la restauración directa no demostró

alteraciones morfologicas relacionadas a la degradación

acuosa, aunque si aparecieron pérdidas de estructura causadas

por la oclusión.

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5.5. Résumé

La rétention est l’un des aspects majeurs en ce qui concerne le succès clinique des

tenons canalaires renforcés en fibres (TRF). La recherche dans les domaines de

l’endodontie et de l’adhésion dentaire a amélioré la qualité et la longévité des

complexes TRF/dentine/faux-moignon (Akkayan and Gulmetz, 2002) (Newman et

al., 2003). Toutefois, la force d’adhésion à l’interface entre les matériaux

composant le faux-moignon et les TRF demeure faible en raison principalement de

leur incompatibilité chimique (Aksornmuang et al., 2004) (Goracci et al., 2005).

Dans le but d’améliorer l’adhésion entre les TRF et les matériaux composant le

faux-moignon, l’étude rapportée au chapitre 1 avait pour but d’évaluer l’influence

du traitement de la surface des TRF par le peroxyde d’hydrogène ou par l’acide

fluorhydrique. Les résultats ont validé l’efficacité du traitement par le peroxyde

d’hydrogène ou de l’acide fluorhydrique suivi par une application de silane pour

améliorer la force d’adhésion. De plus, concernant le faux-moignon, l’étude a

montré que les composite “flowables” présentent la meilleure adaptation à la

surface des TRF.

Le timing de la préparation du logement du tenon et du scellement a également une

influence sur la rétention du complexe TRF/faux-moignon (Ewart and Saunders,

1990). Les TRF peuvent être places immédiatement à la fin du traitement

endodontique ou différés après la prise du matériau de scellement endodontique

(Galen and Mueller, 1998) (Saunders et al.,1991).

Le Chapitre 2 traite de l’effet du scellement immédiat vs. différé de différents

types de TRF dans des canaux obtures à l’aide d’un ciment endodontique eugénate

ou à base de résine époxy. Nonobstant le type de ciment endodontique (eugénate ou

résine époxy), la préparation du logement de tenon et son scellement immédiat ont

entraîné des forces d’adhésion plus faibles entre les TRF et la dentine

intracanalaire. En revanche, une augmentation significative de la rétention a été

enregistrée lorsque le logement canalaire et le scellement étaient différés de 24h ou

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d’une semaine après le traitement endodontique. En concordance avec les

précédentes études de (Schwartz et al., 1998), (Karapanou et al., 1996), les

résultats des études du Chapitre 2 n’ont pas montré de différence concernant la

rétention des TRF lorsque utilisés avec des ciments endodontiques type eugénate

ou résine époxy.

Il est important pour le clinicien de prendre en considération les propriétés

mécaniques des TRF lors du design et l’utilisation des restaurations à tenon sur les

dents traitées endodontiquement. En fait, la qualité du support de la restauration

coronaire se reflète dans la rigidité du tenon comme étant directement reliée à la

perte de rétention de la couronne (Sahafi et al., 2004). Les propriétés mécaniques

des TRF sont affectées négativement par l’exposition à l’eau. En particulier, une

réduction de la résistance à la flexion a été rapportée après stockage dans l’eau

(Lassila et al., 2004) (Mannocci et al., 2001). Le Chapitre 3 analyse l’effet délétère

de l’eau sur la résistance a la flexion de différents TRF. Afin de reproduire la

situation clinique, des canines humaines extraites ont été choisies comme étant

l’une des conditions de stockage testées. Les résultats de ces études ont montré que

le stockage des TRF dans des canines humaines immergées dans l’eau a entraîné

des résistances à la flexion similaires à celles stockées dans l’huiles ou en milieu

sec, et donc aucun effet délétère ne fut enregistré. Par ailleurs, une réduction des

propriétés mécaniques des TRF a été notée après stockage pour les échantillons ou

le TRF avait été préalablement immergé dans l’eau.

Les résultats des études du Chapitre 3 ont montré qu’une fois le TRF scellé dans le

canal, et que sa projection coronaire est noyée dans le matériau composite formant

le faux-moignon, le TRF peut être considéré comme libre de tout effet délétère dû à

l’eau. Toutefois, l’exposition d’un TRF n’est pas rare lors de l’observation de

restaurations directes (Fredriksson et al., 1998). Il était donc intéressant d’évaluer

cliniquement si l’exposition au milieu buccal et la fonction occlusale affectent

l’intégrité structurale des TRF translucides scellées soutenant une restauration

directe en résine composite (Chapitre 4). Les résultats ont montré qu’après 5

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années de service clinique, l’observation microscopique n’a révélé aucun signe de

dégradation des TRF due à l’absorption d’eau. Seul, un taux d’usure limité a été

noté pour les TRF exposés.

Conclusions

Les conclusions suivantes peuvent être tirées de notre évaluation des facteurs

affectant la rétention des TRF et leurs propriétés mécaniques:

1) Le traitement de surface traitement des tenons au peroxyde d’hydrogène ou

l’acide fluorhydrique, suivie par l’application de silane augmente de manière

significative la force d’adhésion à l’interface entre les TRF et les matériaux

composant le faux-moignon. Le pre-traitement du TRF par le peroxyde

d’hydrogène à 24% pendant 10min semble être une méthode simple, facile, et peu

onéreuse capable d’améliorer les performances des TRF à base de méthacrylate de

méthyle.

2) Indépendamment du type de ciment endodontique (eugénate ou résine époxy), la

préparation du logement de tenon et le scellement immédiats ont entraîné des

forces d’adhésion moindres à l’interface TRF/dentine que celles obtenues après un

délais de 24h et une semaine après le traitement endodontique.

3) Les TRF placés dans des racines humaines et immergés dans l’eau se sont

révélés être non affectés par la dégradation due a l’eau. Les TRF stockés en contact

direct avec l’eau ont démontré des valeurs de résistance à la flexion moindres ainsi

que des variations morphologiques indépendamment du type de TRF testé.

4) L’exposition de TRF dans une restauration directe n’entraîne pas l’échec

clinique. Sur un suivi de 5 ans, la surface du TRF exposé dans une restauration

directe en résine composite n’a pas montre de signes morphologiques de

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dégradation due l’eau bien qu’elle ait présenté une perte de substance due à la

fonction occlusale.

5.6 Zusammenfassung

Die Retention ist einer der wichtigsten Aspekte für den klinischen Erfolg von

Faserstiften. Dank der Forschung, haben die Endodontie und die adhäsive

Zahnmedizin die Qualität und die Langlebigkeit des Faserstift-Dentin-

Stumpfaufbau Komplexes verbessert (Akkayan and Gulmetz, 2002) (Newman et

al., 2003).

Dennoch ist die adhäsive Kraft zwischen Stumpfaufbaumaterial und Faserstift noch

relativ schwach, bedingt vorwiegend durch die chemische Incompatibilität

zwischen den unterschiedlischen Komponenten (Aksornmuang et al., 2004)

(Goracci et al., 2005).

Um die Adhäsion zwischen Faserstift und Stumpfaufbau zu verbessern, wurde in

der ersten Studie (Kapitel 1) der Einfluss der Behandlung der Faserstiftoberfläche

mit Wasserstoffperoxid oder mit Fluorwasserstoffsäure untersucht. Die Ergebnisse

haben bewiesen, dass die Behandlung der Faserstiftoberfläche mit

Wasserstoffperoxid und Silan bzw. mit Fluorwasserstoffsäure und Silan eine

wirksame Methode ist, um die adhäsive Kraft zu erhöhen. Außerdem hat die Studie

bewiesen, dass die Flowable-Kompositen die beste Anpassung an die

Faserstiftoberfläche haben.

Auch das Timing der Post-Space Vorbereitung und der Zementierung beeinflusst

die Retention des Faserstift- Stumpfaufbau Komplexes (Ewart and Saunders,

1990). Der Faserstift kann sofort nach der endodontischen Behandlung positioniert

werden, oder nachdem die Wurzelkanalfüllpaste total erhärtet ist (Galen and

Mueller, 1998) (Saunders et al.,1991).

Im Kapitel 2 wurde der Effekt einer sofortigen oder verschobenen Zementierung

des Faserstiftes auf die Retention unterschiedlicher Typen von Faserstiften in

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Wurzelkanälen gefüllt mit Eugenol bzw. Epoxidharz-Paste bewertet. Unabhängig

von dem Typ der Wurzelkanalfüllpaste (Eugenol oder Epoxidharz), haben die

sofortigen Post-Space Vorbereitung und Zementierung niedrige Adhäsionskräfte

zwischen dem zementierten Faserstift und dem Wurzelkanaldentin bewirkt. Im

Gegenteil wurde eine signifikante Erhöhung der Retention beobachtet, wenn die

Post-Space Vorbereitung und die Zementierung des Faserstiftes entweder 24

Stunden oder eine Woche nach der Wurzelkanalfüllung mit Guttapercha eingesetzt

wurden. Die Ergebnisse der Studien im Kapitel 2 haben keinen Unterschied in der

Retention des Faserstiftes gezeigt, wenn eine Eugenol-Wurzelkanalfüllpaste oder

eine Epoxidharz-Wurzelkanalfüllpaste verwendet wurden. Diese Ergebnisse

stimmen überein mit vorhergehenden Untersuchungen (Schwartz et al., 1998),

(Karapanou et al., 1996).

Es ist sehr wichtig, dass der Zahnarzt die mechanischen Eigenschaften der

Faserstifte in Betracht zieht, wenn eine Restauration mit einem Faserstift in einem

endodontisch behandelten Zahn verwendet werden soll. In der Tat kann die

Qualität des Gestells der koronalen Restauration von der Festigkeit des Faserstiftes

beeinflusst werden, die mit dem Verlust der Retention der Krone im

Zusammenhang gebracht wird (Sahafi et al., 2004).

Die mechanischen Eigenschaften der Faserstifte werden negativ von der

Wasserlagerung beeinflusst. Eine Herabsetzung der Biegefestigkeit wurde

besonders nach Wasserlagerung beschrieben (Lassila et al., 2004) (Mannocci et al.,

2001). Im Kapitel 3 wurde daher getestet, ob Wasser einen negativen Effekt auf die

Biegefestigkeit von unterschiedlich durchscheinenden Faserstiften hat. Um

klinische Bedingungen zu simulieren, wurden extrahierte Eckzähne als eine der

Lagerungs-Bedingungen gewählt. Die Ergebnisse dieser Studien haben gezeigt,

dass die Lagerung von Faserstiften in Zahnwurzeln im Wasser, ähnliche

Biegefestigkeitswerte hervorgebracht hat, wie eine Öl oder Trockenlagerung. Ein

negativer Effekt der Wasserlagerung konnte somit nicht festgestellt werden.

Dagegen wurde eine Herabsetzung der mechanischen Eigenschaften der Faserstifte

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nach Wasserlagerung in den Gruppen beobachtet, in denen die Faserstifte direkt im

Wasser eingetaucht wurden. Die Ergebnisse der Studien im Kapitel 3 haben gezeigt

dass, wenn ein Faserstift im Wurzelkanal zementiert wird, und der koronale Teil ist

auf dem Komposit-Stumpfaufbau angebracht, der Faserstift wird von dem

negativen Effekt des Wassers nicht beeinflusst. Trotzdem werden ungedeckten

Faserstiften in direkten Restaurationen häufig beobachtet (Fredriksson et al., 1998).

Deshalb war es interessant klinisch zu bestimmen, ob das Mundmilieu und das

Kauen die morphologische Unversehrtheit zementierter durchscheinender

Faserstifte beeinflussen, wenn die Faserstifte eine direkte Komposit-Restauration

befestigten (Kapitel 4). Die Ergebnisse haben gezeigt, dass, nach 5 Jahren

klinischen Einsatz, keine mikroskopischen Zeichen von Degradation der

Oberfläche des Faserstiftes durch Aufnahme von Wasser beobachtet wurden.

Lediglich wurde ein geringer Verschleiß der ungedeckten Faserstifte nach 5 Jahren

klinischen Einsatz festgestellt.

Schlussfolgerungen

Folgende Schlussfolgerungen können aus unserer Bestimmung der Faktoren, die

die Retention und die mechanischen Eigenschaften der Faserstifte beeinflussen,

gezogen werden:

1) Die Behandlung der Faserstiftoberfläche mit Wasserstoffperoxid und Silan bzw.

mit Fluorwasserstoffsäure und Silan erhöht signifikant die adhäsive Kraft zwischen

Faserstiften und Stumpfaufbau-Materialien. Die Behandlung des Faserstiftes mit

24% Wasserstoffperoxid für 10 Minuten scheint eine einfache, wirksame und

kostenlose Methode zu sein, um das klinische Verhalten von Methacrylat-

Faserstiften zu verbessern.

2) Unabhängig von dem Typ der Wurzelkanalfüllpaste (Eugenol- oder Epoxidharz-

Wurzelkanalfüllpaste), haben die sofortigen Post-Space Vorbereitung und

Zementierung geringere Adhäsionskräfte zwischen dem zementierten Faserstift und

dem Wurzelkanaldentin bewirkt. Im Gegenteil wurde eine signifikante Erhöhung

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der Retention beobachtet, wenn die Post-Space Vorbereitung und die Zementierung

des Faserstiftes entweder 24 Stunden oder eine Woche nach der

Wurzelkanalfüllung mit Guttapercha eingesetzt wurden.

3) Faserstifte, zementiert in Zahnwurzeln eingetaucht im Wasser, wurden von der

Wasser-Degradation effektiv geschützt. Unabhängig von dem Typ des Faserstiftes,

haben Faserstifte in direkter Wasserlagerung signifikant niedrigere

Biegefestigkeitswerte und morphologische Änderungen gezeigt.

4) Die Abdeckung des Faserstiftes in einer direkten Restauration verursachte

keinen klinischen Misserfolg. Die ungedeckte Faserstiftoberfläche in einer direkten

Restauration zeigte auch nach 5 Jahren keine bedingte morphologische

Veränderungen durch Wasser-Degradation, auch wenn ein begrenzter Verlust von

Struktur durch Kauen festgestellt wurde.

5.7 Sumário

Retenção é um dos principais aspectos para o sucesso clinico de pinos de fibra

intra-canais.

Devido às pesquisas endodônticas e as melhorias na odontologia adesiva houve um

aumento na qualidade e a longevidade do conjunto pino-dentina-restauração

(Akkayan and Gulmetz, 2002) (Newman et al., 2003).

Contudo, a força na interface do corpo da restauração e pino de fibra é

relativamente frágil, principalmente devido a incompatibilidade entre diferentes

componentes (Aksornmuang et al., 2004) (Goracci et al., 2005).

De maneira a melhorar a adesão entre pino de fibra e restauração, o primeiro estudo

(Capitulo 1) concentrou em avaliar a influencia do tratamento superficial com

peróxido de hidrogênio ou acido fluorídrico. Os resultados comprovaram a

eficiência do tratamento superficial com peróxido de hidrogênio e aplicação de

silano ou acido hidro-fluoridrico e aplicação de silano como método de melhorar a

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força adesiva. Ainda em respeito ao tipo da restauração, o estudo demonstrou que

resinas fluidas exibiram a melhor adaptação a superfície do pino.

O período de preparação do canal e a cimentação também influenciam a retenção

do conjunto pino-restauração (Ewart and Saunders, 1990). Pinos pode ser

cimentados imediatamente após finalizada o tratamento endodôntico ou num

período pós-operatório após a colocação do cimento obturador endodôntico (Galen

and Mueller, 1998) (Saunders et al.,1991).

No Capitulo 2 o efeito imediato versus mediato da cimentação na retenção de

diferentes tipos de pinos de fibra em canais obturados com cimentos contendo

eugenol ou com uma resina epóxica foram avaliados. Independente do tipo do

cimento obturador ( eugenol ou resina epóxica), a cimentação imediata logo após a

preparação do canal obturador resultou em menor força de resistência entre o pino

e a dentina intra-radicular. Diferentemente, um significante aumento na retenção

quando a preparação do canal radicular e a cimentação do pino foram feita 24 horas

e uma semana após os canais terem sido obturados com guta-percha. Resultados

semelhantes foram encontrados por diversos estudos (Schwartz et al., 1998),

(Karapanou et al., 1996), demonstrando a não diferença em retenção quando um

cimento a base de eugenol ou resina epóxica forma usados como cimentos

endodônticos.

Importante é salientar aos clínicos que as propriedades mecânicas dos pinos de

fibra quando idealizados ou usados em conjunto com a restauração em dentes

tratados endodonticamente. Na verdade a qualidade do suporte pode ser refletida

pela rigidez do pino, sendo correlacionada a perda de retenção das coras (Sahafi et

al., 2004). Em particular a redução da força flexural (Lassila et al., 2004)

(Mannocci et al., 2001) foi reportada após o armazenamento em água. No Capitulo

3 o efeito deletério da água na força flexural em diferentes tipos de pino de fibra foi

testada. De maneira a simular a situação clinica caninos extraídos foram

selecionados como uma das melhores formas de armazenamento. Os resultados

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deste estudo indicaram que o armazenamento de pinos de fibra em raízes imersos

em água foram similares aos armazenados em ambiente seco e óleo em relação à

força flexural, conseqüentemente o efeito deletério não foi identificado. Contudo, a

redução nas propriedades mecânicas dos pinos de fibra após o armazenamento em

água foi observada em grupos nos quais os pinos de fibra foram imerso em água.

Os resultados do estudo no Capitulo 3 demonstraram que uma vez o pino é

cimentado no canal radicular, e a parte coronal e imersa dentro de resina composta,

isto pode ser considerado livre de qualquer efeito deletério da água. Contudo,

encontrar pinos expostos em restaurações diretas é corriqueiro (Fredriksson et al.,

1998). Relacionado a essa afirmação foi avaliado clinicamente se a exposição ao

ambiente oral em contato oclusal afeta a integridade morfológica do pino de fibra

mantido por restaurações em compósito diretas (Capitulo 4). Os resultados

demonstraram que após 5 anos de função clinica nenhum sinal microscópico de

degradação devido a embebição de água foi notado. Somente um pequeno volume

de desgaste devido aos 5 anos de função clinica foi detectado nos pinos expostos.

Conclusões

As seguintes conclusões podem ser assumidas dos nossos estudos dos fatores que

afetam a retenção de pinos de fibra e as propriedades mecânicas:

1) O tratamento superficial do pino com peróxido de hidrogênio e aplicação de

silano ou acido fluorídrico e aplicação de silano significantemente aumenta

a força de adesão entre o pino de fibra e material restaurador. Pinos com

pré-tratamento com 24% de peróxido de hidrogênio por 10 min.

demonstram ser pratico, efetivo e baixo custo; melhorando a desempenho

clinica dos pinos de metacrilato.

2) Independente do tipo de cimento obturador (eugenol ou resina expóxica),

imediatamente a preparação do conduto radicular e cimentação do pino

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resultou em baixa força entre o pino e a dentina intra-radicular.

Diferentemente, uma significante melhora na retenção foi notada quando a

preparação do conduto e a cimentação dos pinos eram realizadas em 24

horas e uma semana após os canais terem sidos obturados com guta-percha

3) Pinos de fibra dentro de raízes de dentes humanos imersas em água

demonstraram promover um efeito de preservação do efeito deletério da

água. Pinos de fibra armazenados em contato direto com a água

demonstram uma significante redução dos valores da força flexural e

modificações a respeito dos pinos testados.

4) A exposição do pino de fibra em restaurações diretas não conduz a falha

clinica. Acima de um período de 5 anos, a superfície do pino exposto em

uma restauração direta não demonstrou modificações morfológicas

relacionadas a degradação pela água contudo demonstrou uma limitada

perda de estrutura devido a função oclusal.

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Curriculum Vitae Dr. Michele Vano Date of birth : May 23th, 1977 Place of birth: Pisa, Italy Civil status: Unmarried Citizenship: Italian Home address: Via Giusti, 18, Pisa, 56127, Italy Telephone number: +393356890180, 057133791 E-mail address: michevano@hotmail.commichevano@unisi.it February 2002: Degree in Dentistry; 110/110 cum laude; University of Pisa, Pisa, Italy Research activity 2002-2003: Master of Oral Surgery, University of Pisa, Pisa, Italy

2003-2004: Master of Science in Dental Materials and their clinical applications,

University of Siena, Italy

2004-2007: PhD Program in Dental Materials and their clinical applications,

University of Siena, Italy

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Professional positions

2002-2004: Intership at the Department of Oral Surgery at the University of Pisa,

Italy.

2004-2007: Contract Professor of Basic Research Principles at the University of

Siena, Italy

Membership in Dental societies

2002-2007 S.I.d.C.O. (Italian Sociaty of Oral Surgery)

2005-2007 - Member of SIDOC (Italian Society of Restorative Dentistry)

2006 - Member of IADR (International Association of Dental Research)

International publications

Simonetti M, Radovic I, Vano M, Chieffi N, Goracci C, Tognini F, Ferrari M. The

influence of operator variability on adhesive cementation of fiber posts. J Adhes

Dent. 2006 Dec;8(6):421-5.

Chieffi N, Chersoni S, Papacchini F, Vano M, Goracci C, Davidson CL, Tay FR,

Ferrari M. Effect of the seating pressure on the adhesive bonding of indirect

restorations. Am J Dent. 2006 Dec;19(6):333-6.

Vano M, Cury AH, Goracci C, Chieffi N, Gabriele M, Tay FR, Ferrari M. The

effect of immediate versus delayed cementation on the retention of different types

of fiber post in canals obturated using a eugenol sealer. J Endod. 2006

Sep;32(9):882-5.

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Vano M, Cury AH, Goracci C, Chieffi N, Gabriele M, Tay FR, Ferrari M.

Retention of fiber posts cemented at different time intervals in canals obturated

using an epoxy resin sealer. J Dent, Submitted.

Graziani F, Vano M, Cei S, Tartaro G, Gabriele M. Unusual asymptomatic giant

sialolith of the submandibular gland: a clinical report. J Craniofac Surg. 2006

May;17(3):549-52.

Hiraishi N, Loushine RJ, Vano M, Chieffi N, Weller RN, Ferrari M, Pashley DH,

Tay FR. Is an oxygen inhibited layer required for bonding of resin-coated gutta-

percha to a methacrylate-based root canal sealer? J Endod. 2006 May;32(5):429-33.

Graziani F, Vano M, Viacava P, Itro A, Tartaro G, Gabriele M. Microvessel

density and vascular endothelial growth factor (VEGF) expression in human

radicular cysts. Am J Dent. 2006 Feb;19(1):11-4.

Chieffi N, Chersoni S, Papacchini F, Vano M, Goracci C, Davidson CL, Tay FR,

Ferrari M. The effect of application sustained seating pressure on adhesive luting

procedure. Dent Mater. 2007 Feb;23(2):159-64.

Vano M, Goracci C, Monticelli F, Tognini F, Gabriele M, Tay FR, Ferrari M. The

adhesion between fibre posts and composite resin cores: the evaluation of

microtensile bond strength following various surface chemical treatments to posts.

Int Endod J. 2006 Jan;39(1):31-9.

Graziani F, Vano M, Tartaro G, Fanelli G, Gabriele M. The use of hydrogen

peroxide in the experimental therapy of cysts. An in vitro analysis. Minerva

Stomatol. 2003 Jul-Aug;52(7-8):373-80.

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Chieffi N, Chersoni S, Papacchini F, Vano M, Goracci C, Davidson CL, Tay FR,

Ferrari M. An in vitro study of the effect of the seating pressure on the adhesive

bonding of in direct restorations. Am J Dent, In press.

Chieffi N, Chersoni S, Papacchini F, Vano M, Goracci C, Davidson CL, Tay FR,

Ferrari M. The effect of adding an antibacterial monomer on the bond quality of a

luting cementation system. Int Dent SA, 2006;8:48-54.

Vichi A, Vano M, Ferrari M. The effect of different storage conditions and duration

on the fracture strength of three types of translucent fiber posts. Dent Mater 2007,

In press.

Vano M, Carvalho C, Sedda M, Gabriele M, Garcia-Godoy F, Marco Ferrari. The

influence of storage condition and duration on the resistance to fracture of different

fiber posts systems. Am J Dent, In press.

Porciani PF, Vano M, Radovic I, Goracci C, Grandini S, Garcia-Godoy F, Ferrari

M. Fracture resistance of fiber posts: combinations of several small posts vs.

standardized single post. J Adhes Dent, In press.

Vano M, Garcia-Godoy F, Goracci C, Vichi A, Ferrari M. Effects of oral

environment and occlusal wear on FRC-posts integrity in clinical service for 5

years. J Adhes Dent, Submitted.

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Abstracts

Vano M, Coniglio I, Cury AH, Goracci C, Chieffi N, Gabriele M, Ferrari M. The

effect of immediate versus delayed post cementation on retention of different types

of fibre post in canals obturated using a resin based sealer. European Federation of

Conservative Dentistry 3rd

Triannual Meeting and Italian Society of Conservative

Dentistry 10th

Annual Meeting, February 9-11, 2006, Rome, Italy. Italian Journal of

Operative Dentistry, Jan-Mar 2006; Supplement IV, 1:63-64.

Vano M, Mazzitelli C, Cury AH, Goracci C, Chieffi N, Gabriele M, Ferrari M.

Retention of different types of fibre post luted at different intervals in canals

obturated using a eugenol sealer. European Federation of Conservative Dentistry

3rd

Triannual Meeting and Italian Society of Conservative Dentistry 10th

Annual

Meeting, February 9-11, 2006, Rome, Italy. Italian Journal of Operative Dentistry,

Jan-Mar 2006; Supplement IV, 1:63-64.

Vano M, Goracci C, Monticelli F, Tognini F, Gabriele M, Tay FR, Ferrari M. The

adhesion between fibre posts and composite resin cores: the evaluation of

microtensile bond strength following various post surface chemical treatments to

posts. European Federation of Conservative Dentistry 3rd

Triannual Meeting and

Italian Society of Conservative Dentistry 10th

Annual Meeting, February 9-11,

2006, Rome, Italy. Italian Journal of Operative Dentistry, Jan-Mar 2006;

Supplement IV, 1:63-64.

Vano M, Magni E, Cury AH, Goracci C, Chieffi N, Gabriele M, Ferrari M. The

effect of root canal filling on retention of different types of fibre posts in canals

obturated using a resin sealer. European Federation of Conservative Dentistry 3rd

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Triannual Meeting and Italian Society of Conservative Dentistry 10th

Annual

Meeting, February 9-11, 2006, Rome, Italy. Italian Journal of Operative Dentistry,

Jan-Mar 2006; Supplement IV, 1:63-64.

Vano M, Raffaelli O, Cury AH, Goracci C, Chieffi N, Gabriele M, Ferrari M. The

effect of eugenol versus noneugenol endodontic sealer on post retention of different

types of fibre post. European Federation of Conservative Dentistry 3rd

Triannual

Meeting and Italian Society of Conservative Dentistry 10th

Annual Meeting,

February 9-11, 2006, Rome, Italy. Italian Journal of Operative Dentistry, Jan-Mar

2006; Supplement IV, 1:63-64.

Chieffi N, Chersoni S, Papacchini F, Vano M, Goracci C, Davidson CL, Tay FR,

Ferrari M. The effect of the seating pressure on self-etch adhesive/chemical cure

resin cement bond. European Federation of Conservative Dentistry 3rd

Triannual

Meeting and Italian Society of Conservative Dentistry 10th

Annual Meeting,

February 9-11, 2006, Rome, Italy. Italian Journal of Operative Dentistry, Jan-Mar

2006; Supplement IV, 1:63-64.

Vano M, Sedda M, Monticelli F, Gabriele M, Ferrari M. The effect of storage time

and media on fiber posts. J Dent Res 2006, 85 (sp issue): abstract 0337.

Chieffi N, Chersoni S, Papacchini F, Vano M, Goracci C, Magni E, Davidson CL,

Tay FR, Ferrari M. Factors affecting the adhesive cementation of indirect

restorations. J Dent Res, 85 (sp issue): abstact 00062. IADR Pan European

Federation 2006, Dublin, September 13-16.

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Graziani F, Cei S, Guerriero A, La Ferla F, Vano M, Tonetti M, Gabriele M.

Adjunctive effect of a systemic biphosphonate in non surgical periodontal therapy

of advanced generalized chronic periodontitis a randomized clinical trial.

Europerio, Madrid, Giugno 2006.

National Publications

Graziani F, Vano M, Gabriele M.

Profilassi dell’alveolite post-estrattiva. Proposte di linee guida. Dental Cadmos

2002;1:55-61.

Graziani F, Vano M, Gabriele M.

Angiogenesi ed espressione del fattore di crescita dell’endotelio vascolare nelle

cisti radicolari dei mascellari. Doctor OS 2003;1:14(1) suppl.1.

Vano M, Cei S, Graziani F.

Inusuale caso di scialolitiasi asintomatica del dotto di Wharton. Doctor Os

2005;16(4):345-347.

Vano M, Tognini F, Goracci C, Gabriele M, Bosco M, Ferrari M.

Vutazione della forza di adesione di differenti resine composite utilizzate nel

restauro di monconi su perni in fibra. Doctor Os 2005;16(1) Suppl.1:33-35.

Graziani F,Vano M, Gabriele M.

Terapia cistica sperimentale: ruolo dell’angiogenesi nelle cisti radicolari delle

ossa mascellari. Atti del 1° congresso nazionale S.l.C.O – S.I.d.C.O. Pescara,

29-30 Novembre 2002.

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Graziani F, Vano M, Gabriele M.

Marcatori immunoistochimici della vascolarizzazione nelle cisti radicolari. 10°

Congresso Nazionale “ Collegio dei docenti di odontoiatria” Roma 9-10-11-12

aprile 2003.

Vano M, Tosi E.G, Graziani F, Gabriele M.

Complicanze post-estrattive: valutazione dei parametri che influiscono sulla

guarigione alveolare. 12° Congresso Nazionale “ Collegio dei docenti di

odontoiatria”Roma 16-17-18-19 marzo 2005.

Cei S, Graziani F, Ducci F, Vano M, Gabriele S.

Valutazione della responsività di cellule mesenchimali stremali isolate da ratti di età

differente. Studio in vitro. 13° Congresso Nazionale del “Collegio dei docenti di

Odontoiatria”5-6-7-8 Aprile Roma 2006.

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Acknowledgements

This thesis is respectfully submitted to Prof. Silvano Focardi, Rector of the

University of Siena, to Prof Alberto Auteri, Dean of the Faculty of Medicine of the

University of Siena, to Prof. Egidio Bertelli, Director of the Department of Dental

Science, University of Siena and to Prof. Marco Ferrari, President of Dental

School, and Director of the PhD Program, University of Siena.

My sincere gratitude and admiration to my promoter Prof. Marco Ferrari. He

patiently and continuously reviewed my work and encoraged me to achieve this

goal.

I would like to thank my Co-promoter Dr. Cecilia Goracci for her scientifical

guidance. Her support was priceless.

I gratefully thank Dr. Simone Grandini for his clinical advice and support.

A deep thankfulness goes to Prof. Franklin Tay, for his unique and precious

scientific support.

I am also grateful to the whole Committee, for spending time on reviewing this

thesis.

I am sincerely grateful to Prof. Mario Gabriele. He has always provided me

guidance and encouragement in all these years.

My appreciation goes to Dr. Francesca Monticelli, Dr. Fernanda Sadek, Dr. Alvaro

Cury, Dr. Federica Papacchini, Dr. Maurizio Sedda, Dr. Nicoletta Chieffi, Dr.

Ivana Radovic, Dr. Filippo Graziani and all the PhD students and candidates for

their scientific support and above all their friendship.

I acknowledge my friends and colleagues for the translation of the ‘Summary and

Conclusions’ chapter: Dr. Elisa Magni (German), Dr. Carlos Augusto Ramos de

Carvalho (Portuguese), Dr. Hani Ounsi (French) and Dr. Claudia Mazzitelli

(Spanish).

I want to thank my family for their support and love.

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