Endodontic Topics Volume 31 Issue 1 2014 [Doi 10.1111%2Fetp.12066] Baba, Nadim Z.; Goodacre, Charles J. -- Restoration of Endodontically Treated Teeth- Contemporary Concepts And

8/18/2019 Endodontic Topics Volume 31 Issue 1 2014 [Doi 10.1111%2Fetp.12066] Baba, Nadim Z.; Goodacre, Charles J. -- R…

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Restoration of endodontically

treated teeth: contemporary concepts and future perspectivesNADIM Z. BABA & CHARLES J. GOODACRE

The concept of using a root for the restoration of a missing crown is not new. Through continuous research, our

understanding of the causes of failure has improved. Recent research on endodontically treated teeth has changed

contemporary views concerning some principles while consolidating others. Clinical success in restoring

endodontically treated teeth depends on our ability to use the latest materials available in conjunction with soundclinical methods. A number of articles have discussed the major factors that play a key role in the long-term

survival of endodontically treated teeth and associated restorations. The purpose of this article is to identify key

principles that affect tooth and restoration survival and to present expectations regarding optimal future solutions

for the long-term retention of endodontically treated teeth.

Received 23 September 2014; accepted 2 October 2014.

Various methods and materials have been proposed

over the years for restoring pulpless teeth (1–3). Root

fractures and other difficulties encountered with theseearly treatments led to the development of cast post

and cores that continue to be used today. Recently,

in response to an increased demand for esthetic all-

ceramic restorations, a variety of non-metallic

prefabricated tooth-colored post systems have been

introduced as an alternative to metal posts. Today, the

prosthodontic and endodontic aspects of restoring

endodontically treated teeth (ETT) have appreciably

advanced and a significant body of scientific

knowledge on which to base our clinical treatment

decisions is available. However, retainingendodontically treated teeth throughout life requires

careful restoration and adherence to available

evidence.

Although the collaboration between different

specialties coupled with modern therapies allows

patients to retain severely compromised teeth for

longer periods of time, the restoration of such teeth

remains a challenge. Despite a number of innovations

and decades of research on posts, failures can still

occur when endodontically treated teeth are restored

(Fig. 1) (4). Fortunately the failure rate is relatively

low, but it could be even lower. As professionals,it is our obligation to do everything possible to

minimize complications. Some of the post

complications encountered clinically are pos

loosening, root fracture (Fig. 2), endodontic failure

(Fig. 3), root perforation (Fig. 4), post fracture

(Fig. 5), caries, and periodontal failure. The most

common post complications have been identified as

post loosening and root fracture (4). Several authors

(5–10) discussed the multifactorial origins of the

causes of cracks and fractures in ETT. Loss of tooth

structure, the use of endodontic irrigants andinstrumentation, a reduced level of proprioception,

changes in dentin, and the restorative procedures are

the main factors proposed as causes of fracture (i.e.

post placement). In addition, different variables, such

as the arch position, the presence of opposing occlusal

contacts, periodontal tissue support, endodontic

status, and the amount of remaining dentin, play an

important role in the prognosis of ETT. A number of

articles have discussed the major factors that play a key

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Endodontic Topics 2014, 31, 68–83

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ENDODONTIC TOPICS

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role in the long-term survival of endodontically

treated teeth and associated restorations (11,12). The

purpose of this article is to identify key principles that

affect tooth and restoration survival and to present

expectations regarding optimal future solutions for the

long-term retention of endodontically treated teeth.

Effect of endodontic treatment onthe tooth

When performing root canal therapy, the access cavity opening causes loss of coronal tooth substance (Fig. 6)

(13,14). In addition, root canal treatment as well as

retreatment can cause damage to the root dentin. A

study looked at the influence of retreatment

procedures on the appearance of defects on the root

canal walls (15). It was concluded that retreatment

caused more defects in dentin than initial treatment.

During initial treatment, craze lines and cracks can be

formed in the dentin. The latter can develop into

a c

b

Fig. 1. (a) A separated instrument within the mesial root canal of a mandibular right second molar. (b) Perforationof the roots of a mandibular second molar, the result of post space preparation with instruments not held parallel tothe root canals. (c) A radiograph of a fractured maxillary lateral with a prefabricated non-metallic post.

Fig. 2. Radiograph displaying a very short post in theroot of a maxillary first bicuspid that caused rootfracture.

Restoration of endodontically treated teeth: contemporary concepts and future perspectives

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fractures during retreatment and under the functionalstresses applied to the tooth during chewing and

parafunction. Several studies (16,17) compared the

effect of hand files and rotary files on dentin after canal

preparation. They concluded that rotary instruments

caused more dentinal defects, such as craze lines and

cracks, which possibly could develop into fractures

after restorative treatment.

Several methods have been proposed for detecting

cracks and fractures when they are not visible clinically.

The most commonly used techniques are trans-

illumination (Fig. 7), occlusal tests, endodontic

microscopes, dyes, and quantitative percussion

diagnostics (18–22). Recently, cone beam computed

tomography (CBCT) has been suggested as a tool to

diagnose fractures, perforations, or suspected cracks

(23,24).

Another factor that could affect the mechanical

properties of dentin is the use of endodontic irrigants

Fig. 3. Radiograph displaying an inadequate root canaltherapy that caused a radiolucent apical lesion.

Fig. 4. Inappropriate placement of a screw post createda perforation in the pulpal floor of the maxillary firstmolar.

Fig. 5. Radiograph of a fractured maxillary lateralincisor with a prefabricated screw post.

Fig. 6. Excessive enlargement of the access cavity following root canal therapy.

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and medications (25–27). Following contact with

these products, chemical degradation of dentin is

evident and the dentin becomes weaker because of areduction in microhardness. However, the degree of

dentin change is related to the amount and duration of

contact between products and dentin. Other irrigation

agents such as mineral trioxide aggregate and bioactive

glass do not seem to affect the flexural strength of root

dentin (28–29).

In addition to the use of irrigants and medications,

Ferrari et al. showed that 10 to 12 years after

endodontic treatment, there is progressive degradation

of the demineralized collagen matrices (30). The aging

dentin becomes sclerotic and exhibits very limited

yielding before failure. The fracture toughness is lower,and the stress–strain response is characteristic of brittle

behavior (31). Most importantly, there is a reduction in

the stiffness and elasticity of dentin and a reduced

resistance to crack propagation (6,13,32,33).

These factors can affect the prognosis of the

endodontically treated tooth. As a consequence,

practitioners should strive to use restorative materials

with properties similar to that of dentin, along with

sound clinical principles to counteract the changes in

a

c

b

d

Fig. 7. (a) Clinical photo shows a crack line on the occlusal surface of a maxillary first molar. (b) The amalgamrestorations were replaced with new ones and the tooth was prepared to receive a partial coverage restoration. (c) A trans-illumination picture shows the crack running between the amalgams across the transverse ridge. (d) Occlusal

view of the 3/4 crown showing that it encompassed the buccal cusps.


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mechanical properties of dentin as well as the loss of

tooth structure following root canal treatment (RCT).

A systematic review investigated tooth survival after

RCT (34); 14 studies met the inclusion criteria. Four

key factors were identified as enhancing the survival

of teeth after RCT: the presence of interproximal

contacts, no plans for using the treated teeth asabutments for fixed or removable partial dentures,

tooth type, and crown restoration.

The restorative dentist plays an important role in the

success and failure of endodontic treatment. Before

endodontic treatment is contemplated, the restorative

dentist should: (i) have an overall treatment plan

for the patient based on their chief complaint

and desires; (ii) assess the restorability of the tooth,

which may involve the removal of all existing

restorations and/or caries to determine the tooth’s

restorability, and examine the tooth for the presence of cracks; and (iii) evaluate the need for any periodontal

treatment and appraise the periodontal prognosis of

the tooth to be restored. After endodontic treatment

has been performed, the dentist should minimize

recontaminating the root canal system.

A study by Balto et al. (35) found that all of the

provisional materials they tested in post-prepared root

canals failed to prevent coronal leakage when used for

an average of 30 days. Similarly, delayed placement of

the definitive restoration had an impact on the

prognosis of ETT. These teeth had a higher successrate when they were restored with a definitive

restoration than with a provisional coronal access

restoration (36). An in vitro study looking at bacterial

penetration of coronally unsealed endodontically

treated teeth found that defective restorations could

cause reinfection of the root canal system within 19

days (37). A combination of poor endodontic

treatment and poor restoration caused a high failure

rate for ETT (38). In comparing endodontic

treatment quality with restoration quality, Tronstad

et al. (39) found that the quality of root canaltreatment is more crucial than that of the coronal

restoration for the survival of ETT.

A well-fitting provisional restoration followed by a

post and core and a definitive coronal restoration

should be planned and cemented in as short a time as

possible. Avoiding reinfection of the root canal and

preventing mechanical failures such as fractures

enhances the survival of ETT (40,41). In a

retrospective study, Willershausen et al. (42) evaluated

775 ETT in 508 patients and found a higher survival

rate for teeth restored within 2 weeks.

If immediate restoration of the tooth is not possible,

it is recommended to protect the root canal system by

sealing the orifice of the canals and the floor of the

pulp chamber with intracoronal barriers (43–45).

Among the suggested materials to be used are flowablecomposite resin, mineral trioxide aggregate (MTA),

glass ionomer, fissure sealant, and conventional

restorative composite resin. This type of treatment has

mostly been suggested to protect the root canal system

from contamination during the provisionalization

period.

The use of digital impressions and CAD/CAM

fabrication can help the restorative dentist to seal the

filled root canal system and protect the tooth as soon

as possible, either with a provisional or definitive

restoration.

Principles that enhance success when restoring endodontically treated teeth

The prognosis of ETT does not depend solely on the

quality of the RCT or the quality and time required

for definitive restoration (38,46). Survival of the

restoration also depends on several basic principles

that affect tooth and restoration survival.

Cuspal coverage

ETT can benefit from the placement of crowns. An

epidemiological study in a large patient population

found that while 97% of teeth were retained in the oral

cavity 8 years after initial non-surgical endodontic

treatment, an analysis of the teeth that were extracted

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higher long-term survival rate compared to those not

restored with crowns (Figs. 8 and 9). A retrospective

cohort study found that the 5-year survival rate of

teeth without cuspal coverage was 36% (52). However,

while crowns significantly improved the success of

endodontically treated posterior teeth, they did not do

so for anterior teeth (53). Intact endodontically treated anterior teeth only require a crown when they

are weakened by large or multiple existing restorations

or when they require significant changes to their form

or color that are not manageable by conservative

restorations.

Several studies (54–56) indicated that ETT with

intact coronal surfaces (except for the access opening)

can be successfully restored using composite resin

restorations. However, the survival rate of ETT will

likely be lower when ETT have lost excessive amounts

of tooth structure. Sedgley & Messer (57) concluded

that the loss of axial dentin walls weakens the teeth.Composite resin is a popular core buildup material

because of its ease of use, and the possibility of

preparing and finishing it immediately (46). Some

clinicians consider composite resin as an esthetic

replacement for cuspal coverage crowns. Composite

resin appears to be an acceptable core material when

substantial coronal tooth structure remains but a poor

choice when a significant amount of tooth structure is

missing (56,58,59). The authors believe that if less

than 50% of the coronal tooth structure of an

endodontically treated tooth remains, a post should beused to retain the core material. The choice of buildup

material depends on the remaining adjacent teeth,

occlusion, and the planned definitive restoration. One

disadvantage of composite resin is that it is

dimensionally unstable (60). The setting shrinkage

during polymerization causes stress on the adhesive

bond resulting in cuspal strain with a disruption of the

bond, and gap formation that might contribute to

long-term bond failure followed by microleakage and

recurrent caries (54,55). The amount of shrinkage is

related to the amount of filler content in thecomposite resin. A reduced amount of filler will cause

greater shrinkage. For this reason it is necessary to

avoid using flowable composite resins as buildup

materials because of their low filler content and their

reduced mechanical properties (61).

A recent systematic review looking at the effects of

the restoration of ETT by crowns versus conventional

filing materials concluded that there is no evidence to

support or refute the effectiveness of crowns over

filling materials for the restoration of ETT (46).

After considering the available contrasting data, theauthors acknowledge the potential benefits of using

composite resin to restore posterior teeth that are

intact except for a conservative access opening.

However, when occlusal wear, heavy forces, or para-

functional habits are present in the mouth, more

clinical data are required to determine the long-term

survival of these teeth when large composite resin

restorations are present. For this reason, we

recommend that endodontically treated teeth which

Fig. 8. Occlusal view showing the fractured buccal cuspof an endodontically treated mandibular left first molar

without cuspal coverage.

Fig. 9. Fracture of the palatal cusp of a maxillary rightfirst molar with significant amount of tooth structuremissing restored with a composite resin and withoutcuspal coverage.


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have been previously restored and weakened by prior

tooth structure removal be restored with a crown that

encompasses the cusps. Conversely, it may be possible

to avoid crowns on some previously restored posterior

teeth with only a conservative access opening and

little-to-no wear present that would indicate the

presence of detrimental occlusal forces.It is highly recommended that a rubber dam be

placed when a composite resin is used as the core

buildup material. Composite resin is a technically

demanding material that requires careful adherence to

material-handling protocols. To ensure success, the

use of low-shrinkage composite resin (62), the buildup

of the core in small increments (63), and the use of

liners (64) has been advocated.

The high demand for esthetic restorations, the need

for an occlusal material stiffer than dentin, and the

benefit of covering the cusps has caused someclinicians to use all-ceramic onlays and crowns as a

conservative and effective treatment modality to

restore ETT (65–67). A suggested conservative

technique to restore ETT is the use of an endocrown

(68–70). This restoration consists of an onlay or

crown with the core material in a single unit (Fig. 10).

The core material engages in a cavity prepared into the

pulp chamber. A study by Magne et al. (68) found that

an endocrown fabricated from a resin nanoceramic has

a favorable mode of failure when ETT with no buildup

material are used. These crowns were found to be

more resistant to failure than teeth that had been

restored with a post, composite resin core, and a

ceramic crown (69,70). It is unknown whether this

type of conservative restoration will produce the same

problems as the one-piece crown–post combinationsmade using metal. Also, the impact of their subsequent

removal upon structure integrity is unknown.

Tooth preservation

Maximum preservation of coronal and radicular tooth

structure is a guiding principle for the restoration of

ETT. As clinicians we should preserve intact tooth

structure whenever possible in order to maintain an

adequate retention and resistance form of the final

restoration. The position of the tooth in the arch,the presence of opposing occlusal contacts, the

periodontal tissue support, the endodontic status, and

the amount of remaining dentin aids in selecting

the appropriate material for the definitive restoration.

The authors believe that gold onlays or crowns are

excellent restorations where esthetics is not of major

concern, on teeth with limited interocclusal space, and

when restoring heavy bruxers.

Cervical ferrule A ferrule can be established by the crown

encompassing sound tooth structure (Fig. 11) (71–

76). The data indicates that cervical ferrules increase

the tooth’s resistance to fracture (71,72,77). In spite

of the data supporting the benefit of cervical ferrules,

not all practitioners recognize their value. A survey

published by Morgano et al. (78) evaluated the

percent of respondents who felt that a ferrule increased

a tooth’s resistance to fracture: 56% of general dentists,

67% of prosthodontists, and 73% of board-certified

prosthodontists felt that core ferrules increased atooth’s fracture resistance.

Different lengths and forms of the ferrule have been

studied (71,73,74,79) and are essential factors for

the success of the “ferrule effect.” When possible,

encompassing 2.0 mm of intact tooth structure

around the entire circumference of a core creates an

optimally effective crown ferrule. Grasping larger

amounts of tooth structure further enhances ferrule

effectiveness. The amount of tooth structure engagedFig. 10. All-ceramic restoration consisting of a crown

with a core material in a single unit.

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by the overlying crown appears to be more important

than the length of the post in increasing a tooth’s

resistance to fracture.

If insufficient cervical tooth structure remains to

develop a ferrule, surgical crown lengthening or

orthodontic extrusion should be considered to expose

more tooth structure.

In some situations where teeth have been extensively

restored, have been subject to trauma, or have

substantial caries, it will be difficult to obtain a ferrule.In such cases it may be prudent to extract the tooth

and replace it with an implant and crown. Extraction

of ETT may also be required when crown lengthening

would create an unacceptable esthetic environment or

produce a furcation defect, or when a short root is

present that would not permit an appropriate post

length to be developed (80).

Studies have shown that a uniform ferrule produces

significantly greater fracture resistance than a non-

uniform ferrule (74,76,81), with the greatest variation

in failure load associated with the absence of portionsof the crown ferrule. The presence of a 2-mm ferrule

on the facial, lingual, distal, and mesial surfaces of the

tooth produces the most favorable resistance to tooth

fracture and decreases the weakening effect of a post

(Fig. 12) (76).

Need for a post

Studies have compared the fracture resistance of

endodontically treated extracted teeth without posts

or crowns with the fracture resistance of teeth restored

with posts and cores and crowns. Maxillary incisors

without posts resisted higher failure loads than the

other groups with posts and crowns (82) and

mandibular incisors with intact natural crowns

exhibited greater resistance to transverse loads than

teeth with posts and cores (83). These studies have

shown no evidence of a strengthening reinforcement

effect of posts. However, several studies showed arelatively high failure rate of endodontically treated

teeth that were restored with a composite resin filling

without a post (84–86). The failures occurred when

the teeth had small and curved roots. A study by Salvi

et al. (87) evaluated ETT restored with and without

post and cores in a specialist practice. They concluded

that there was no significant difference between teeth

restored with or without posts provided that at least

two-thirds of the dentin remained. They also found

Fig. 11. A ferrule will be created by the overlying crownengaging tooth structure. The final restoration is at least

2 mm apical to the junction core/tooth.

a

b

Fig. 12. Post and crown loosened from maxillary caninea few months after placement. (a) Both the post/prefabricated post and the crown came off. (b) Clinicalphoto shows the absence of cervical tooth structure(ferrule) for retention of the crown.


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that 11 out of 13 failures in mandibular molars were

due to fractures (Fig. 13).

Clinical studies have failed to provide definitive

support for the concept that posts strengthen

endodontically treated teeth (53,85,87). An analysis of

data from multiple clinical studies noted that 3% of

teeth with posts fractured with no evidence that posts

enhanced the survival of teeth (88). Posts have had

little enhancing effect on the clinical survival of fixed

partial denture abutments, but they did improve

the clinical survival of removable partial dentureabutments compared to endodontically treated

abutments where no posts were used (53).

Because clinical and laboratory data indicate teeth

are not strengthened by posts, their purpose is for the

retention of a core that will provide adequate retention

and support for the definitive crown or prosthesis.

When enough tooth structure is present in an

endodontically treated molar, there is absolutely no

need for a post (Fig. 14). The presence of adequate

dentin coupled with no preparation of a post space

helps avoid weakening the tooth, eliminates the risk of perforation during post preparation, and aids in

preventing the development of cracks that could be

detrimental to the ETT. In endodontically treated

molars, buildup materials usually have sufficient

retention from the pulp chamber, divergent coronal

portions of the root canals, and undercuts created in

the pulp chamber during removal of caries and RCT.

For endodontically treated anterior teeth and

premolars, if sufficient tooth structure remains to

a b

Fig. 13. (a) Radiograph of a broken mesial root of an endodontically treated mandibular right molar restored witha crown and no post. (b) Extracted tooth showing the fractured mesial root.

a

b

Fig. 14. (a) Occlusal view of a maondibular secondmolar showing the presence of enough tooth structureto retain the core. (b) Radiograph of the root canaltreatment.

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retain the core, the use of a post is not required;

bonding a core buildup material to dentin is sufficient.

However, if a substantive amount of tooth structure is

missing in these teeth, a post is needed in order to

retain the core and optimize the resistance form. The

best prognosis is obtained when a 2-mm ferrule

encompasses intact tooth structure around the entirecircumference of the core no matter what type of post

is used. Because posts do not reinforce a tooth, they

should only be used when the core cannot be retained

by some other means.

Types and properties of posts

In recent years, prefabricated posts have become quite

popular and a wide variety of systems are now

available. In response to a need for tooth-colored

posts, several non-metallic posts such as zirconia, glassfiber-reinforced epoxy resin (GFR), and ultra-high

polyethylene fiber-reinforced posts are available; early

data indicates that they can be acceptable alternatives

to metallic posts. However, gold alloys, titanium, and

chrome–cobalt are still clinically viable and are widely

used.

Among the non-metallic posts, GFR posts are the

most popular. They are available in different shapes:

cylindrical, cylindroconical, or conical. An in vitro

assessment of several GF post systems indicated that

parallel-sided GF posts are more retentive than taperedGFR posts (89). These posts could be made from glass

or silica fibers (white or translucent) but the most

commonly used fibers are silica based. The matrix

for this post is an epoxy resin. The fibers are in the

vicinity of 14 μm in diameter and uniformly

embedded in the epoxy resin matrix. The fibers are

stretched before injection of the resin matrix to

maximize the physical properties of the post. When

compared to metallic posts, GFR posts have a low

modulus of elasticity and are more flexible (90). This

flexibility induces more stress cervically, which, in thecase of minimal or no ferrule, causes a higher risk of

post fracture, debonding of the core, and loss of

retention of the post followed by microleakage and

secondary caries (Fig. 15). Several studies (91,92)

have determined that there is a 40% decrease in the

strength of GFR posts after thermocycling and cyclic

loading. In addition, contact of the post with oral

fluids (short- and long-term) reduced their flexural

strength. While failure with fiber posts might be less

likely to produce root fracture, post removal may

damage the root, and the cost to the patient versus

time of service before failure is a concern.

In contrast, metallic posts are stiffer than dentin and

can take more load than GFR posts. Their stiffness can

induce more stress apically, causing catastrophic root

fractures (Fig. 16). Similarly to GFR posts, metal postsalso undergo a process of cement failure during cyclic

loading (93). Metal posts have a longer lifespan than

GFR posts and they fracture less; but when they fail,

the failure is non-restorable (94).

A comprehensive review of the English literature was

conducted on evaluating the clinical performance of

GFP in order to seek evidence for the treatment of

teeth with non-metallic posts (95). Clinical research

articles showed that non-metallic posts have favorable

a

b

Fig. 15. (a) A radiograph of a fractured mandibularsecond premolar with a prefabricated non-metallic post.(b) Crown with broken post.


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mechanical and physical properties and the studies

presented with a wide range of reported failurepercentages, from 0% after a mean of 2.3 years to

11.4% after 2 years. Post debonding, post fracture,

crown debonding, and root fracture were the most

commonly reported complications. Post debonding

was reported in 16 of the 23 studies. A 10-year

prospective study on GFR posts found that the overall

failure rate of these posts was 37%, of which 11% were

due to post debonding (96). From these results, it can

be concluded that the failure might be due to

weaknesses in the bonding of composite resin to

the post and/or to the dentin. Studies (97–99)demonstrated that radicular dentin is different from

coronal dentin. It contains fewer tubules and forms a

thinner hybrid layer than coronal dentin. The efficacy

of bonding to radicular dentin could be compromised.

It is strongly recommended that chemical or dual-cure

composite resin cement be used to ensure complete

polymerization of the cement in the canal.

Another reason for post debonding could be the lack

of retention between the composite resin cement and

the surface of the GFR post. Studies have shown that

there is a low bond strength (5 to 6 MPa) between theGFR posts and composite resin (100,101). Differences

exist among brands of GFR posts in term of structural

characteristics and fatigue resistance (102,103). GFR

posts could present with voids and irregularities within

the resin and discontinuity at the interface between the

fibers and the matrix. It is recommended to condition

the surface of GFR posts prior to cementation with

soft air abrasion (2 bars) and the application of silane

(104,105).

Post debonding could be due to the polymerization

shrinkage of the composite resin cement, the

technique-sensitive cementation process, the difficult

access and visibility during cementation, the lack of a

clear and universal cementation protocol, the lack of

ferrule effect, or an inadequate choice in the type of

post for the given clinical situation and tooth. The wide range of failure percentages reported with GFR

posts may also be indicative of variations amongst

clinicians and differences in their experiences/

restorative techniques. It appears that more long-term

clinical data is needed in order to determine the

efficacy of fiber-reinforced posts.

A 10-year retrospective study of the survival rate of

teeth restored with metal prefabricated posts and cast

metal posts and cores found that their overall failure

rate was 15.4% and 17.4%, respectively (106). When

we compare these results to the high overall failure rateof non-metallic post, the authors believe that the GFR

posts are not superior to metallic or cast posts.

There are challenges related to the use of cylindrical

prefabricated posts when restoring teeth with ovoid,

wide, or particularly tapered canals. The lack of

intimate adaptability of these posts to the tooth

structure compromises their retention in the canal.

In addition, the low success rate of GFR posts

encouraged researchers to look for alternative

materials to restore ETT. Polyethylene fiber-reinforced

(PFR) posts made out of ultrahigh-molecular weightpolyethylene woven fiber ribbon (Ribbond, Seattle,

WA) have been proposed. It is not a post and core in

the traditional sense. It is a polyethylene woven fiber

ribbon that is coated with a dentin bonding agent and

packed in the canal, where it is then light polymerized

into position (107). Another proposed material is a

customized glass-fiber post (108,109). Costa et al.

(108) compared the root fracture strength of single-

rooted premolars restored with GFR posts to the ones

restored with customized GFR posts. They concluded

that the customized GFR posts did not show improved fracture resistance or differences in failure

patterns when compared to GFR posts. Some authors

suggested combining PFR with a customized GFR

post to restore ETT (110). Custom-milled zirconia

posts have also been suggested as an alternative

material to GFR posts in anterior teeth where the use

of a custom post is indicated. An in vitro study

comparing a one-piece milled zirconia post and core

to different core systems concluded that the mean

Fig. 16. A radiograph of a fractured maxillary secondpremolar with a metallic prefabricated post.

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load-bearing capacity of the one-piece milled zirconia

post and core was comparable to that of a cast gold

post and core (111). One explanation as to why

these post behaved similarly to cast post and core is the

absence of an interface between the post and the core,

which eliminates the debonding of the core evidenced

with GFR posts and cores.The authors believe that until more long-term

clinical data becomes available, fiber-reinforced resin

posts should be used with caution because of the wide

range of reported failure rates in available clinical

studies.

Future directions

In the future, we foresee that the advancement of

CAD/CAM technology, milling, and laser printing

along with an improvement in digital impressiontechnology will make it possible to more easily and

accurately fabricate customized post and cores from

several different materials. In addition, more

conservative endodontic treatment procedures are

likely to emerge and reduce the need for posts and

crowns. Pulpal regeneration procedures may even

eliminate or substantially reduce the need for the use

of crowns and posts and cores.

In future studies of ETT and new technologies, we

believe in vitro studies should be performed using

fatigue loading and chewing simulation conditions.

Summary

Based on this review of available evidence, the

following clinical recommendations are proposed:

1. When performing root canal therapy, the tooth

needs to be evaluated for the presence of cracks and

craze lines using several of the diagnostic tools

available. The restorability of the tooth needs to be

assessed along with the periodontal prognosis.

2. Following root canal therapy, the tooth needs to berestored with a definitive restoration in as short a

time as possible. If immediate restoration is not

possible, it is recommended to seal the orifice of the

canals and the floor of the pulp chamber with

intracoronal barriers.

3. Crowns are not needed on many endodontically

treated posterior teeth to enhance their long-term

survival because their structural integrity is often

compromised. There is some data indicating

posterior teeth that are intact except for the access

opening can be satisfactorily restored with

composite resin rather than a crown. However, the

long-term success of this more conservative

treatment is not known in the presence of heavy

occlusal forces.

4. Posts weaken teeth and they should only be used when the core cannot be adequately retained by

some other means.

5. When crowns are placed on endodontically treated

teeth, they should encompass 2.0 mm of tooth

structure apical to the core whenever possible since

crown ferrules increase the resistance of teeth to

fracture.

6. Until more long-term clinical data becomes

available, fiber-reinforced resin posts should be

used with caution due to the wide range of

reported failure rates in available clinical studies.7. Procedures will become available that preserve or

regenerate pulp vitality and may reduce or even

eliminate the need for restorations. For those teeth

that need RCT, even more conservative endodontic

procedures will be developed; and when combined

with new materials it may not be necessary to place

crowns on these teeth. When posts are needed due

to tooth condition, digital technologies will make it

possible to fabricate customized posts and cores

from a variety of materials.

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Documents

Endodontic Topics Volume 31 Issue 1 2014 [Doi 10.1111%2Fetp.12066] Baba, Nadim Z.; Goodacre, Charles J. -- Restoration of Endodontically Treated Teeth- Contemporary Concepts And