Contemporary Perspectives On Post-Core Systems

By Dr Tom Berekally, BDS (ldel). MDS. YHACDS, Dental School, Faculty of Health Sciences, The University of Adelaide. Address for correspondence: Dr T. Berekally, Dental School, Facult) of Health Sciences, The llniversity of Adelaide, Frome Road, Adelaide, SA, 5000.

Email: [email protected]

Contemporary Perspectives On Post-Core Systems Editor's Note:

This article is based on a presentation to the SA Branch of the ASE in July 2003.

Abstract The challenge of restoring endodontically-treated teeth has spawned a considerable diversity in foundation restorations and a plethora of publications in the dental literature. Moreover, it seems that an inverse relationship has developed between the escalating complexity in selecting a post-core system and the volume of reliable scientific data upon which clinicians base their treatment decisions. In the quest to restore aesthetics, function, and reduce the risk of treatment failure there is now a much greater emphasis on the preservation of sound tooth structure, tooth isolation for intracanal procedures, sealing the root canal and adapting the advantages and limitations of dental materials to the presenting clinical situation. The relatively recent introduction of metal-free posts into mainstream prosthodontics has added an aesthetic dimension to treatment planning. N e w adhesive systems and resin-based luting agents have the potential to create a genuine adhesive continuum between the tooth and post- core complex. While these developments may have significant ramifications with respect to treatment prognosis, the long-term clinical performance of contemporary post-core systems is unclear.

Introduction Many coronally deficient endodontically-treated teeth require

the placement of foundation restorations in order to restore aesthetics and function Although this subject is a recurring theme in numerous research publications and modern reference texts the concept of using a post to retain a coronal restoration is certainly not new In the 17008, Pierre Fauchard placed hickory dowels into devitalised teeth in order to secure ceramic crowns In time, these wooden posts would have absorbed moisture and expanded, leading to an initial improvement in retention, but later, not sur- prisingly, a vertical root fracture was likely In time, many novel

dowel designs were tried In I869 Dr James Bean placed a hollow gold tube with a closed apical end into a root canal and stabilised it with gold foil that was malleted at the coronal end of the root ( I ) Interestingly, securing the crown to a post posed far greater challenges to our 18th Century colleagues than post retention Bremner ( I ) described an earlier type of bonding technique whereby a post was cemented into the root canal by wrapping it with a coating of cotton fibres soaked in resin

For many years after their introduction metal posts were placed in endodontically-treated teeth on the precept that they would strengthen an inherently weak crown-root complex There is ample evidence in the dental literature now to challenge this notion (2-4) Indeed, there has been a significant shift away from this paradigm in recent years and the use of post-core systems is now largely based on biomechanical principles encompassing knowledge of tooth anatomy patient factors and the properties of restorative materials

The introduction of metal-free posts has added a new aesthetic alternative to the growing number of treatment options with foundation restorations ( 10) Their development was also driven by an expectation that materials with a lower elastic modulus than metals would cushion functional forces transmitted to the root and thereby reduce the potential for root fracture Further advantages included enhanced aesthetics in post-core build ups and the elimination of problems relating to corrosion and delayed hypersensitivity type reactions to dental alloys

In vitro research suggests that new adhesive systems and resin-based luting agents have the capacity to form an adhesive continuum' between the post-core restoration and tooth structure ( I I 12) This adhesion has a special significance with respect t o reducing marginal leakage, preventing bacterial ingress into root canal, improving the retention of the restoration and possibly reinforcing the crown root complex In the N e w Millennium, it

appears that adhesive dentistry has given clinicians the means to push the envelope by trying restorative treatments previously unattainable

Although the restoration of endodontically-treated teeth is com prehensively covered in the dental literature, there is little consensus about the best method of treatment With so many variables involved in each case treated, it could be argued that patients are better off, because clinicians have the flexibility t o make a choice from a range of materials and techniques to suit the clinical challenge at hand At the same time, there is little long term evidence-based clinical data that can reliably guide dental practitioners through the quagmire of techniques designs and materials relating to post-core systems Rather than attempting to review the complex topic of

(5-9)

1 LO AUSTRALIAN LNDODONTIC JOUKNAL VOLUME 29 No 3 DECLMULR 2003

post-core systems, this paper will focus on some contemporaty trends in this continually ievolving area of prosthodontics

Treatment Planning The main problems associated with endodontically-treated teeth

can be divided into biolclgical failure (caries, periodontal and endodontic pathology) and mechanical failure (loss of attachment or fracture in the tooth-posUcore complex) Accordingly. the primary aim of any treatment plan is to prevent these anomalies Risk- management must be based on a detailed assessment of the tooth and the contributory pdient. operator and restorative material variables While there is jome debate over which factors influence treatment success, it appears that the answer lies with a coni- bination of technical quality in the root canal obturation ( 13) and coronal restoration ( 14)

Tooth Preparation And Temporisation Success in endodontic. therapy is assured via an accurate diag-

nosis, isolation of the operative field, a thorough chemo-mechanical debridement of the root canal complex and a good apical seal The problems linked to microleakage in the endodontically-treated tooth are well documented ( 15- 17) In a recent paper, Barthel and Roulet ( 18) reminded practitioners that sterile conditions are mandatory for all root canal therapies including post endodontic procedures such as post-hole preparations There is also a con- vincing body of evidence demonstrating that temporary post- crowns leak significantly more than the definitive restorations ( 19-2 I ) Some effective G,trategies to minimise microleakage include placement of a final post and core immediately after oDturation (in the absence of a periapic al lesion), provision of a custom cast post and core very soon after placement of the provisional restoration or the use of an interim removable partial denture The last method has the benefit that the coronal seal of the root-filled tooth remains undisturbed until the final restoration is placed (22) Calcium hydroxide-based intracanal materials have also been shown to reduce bacterial penetration and slow the rate of any future microleakage by alkalisation of the root canal ( 18)

The Ferrule Effect Various definitions of the ferrule effect have appeared in the

dental literature Eissman and Radke (23) used this term1 to describe a full circumferential ring of cast metal extending from the core onto a subgingival root margin with the aim of providing an extracoronal bracing to prevent root fracture There is a general consensus that the final coronal restoration margins should extend at least 2 m m apical to the junction of the core and remaining tooth structure (23, 24) lsidor et a/ (25) concluded that resistance to failure was optimal when the longest posts were used in concert with the longest ferrules Libman and Nicholls (26) reported an improved cement seal around a crown where the crown margin extended at least I 5 m m apical to the margin of the core A retrospective clinical study by Torbjorner et a/ (27) assessing the survival and failure characteristics of post crown restorations, indicated a higher risk of post fracture when luted crowns did not provide a ferrule

In cases of complex crown-root fractures interdisciplinary treatments may be required to create a ferrule Orthodontic extrusion of the endodontically-treated tooth is often preferable to crown- lengthening because a rnore favourable crown-root ratio is produced (28 29) Gegaufl (30) supported this concept via a recent investigation on resin tooth analogues and proposed that the use of

rcw cements may preclude the need for costly crown-lengthening procedures Cutting into root structure to achieve a ferrule can weaken the root and a narrower cross-section in an extruded tapered root will almost certainly create a prosthodontic challenge with respect to the emergence profile of the final restoration Stankiewicz and Wilson (3 I ) supported the creation of a ferrule but not at the expense of weakening the root Clearly, crown- lengthening and extrusion techniques must be preceded by a very cxeful clinical and radiographic examination

Tooth Reinforcement For many years, it was thought that endodontically-treated teeth

were rendered brittle and weak via water loss and alterations to the root canal dentine ,% a result, it became standard practice to place posts in root-filled teeth on the presumption that they reinforced the crown-root complex and assured a more favourable prognosis for the restored tooth The contemporary view IS that tooth strength is more a product of the remaining volume of dentine (32) and the past restorative history of the treated tooth (5) However, some recent publications (33, 34) suggest the possibility of internally reinforcing root structure with contemporary adhesion systems as a substitute for the extracoronal ferrule Pierrisnard et a/ (35) concluded from a finite element analysis of restored pulpless teeth that the presence of a post reduced the intensity of stresses in the cervical zone of the tooth and posts of a higher elastic modulus produced a lower cervical stress

Although many of the conclusions drawn from laboratory investigations addressing the issue of tooth reinforcement are interesting from an academic standpoint, they are largely equivocal in the clinical sening Hence, it is not surprising to read in one compre hensive review of foundation restorations that the internal reinforcement concept lacks clinical evidence-based support and so the traditional use of ferrule is recommended (36)

The challenge of choosing a final restoration for posterior teeth was revisited recently by Assif et a/ (37) who tested the fracture resistance of endodontically-treated molars restored with amalgam 1 he authors stated that treatment options for posterior teeth vary considerably from the exclusive use of cast onlay or full coverage restorations to less costly complex amalgams Moreover, those molars with a conservative endodontic access or coverage of all cusps by amalgam demonstrated the highest resistance to fracture loads In an earlier, frequently cited laboratory study, Linn and Messer (38) also demonstrated the importance of cusp-coverage restorations for molars

Metal-Free Post Systems I. Carbon-Fibre Posts

In the early nineties Duret et a/ (39) came up with the novel idea of fabricating an epoxy resin post, reinforced with carbon-fibre, for dental use The design evolved from an expectation that a metal-free material with a lower stiffness would dampen functional stresses on the root and thereby reduce the potential for fracture lsidor et a/ (40) verified this hypothesis in their study performed on bovine teeth

Dietschi et a/ (41) suggested that the inherent flexibility of carbon-fibre posts could be a disadvantage if there is little or no dentine ferrule, because functional loads may cause flexure in the post and the resultant micro-movement in the core build up could compromise the cement seal

Various carbon-fibre post systems have appeared, but it is their distinctive black colour that can cause problems where a high

AUSTKALIAN ENDODONTIC jOURNAL VOl-UME 29 No 3 DECEMBCR 2003 I21

degree of aesthetics is required In response to this anomaly mineral-coated carbon fibre posts were developed

Carbon-fibre posts are radiolucent therefore radiopaque resin luting agents should be used to place them so that the outline of the post can be detected on an intraoral radiograph Dental prac titioners who are not familiar with carbon fibre posts can be misled into believing that a root canal is not well obturated due to an apparent space arising from the inherent radiolucency of the posts In a public dental health system or group dental practice accurate records of the restorative materials used must therefore be kept in the patient case records for the benefit of other operators In the solo private setting it is wise to ask patients if they are aware of the use of carbon-fibre posts in their teeth Alternatively, their use may need verification via past dental records Mineral coated carbon- fibre posts have a degree of radiopacity to make detection easier

O f the metal-free systems available today, carbon-fibre posts have been in clinical use the longest A number of retrospective studies indicate that their clinical performance is promising (42 43) The results of some prospective trials have also been published, but the conclusions drawn are tempered somewhat because of the small sample sizes (44, 45)

2. Glass/Quartz Fibre-Reinforced Composite Posts

An increasing demand for durable highly aesthetic restorations and the prospect of delayed hypersensitivity-type reactions to dental alloys has prompted the development of all-ceramic and indirect resin composite restorations For many of these systems, the dark colour of a carbon-fibre or metal post can significantly compromise their optical properties In response to this short- coming glass/quartz fibre-reinforced composite post systems evolved

The potential for crown-root fracture can be reduced with these posts and it appears that quartz fibre posts have superior fatigue strength in comparison to glass-fibre products (46) However, the clinical significance of this observation has yet to be ascertained

The geometry of the glass/quartz fibre post systems varies and a retentive coronal end for the post may be a desirable feature to enhance retention of a resin core build up Moreover, the flexibility of these materials may preclude their use in decoronated teeth where support for the core is diminished (47)

Although many glass/quartz fibre post systems have retentive surface features along the post length, some manufacturers still recommend a silane coating to enhance their retention in the root canal The clinical efficacy of this surface treatment is unknown

Most of the aesthetic fibre-reinforced composite posts available are intended for direct post and core restorations The Luscent Anchor (Dentatus. N e w York, NY, USA) allows light conduction down the length of the glass fibres in the post t o help polymerisation of the resin cement within the root canal It appears that the depth of cure possible with these posts is sufficient to meet clinical requirements (48, 49) TargisNectris (IvoclarNivadent, Amherst, NY USA) is another fibre-reinforced resin composite system that can be used in the fabrication of indirect post-cores (50) Long-term clinical data on the performance of these posts is lacking

Since the radiopacity of glass/quartz fibre post systems is at best variable radiopaque resin luting materials are recommended for cementation in order to highlight the post outline on radiographs

There is very little clinical data in the dental literature on glass/quartz fibre post systems Ferrari et a/ (43) reported their retrospective findings on 1,304 fibre posts The survey sample included 840 Composiposts (carbon fibre), 2 I 5 Aestheti-posts (mineral-coated carbon-fibre) and 249 Aestheti-Plus posts (quartz fibre) There was no significant difference in the clinical performance

of the post systems A 3 2% failure rate was attributed to loss of attachment in 25 posts during temporary crown removal and 16 teeth showed periapical lesions during radiographic examination The authors remain guarded about the performance of fibre posts stating that more definitive conclusions could be derived from multicentre prospective clinical trials

3. Zirconia Posts

In response to the high degree of aesthetics required of all ceramic restorations. an alternative type of post system composed of fine grain dense tetragonal zirconium oxide polycrystals was developed The crystals are stabilised with calcium magnesium or yttrium oxides Conventional ceramics ultimately fail via the propagation of microcracks If such cracks arise in zirconia posts, the oxide inclusions allow conversion of the tetragonal polycrystals into a larger monoclinic form that impedes further crack propagation This transformation strengthening gives zirconia posts a very high flexural strength and toughness (5 I , 52) These properties may be advantageous in giving resin composite cores good stability coronally, reducing the potential for microleakage at the core-tooth interface via micro-movement (4 I ) An added advantage of zirconia posts is their excellent radiopacity in comparison to the glass/quartz and carbon-fibre systems The manufacturers of zirconia posts recommend the use of resin luting agents for cementation These posts do not have retentive features at the coronal end, so there may be concerns with the bond strength between the post and resin cores

IvoclarNivadent (Amherst NY, USA), manufacturers of the Cosmopost system, state that a pressable dental ceramic core can be cast onto the post surface The retention of various core materials to zirconia posts and the integrity of the post-core complex may be compromised by a mismatch in the coefficients of thermal expansion of the post and core materials used (53) Heydecke et a/ (54) concluded from their laboratory investigation that zirconia posts with either ceramic or direct resin composite cores can be used as an aesthetic alternative to cast post-cores However as is often the case with published laboratory trials, the authors point out the limitations of their test methods and state that clinical trials should be conducted to verify in vitro observations To date, this author is not aware of any published clinical data pertaining to zirconia post systems

4. Woven-fibre Composite Systems

Flexible woven fibre impregnated with particulate composites can also be used to fabricate foundation restorations (55-57) The composition and configuration of these materials vary Those types currently in clinical use include a plasma-coated high molecular weight polyethylene ribbon (e g Ribbond - Ribbond Co, Seattle Washington USA, Connect SDS/Kerr Orange CA USA), flexible E-glass fibre that has been pre-etched and silanated (Glasspan - GlasSpan C o Exton, PA, USA) or glass fibre pre impregnated with resin (e g TargisNectris - IvoclarNivadent. Amherst, NY USA) The various fibre weaves and surface coatings are designed to enhance the adhesion between the flexible fibre and resin composite

Sirimai et a/ (58) concluded from their in vitro study that although the woven fibre composite core build-ups were significantly weaker than cast post-cores, the strength of the fibres could be enhanced with the inclusion of a prefabricated post Woven fibre based foundation restorations are aesthetic and highly adaptable to the root canal morphology However, any practitioner Contemplating using this technique should try it several times on an extracted tooth Since a self-curing resin cement is placed in the root canal,

I 2 2 AUSTRALIAN ENDODONTIC IOURNALVOLUME 29 No 3 DECEMBER 2003

the woven fibre strips must be packed very efficiently into the canal well before the cement hardens Furthermore Panavia-2 I and Panavia F (Kuraray Co Osaka Japan) resin cements should not be used lor this technique because the self-etching primer that is placed into the root canal contnins polymerisation accelerators that will definitely set these luting i ems well before the woven fibre packing can be completed

Woven fibre posts tnay be appropriate for flat ed toot canals or 3lternatively, may help tc stabilise metallic 0 1 n o n - t n e t k posts in

wch canals At best, these techniques are largely experinimtal and no firm conclusions can be drawn about their long-twm viability based on the scant number of reports in the dental Iitw atcit e

5. Ceramic Posts

Kwiatowski and Geller (59) reported on the use of a cast ceramic \ystem, Dicor for post-cores The sample of restorations for this novel technique was smd and the review period ver, shott One post-core had failed A MedLine search has not revealed any follow-up wot k b) these authors Sevuk ei a/ (60) described a case where one-piece t etamic post-laminate veneer<, f,ibt icdtfd via a copy milling technique were used to restore hvo rnaxillaty lateral incisots Whilst the restorations desct ibed are interesting the authors ate uncettciin ,about their long tet m performance

Core Ma Lc r ia I s

Amalgam has been used for many years by dental ptactitionet-s as a reliable and durable core material. As a dir-ecl r-estorative, amalgam has several advantages in relation to its conipr essive stt-ength. rigidity. weat- ,.esistance. tolerance of moisture in the operating field and its ability to be condensed into retentive undet-cuts and toot c m a l s . Over- the yexs, resin cot-'posites and glass iononiet- cements have entet-ed the playing field cij altet-n,itive core materials. Irripi-ovements in their- physical pi-opetties. their capacity to adhet-e to tooth structure and their aesthetic appearance make them potential competitor<; t o amalgam in selected cases. To date. there is vet-y littli.: comparative clinical data about thec,e matet-ials as foundation I estorations One Liboratory investigation by Kovat-ik ( '1 nl (6 I ) compared the fatigue life of ail-algarn allcmy. resin composite m d g,lass ioriomer c.ement undct, simulated chewing conditions. Arnalgam had the superior- p(:tforrnance. Burt-ow ( 'f oi (62) showed that the bond sti-ength of testPC t-esiii-

based dentine cidhesive,, deteriorated significantly a c r tile test pet-iod of tht-ee ye'ir-s <mi so the capacity of resin adhwve systems to r-educe micr-ole,ikage is not reliable in the long-tetni It follows that resin composite coie build-ups must also rely on tncchanical retention to ensure success and the dentine-core intc!if,icr: should be protected by fully covering it with a final crown (>n tti is bass, decoi-onated tecth. without a fert-ule and little cot-onal support f a a resin cot-e. are likely to have a guarded prognosis.

Glass ionoinet- cements are a very good dentine substitute but their t-ecot-d of poot- perlot-niance in load bearing and cyclic fatigue testing (63, 64) sugge5ts that they are genet-ally contr,iiridic,ited fat- large co i r build-ups. Cur-rently, restorative glass ionoinet- cemerts may have gr-eater succes', in sealiig conservative endodont!c. access cavities in postct-lot- teetii intended foi- crowns. ot for blocking out smaller under-cuts in ct-own preparations

A welcome irinovatiori in the applic;ition of resin cc;r-e iriateri,ils has been the developrnent of automix delivery systems. The availability of diial-cut-inll, and self-curing injectable rridterials has eliminated some of th? anomAes associ,ited with tnct emental placement of resin cotnposite. It appear-s that a denset; lesi pot-oi~s core trestoration results after the injection method of tielivriy (65)

O'Keefe and P o w m (66) recently reported a disturbing prob leni relating to suboptimal adhesion between a self curing resin core material and a single bottle (pi imer/adhesive) system One explanation for this aiomdy could be that an abundance of non polymerised acidic mwomers in the adhesive layer combine with ot ganic amines in the ovet lying core material reducing the number ot free radicals in the cate resin an essential prerequisite to start the self-curing polymer isation reaction In order to alleviate this pi oblein, some adhesibei are now available in dual cure versions incorporating activators that are claimed to be compatible with sdf and dual-cured coinposites Cut rently, there is no published long-term clinical dat,i vet ifying the benefits of dual cured adhesive systems

Post Cementation Dental cements perform two key rolei with I espect to post-cot e

t~storatioris namely retention of the post and the creation of a wal at the core dentine interface Compressive strength tensile strength and adhesibe pi opetties ate considered to be reliable pvedictors of success in post retained restorations Indeed several other cement ptopetties may contribute to the suwival of restot ations iuch as plastic dcfoi m&on watet uptake setting behavtout and operator-related vari,ibles (36)

Clue to its phenolii. composition, eugenol can interfere with the free-radic dl polymeri%itiori of resin composites Since many root cmal sealers contain ti m > s of eugenol that can penetrate into the

root dentine the common perception is that this can impede the scltttng of resin cements However some recent in vitro work by

Fiqure 3 Optrbond Solo Pius orid ActiLotoi (SDSiKerrj

Figure 4 ProTec Ch" jlvoclorPivodentj

Tjan and Nemetz (67) suggests that eugenol-containing endodontic sealers have little effect on the retention of resin cement retained prefabricated posts Manocci et a1 (68) found that traces of eugenol had little effect o r the quality of marginal seal at the core resin interface A new root canal sealer called Endo-REZ (Ultradent, South Jordan. UT USA) is composed primarily of a urethane dimethacrylate polymer The chemical affinity of this sealer t o resin cements may enhance the adhesive continuum between post-core and tooth structure To date there is no data available about the clinical efficacy of this new product

Another avenue of research reported in the dental literature involves the testing of various protocols for chemical preparation of the root canal prior to post cementation Varela et a1 (69) examined the use of sodium hypochlorite solution in combination with a self-etching primer and observed that the adhesion of the resin cement was enhanced. possibly as a result of the wider resin tags in the 'hybrid layer' Many variables may influence this adhesion such as the length of the tags the presence of lateral tags and hybrid layer properties such as thickness and continuity Periconductual dentine is a new term used by these authors presumably in reference to root canal dentine

Kwong et a/ (70) proposed that a 'total etch' technique in- volving the sequential application of etchant, primer and adhesive

may provide a superior adhesion to sclerotic dentine compared to single-bottle (self etching primer) systems A recommendation made by the authors is to remove the sclerotic dentine layer using a diamond bur The Cerapost System (Fig I ) introduced by Brassler/Komet (Savannah Georgia USA) includes a tapered diamond root canal drill designed to roughen the root dentine for the purpose of enhancing post retention In the manner that it is

used it is most likely that the drill also removes any sclerotic dentine layer Manocci et 01 (68) also demonstrated that a 3-step or 'total etch technique produced less microleakage than the self-etching primer/adhesive method The results are most likely related to a better quality of hybrid layer in the dentine Dietschi et a1 (4 I ) produced some very interesting SEM images of post dentine interfaces via their investigation of various metal free post core combinations They observed that the post resin dentine adhesion zone with carbon fibre posts was gap free in direct contrast to zirconia post specimens where the zone showed voids and fractures in the resin cement layer and dentine It appears that the higher elastic modulus of zirconia posts may not be a desirable property within the root canal

Pest et a/ ( I 2) drew the following conclusions from their investigation a chemical affinity between the post and resin cement can improve retention injection delivery of the luting agent will produce less porosity in the cement layer and the use of a light conductive post and light curing resin cement produced the best continuum in the post-cement-dentine adhesion zone However questions still arise about how well the resin cement is polymerised with the technique used hence self-curing adhesive systems still warrant further investigation The IvoclarNivadent Company has been pro active in trying to resolve the polymerisation problem within the dark confines of a root canal via a self curing adhesive resin called Excite DSC The adhesive is placed into the root canal via a narrow bristle brush The bristles of the brush are coated with beads of a chemical initiator (Fig 2) that facilitates the self-cure reaction in the resin adhesive and luting cement

SDS/Kerr has also introduced an activator component to its adhesive system to ensure a dual cure capacity for its single bottle primer adhesive (Fig 3)

Another class of luting agent that has entered mainstream dentistry includes the resin modified glass ionomer cements These are hybrid products formulated to produce the desirable properties of a resin composite and glass ionomer There is some anecdotal information suggesting that these materials are contraindicated for post cementation on the basis that they have a tendency to imbibe water and expand This volumetric expansion within the confines of a root canal may cause root fracture lvoclar introduced a product called ProTec CEM and it is claimed that the expansion tendency is

reduced some 30% as a result of an improved degree of cross- linking between (- C O O ) carboxylate groups during the setting reaction Such a desirable property may however, come at the expense of a reduced adhesion to dentine because less carboxyl groups are available for bonding to calcium ions

ProTec CEM (Fig 4) is dispensed as a powder and liquid and is

hand mixed Operator variables and the tendency for powderAiquid mixes to contain porosities may influence the performance of this cement However, the clinical efficacy of ProTec CEM with different post systems is unknown

Post Retrieval Periapical pathology o r post fractures often necessitate recovery

of a post prior to endodontic re-treatment. There is little information in the dental literature about post retrieval apart from some

124 AUSTRALIAN LNDODONTIC JOURNAL VOLUME 29 No 3 DLCLMBLK LOO3

Figure 5 Post retrievoi btir kit (Bisco)

descriptive case reports (7 I ) Many practitioners avoid post remo\al for fear of causing root fracture or decoronation in the restored tooth In a survey of endodontists conducted by Casttisos arid Abbott (72) it was shown that most of the responderTts prefer red to remove the post and complete orthograde therapy in preferenr e to carrying out periapical surgery

Post removal can be a1 hieved via the use of ultrasontrs or various mechanical devices In many cases, a small space iieeds to be created around the post to assist retrieval If this is taken to excess the root can be significantly weakened Fibre-reinforcc.d poc,ts have an advantage over metal and zirconia posts systems because they can be drilled out of the root canal The Bisco Company has developed a post I etrieval kit designed to remove fibr ereinfor cc,d posts (Fig 5) De Rijk (7 3) described the use of this kit in detail arid recommends that a new drill may be needed for each post removal since the side cutting blade of the drills may be dulled via repeatcld contact with glass and quartz fibres

Conclusions Case selection m d trcxatment choices for post corc restorations

should be based on a detailed assessment of tooth strurture, patient variables and the advantages and limitations of dentil materials Several other irnportant issues need to be considered prior to clinic'il decisions the conservation of tooth structure aesthetics, future post retrieva and the need to provide a found,ition restor ation that is well sealed to prevent reinfection in the root carlal complex There is now a greater emphasis on tooth isolation for intra-radicular procedurrs and maintaining an effective seal with provisional restorations Current research examining nr'w ,idhesive systems and resin luting agents may challenge the contempot ary view that posts do not reinforce teeth and offer a ray of hope in creating a genuine adhwve continuum between the post-core systern and tooth structut e However more research is reqiiired to determine the defining factors that lead to a durable long-tet m seal and success in foundation restot ations Along with their aesthetic advantages, toughnes, and capacity to adhere to r e w cements fibre-reinforced posts can be easily recovered from the root canal when endodontic i e tre<itment is required

While there is a con5iderable diversity in choice of post core systerns it is fair to say that patients may have benefited ftom this variety of techniques and materials since it offers dental practitioners a range of solutions to clinical problems Evidence baed data is

gradually evolving as the benchmark for treatmeit planning decisions and the basis for discussions with patients While some interesting observations and conclusions are drawri from the plethora of published laboratory studies, the information is mostly equivocal and not vety helpful from a clinical perspective These

4US1 KAI IAN I NI>OI)ON I IC JOUKNAL VOLUMI 29 No 3 [)I C I l l l i l K '003

investigations remain 'bench top simulations' with their often-cited inherent limitations Tierefore, more time and effort must be directed towards well controlled multicentre clinical trials Only then can the true success of contemporary ideas and restorative materials be gauged

Acknowledgements The assistance of IDr Adam Huseiri in generating SEM images of

the Excite DSC applicator tips is greatly appreciated I also wish to thank Dr Tony Coates for his constructive comments in relation to this paper

References I . Brernner M.D.K. The Story of Dentistry. N e w Yor-k: Dental

Items of Interest Publishing Co. , 1939. 2. Sorensen / . A , Moflriiof / T lntracoronal reinforcement and

coronal coverage: a study of endodontically-treated teeth. J Prostlet Dent 1984; 5 I : 780--4.

3. Sorensenj A . Preservation of tooth structure. J Calif Dent Assoc 1988; 16: 15-22,

4. Abou-Rass M . Post and core trestoration of endodontically- treated teeth. Curr O p Dent 1992; 2: 99- 107.

5. PAanning K . E . , YLi D.C. , Yu H.C., Kwon E . W Factors to consider for predictable post and core build-ups of endodontically- ti-eated teeth. Part I : Basic theoretical concepts. J Can Dent Assoc 1995; 6 I 685-~95.

6. Gutmonn / i. The dentin-root complex: anatomic and biological considerations in restoring endodontically-treated teeth. J Prosthet Dent 1992: 67: 458 -67.

7. Sigers / . E . . johnson WT. Restoration of endodontically-treated teeth. Dent Clin Notth Am 1992: 36: 63 I 50.

8 . Morgano S M . Restoration of pulpless teeth: application of traditional principles in present and future contexts. J Prosthet Dent 1996; 75: 375 ~ 80.

9. McLcon A . Predictably restoring endodontically-treated teeth. J Can Dent Assoc 1998; 64: 782--7.

10. Giuskin A.H.. Ahmat! I , Herrero D.B. The aesthetic post and core' unifying radicular form and structure. Pac Proced Aesthet Dent2002; 14.313 21.

I I . Bochicha WS., Difiore PM., Miiier D.A. . Lautenschiager E.P. Pashiey D.H. Microleakage of endodontically treated teeth restored with posts. J Endod 1998: 24: 703 ~ 8.

12. Pest L .B . . Cavoiii 5. Bertoni P. Gagliani M Adhesive postendodontic restorations with fibre posts. Push out tests and SEM observations. Dent Mater 2002; 18: 596-602.

13. Ray H.A., Trope N. Periapical status of endodontically-treated teeth in relation to technical quality of the root canal filling and the coronal restoration. Int Endod J 1995; 28: 12- 18.

I 4. Tronstad L., Asbjormeri K . , Doving L . , Pedersen l . , Eriksen H. H. Influence of cororial restorations on the periapical health of endodontically-treated teeth. Endod Dent Traumatol 2000: 16: 2 18-2 I

15. Swanson K , Madison 5. An evaluation of coronal microleakage in endodonticallytreated teeth. Part I . Time periods. J Endod 1987: 13: 56-9.

16. Fogei H.M. Microleakage of posts used to restore endodontically-treated teeth. J Endod 1995; 2 I : 376- 9.

17. Wu M . . De Gee A]., Wesseiink PR.. Morrer WR Fluid transport and bacterial penetration along root canal fillings. Int Endod J 1993; 26: 203-8.

18. Barihel C.R.. Roulet /.-i Can we fulfil even the basics of

I > 5

endodontic therapy? Ann R Australas Coll Dent Surg 2002; I 6: 30-6.

19. Fox K . , Gutteridge D.L. An ' in vitro' study of coronal microleakage in root-canal-treated teeth restored by the post and core technique. Int Endod J 1997; 30: 36 1-8.

20. Demarchi M.G.. Sato E.FI Leakage of interim post and cores used during laboratory fabrication of custom posts. J Endod 2002; 28: 328-39.

2 I , Naoum HI.. Chandler N.P. Temporisation for endodontics. Int Endod J 2002; 35: 964-78.

22. Messer H.H. , Wilson PR. Preparation for restoration and temporisation. In: Walton R.E., Torabinejad M . editors. Principles and Practice of Endodontics. 2nd ed. Philadelphia, USA: W.B. Saunders: 1998. p, 260-76.

23. Eisman H.E. Radke R.A. Post-endodontic restoration. In: Cohen S., Burns R.C. editors. Pathways of the Pulp. St. Louis: Mosby; 1987. p, 640 83.

24. Trabert K.C., Cooney J . P The endodontically-treated tooth: restorative concepts and techniques. Dent Clin North Am 1984; 28: 932-5 I ,

25. Isidor F , Brondum K . , Rovnholt G. The influence of post length and crown ferrule length on the resistance to cyclic loading of bovine teeth with prefabricated titanium posts. Int J Prosthodont 1999; 12: 78-82.

26. Libmon WJ,, Nicholls / . I . Load fatigue of teeth restored with cast posts and cores and complete crowns. Int J Prosthodont 1995; 8: 155-6 I .

27. Torbjorner A., Korlsson S., Odman PA. Survival rate and failure characteristics for two post designs. J Prosthet Dent 1995; 73: 439-44.

28. Heithersay G.S. Combined endodontic-orthodontic treatment of transverse root fractures in the region of the alveolar crest. Oral Surg Oral Med Oral Pathol 1973; 36: 404- 15.

29. Heithersay G.S., Mode A,/. Anterior subgingival fractures: a review of treatment alternatives. Aust Dent J 1982: 27: 368-76.

30. GegauffA. Effect of crown lengthening and ferrule placement on static load failure of cemented cast post cores and crowns. J Prosthet Dent 2000; 84: I69--79.

3 I . Stankiewicz N.R.. Wilson PR. The ferrule effect: a literature review. Int Endod J 2002; 35: 575-8 I ,

32. Nayyor A., Walton R.E.. Leonard L.A. An amlagam coronoradicular dowel and core technique for endodontically-treated posterior teeth. J Prosthet Dent 1980; 43: 5 I I - 15.

33. Saupe WA.. Gluskin A.H., Radke /.A. A comparative study of fracture resistance between morphologic dowel and cores and a resin-reinforced dowel system in the intraradicular restoration of structurally compromised roots. Quintessence Int 1996; 27: 483-9 I

34. Lui J.L. A case report of reattachment of fractured root frag- ment and resin-composite reinforcement in a compromised endodontically-treated tooth. Dent Traumatol 200 I ; 17: 227-30.

35. Pierrisrand L.. Bohin FI , Renault P, Barquin M. Coronoradicular reconstruction of pulpless teeth: a mechanical study using finite element analysis. J Prosthet Dent 2002; 88: 442-8.

36. Morgano S.M., Brackett S.E. Foundation restorations in fixed prosthodontics: current knowledge and future needs. J Prosthet Dent 1999; 82: 643-57.

37. Assif D. , Nissan / . , Gafni Y. Gordon M. Assessment of the resistance to fracture of endodontically-treated molars restored with amalgam. J Prosthet Dent 2003; 89: 462-5.

38. Linn J . , Messer H.H. Effect of restorative procedures on the

strength of endodontically-treated molars. J Endod 1994; 20: 479-85.

39. Duret €3.. Duret FI. Raynaud M . Long-life physical property preservation and postendodontic rehabilitation with the Com- posipost. Compend Contin Educ Dent 1996; Supplement N o . 20: S50--6.

40. Isidor F , Odman P, Brondum K. Intermittent loading of teeth restored using prefabricated carbon-fibre posts. Int J Prosthodont 1996; 9: I3 1-6.

4 I . Dietschi D. , Romelli M., Goretti A . Adaptation of adhesive posts and cores to dentin after fatigue testing. Int J Prosthodont 1997; 6: 498-507.

42. Fredrikkson M.. AstbackJ., famenius M., Arvidson K. A retrospective study of 236 patients with teeth restored by carbon fibre-reinforced epoxy resin posts. J Prosthet Dent 1998; 80: 151-7.

43. Ferrari M . , Vichi A . , Monnocci F , Mason PN. Retrospective study of the clinical performance of fibre posts. Am J Dent 2000: 13: 9B- 136.

44. Glazer B. Restoration of endodontically-treated teeth with carbon-fibre posts - a prospective study. J Can Dent Assoc 2000: 66: 6 13-8.

45. King PA., Setchell D./,, ReesJ.8. Clinical evaluation of carbon- fibre reinforced carbon endodontic post. J Oral Rehab 2003; 30: 785-9.

46. Akkayan B . , Gulrnez T Resistance to fracture of endodontically- treated teeth restored with different post systems. J Prosthet Dent 2002; 87: 43 1-7.

47. fegoretti A,, Fambri L., Zappni G., Bionchetti M. Finite element analysis of glass fibre reinforced composite endodontic post. Biomaterials 2002; 23: 2667-82.

48. Lui J .L . Depth of composite polymerisation within simulated root canals using light-transmitting posts. Oper Dent 1994; 19: 165-8.

49. Strassler H.E. Restoring endodontically compromised teeth with fibre-reinforced light transmission anchors. Contemp Esthet and Rest Pract 1999: March: 59-60.

50. Blitz N . Adaptation of a fibre-reinforced restorative system to the rehabilitation of endodontically-treated teeth. Pract Periodontics Aesthet Dent 1998: 10: I9 1-3.

5 I . Schweiger M., Frank M., Von Clausbrusch S.C., Holond W . Rheinberger V Microstructure and properties of a pressed glass- ceramic core to zirconia post. Quintessence Dent Tech 1998; 73-9.

52. Luthardt R., SandkhulL O., Reitz B. Zirconia-TZP and alumina - advanced technologies for the manufacturing of single crowns. Eur J Prosthodont Rest Dent 1999; 7: I 13-1 9.

53. EdelhoffD., Sorensen A. Retention of selected core materials to zirconia posts. Oper Dent 2002: 27: 455-6 I .

54. Heydecke G., Butz F , Hussein M., 8trubJ.R. Fracture strength after dynamic loading of endodontically-treated teeth restored with different post systems. J Prosthet Dent 2002; 87: 438--45.

55. Hornbrook D.S., Hustings L.H. Use of a bondable reinforcement fibre post for post and core build-up in an endodontically-treated tooth: maximising strength and aesthetics. Pract Periodontics Aesthet Dent 1995; 7: 33-42.

56. Freilich M.A., Meiers J.C., Duncan /.P, Goldberg A,/, Fibre- reinforced composites in clinical dentistry. Illinois: Quintes- sence Publishing: 2000.

57. Karna J.C. A fibre composite laminate endodontic post and core. Am J Dent 1996: 9: 230-2.

58. Sirimai S., Riis D.N., Morgano S,M. An in vitro study of the

I26 AUSTRALIAN ENDODONTIC JOURNAL VOLUME 29 No 3 DECEMBER 2003

fracture resistance and the incidence of rroot fracture of pulpless teeth restored with six post core systems. J Prosthet Dent 1999: 8 I : 262--9.

59. Kwia to~k i 8.. Geiier W A preliminary investigatiori of the glass-ceramic dowel post and core. Int J Prosthodont 1989: 2: 5 1-5.

60. Sevuk <,, Gur H., Akkayari 6. Fabrication of one-piece all- ceramic coronal Dost and laminate veneer restoration: a clinical report. J Prosthet Dent 2002; 8: 565-8.

6 I , Kovonk R. E . , Breedir ig L. C., Cuaghrnan W F Fatigue life of three core materials under simulated chewing conditions. J Prosthet Dent 1992: 68: 584- 90.

62. Burrow M.E, Satoh M.. Jagomi /. Dentin bond durability after three years using dentin bonding agent with and without priming. Dent Mater 1996: 12: 302-7.

63. Russell M.L., Masood M., Cunnrn,gham L. The behaviour of post-retained core materials supported by coronal tooth structure in vitro. In1 Endod J 1997; 30: 408- 12.

64. Cohen B.I., Pa,gni/lo M . K . , Cosmos S , Deutsch A.S. Cyclic fatigue testing of five endodontic post designs supported by four core materials. J Prosthet Dent 1997: 78: 458-64.

65. Mentink A.G., Meeuwissen R., Hoppenbrouwers PP, Koyser A . F, Muider J , Porosity in resin composite core restorations: the effect of manipulatibe techniques. Quintessence Int 1995: 26: 81 1-15.

66. O'Keefe K . L . , Powers j.M. Adhesion of resin composite core materials to dentin. Int J Prosthodont 200 I : 14: 45 I -6.

67. 7jari A . H . . Nernetz 1 . 1 Effect of eugenol-containing endodontic sealer on retention of prefabricated posts luted with an adhesive composite resin. Quintessence Int 1992: 23: 839 ~44.

68. Marmocci E, Ferrciri M , Wotson T F Microleakage of endodontically-treated teeth restored with fibre posts and composite cores after cyclic loading: a confocal microscopic study. J Prosthet Dent 200 I : 85: 284 -9 I .

69. Vareio 5 G.. Rabode L . B . , Lombardero P R , Sixtoj M.L , Bahillo j . 0 .C . . Pork S A.P in vitro study of endodontic post cementation protocols that use resin cements. J Prosthet Dent 2003: 89: 146 53.

70. Kwong S.M.. Chwrig G 5 , Kei L.H. Microtensile bond strengths to sclerotic deritiri using self-etching and total etching technique. Dent Mater 2002; 18: 359- 69.

7 I . Ahbott PV Incidence of root fractures and methods used for post removal. Int Endod J 2002; 35: 63 7.

72. Castrisos T . Abbolt PV A survey of methods used for post removal in specialist endodontic practice. Int Endod J 2002; 35: 172-80.

73. De R,ik WG. Removal of fibre posts from endodontically- tr-eated teeth. Am J Dent 2000: 13: 198-2 I B.

Erra t u in In the article by D r Geoffrey Heithersay, published in the last issue of the Australian Endodontic journal Figuie 7 was mistakenly also presented as Figure I I This was an editors error (rrtea cuipa) The correct Figure I I is shown here

Radiograph of I i lhirty rnonths after repiontotion showing furthe, narrowing of the

root conoi and no cviderice of periratlicular potl1oiogy

Documents

Contemporary Perspectives On Post-Core Systems