POST CORE

2005;136;611-619 J Am Dent Assoc

WILLIAM CHEUNG restoration

treated teeth: Post, core and the final A review of the management of endodontically

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A review of the management ofendodontically treated teethPost, core and the final restoration

WILLIAM CHEUNG, D.M.D.

In a separate article that describes the basic con-cepts in restoring endodontically treated (ET)teeth, I mentioned that endodontic treatment isperformed often and that there is a high demandfor the restoration of ET teeth.1 Some of the basic,

yet important, concepts in the management of ET teethare microleakage, the ferrule effect and biological width.It generally is agreed that the successful treatment of a

badly broken down tooth with pulpaldisease depends not only on goodendodontic therapy, but also on goodprosthetic reconstruction of the toothafter endodontic therapy is completed.

In this article, I review the principlesin the use of a post, including when touse a post, types of posts, post materials,post design, post space preparation interms of length and width, and thecementation of a post. I also discuss theprinciples in core buildup and theoptions available in final restorations.

PRINCIPLES IN THE USE OF A POST

Do posts strengthen ET teeth? It has been suggestedthat ET teeth dry out over time2 and that the dentin inET teeth undergoes changes in collagen cross-linking.3

Therefore, it has been suggested that ET teeth are morebrittle and may fracture more easily than non-ETteeth.4-6 It is believed that it is the loss of tooth structurefrom caries, trauma or both that makes ET teeth more

A B S T R A C T

JADA, Vol. 136 www.ada.org/goto/jada May 2005 611

Restoration ofteeth afterendodontic

treatment isbecoming an

integral part ofthe restorative

practice in dentistry.

Background. The clinical decision as towhether an endodontically treated (ET) toothrequires a post and a crown poses a challengeto dental practitioners. The author conducteda review of the principles for the use of postand core and the newer materials such asceramic and fiber-reinforced posts.Types of Studies Reviewed. Using aMEDLINE search and resulting cross-refer-ences, the author selected original researcharticles and previous review articles on thetopic of ET teeth, as well as that of post andcore.Results. The author reviewed the princi-ples for the use of posts in terms of when it isnecessary to use a post, different types ofposts, various post materials and designs. Healso reviewed the criteria and technique forpost space preparation and post cementation.Finally, he discussed the principles of corebuildup, as well as options for the final restorations.Clinical Implications. The author pro-vides a review of the principles for the use ofpost and core, crowns and the differentmaterials available today to help cliniciansmake a clinical decision based on sound evidence.Key Words. Post; core; endodonticallytreated teeth; fiber-reinforced post.

susceptible to fracture.7,8 Some cliniciansbelieve that a post should be placed into theroot after endodontic treatment tostrengthen or reinforce it. Some studies,however, point out that posts do notstrengthen teeth, but instead that the prepa-ration of a post space and the placement of apost can weaken the root and may lead toroot fracture.9-12 These studies further sug-gest that a post should be used only whenthere is insufficient tooth substanceremaining to support the final restoration.In other words, the main function of a post isthe retention of a core to support the coronalrestoration.

Perhaps using new adhesive materialsand technology, clinicians can bond the postsecurely to the dentin in the root canalspace, the core to the post and the final

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restoration to the core and tooth. With all compo-nents having similar physical properties success-fully bonded together, dentistry may be able toclaim that a post can strengthen and reinforce theroot. However, dentistry can say only that a postis used primarily to retain a core in a tooth withextensive loss of structure; the post does notmake the tooth stronger.

When to use a post. Since a post does notstrengthen an ET tooth and the preparation of apost space may increase the risk of root fractureand treatment failure,13 the decision whether touse a post in any clinical situation must be madejudiciously. Most teeth require endodontic treat-ment as a result of trauma, extensive caries orrestoration. The practice of endodontic therapyprefers an access cavity preparation that givesendodontic instruments “straight line” access intothe canal space. This, along with the concept of“crown down” in endodontic therapy, means thatmore sound coronal and radicular dentin must beremoved for efficient cleaning and shaping of theroot canal system. Therefore, the evaluation ofwhether a post is needed is based on how muchnatural tooth substance remains to retain a corebuildup and support the final restoration aftercaries removal and endodontic treatment arecompleted.

Many ET molars do not require a post becausethey have more tooth substance and a larger pulpchamber to retain a core buildup.14 When a post isrequired as a result of extensive loss of naturaltooth substance, it should be placed in the largestand straightest canal to avoid weakening the roottoo much during post space preparation and rootperforation in curved canals. The distal canal ofmandibular molars and the palatal canal of max-illary molars usually are the best canals for postplacement. When core retention still is insuffi-cient after a single post is inserted, placement ofpins can be considered for additional retention.14

Premolars have less tooth substance andsmaller pulp chambers to retain a core buildupafter endodontic treatment than do molars, andposts are required more often in premolars. Inaddition to root taper and curvature, many pre-molar roots are thin mesiodistally, and some haveproximal root invaginations. Furthermore, theclinical crown of the mandibular first premolaroften is inclined lingually in relation to its root.These anatomical characteristics must be consid-ered carefully during post space preparation toavoid perforating the root.

A few studies have concluded that a post is notnecessary in an ET anterior tooth with minimalloss of tooth structure.9,10,12 These teeth may berestored conservatively with a bonded restorationin the access cavity.10,15 Should tooth discolorationbecome a concern, whitening and placement ofveneers can be considered, since a study byBaratieri and colleagues16 concluded that the useof posts did not improve the fracture resistance ofET maxillary incisors that received veneers withdirect composite. If an anterior tooth must be prepared to receive a crown after endodontictreatment because a good amount of tooth struc-ture was lost, a post may be necessary to retainthe core so that these teeth can resist functionalforces. Special care must be exercised whenplacing posts in mandibular incisors, as they havethin roots in the mesiodistal dimension, whichmakes post space preparation difficult.

Types of posts. There are two main categoriesof posts: custom-fabricated and prefabricated.Custom-fabricated cast gold post and core hasbeen used for decades as a foundation restorationto support the final restoration in ET teeth. Onesix-year retrospective study17 reported a successrate of 90.6 percent using a cast post and core asa foundation restoration. Cast gold alloy (type IIIor IV) is an inert material with modulus of elas-ticity (stiffness of 14.5 × 106 psi) and coefficient ofthermal expansion (≈ 15 [C–1] × 106) similar tothose of enamel, and yet it has good compressivestrength that can withstand normal occlusalforces.

Other base metal alloys have been used, buttheir hardness might be a major disadvantage inadjustment and may predispose the tooth to rootfracture. Many practitioners prefer to use a castgold post and core for ET anterior teeth. Its majordisadvantage, however, is esthetics, as the metalshows through the newer all-ceramic restorations.One way to overcome this is to make a porcelain-fused-to-metal post and core from a metal ceramicalloy to mask the shade of the metal.18

Another disadvantage of the cast post and coreplacement procedure is that it requires two visitsand laboratory fabrication. An alternative is aprefabricated post that can be adjusted andinserted in a single visit. Many types of prefabri-cated posts (in terms of shape, design, material)are available, and I will discuss them later in thearticle.

A photoelastic stress analysis of post design ledto the conclusion that cement-retained posts and

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parallel posts were the least stressful to the root,but they also were the least retentive.19 Certainscrew-type posts offer more retention, but theyexert more stress on the root and should be con-sidered only in short roots in which obtaining sufficient retention within the root is difficult.Pontius and Hutter20 speculated that the suc-cessful bonding of fiber-reinforced posts mayassist in the retention of posts in the root canalspace so that shorter posts may be used.

In regard to conservation of tooth structure,the use of tapered posts requires removing lessdentin because root canal spaces are cleaned andshaped in a tapered fashion. Although parallelposts and screw posts are more retentive in theroot canal, more dentin removal is required intheir post space preparation. This can be undesir-able, especially in post space preparation for par-allel posts, as more dentin is removed from thethinner apical and middle aspects of the rootcanal walls.

Materials. Stainless steel, tita-nium and titanium alloys, gold-plated brass, ceramic and fiber-reinforced polymers have been usedas materials for prefabricated posts.The ideal post and core materialshould have physical properties—such as modulus of elasticity, com-pressive strength and coefficient ofthermal expansion—that are similarto those of dentin. In addition, pre-fabricated posts should not be corro-sive and should bond easily andstrongly to dentin inside the root using suitablecement so that the entire assembly of a post andcore resembles the original tooth. Unfortunately,no such material is available to date even thoughfiber-reinforced posts look promising; I discuss itin more detail later.

Stainless steel has been used for a long time inprefabricated posts. However, it contains nickel,and nickel sensitivity is a concern, especiallyamong female patients. Stainless steel and brasshave problems with corrosion. Pure titanium hasslightly lower physical properties such as in com-pressive and flexural strength than alloys, but itis the least corrosive and most biocompatiblematerial.21 Titanium posts, however, have lowfracture strength and tend to break more easilycompared with stainless steel posts duringremoval in retreatment cases. Furthermore, mosttitanium alloys used in posts have a density sim-

ilar to that of gutta-percha when seen on radio-graphs, which makes them more difficult todetect. Ceramic has good biocompatibility, highflexural strength and fracture toughness,22-24 andit is esthetically pleasing, especially under all-ceramic crowns. However, two in vitro studiesreported poor resin-bonding capability of ceramicposts to dentin under fatigue testing.25,26 This typeof post is relatively new, and long-term clinicalresults are not yet available.

Another newer type of post is the fiber-reinforced polymer post. It is made of carbon orsilica fibers surrounded by a matrix of polymerresin, which usually is an epoxy resin. The fibersare 7 to 10 micrometers in diameter and areavailable in a number of different configurations,including braided, woven and longitudinal.According to two in vitro studies,27,28 the physicalstrength of fiber-reinforced post is significantlyweaker than that of cast metal posts and cores.The highly rigid metal would transfer lateral

forces without distortion to theless rigid dentin and lead to ahigher chance of root fracture.The lower flexural modulus offiber-reinforced posts (between 1 and 4 × 106 psi), on the otherhand, measures closer to that ofdentin (≈ 2 × 106 psi) and candecrease the incidence of root frac-ture.27,29 In the event of failurewhen restored with fiber-reinforced posts, teeth are morelikely to be restorable.28,30,31

Fiber-reinforced posts are fabricated to bondwith most resin cements and resin-based com-posite core materials. In vivo bonding of fiber-reinforced posts to the dentinal wall of the rootcanal space using resin cement has been demon-strated.32-34 Scanning electron microscopic (SEM)evaluation has shown clearly the formation of ahybrid layer, resin tags and an adhesive lateralbranch. Successful bonding minimizes thewedging effect of the post within the root canal,requires less dentin removal to accommodate ashorter and thinner post and leads to lower sus-ceptibility to tooth fracture.20 Successful bondingalso means that the shape (parallel versustapered) of the fiber-reinforced post may be lesssignificant in relation to its retention than for ametal post.35

Since fiber-reinforced posts are metal-free, theydo not cause metal allergies or corrode. They offer


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Titanium posts havelow fracture strength

and tend to breakmore easily compared

with stainless steelposts during removalin retreatment cases.


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good esthetics in easily visible areas of the mouth,especially under the all-ceramic crowns andbridges. Finally, fiber-reinforced posts can beremoved easily in case of an endodontic failurerequiring re-treatment.30 One study that evalu-ated three types of fiber-reinforced posts over oneto six years reported a failure rate of only 3.2 per-cent, and the authors concluded that these postscan be used routinely in combination withbonding materials.36 Two other retrospectivestudies up to four years long also reported a suc-cess rate of approximately 95 percent using fiber-reinforced posts to restore ET teeth.37,38 Like theceramic posts, fiber-reinforced posts are relativelynew, and data on their long-term clinical perform-ance are not available yet.

Post designs. In addition to the custom castpost and core, many commercially available pre-fabricated posts exist. For example, the axial formis either tapered or parallel, and the surface canbe smooth, serrated with orwithout vents, or threaded usingtaps or self-threading. Caputo andStandlee39 categorize these different design features into threebasic combinations:dtapered, serrated or smooth-sided, cemented into a post spaceprepared with a matched-size post drill;dparallel-sided, serrated orsmooth-sided, cemented intomatched cylindrical channels prepared by a postdrill;dparallel-sided, threaded and inserted into pre-tapped channels.

In general, parallel-sided posts are moreretentive than tapered posts, and threaded postsare more retentive than cemented posts. Withrespect to their installation mode, all posts arereferred to as either active or passive. Activeposts engage dentin within the root canal spaceand transfer more stress to the remaining rootstructure. Passive posts, even though they do notengage dentin in the root canal space, stilltransfer stress to the remaining root structure,but to a lesser extent.39

Post space preparation. Knowing the rootanatomy of different teeth is important beforeattempting to prepare any canal space for postinstallation. For instance, clinicians must beaware that root diameter may differ in the facial-lingual and mesiodistal dimensions. To determine

the appropriate post length and width to avoidroot perforation, clinicians must consider condi-tions such as root taper, proximal root invagina-tions, root curvatures and angle of the crown tothe root during the mechanical preparation of apost space. Gutmann40 gave a good review ofanatomical and biological considerations inrestoring ET teeth.

Dentists often use mechanical preparationtechniques for post spaces because it is faster.Mechanical preparation is associated with ahigher risk of root perforation and may disturbthe apical seal. The thermal method of removinggutta-percha using heat pluggers is safer butmore time-consuming. When mechanical prepara-tion is preferred, it has been established thatGates-Glidden drills and P-type reamers used onlow speed are the safest instruments.41 Use of oneof these instruments should precede the use ofany post drill that comes with the prefabricated

post kit. A combination of removinggutta-percha by heat pluggers fol-lowed by the post drill should beconsidered by inexperienced opera-tors to minimize the risk of perforation.

Post length. Many authors haveoffered guidelines for determiningthe desired post length. It is not dif-ficult to understand that the longerthe post in the canal, the moreretentive it is. However, increased

post length also increases risk of fracture and per-foration of the remaining root.42 It generally isaccepted that the apical 3 to 6 mm of gutta-percha must be preserved to maintain the apicalseal.43-45 Acceptable guidelines for determining thepost length include the following:dthe post length should be equal to the clinicalcrown length46,47;dthe post length should be equal to one-half totwo-thirds of the length of the remaining root4,48;dthe post should extend to one-half the length ofthe root that is supported by bone.49

As I stated previously, root anatomy variesfrom tooth to tooth and even within the sametooth in different patients. Clinicians must con-sider these variations along with the guidelines.Each clinical situation is unique, so the prepara-tion of the post space must be evaluated carefullyand planned for accordingly.

Post width. It is accepted widely that the postdiameter makes little difference in the retention of


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to prepare any canalspace for post installation.


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the post. An increase in the post’s width, on theother hand, will increase the risk of root frac-ture.39,50 In general, the post width should notexceed one-third of the root width at its narrowestdimension, and clinicians should bear in mindthat most roots are not perfectly rounded.11 A min-imum of 1 mm of sound dentin should be main-tained circumferentially, especially in the apicalarea where the root surface usually becomes nar-rower and functional stresses are concentrated.51

The cleaning and shaping procedures used inmodern endodontic treatment are aggressive inthe removal of dentin within the root canal space;therefore, removal of more dentin from the canalwall in the preparation of the post space should bekept to a minimum to preserve tooth substanceand minimize root fracture.

Post cementation. Among the most commonlyused dental cements—zinc phosphate, polycar-boxylate, glass ionomer cement, resin-based com-posite and the hybrid of resin and ionomercements—zinc phosphate has had the longest his-tory of success. In addition to having an extendedworking time, it is compatible with zinc oxideeugenol (ZOE), which is contained in most rootcanal sealers. In the case of an endodontic failure,a metal post that is cemented in the canal spacewith zinc phosphate is easier to remove and has alower risk of root fracture compared with a metalpost that is bonded strongly with a resin-basedcomposite cement in the root canal space.

Microleakage is the major concern when usingpolycarboxylate and glass ionomer cements.These cements also have a much lower modulusof elasticity than zinc phosphate and dentin.Resin-based composite, on the other hand, isbecoming increasingly popular because of itspotential to bond to dentin. Some authors haveexpressed concerns regarding microleakage andthermocycling of resin cements.52,53 Others, how-ever, have demonstrated improved retention ofposts54-57 and decreased microleakage58-60 andhigher fracture resistance of teeth61 when postsare cemented with a resin cement than with othercements. Furthermore, thermocycling of resincement used in thin film thickness probably is notas significant a problem compared with otherrestorative procedures, and the modulus of elas-ticity of resin-based composite is similar to that ofdentin.

Bonding resin cement to the dentinal wall ofthe root canal space must be done carefully toimprove bonding and minimize microleakage.

First, any residual gutta-percha and root canalsealer must be removed from the dentinal wallsto ensure proper bonding of resin to dentin. Thiscan be accomplished by removing gutta-perchausing thermal methods, mechanical methods orboth, followed by cleansing the walls using a longPeeso brush with pumice slurry. Thoroughrinsing of the canal space can be achieved byusing a three-in-one syringe and an irrigationsyringe. While it generally is believed thateugenol-containing root canal sealers can inhibitthe polymerization of resin cements, studies haveshown that there is no adverse effect on marginalseal60 and post retention62 when canals are obtu-rated using an eugenol-containing sealer and apost is placed with a resin cement, as long as thecanal walls are cleaned thoroughly.63 Second,removal of the demineralized collagen layer usinga specific proteolytic agent such as sodiumhypochlorite has been shown in an SEM study toimprove the bonding of resin to the root canalwall owing to the penetration of resin tags intodentinal tubules along the wall.56 Finally, removalof the smear layer through acid treatment andthe wet bonding of dentin without contaminationmust be done carefully as with other restorativeprocedures using resin-based composite toachieve success. A lentulo spiral can be used tocarry acid etchant into the post space, while afine-tipped microapplicator can be used to coatthe canal walls with bonding agent. Othermethods of preparing the canal walls for bondingalso have been suggested.55,57,63-65

Another concern of using resin to cement ametal post is the difficulty in removing the post incase of endodontic failure. It is difficult and time-consuming to remove a well-bonded resin-cemented metal post, and the risk of a root frac-ture remains a concern. This problem, however, isnot encountered if fiber-reinforced posts are usedin combination with resin cement, since fiber-reinforced posts can be removed easily.

The use of various types of fiber-reinforcedposts and resin cement is becoming more popular.However, dental practitioners must keep in mindthat though preliminary studies on the use ofthese materials are promising, long-term clinicalresults still are not available.

Numerous in vitro and in vivo studies havebeen conducted to compare failure mode, reten-tion and fracture strength of various post systemsusing continuous or intermittent loading withmixed results. Schwartz and Robbins66 offered a


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good summary of these studies in their review ofpost placement and restoration of ET teeth.

PRINCIPLES OF CORE BUILDUP

The construction of a core buildup is necessary asthe amount of residual tooth substancedecreases,67 and the buildup augments the devel-opment of retention and resistance provided bythe remaining tooth structure.68 Morgano andBrackett68 described some of the desirable fea-tures of a core material. They include adequatecompressive strength to resist intraoral forces,69

sufficient flexural strength,69 biocompatibility,70

resistance to leakage of oral fluids at the core-to-tooth interface,71,72 ease of manipulation,73 abilityto bond to remaining tooth structure,74-76 thermalcoefficient of expansion and contraction similar totooth structure,71 dimensional stability,77 minimalpotential for water absorption78-80 and inhibition ofdental caries.81 Unfortunately, as the commonlyused materials all exhibit certain strengths andweaknesses, such an ideal core material does notexist.

The most commonly used core materials arecast gold, amalgam, resin-based composite andglass ionomer cement. Both cast gold andamalgam have been used successfully for manyyears, as they exhibit high strength and low solu-bility, and their coefficient of thermal expansionis similar to that of tooth substance. Placing castgold post and core, however, is an indirect pro-cedure requiring two visits. Placing an amalgamcore requires a prolonged setting time, making itdifficult to prepare immediately after placementif a crown is the final restoration. Placingamalgam can be challenging in badly broken-down teeth, and many patients are concernedabout the presence of mercury in amalgam,regardless of whether there is scientific evidenceto support the claim of toxicity. Both gold andamalgam are not esthetically pleasing, especiallyunder the newer all-porcelain restorations.

Resin-based composite offers an estheticallypleasing material especially in the anterior sec-tion under an all-porcelain restoration. It hasgood strength characteristics and low solubility.Some of the negative features of resin-based com-posite are polymerization shrinkage, hydroscopicexpansion as a result of water adsorption andincorporation of voids in the buildup because itcannot be condensed like amalgam. Furthermore,resin-based composite is incompatible with ZOEin many root canal sealers, which can result in

resin that is not cured completely. These negativefeatures may lead to microleakage if they are notaddressed properly during placement of thematerial. Proper removal of the residual rootcanal sealer coupled with a small incrementalbuildup using a condensable resin-based com-posite material may help alleviate the potential ofmicroleakage.

One in vitro study comparing resin-based com-posite, amalgam and cast gold as core materialunder a crown in ET teeth found no significantdifference in fracture and failure characteristicsamong these materials, provided a 2-mm ferruleexisted on the margin of healthy tooth sub-stance.82 Glass ionomer cement, on the otherhand, was shown to be weak in tensile and com-pressive strengths, and it had low fracture resis-tance as a core material in another study.83 Glassionomer cement also exhibits a low modulus ofelasticity, poor bonding characteristics to dentinand enamel, poor condensability and high solu-bility. Therefore, the use of glass ionomer cementas a core material should be avoided.

THE FINAL RESTORATION

As I stated earlier, ET anterior teeth with min-imal loss of tooth structure may be restored con-servatively with a bonded restoration in theaccess cavity.10,12,15 Neither a post nor a crown isrequired unless a great deal of natural tooth sub-stance is lost as a result of caries or fracture.

Castings such as gold onlay, gold crowns,metal-ceramic crowns, and all-porcelain restora-tions with cuspal coverage are used routinely asstandard and acceptable methods to restore pos-terior ET teeth. These restorations can provideET teeth with the desired protection; however,they require extensive tooth preparation and canbe expensive. In my review of the literature, I found mixed opinions as to whether full cuspalcoverage should be carried out routinely on ETteeth.

Reeh and colleagues84 compared the contribu-tions of endodontic and restorative procedures tothe loss of cuspal stiffness by using nondestruc-tive occlusal loading on extracted intact humanteeth. They concluded that endodontic proceduresreduced the relative stiffness by only 5 percent.An occlusal cavity preparation, on the other hand,caused a 20 percent reduction of cuspal stiffnessand mesial-occlusodistal cavity preparationcaused a 63 percent reduction. They concludedthat endodontic procedures do not weaken teeth


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with intact marginal ridges. These researchersconfirmed in another study that it is the loss ofmarginal ridges that was primarily responsiblefor the change in stiffness.7 Oliveira and col-leagues8 concluded that the greatest factor influencing the strength of ET teeth (specificallypremolars) was the amount of remaining toothstructure. If a tooth is not fractured or severelydamaged by caries before endodontic treatment, itmay be sufficient to treat the endodontic accesswith a simple restoration.

If only a routine restoration is necessary, resin-based composite with acid etching of enamel anddentin is the restoration of choice.7,85 In a three-year clinical study, Mannocci and colleagues86

concluded that the clinical successrates of ET premolars with limitedloss of tooth structure restored withfiber-reinforced posts and directcomposite were equivalent to fullcoverage with metal-ceramiccrowns. Restoring teeth with resin-based composite coupled with acidetching of enamel and dentin canresult in recovery of tooth stiffnessof up to 88 percent of that of unal-tered teeth.7 It can be concludedfrom these studies that the routineuse of crowns on ET teeth may notbe necessary if the marginal ridges are intact andmost of the natural tooth substance is preserved.

Panitvisai and Messer87 studied the extent ofcuspal flexure after endodontic and restorativeprocedures and found that cuspal deflectionincreased with increasing cavity size inmandibular molars, and it was greatest afterendodontic access. The authors concluded thatcuspal coverage is important so as to minimizethe danger of marginal leakage and cuspal frac-ture in ET teeth. In a 10-year retrospective studyof ET teeth, Aquilino and Caplan88 found that ETteeth that did not receive crowns after obturationwere lost six times more often than teeth thatreceived crowns after obturation. The authorsobserved a strong association between crownplacement and the survival of ET teeth.

In view of the conflicting results of thesestudies, it is necessary for dental practitioners toevaluate each clinical situation carefully to deter-mine if full cuspal coverage is required for long-term clinical success. Unless the majority of nat-ural tooth substance remains after endodontictreatment, it probably is safer to provide some

kind of cuspal coverage in the final coronal resto-ration since most teeth that require endodontictreatment usually are damaged severely as aresult of caries, fracture or both.

Other restorative options. When themarginal ridges are lost as a result of extensiveloss of tooth structure from caries, fracture orboth, cuspal protection may be necessary for long-term preservation of the remaining toothstructure. An onlay, which conserves more toothstructure, or a crown can accomplish this. Cast-ings have been used for many years with goodsuccess. In the past decade, porcelain onlay anddifferent types of all-ceramic crowns also havebeen fabricated with good results. Recently,

dental material research hasfocused on the development ofesthetic materials such as resin-based composite with improvedbonding and the all-ceramic resto-rations. Porcelain crowns have beenin service for a number of years,and all-ceramic bridges also areavailable.

When a tooth is needed to sup-port a removable prosthesis but it iscompromised periodontally or hasan unfavorable crown-to-root ratio,endodontic treatment followed by a

metal coping or magnet installation can supportan overdenture with good success. This way, thepatient can function with improved propriocep-tion and better stability of the denture than witha complete denture.

CONCLUSIONS

The number of endodontic procedures hasincreased steadily in the past decade with highlypredictable results. Therefore, restoration of teethafter endodontic treatment is becoming an inte-gral part of the restorative practice in dentistry.Proper restoration of ET teeth begins with a goodunderstanding of their physical and biomechan-ical properties, anatomy, and a sound knowledgeof the endodontic, periodontal, restorative andocclusal principles.1 Although many new restora-tive materials have become available over thepast several years, some basic concepts inrestoring ET teeth remain the same.

In this article, I reviewed the principles in theuse of posts and the various types of posts thatare available. A thorough understanding of postsis necessary to make the right selection, as there


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It is necessary fordental practitioners

to evaluate each clinical situation

carefully to determineif full cuspal coverage

is required for long-term clinical

success.


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are so many choices available. Finally, the choiceof core material and the final restoration areimportant in achieving long-term clinical success.

As a result of this review, I have concludedthat posts do not strengthen ET teeth and shouldnot be used in them routinely. The main functionof a post is for the retention of a core if there isinsufficient tooth substance left to support thecoronal final restoration.

The reason that many different types of postswith different designs and materials are availableis because they all have certain strengths andweaknesses. Selection criteria should include adequate strength, modulus of elasticity, reten-tion, biocompatibility, esthetics and retrievability.The new fiber-reinforced posts offer impressiveresults, but clinical evaluation is necessary over alonger term.

Post space preparation requires good under-standing and knowledge of tooth anatomy toavoid unnecessary mishaps. Cementation of postswith resin cement seems to offer better retention,less microleakage and higher resistance to toothfracture. However, cementing a post with resincement must be performed meticulously, as thisprocedure is technique-sensitive.

Gold, amalgam and resin-based composite areacceptable core materials, and each has its advan-tages and disadvantages. However, the use ofglass ionomer cement as a core material shouldbe avoided, owing to its low strength, low stiff-ness, poor bonding characteristics and high solubility.

Although many promising new materials areavailable and there are definite indications fortheir use, long-term clinical evaluations areneeded. Clinicians must keep this fact in mindwhen selecting these materials. ■

Dr. Cheung maintains a multispecialty private practice, Dr. WilliamCheung & Associates, Suite 503, AON China Building, 29 Queen’sRoad Central, Hong Kong SAR, China. Address reprint requests to Dr. Cheung.

The author wishes to thank Dr. Robert Ng and Miss Vivian Wong fortheir kind assistance in the literature search and the manuscriptpreparation, respectively.

1. Cheung W. Properties of and important concepts in restoring theendodontically treated teeth. Dent Asia 2004;Sept./Oct.:40-7

2. Helfer AR, Melnick S, Schilder H. Determination of the moisturecontent of vital and pulpless teeth. Oral Surg Oral Med Oral Pathol1972;34:661-70.

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