restorative considerations in ce endodontically treated...

There are essentially three major as-pects to discuss when considering

whether to restore or remove a question-able tooth that is biologically healthy.The first is structural—is it possible torestore the tooth in such a manner thata good long-term prognosis exists? Thesecond is esthetic—is it possible to createa pleasing final appearance and maintainthe tooth? And the final area is value—what will the cost be both financiallyand in time and energy to maintain thetooth as opposed to removing it?

Structural IssuesThe structural issues of whether to

retain or remove a tooth relate to theamount of remaining tooth structure.If the tooth has had endodontic therapy,has the majority of its coronal form re-maining, and is endodontically and perio-dontally healthy, there is little question inmost cases about whether to remove orrestore the tooth.

Making the decision to restore or re-move teeth that are biologically healthybut missing the majority of their coronalform is not always clear. In these teeth,which often are fractured, the challengeis getting the necessary tooth structureto make a predictable restoration. It ishelpful at this point to discuss how muchtooth structure is necessary.

Classically, prior to the era of adhe-sive bonding, the geometry of the toothpreparation was solely responsible forretention and resistance form. In that

era, the typical goal in describing anadequate tooth preparation was 3 mmof vertical height with 6° of taper.1 Theability to bond a restoration has alteredthose requirements to some degree, al-though it is difficult to identify specif-ically how little tooth structure is anacceptable amount for both retentionand resistance form when bonding isused. There is, however, a significantamount of clinical research that identi-fies the method of failure of endodon-tically treated teeth when inadequatetooth structure was available and thetooth had been restored with a postand core.2 The most common failure isa loss of retention of the post, the core,and the crown, with the result that thepatient arrives at the office with therestoration in their hand. The secondmost common method of failure is afracture of the post with the crown andcore now in the patient’s hand, but thepost still cemented in the tooth. Andfinally, the third most common methodof failure is the root of the tooth split-ting vertically.

All of these methods of failure havebeen linked to a lack of tooth structureor, more specifically, what is known asa lack of ferrule.3 Ferrule is defined asthe amount of tooth structure betweenthe margin of the restoration and themargin of the build-up (Figure 1). Tounderstand how ferrule plays a role infailure, it is helpful to consider how forcesare applied during function.

Restorative Considerations in Deciding Whether to Restore or RemoveEndodontically Treated Teeth

Learning Objectives

After reading this article, thereader should be able to:

• discuss the criteria that mustbe met during the restorativedecision-making process toensure long-term predictabilityof teeth that have already beentreated endodontically.

• identify the three major aspectsto consider when decidingwhether to restore or remove atooth that is biologically healthy.

• describe the major causes inthe failure of restored teeth thathad been previously treatedendodontically.

Frank M. Spear, DDS, MSDFounder and Director

Seattle Institute for AdvancedDental Education

Seattle, Washington

Affiliate Assistant ProfessorUniversity of Washington

School of DentistrySeattle, Washington

Private PracticeSeattle, Washington

Abstract:The interdisciplinary team is often confronted with the decision of whether to retain or remove ques-tionable teeth that have already been treated endodontically. The purpose of this article is to review therestorative criteria that must be met in order for these teeth to be predictable over the long term. In manyinstances, the decision of whether to restore or remove a tooth is quite clear. Untreatable periodontalconditions, untreatable endodontic conditions, unmanageable root resorption, or root fractures makethe decision to remove a tooth an easy one. For the purpose of this article the author is going to assumethat the teeth in question are treatable endodontically as well as periodontally and focus specifically onthe issues of restorative predictability.

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2 ADVANCED ESTHETICS & INTERDISCIPLINARY DENTISTRY MARCH 2007—VOLUME 3, NUMBER 1

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Using a maxillary anterior tooth asan example, loading during excursivemovements or during the incising offood creates a compressive force on thefacial margin of the restoration and a ten-sile force attempting to open up the lin-gual margin of the restoration (Figure 2).Normally, the stiffness of the dentin,combined with the quality of the restora-tion, prevents any kind of failure underload. Compare the loading of a tooththat is fractured level with the gingivaltissue to the retention and resistance ofthe entire restoration supported by a postand core, and one can understand how,under loading, the management of anyforces depends on the quality of the postand core because there is no natural toothstructure to which the crown is cemented(Figure 3). The more flexible the post,the more likely the lingual margin is toopen up because of the tension thatoccurs with the occlusal forces.

Once the lingual margin has opened,it is now possible for leakage to enter thegap between the crown and the toothand start working its way toward thepost and apically in the canal. When theleakage moves far enough in an apicaldirection that there is an inadequateamount of post still cemented to retainthe core, then the post, core, and thecrown all fall out. This entire event isoften preceded for months and some-times years by the patient presentingwith a complaint of a bad taste or offend-ing odor around the questionable tooth.And yet, at each appointment the marginof the restoration seemed intact becausethe crown was still cemented to the coreand the post was still cemented in thecanal. The more rigid the post, the more

likely the post is to potentially fatigueand fracture, resulting in the loss of thecrown and core or, worse, a vertical frac-ture of the root of the tooth.

One of the major goals in makingthe decision to restore or remove anendodontically treated tooth is to deter-mine if adequate tooth structure existsto prevent the types of failures describedpreviously, and if not, determining ifcould it be created. Knowing how muchtooth structure is necessary, and where itnecessary, is a key part of this decision-making process.

Literature ReviewTo answer these questions, the author

is going to reference a series of researchprojects that have evaluated the influenceof the amount of tooth structure, typeof build-up, type of post, and the methodof luting to the fatigue resistance of thefinal result. And while many researcharticles have been published on thistopic, the author is going to use a spe-cific series of articles done by studentsfrom the University of Washington post-graduate prosthodontics program. The

author was not directly involved withany of this research, but because he grad-uated from the same program 25 yearsago, he is very aware of how each articleevaluates a specific variable in the fatigueresistance of the restoration of endodon-tically treated teeth. At the heart of thisseries of articles is the concept thatfatigue resistance is the critical elementin the long-term predictability of endo-dontically treated teeth. Success requiresa tooth be able to accept repeated forcesat a lower level to succeed long termrather than be resistant to one maximaltraumatic event. This varies significant-ly from the common methodology ofusing an Instron machine and increasingthe load until a traumatic failure occursas a way of in vitro testing differentrestorative variables.

In the first study, Libman comparedthe amount of remaining ferrule and itsinfluence on when preliminary failureoccurred.4 Preliminary failure is definedas the moment the restoration marginopens up, loses its integrity and beginsthe microleakage process (Figure 4). Butbecause the restoration is still cemented

Figure 1—The concept of ferrule, the amount oftooth between the margin of the build-up andthe margin of the restoration.

Figure 2—An illustration of the distribution ofcompressive and tensile forces on a normalrestoration.

Figure 3—An illustration showing that when thetooth is even with the gingival level, all of theresistance to force is borne by the post and core.

Figure 4—The concept of preliminary failure, when the margin of the restoration is no longercemented to the root of the tooth.

MARCH 2007—VOLUME 3, NUMBER 1 ADVANCED ESTHETICS & INTERDISCIPLINARY DENTISTRY 3

to the build-up and the post is stillcemented in the canal, the restorationappears clinically sound. Libman’s focuswas to use standardized-length, cast-gold post cores cemented with zinc phos-phate into extracted central incisors. Thelength and dimensions of the toothpreparations were kept as identical aspossible. The only variable was the dif-ference in the ferrule length for each ofthe samples, varying from a control withno post core, up to a 2-mm ferrule, in0.5-mm increments. A cast-gold crownwas cemented using zinc phosphate ontop of the preparation and build-up.The complete restoration and extractedroot was embedded in an acrylic blockand prepared for fatigue testing. A straingauge was cemented over the lingual mar-gin of the restoration to act as a chartrecorder. This recorder was able to readany change occurring at the lingual mar-gin under tension from repeated loadingor fatigue. The results showed that ittook only 213 cycles to produce prelim-inary failure when a 0.5-mm ferrule waspresent; 1,140 cycles when a 1-mm fer-rule was present; 71,651 cycles when a1.5-mm ferrule was present; 70,045cycles when a 2-mm ferrule was pres-ent; and 91,208 cycles for the controlnatural tooth.

The data from this study clearly show-ed that at least a 1.5-mm ferrule for pre-dictable fatigue resistance is required.The challenge of Libman’s original mod-el is that the materials and techniquesused—namely cast-gold post cores andzinc phosphate cement—are not used ascommonly today. It was therefore neces-sary to create a series of research studiesusing the same methodology as Libmanbut altering specific variables to seetheir impact. In evaluating the variablesthat must be controlled when restoringendodontically treated teeth, the cementused to retain the post, the cement usedto retain the restoration, the type of postused, and the type of build-up materialused must all be considered.

Junge modeled his research afterLibman’s using extracted central inci-sors, cast-gold post cores cemented withzinc phosphate cement, and a 1.5-mmcircumferential ferrule, but he alteredthe cement used to place the cast-goldcrown.5 After cementation of the cast-gold post cores and the creation of the

1.5-mm ferrule, the teeth were separatedinto three groups: in Group 1 the cast-gold crowns were cemented with zinc-phosphate cement; in Group 2 the crownswere cemented with a resin-modified,glass-ionomer cement; and in Group 3the crowns were placed with an adhe-sive resin cement. Again, each tooth wasmounted in an acrylic block with a straingauge cemented to the lingual marginand placed into the device for fatiguetesting. The load used in Junge’s studywas different then that used in Libman’s,therefore, a direct correlation of thenumerical values required to achieve fail-ure cannot be made between the twostudies. However, Junge used zinc phos-phate cement as one of his variables, sothe impact of the different cements onthe number of cycles required to reachpreliminary failure can be easily seen.In Group 1, failure occurred at 5,646cycles. In Group 2, failure occurred at6,795 cycles. In Group 3, failure was notrecorded because the machine was shutoff at 100,000 cycles and none of theteeth had yet failed.

This study clearly shows the impor-tance of using adhesive resins in cement-ing the final restoration over any postand core build-up. And yet it leaves sev-eral unanswered questions. Would theresults be the same if the ferrule was lessthan 1.5 mm? Would the results be thesame if a different post-and-core systemhad been used? How would the resultsvary if the ferrule was not the sameheight circumferentially around thetooth? To answer these questions it willbe necessary to complete another seriesof studies looking at different variables.

Thu did exactly that, also using threegroups as Junge, except that he usedresin cement to place all of the postsand cores, followed by glass-ionomercement to place the crowns over theposts and cores.6 Like the others, a cir-cumferential 1.5-mm ferrule was usedfor each tooth. Comparing the resultsof Thu’s research to Goto’s is quiteastounding given that the only changedvariable was the cement used to placethe posts. Group 1 (cast-gold post core)required 163,326 cycles to reach failure;Group 2 (the stainless steel para-postwith a bonded core) required 244,315cycles to reach failure; and Group 3(fiber post with composite core) required

40,511 cycles to reach failure, which isvery similar to the number from Goto’sstudy using identical methods for plac-ing the posts, core, and crown.

In analyzing the results from thesethree studies, several things becomeobvious. First, the type of cement usedto retain the crown over the post andcore has an enormous impact on fatigueresistance, with adhesive resin being dra-matically better than zinc phosphate orresin-modified glass ionomer. The samedramatic change can also be seen whencomparing the different methods ofluting the post in the canal, with adhe-sive resin being the clear choice. Twoquestions, however, remain unanswered.First, is it necessary to have a ferrulecircumferentially around the tooth? Andsecond, is it necessary to have a 1.5-mmferrule if adhesive resin is used to placethe post core and the crown?

Wong was interested in whether acircumferential ferrule was necessary.7

Using the fatigue apparatus describedpreviously with extracted natural teeth,bonded fiber posts, composite cores,and cementing the crowns with a resin-modified glass ionomer, his study wasseparated into two major groups. Group1 had a 2-mm circumferential ferrule.Group 2 had the margin of the prepara-tions scalloped to provide 2 mm of fer-rule on the buccal and lingual surfaces,but none interproximally. The findingswere very conclusive in that the criticallocation for the ferrule is on the buccaland lingual surfaces, and whether anyferrule was present interproximally didnot affect the outcome. This is quiteeasy to understand when the distribu-tion of force to the restoration duringloading is evaluated, with the facial sur-face being compressed while the lingualsurface experiences tension but the mid-interproximal is essentially a zone of nostress (Figure 5). The final question re-maining is whether it is, in fact, neces-sary to have a 1.5-mm or 2-mm ferruleif adhesive resin is being used to placethe post core and the crown.

Ma developed a study8 where the vari-able to be altered was the actual height ofthe ferrule, again using a similar method-ology to the previous studies. Eachgroup consisted of a fiber post and com-posite core, both bonded to place, and an


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all-ceramic crown also bonded to place.The variables were: Group 1, no ferrule;Group 2, a 0.5-mm circumferential fer-rule; and Group 3, a 1-mm circumfer-ential ferrule. An analysis of the resultsshows how critical the adhesive resincement is to success, but also points tothe necessity of having some ferrule pres-ent. Group 1 failed in only 213 cycles;Group 2 failed at 155,137 cycles; andGroup 3 failed at 262,872 cycles.

Clearly the fatigue resistance andlong-term predictability of an endodon-tically treated tooth are affected by theamount of ferrule, the cement used toretain the crown, and the cement usedto place the post and core. At this pointit is difficult to identify how muchimportance the post/core system usedhas in the fatigue-resistance process.From Thu’s work, when resin-modified,glass-ionomer cement was used to retainthe crown, the stainless-steel post bondedin place with a composite core requiredthe most cycles to failure, followed bya bonded cast post core and the weak-est of the three, the bonded fiber core.However, we do not have research thatcompares the three post/core systemsto each other when the crown also wasbonded, but it would appear that thechoice of post may be the least impor-tant decision one has to make in how torestore an endodontically treated tooth.

In using the previous research aspart of the decision-making process forwhether an endodontically treated toothshould be restored or removed, it isobvious that the ability to get a 1-mmferrule on both the buccal and lingualsurfaces is critical to long-term success.And, any restorations done where noferrule is present regardless of the adhe-sive or the post used is doomed to ear-ly failure. In addition to the height ofthe ferrule, it is also important to notethat the thickness of the remaining wallsof the tooth will have an impact on thesuccess of the ferrule. That is, a 1-mm-tall ferrule that has only a few tenths ofa millimeter of wall thickness is proba-bly inadequate.

Unfortunately, the author is unawareof any research that has evaluated thethickness of the remaining walls onlong-term success. Another importantquestion in determining whether to

restore or remove an endodonticallytreated tooth is whether or not a ferrulecan be created on the tooth in questionwithout long-term negative implicationsfor the patient.

In general, two methods exist to cre-ate a ferrule when one is absent. Thefirst is surgical in nature, apically posi-tioning the gingival tissues either throughgingivectomy or osseous surgery to ex-pose more of the tooth, allowing a ferruleto be created when the tooth is prepared

(Figure 6 through Figure 9).9,10 Thesecond is to use orthodontic extrusionto erupt the tooth to a more coronallevel, followed by apically positioningthe tissue to expose the required toothstructure.11-14 In some cases this ortho-dontic extrusion can be done quiterapidly, attempting to pull the toothout of the attachment and avoid thesecondary surgery. Whether surgery ororthodontic extrusion is attempted toobtain a ferrule the net effect will always


Figure 6—Facial view of a fractured endodon-tically treated tooth with minimal facial ferrule.

Figure 8—After minor palatal crown lengthen-ing and the placement of a tooth-colored postand core, it is possible to gain 1.5 mm to 2 mmof palatal ferrule.

Figure 9—The completed restoration.

Figure 7—The same tooth in Figure 6, showingminimal lingual ferrule.

Figure 5—An illustration showing a lack of compressive or tensile force at the mid-interproximal,eliminating the need for an interproximal ferrule.

be that there will be less root in thebone after treatment than there wasbefore treatment; surgery will oftenremove bone and increase the crown-to-root ratio, and eruption pulls theroot out of the bone, again reducing thecrown-to-root ratio, although not asseverely as surgery alone (Figure 10).As a general rule, whether using sur-gery or forced eruption and surgery, itwill be necessary to have at least 4 mmof tooth exposed above the bone onboth the buccal and lingual surfaces.This allows for a 1.5-mm ferrule to beprepared while maintaining the margin2.5 mm from the underlying bone. Inaddition to determining how much toothstructure needs to extend coronally tothe bone, one must consider the amountof root that will remain in the bonewhen determining whether the toothshould be retained or removed.

Classically, clinicians have spoken ofwanting to maintain a 1:1 crown-to-rootratio when deciding to retain a tooth orto remove it.15 The challenge, of course,is that all clinicians have seen patientswith significantly less than a 1:1 ratioand yet completed a very successful res-toration. It is necessary for clinicians todecide how much root is believed to benecessary to choose restoration vs re-moval. For a maxillary anterior tooth, ifthe author can retain 8 mm to 9 mm ofroot in the bone he will generally con-sider retaining the tooth. Because 4 mmof tooth structure is needed coronal tothe bone, this means that the tooth mustbe 12 mm to 13 mm long to have 8 mmto 9 mm of root in the bone and 4 mmcoronal to the bone. If these dimen-sions cannot be met it is difficult topredict long-term success and removalshould be considered (Figure 11 throughFigure 17).

Figure 11—A patient with a severely fracturedmaxillary right central incisor. Endodontic therapy,a post and core, and a temporary crown havebeen placed.

Figure 14—Because it will be necessary toexpose 4 mm of tooth above the crest of bone,the orthodontics has been set up to erupt thetooth 4.5 mm; in addition, a fiberotomy wasperformed to the crest of bone.

Figure 15—The tooth after the orthodonticextrusion. Note the gingival levels have remainedthe same but the margin of the restoration isnow exposed.

Figure 12—A radiograph showing that theextent of the fracture on the right central incisor,from the most apical portion of the fracture tothe apex of the tooth, is 12 mm and the decisionwas made to erupt the tooth to obtain a ferrule.

Figure 16—Following three months of healingnote the gingival health and a 1.5 to 2 mm fer-rule apical to the margin of the buildup.

Figure 17—The completed smile view of thepatient seen in Figures 11 through 16. Note themaintenance of gingival levels and interproximalpapilla because eruption was used to obtain theferrule rather than surgery.

Figure 13—The extent of the lingual fracturegoing 0.5 mm below the palatal crest of bone.

Figure 10—An illustration comparing the different methods of obtaining a ferrule on a fracturedtooth, eruption vs crown lengthening. Note the differences in crown-to-root ratio between thedifferent techniques.


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The one exception to these rules is theyoung patient who has not completedgrowth. In these patients, the mainte-nance of a root—no matter how weak orhow inadequate the ferrule—is a betterchoice than removing the tooth at ayoung age and dealing with the conse-quences later. It is far better to attemptto maintain the tooth, knowing that itwill eventually fail, but getting the patientthrough the critical period of growthand then determining how to ultimate-ly replace the tooth.

Another structural factor that mustbe taken into account when determin-ing whether to consider restoring a toothor removing it is to consider whether thetooth will have excessive forces placedon it. Does the patient have a history ofsevere parafunction or bruxism? If so, itis extremely important that the toothmeet the ideal requirements of ferruleheight and wall thickness if it is to suc-ceed. If that is not possible, it is prob-ably in the best interest of the patientto remove the tooth and consider someform of replacement. The same is alsotrue if the tooth is to be a terminal abut-ment for a complex fixed prosthesis.The opposite of these circumstances alsoapplies. If the patient has no history oftooth wear and the tooth is to be a single-unit restoration, particularly in the ante-rior, it may be possible to have less thanthe ideal ferrule height or wall thick-ness and still be successful, albeit lesspredictable, than if more tooth struc-ture was present.

Esthetic IssuesIn addition to the structural require-

ments described previously concerningwhether a tooth should be restored orremoved, there are other considerationsthat have to be taken into account,specifically the impact of retaining orremoving the tooth on esthetics. Thereare situations where it would be possi-ble to create an acceptable ferrule ona maxillary anterior tooth and haveadequate root length in bone, but theresulting gingival esthetics would becompletely unacceptable because of thesurgical procedure necessary to exposeadequate tooth structure. In these cases,removal of the tooth and replacing itwith either an implant or a fixed pros-thesis would better serve the patient

over the long term than removing boneand gingiva and leaving the patient ina less desirable situation for future toothreplacement (as well as dealing with aless pleasing esthetic result after thecurrent treatment). Not doing heroictreatment to save an isolated singleanterior tooth also makes sense becauseof the predictability of tooth replace-ment for single missing anterior teeth.A large part of this predictability is thatthe presence of adjacent teeth ensuresgood interproximal bone height withacceptable interproximal papilla heights,unless prior bone loss has already oc-curred. As a general rule, if the tooth tobe removed has no periodontal disease,it is possible to replace it very predictablyusing a single-tooth implant and get avery pleasing esthetic result, largely dueto retaining the adjacent natural teeth(Figure 18 through Figure 21).

There are times, however, when theremay be multiple questionable teeth andthe clinician must decide whether toremove all of them or retain some ofthem. If none of them can be managedstructurally, the decision would typi-cally be to remove them all and replacethem prosthetically. In certain instances,however, the ability to retain one or twomaxillary anterior teeth can greatlyenhance the final esthetic outcome ofthe restoration because of their abilityto retain interproximal bone.

For example, retaining one maxil-lary central incisor and the oppositemaxillary lateral incisor has the abilityto maintain the papilla heights acrossall of the maxillary anterior teeth ifimplants are used to replace the miss-ing teeth. The retained maxillary cen-tral will maintain the papilla betweenthe opposite central and the lateralincisor implant on the side of the re-tained central. The retained lateral inci-sor will maintain the papilla between itand the maxillary central that is replacedby the implant on its side, and also willmaintain the papilla between it and thecanine that is replaced by an implanton the same side. Treatment planningto maintain some isolated maxillaryanterior teeth is especially helpful inpatients who are very esthetically con-scious and have a high lip line. Thereare many cases where esthetics need to

Figure 21—A four year recall photograph of thepatient seen in Figures 18 through 20.

Figure 18—A patient with an extremely highlip line and a fractured right central incisor.

Figure 20—A photograph following the removalof the root placement of an implant and fivemonths of healing. Note the excellent papilladue to the maintenance of the adjacent teeth.

Figure 19—The adjacent teeth are periodon-tally healthy and it would be virtually impossibleto save the root of the right central and have therestoration be predictable.



Figure 22—A patient presenting for esthetic enhancement with an endo-dontically treated maxillary right central incisor with a large access cavity.

Figure 25—The solution was to utilize thin bonded ceramic crowns witha zirconium oxide and pressed ceramic post and core minimizing theamount of facial reduction that had to be performed.

Figure 23—As the tooth is prepared it is also obvious the root is moder-ately discolored.

Figure 24—An incisal view shows how thin the walls of the remainingtooth structure are; a normal 1.2 mm reduction on the facial would removethe entire facial wall.

Figure 26—Internal bleaching was performed on the right central incisorminimizing the need for a thick restoration to mask the discolored root.

Figure 27—A six year recall photograph of the final restorations in place.

be considered in addition to the struc-tural condition of the tooth when decid-ing if the patient is better served byretaining and restoring the tooth orremoving and replacing it (Figure 22through Figure 29).

The Value AspectThe final area that must be evaluat-

ed with regard to restoration vs removal

is value, specifically, what are the costsvs the benefits to the patient whencomparing the retention of the toothvs the removal and replacement of thetooth. And value is something that onlythe patient can determine. It is not upto the clinician to determine whethermaintaining a tooth, even if it only lasts2 more years, is worth it, but rather itis up to the patient to be informed of

the potential costs, the potential risks,and what it will mean if there is earlyfailure of the retained tooth. Before theevolution of implants, it was rare tonot consider going through heroic meansto retain a tooth. In fact, it was com-mon to consider endodontic therapy, acast post core, crown-lengthening sur-gery, and the final restorations as a nec-essary part of treatment planning to

provide patients with a fixed restoration.Today, however, with the predictabilityof implants and the high cost of endo-dontic therapy, the post core, perio-dontal surgery, and final restorations,it has become increasingly importantto educate patients on the relative valueof removing a questionable tooth andrestoring it by means that are more pre-dictable. The biggest challenge that theauthor personally sees in this process isthat often the questionable tooth endsup being treated endodontically beforea definitive treatment plan is complet-ed. This usually occurs because the toothfractured and to get the patient com-fortable endodontics was necessary. Nowthe patient has already paid for the endo-dontic therapy and the clinician is in abind of how to tell the patient that theymay be better served by removing thattooth. And yet, in the long term, if thetooth is not predictable, the patientwill go on to pay for the post core andfor the crown only to ultimately haveto pay for the removal of the tooth andits replacement. It is for these reasonsthat it is critical before performing endo-dontics on questionable teeth to con-sider both the structural and estheticramifications of whether that tooth canbe predictably restored before movingforward with the decision to retain it.

ConclusionThe purpose of this article has been

to identify, as specifically as possible,what criteria are necessary at this pointin time to be able to restore an endodon-tically treated tooth and have that restora-tion be both esthetic and lasting. Themost structurally important of thesecriteria is the presence of at least a 1-mmtall ferrule on both the buccal and lingualsurfaces. In addition, the use of adhe-sive resin cements for the post and coreas well as the final restoration is critical.A brief review of the procedures that canenhance the presence of a ferrule has alsobeen presented, specifically the use ofcrown lengthening or forced eruption.

One final comment on maintaininga ferrule: it is not uncommon to see ananterior tooth that may have had endo-dontic therapy with a very large accessopening and a significant amount ofinternal tooth structure removed. If thetooth is now prepared for a traditionalcrown with 1.2 mm of facial reduction,there may be no remaining ferrule. Onesolution is to use a bonded all-ceramiccrown without any internal core, eitherpressed or powder and liquid, and keepthe facial reduction at 0.5 mm to 0.7 mmto retain a significant amount of toothstructure. If the root is dark, it maybe bleached internally coronal to the

periodontal attachment to allow theuse of a thinner, more translucent crown.This could be followed by a zirconiumoxide post core with a pressed-ceramiccore bonded with resin cement, whichhas been very successful for the authorover the long term. Finally, the authorhopes that this material stimulates thethought process for the clinician to pres-ent the concept of value in terms of cur-rent expenses for treatment vs long-termpotential expenses for treatment so thatthe patient can make an educated deci-sion in determining whether or not atooth should be restored or removed,as opposed to the clinician feeling thepressure of having to make that deci-sion alone.

References1. Shillingburg HT, et al. Fundamentals of Fixed

Prosthodontics. 3rd ed. Quintessence Pub-lishing Co. Inc; 1997.

2. Schwartz RS, Robbins JW. Post placementand restoration of endodontically treatedteeth: A literature review. J Endodont. 2004;30(5):289-301.

3. Nicholls JI. The dental ferrule and the endo-dontically compromised tooth. QuintessenceInt. 2001;32(2):171-173.

4. Libman WJ, Nichols JI. Load fatigue of teethrestored with cast post cores and completecrowns. Int J Prostho. 1995;11:311-324.

5. Junge T, Nicholls JI, Phillips KM, Libman WJ.Load fatigue of compromised teeth: a com-parison of 3 luting cements. Int J Prosthodont.1998;11(6):558-564.

6. Thu K. Fatigue life of restored teeth withthree bonded post and core systems. Unpub-lished data.

7. Wong Y, et al. Effect of proximal ferrule lengthon the fatigue life of endodontically treatedteeth. Unpublished data.

8. Ma SC. Load fatigue of teeth with differentferrule lengths, restored with fiber posts,composite cores, and all-ceramic crowns.Unpublished data.

9. Rosenburg ES, Garber DA, Evian CI, et al.Tooth lengthening procedures. Compendium.1980;1:161-172.

10. Bragger U, Laachenauer D, Lang NP.Surgical lengthening of the clinical crown.J Clin Periodontol. 1992;19:58-63.

11. Ingber JS. Forced eruption. Part II: Methodof treating non-restorable teeth—periodontaland restorative considerations. J Periodontal.1976;47:203-216.

12. Lemon RR. Simplified esthetic root extrusiontechniques. Oral Surg Med Oral Pathol. 1982;54:93-99.

13. Berglundh T, Marinello CP, Linde J, et al.Periodontal tissue reactions to orthodonticextrusion. J Clin Periodontal. 1991;18:330-336.

14. Pontoriero A, Celenza F Jr, Ricci G, CarnevaleG. Rapid extrusion with fiber resection: Acombined orthodontic-periodontic treatmentmodality. Int J Perio Rest Dent. 1987;5:31-43.

15. Penny RE, Kraal JH. Crown-to-root ratio: itssignificance in restorative dentistry. J ProsthetDent. 1979;42(1):34-38.

Present the concept of value in terms of current expensesfor treatment vs long-term potential expenses for

treatment so that the patient can make an educated decision in determining whether or not a tooth

should be restored or removed.

Figure 28 and Figure 29—Comparative frontal smile photographs pre- and post-treatment.



1. What are the three major aspects to discusswhen considering whether to restore orremove a questionable tooth that isbiologically healthy?a. esthetic, periodontal, timeb. structural, esthetic, valuec. structural, periodontal, functionald. esthetic, functional, time

2. The structural issues of whether to retain orremove a tooth relate to the amount of:a. gingival inflammation.b. periodontal health.c. remaining tooth structure.d. the patient’s facial anatomy.

3. Prior to the era of adhesive bonding, thetypical goal in describing an adequate toothpreparation was:a. 1 mm of vertical height with 2º of taper.b. 2 mm of vertical height with 4º of taper.c. 3 mm of vertical height with 6º of taper.d. 4 mm of vertical height with 8º of taper.

4. The most common failure is a loss ofretention of:a. the post and the coreb. the post and the crownc. the core and the crownd. the post, the core, and the crown

5. In a maxillary anterior tooth, loading duringexcursive movements creates a compressiveforce on what aspect of the restoration?a. facial marginb. lingual surfacec. gingival margind. labial surface

6. Because of the tension that occurs with theocclusal forces, the more flexible the post, the more likely which of the following is toopen up?a. the gingival marginb. the lingual marginc. the facial margind. the biologic width

7. In general, how many methods exist to createa ferrule?a. 1b. 2c. 3d. 4

8. As a general rule, it will be necessary to haveat least how much tooth exposed above thebone on both the buccal and lingual surfaces?a. 2 mmb. 3 mmc. 4 mmd. 5 mm

9. Classically, clinicians have spoken of wantingto maintain what crown-to-root ratio whendeciding to retain a tooth or to remove it?a. 0:1b. 1:1c. 1:2d. 2:1

10. Because 4 mm of tooth structure is neededcoronal to the bone, the tooth must be howlong to have the needed dimensions forlong-term success?a. 10 mm to 11 mmb. 11 mm to 12 mmc. 12 mm to 13 mmd. 13 mm to 14 mm

Continuing Education QuizTufts University School of Dental Medicine provides 1 hour of Continuing Education credit for this article for those who wishto document their continuing education efforts. To participate in this CE lesson, please log on to www.AEID.AEGISCE.net,where you may further review this lesson and test online for a fee of $14.00. To obtain mailing instructions or for moreinformation, please call 877-4-AEGIS-1.

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