Commentary

Strategic Extraction: A Paradigm Shift That Is ChangingOur Profession

Richard T. Kao*

The greatest challenge in treatment planning is toassign an accurate prognosis and develop a predict-able protocol. In the era of evidence-based dentistry,outcome studies have forced us to reexamine ourtreatment approaches and decide if superior treat-ment options should be pursued. As endosseous den-tal implants gain greater acceptance because of highsuccess rates, the critical question is whether a toothwith a questionable prognosis should be managedconservatively in a traditional fashion or be strategi-cally extracted in preparation for a dental implant.The outcomes of traditional periodontal, endodontic,and prosthodontic treatment approaches are com-pared to the option of strategic extraction. J Periodon-tol 2008;79:971-977.

KEY WORDS

Dental implants; prognosis; treatment.

Strategic extraction originally described the re-moval of a tooth or root to create a morehygienic environment.1,2 The objective was to

enhance the status and prognosis of an adjacenttooth or the overall prosthetic treatment plan, i.e.,eliminate the high-risk element to improve the over-all periodontal prosthetic prognosis. Prosthodontistsbegan using this strategy to extract teeth that did notcontribute to the removable partial denture designor compromised the final fixed prosthesis. Ortho-dontists expanded this concept of the extraction ofhealthy teeth in crowded dentition to achieve idealocclusion. With the acceptance of dental implantsand the use of recombinant biologic modifiers forimplant site preparation, strategic extraction meritsreexamination.

The decision to apply strategic extraction is basedon each clinician’s prognosis for each individual toothas well as the overall dentition. Although there issome general agreement, there are subtle differencesamong practitioners based on opinions about whattooth or teeth can be successfully treated. These dif-ferences are the result of our personal clinical experi-ences, interpretation of the literature, and techniquesat our disposal. With strategic extraction, the prog-nostic decision process is essentially the weighingof one option against another to determine which of-fers the best chance of success. As implants become amore accepted treatment, it is important to assesstheir value compared to other treatment modalities.Selecting implant treatment is essentially a decisionto use strategic extraction, but there have been few ar-ticles3-5 on this subject. This commentary examinesthe therapeutic outcomes of placing dental implantscompared to periodontal, prosthetic, and endodontictreatment options.

COMPARISON OF TREATMENT OPTIONS

Comparing treatment options is a complex balancebetween relying on evidence-based dentistry and per-sonal clinical experience.6 Nevertheless, the princi-ples of evidence-based dentistry require us to be

* Private practice, Cupertino, CA; Division of Periodontology, University ofCalifornia at San Francisco, San Francisco, CA; Department ofPeriodontology, University of the Pacific, San Francisco, CA. doi: 10.1902/jop.2008.070551

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familiar with outcome studies for the various treat-ment options.

Periodontal ConsiderationsDetermining an accurate prognosis for each individ-ual tooth and for the overall dentition is difficult. Fore-casting individual tooth prognoses is usually basedon clinical and radiographic parameters (e.g., radio-graphic bone loss, probing depths, clinical attachmentlevels, bleeding on probing, furcation involvement,and mobility). Classic studies by Hirschfeld andWasserman7 and other investigators8-10 showed thateven with highly compliant patients, it is almost im-possible to predict the survival of a periodontally com-promised tooth. During the period these patients weremaintained, tooth loss ranged from 6.2% to 9.8%, withan annual average of 0.08% to 0.11%. Tooth loss forthe treated, but not maintained, population was higher,with an annual tooth loss rate of 0.22%.10 These stud-ies also generally indicated that it is more difficult toaccurately forecast the prognosis of teeth with furca-tions and/or the multirooted tooth versus the single-rooted tooth.

In a series of articles, McGuire and Nunn11-13 deter-mined that clinical parameters were ‘‘ineffective inpredicting any outcome other (than those teeth with)good’’ prognosis.13 The forecasting accuracy for teethassigned a good prognosis was 81% after 8 years, butthis decreased to 35% when applied to teeth with aninitial prognosis of less than good.12 In a recent liter-ature survey,5 the long-term retention of teeth withquestionable prognoses ranged from 38% to 97%. Adirect comparison of these studies is not possible be-cause of differences in subject populations, clinicalevaluation parameters, maintenance methods, andthe number/type of teeth monitored. Most impor-tantly, there were no standard criteria to define a ques-tionable prognosis.

Extensive research efforts have focused on clinicalparameters as predictors of disease progression.Bleeding on probing is a poor predictor of periodontaldisease progression, and its absence on sequentialvisits was shown to be a good predictor of no futureattachment loss.14 Several retrospective studies7-9

suggested furcation involvement was one of the mainreasons for tooth loss. In a review of therapeutic out-comes, retention rates of furcated teeth ranged from43% to 98%, suggesting that the actual retention rateis better than the long-term prognostication.5 Toothmobility has also been proposed as a risk factor for at-tachment and tooth loss,15,16 but other reports sug-gest hypermobility is not always associated withadvanced disease progression17 or worsening prog-nosis.12 Some studies18-20 suggested that deep prob-ing depths predict future attachment loss; however,another study20 suggested that this relationship is

not absolute. Deep probing depth seems to be associ-ated with a higher risk for further attachment losscompared to shallow probing depth; however, furtherdisease progression is not inevitable, although treat-ment can reduce this possibility. It is the absence ofdeep probing depth, similar to bleeding on probing,which is a good forecaster of periodontal stability.These clinical parameters have not been reliable fore-casters of disease activity.

In addition to the lack of reliable prognostic de-terminants for periodontal stability, the clinician ishampered by patient management issues that maycomplicate the periodontal forecast. The first issueis patient compliance with home care instructions andmaintenance therapy appointments. Studies21-23 in-dicated that 20% to 30% of treated patients do notcomply with the recommended maintenance therapy,and of those who do comply, approximately half areerratic in their care. As expected, erratic compliers re-quire more retreatment compared to patients who fol-low home care guidelines and regularly present formaintenance.23 The second issue is systemic diseaserisk factors, such as smoking, diabetes, and immu-nosuppression; these are not within the scope of thisdiscussion, but they contribute to the difficulty of peri-odontal evaluation.

When analyzed in conjunction with the clinical pa-rameter studies, these two issues result in a confound-ing combination of information. Like statistics wherethe odds that an event may occur under one situationare analyzed in a myriad of situations, the results arenot additive, but synergistic. This is where the art ofperiodontal prognosis begins and why our opinionsvary so widely. The decision to extract or preserve atooth should be based on knowledge of the literature,accurate collection of clinical information (clinical pa-rameter data and medical-social history), our past clin-ical experiences, and consideration of the patient’svalues.

But exactly when should strategic extraction be in-voked? How should teeth with a questionable progno-sis be managed? It is important to recognize thatperiodontal therapy and prognosis is not a static pro-cess. Despite the limited success associated withsome treatments, the option for therapy and a chancefor disease control are determined, in part, by the cli-nician’s skills and information in the literature. Thecritical part of this decision is based on the discussionwith the patient to determine his/her preferences. Ifthe decision is made to begin periodontal treatmentto control the disease, then reevaluation of the clinicalresponse will result in a new prognosis. Similarly,maintenance requires constant monitoring and refor-mulation of the prognosis. Periodontal prognosis isshaped by how the clinical condition responds toour periodontal management and the patient’s home

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care. At any point in this process, the relative value ofstrategic extraction must be reviewed with the patient.The decision about strategic extraction should bemade when a potential implant site is in danger be-cause of continual bone loss, and it should be basedon to what extent we can still predictably offer the pa-tient the implant option.

Endodontic TherapyClassically, when a tooth has a pulpal involvementsecondary to tooth fracture and carious lesion, end-odontic therapy has been the treatment of choice.However, dental implants have become an alternativefor such therapy. In a systematic review24 of the end-odontic literature, the survival rate after root canaltreatment followed by coronal restoration rangedfrom 81.2% to 100% over 3 to 25 years. In the samereview,24 the survival rates of single-tooth implantsand restored endodontically treated teeth were statis-tically similar after 5 to 7.8 years. The investigatorsconcluded that the decision to treat a compromisedtooth endodontically or replace it with an implantshould be based on factors other than treatment out-come. Endodontic factors to be considered includethe presence/absence of a periapical lesion, the typeof endodontic treatment, and the postendodontic re-storative situation.

The presence of preoperative periapical lesionsdecreases the endodontic success rate by ‡10%.25

A recent study26 reported that in the absence of suchlesions, the healing rate was 94% compared to 79% insites with lesions. Approximately 45% of the lesionsslowly decreased in size. This has been interpretedas slow but progressive healing. Approximately 6%of the teeth had a persistent lesion 10 years after treat-ment.26

Endodontic retreatment can significantly reducethe 97% success rate seen with initial endodontic ther-apy.27-29 Surgical retreatment of a poorly endodonti-cally filled tooth can reduce the success rate by asmuch as 13% to 29%, with a reported mean healingrate of 78%.30,31 These findings are consistent witha recent review28 that suggested the chance of suc-cess ranged from 37% to 85%, with an average of70%. In one study29 of endodontic retreatment, perfo-rations were seen in 12% of the cases; the outcomeand prognosis were so poor that these teeth wereexcluded from analysis. These studies suggest thatsurgical retreatment of root perforation and poorroot-filling quality are strong predictors of poor end-odontic outcome.

Periapical lesions, root perforations, and poor end-odontic fill are factors that complicate endodonticevaluation; the restorability of the endodonticallytreated tooth is of greater importance. A systematicreview24 suggested that root canal treatment followed

by coronal restoration has a success rate similar toimplants. The review has limited value because of theshort mean time (7.8 years) used to evaluate tooth sur-vival, the assumption that all endodontically treatedteeth will be coronally restored, and because moni-toring occurred after restorations were placed. Theevaluation period may be too short to support the as-sumption that all endodontically treated teeth can besuccessfully restored. The clinical reality is that not allendodontically treated teeth are restored; other fac-tors, such as postplacement fracture or perforation,types of posts inserted, form of supracoronal restora-tions, and prosthetic issues, were not addressed andmay have resulted in an overestimation of the successrate. In a survey32 of 12 studies with a 6-year follow-up, 10% of teeth with posts had complications. Othercomplications that occurred with conventional singlecrowns included crown fracture (7%), loss of retention(2%), post and core loosening (5%), root fracture(3%), and caries (3%).32 Some studies33-35 reportedthat 24.2% to 85% of root canal–treated teeth were ex-tracted because they were not properly restored. Untilthere are more outcome studies that evaluate theseindividual factors, equating the success rate of endo-dontically treated teeth to that of implants should beaccepted with the caveat that there are limitationsto this comparison.

Prosthetic TherapyThere are limited longitudinal studies assessing thesurvival of fixed partial dentures (FPDs) to replacemissing teeth. Additionally, the results are difficultto analyze because of different follow-up periodsand definitions of failure. The only meta-analysis36

that assessed the overall effectiveness of FPD therapyreported that <15% of FPDs had been removed orneeded replacement at 10 years; the figure increasedto nearly one-third after 15 years. In another study,32

the three most commonly reported FPD complica-tions were caries (18% of abutments), need for endo-dontic treatment (11% of abutments), and loss ofretention (7% of prosthesis). These complicationsare costly financially and often require additional pro-cedures that increase the chances for failure.

ImplantsThe efficacy and predictability of endosseous im-plants in treating partially and totally edentulous caseshave been well documented.37-39 Regardless of theimplant system used, functional success was achievedin >90% of the patients after 8 to 15 years.37,38 In sit-uations involving limited bone volume, socket or ridgepreservation, guided bone regeneration, and distrac-tion osteogenesis can be effective ridge-enhancementtechniques.40,41 Nevertheless, the principle challengesin implant dentistry are to regenerate adequate bonevolume and clinical esthetics.

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Although implant survival and function successrates are high, there are clinical complications. Ac-cording to a review by Goodacre et al.,42 the mostcommon surgical complications were hemorrhagerelated, mostly hematomas and ecchymosis (24%),followed by neurosensory disturbance (7%), andmandibular fracture (0.3%). However, most of thebleeding and neurosensory situations were transitoryand had no effect on long-term implant success.42

Other complications included implant loss in irra-diated maxillae (25%), type IV bone (16%), andpatients with diabetes (9%).42 These latter compli-cations and those observed with mandibular fractureare more accurately identified as issues relating tocase selection and evaluated as implants placed incompromised sites or in high-risk patients. Prostheticcomplications included loosening of the overdenture-retentive mechanism (33%), resin veneer fracture withfixed partial dentures (22%), implant loss with max-illary overdentures (21%), overdentures needing tobe relined (19%), and overdenture clip/attachmentfracture (16%).42 Most prosthetic complications arerelated to the use of implants with overdentures orfixed removable prostheses. Although these issuesmay be classified as complications, most of themare normal events associated with prosthetic mainte-nance and are generally correctable. From a func-tional perspective, esthetic complications occurredwith a mean prevalence of 10%, and phonetic compli-cations occurred with a mean prevalence of 7%. Fromthis survey, Goodacre et al.42 concluded that implantsand implant prostheses had a trend toward a greaterincidence ofcomplicationscompared tosinglecrowns,FPDs, all-ceramic crowns, resin-bonded prostheses,and post and cores. Although the incidence ratemay be higher, most of the situations identified canbe resolved with no long-term negative conse-quences. Lastly, the data collected included a widecross-section of implants used in compromising situ-ations, such as removable denture design, or in high-risk patients.

DISCUSSION

Strategic extraction has been and will continue to be asubject of debate, with no clear algorithm for decisionmaking. In the review of periodontal, endodontic, andprosthetic options by Goodacre et al.,42 the conclu-sion is that this decision-making process is difficult.As we compile outcome data, we start to understandthat any clinical situation may have a multitude of fac-tors that need to be considered before a treatmentplan is developed. An example is a carious pulpalexposure on a tooth with a furcation involvement. In-stead of considering only the outcome of endodontictreatment, we need to consider the periodontal prog-nosis of the furca, the success rate of the post and core

placement, and the long-term crown survival. Withmany situations, we may know the probability of suc-cessful outcome for any single aspect, but when thereare so many confounding factors, the possibility ofsuccessful treatment decreases. In addition, the pa-tient’s concern over losing a tooth, possible changesin esthetics, and the length and cost of treatment mustbe considered in the decision-making process.

Because of the high success rate of dental implants,there are concerns that teeth with a guarded prognosiswill be prematurely extracted to be replaced with den-tal implants.5 Although this author shares some ofthese concerns, the critical premise on which strategicextraction should be based is: Do not take a stance ofwatchful waiting. That is, do not postpone extractionuntil the situation deteriorates to the point where otheroptions are eliminated or compromised. In many sit-uations, implants provide a good functional optionwith acceptable esthetics. A major key to implant suc-cess is adequate bone volume: ideally, native bone.Strategic extraction should be considered if othertherapeutic options compromise the potential to ob-tain or preserve this bone volume. Situations in whichthis guiding principle may not apply are elderly pa-tients if there are other serviceable options, when sat-isfactory esthetic results cannot be achieved, or whenthe patient objects to a perceived premature toothloss.

One of the main limitations to successful implantplacement is inadequate bone volume at the recipientsite. Our ability to work with compromised sites hasimproved with the variety of techniques available forincreasing bone volume through ridge preservation,augmentation, sinus grafting, and distraction osteo-genesis.40,41

Incorporating recombinant biologic modifiers in re-generative therapeutics further increases the possibil-ity of success. Within the past 2 years, the UnitedStates Food and Drug Administration (FDA) has ap-proved two recombinant protein therapeutic pro-ducts: recombinant human platelet-derived growthfactor (rhPDGF)-BB and recombinant human bonemorphogenetic protein (rhBMP)-2. rhPDGF has beenused in the treatment of severe periodontal intrabonyand Class II furcation defects,43-45 and its potentialuse in bone augmentation procedures46,47 and softtissue reconstruction47,48 may improve implant sitedevelopment. Similarly, rhBMP has been used suc-cessfully for bone augmentation in the maxillary sinusfloor, extraction sites, and alveolar ridge defects.49,50

Three obstacles have prevented the rapid incorpo-ration of these products into clinical practice. The firstis that the exact requirements for clinical use are beingrefined. The ideal carrier/regenerative scaffolding isstill being explored to optimize release kinetics andto serve as scaffolding for the early cellular events

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associated with bone formation. rhPDGF and rhBMP-2exhibit a biphasic mode of action. Three concentra-tions of rhPDGF were used in the FDA trial. The inter-mediate concentration of 0.3 mg/ml proved optimalfor periodontal regeneration, whereas the other twoconcentrations yielded a lower response.45,51 Thiswas also true in rhBMP-2 studies;50,52 the lower con-centrations (0.43 and 0.75 mg/ml) were less effectivefor ridge preservation than the highest concentration(1.5 mg/ml). These optimal concentrations were es-tablished for a specific defect situation, and it remainsto be determined if these concentrations deliver theoptimal regenerative response under different clinicalsituations. These are challenges that clinicians usingthese biologic modifiers need to address throughclinical studies. The second issue is whether the re-generated bone possesses adequate bone quality, es-pecially in terms of bone density, to support implantosseointegration. The third issue is the relatively highcost for one of these products. Given the current cost,it is difficult for clinicians to incorporate them intopractice until there is clear evidence of technique su-periority and well-documented treatment protocolsare established. However, these recombinant biologicmodifiers seem to hold great promise and may changehow we define the critical time point to implementstrategic extraction.

CONCLUSIONS

Although periodontists are viewed by the dental pro-fession as experts in forecasting tooth prognosis, wehave no infallible method for making these decisions.Although there is an ingrained tendency to try to saveteeth, we must remember that our therapy works bestwith good patient compliance. Additionally, shouldour results be unsuccessful, we must readily considerother options, including strategic extraction.

As we increasingly accept evidence-based dentis-try as a basis for practice decisions, we discover thatlimited outcome studies are the foundation for thisapproach to treatment. Further complicating the de-cision-making process is the fact that many clinicalsituations require us to consider a multitude of con-founding factors. Nevertheless, we recognize thatthere is a critical point where elective or strategic ex-traction is the best solution for dealing with compro-mised dentition. Because of the high success rate ofdental implants, this critical point has shifted towardan earlier strategic extraction to preserve the bonevolume necessary for implant placement. Addition-ally, with the availability of recombinant biologicmodifiers, this critical point may shift again. The crit-ical point for each practitioner will reflect individual in-terpretations of the outcome studies discussed aboveand personal experience. It is important to reempha-size that patient age, personal preferences, and fi-

nances must always be part of the decision-makingprocess. In summary, because of the acceptance ofdental implants, the emergence of biologic modifiers,and growing reliance on evidence-based dentistry,our profession needs to change its view of prognosisand its clinical implications for treatment. It is imper-ative that we understand this situation and alter oureducational focus to adequately prepare periodon-tists for this future.

ACKNOWLEDGMENT

The author reports no conflicts of interest related tothis study.

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of recession defects: A case series. Int J PeriodonticsRestorative Dent 2006;26(2):127-133.

49. Boyne PJ, Lilly LC, Marx RE, et al. De novo boneinduction by recombinant human bone morphogeneticprotein-2 (rhBMP-2) in maxillary sinus floor augmen-tation. J Oral Maxillofac Surg 2005;63:1693-1707.

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52. Cochran DL, Jones AA, Lilly LC, et al. Evaluation ofrecombinant human bone morphogenetic protein-2 inoral applications including the use of endosseousimplants: 3-year results of a pilot study in humans.J Periodontol 2000;71:1241-1257.

Correspondence: Dr. Richard T. Kao, 10440 S. DeAnzaBlvd., Suite #D-1, Cupertino, CA 95014. Fax: 408/252-9596; e-mail: richkao@sbcglobal.net.

Submitted October 15, 2007; accepted for publicationDecember 3, 2007.

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