Is endodontic re-treatment mandatory for every relatively old temporary restoration?: A narrative...

2011;142;391-396 J Am Dent Assoc

David Keinan, Joshua Moshonov and Ami Smidt narrative review

every relatively old temporary restoration?: A Is endodontic re-treatment mandatory for

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Endodontists long have con-sidered the success ofendodontic treatment to beinfluenced by the quality of

the coronal restoration. Researchershave recommended sealing ofcoronal restorations to preventmicroorganisms in the oral environ-ment from recolonizing the canalsystem and to bar nutrients in theoral environment from supportingmicroorganisms left in the canalsystem after treatment.1 A possibleassociation between coronal leakageand endodontic failure was firstreported by Marshall and Massler2

in their radioisotope leakage studyof extracted endodontically treatedteeth. The interest in microleakagesubsequently developed into a majorthrust of endodontic research, andby the 1980s, almost 20 percent ofthe articles published in Journal ofEndodontics dealt with this issue.However, the majority of thesestudies were conducted as shortresearch projects by graduate stu-dents who used a diverse array ofmethods, thereby making compari-sons difficult. Indeed, the studies

Dr. Keinan is an instructor, Department of Endodontics, School of Dental Medicine, The Hebrew University-Hadassah, Jerusalem. He also is head, Department of Endodontics, Medical Corps, Dental Center, Sheba Medical Center, Tel-Hashomer, Israel. Address reprints to Dr Keinan at the Department ofEndodontics, School of Dental Medicine, The Hebrew University-Hadassah, Jerusalem, Israel 91120, e-mail “[email protected]”.Dr. Moshonov is the acting chairman, Department of Endodontics, School of Dental Medicine, The Hebrew University-Hadassah, Jerusalem.Dr. Smidt is the head, The Center for Graduate Studies in Prosthodontics, Department of Prosthodontics, School of Dental Medicine, The Hebrew University-Hadassah, Jerusalem.

Is endodontic re-treatment mandatory for every relatively old temporary restoration?A narrative reviewDavid Keinan, DMD, MSc, PhD, MHA; Joshua Moshonov, DMD; Ami Smidt, DMD, MSc

AB ST RACTObjectives and Background. In this review, the authorsexamine whether there is any decisive evidence to support the revi-sion of root fillings that have been exposed to the oral environmentfor more than three months, undertaken solely because of suspicionsof microleakage. Researchers in numerous endodontic studies haveaddressed the evaluation of coronal microleakage by using differenttracers and techniques. The need to achieve a tight, permanentcoronal seal as soon as possible after the completion of endodontictreatment is obvious. However, the clinical importance ofmicroleakage studies recently has been questioned because of theirwide range and even contradictory results, and findings from only afew clinical investigations have demonstrated a clear relationshipbetween the endodontic success rate and failure rate owed to coronalmicroleakage in cases involving high-quality endodontic therapy.Methods. The authors analyzed commonly cited articlesregarding the clinical relevance of microleakage studies and the suc-cess rate of teeth with compromised restorations.Conclusions. In a review of the literature, the authors found noclear evidence to support immediate replacement of well-obturatedendodontic treatment that has lasted more than three months solelybecause of suspicions of microleakage. It may be prudent in suchcases to make a new coronal restoration immediately and to observethe tooth for at least three months before placing the permanentcrown.Key Words. Microleakage; coronal restoration; endodontic success.JADA 2011;142(4):391-396.

JADA 142(4) http://jada.ada.org April 2011 391

P R A C T I C EC L I N I C A L

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392 JADA 142(4) http://jada.ada.org April 2011

never were validated as clinically relevant,3

leading to increasing doubts about their impor-tance and clinical applicability.4-7

Important questions raised by the editorialboard of Journal of Endodontics8 in a 2008 edito-rial include the following: dAre laboratory-based leakage studies of anyclinical relevance? dCan the quality of endodontic fillings andsealing of coronal restorations be assessed onthe basis of radiographs?

To these, Wu and colleagues9 added anotherquestion: are radiographic films capable ofrevealing the presence of periapical pathosis?

To answer these questions, we conducted a review with the aim of determining whetherthere is a definite need for endodontic re-treatment in cases of well-conducted treatmentof root canals involving a temporary restorationof more than three months’ duration, solely onthe basis of suspected microleakage.

IN VITRO MICROLEAKAGE STUDIES: TECHNIQUES AND LIMITATIONS

To understand the difficulties encountered inextrapolating to clinical practice the findingsfrom in vitro studies of microleakage, it isimportant to bear in mind the wide range ofparameters in study design. We have identifiedthe following limitations of in vitro micro-leakage studies.

Tracer characteristics. Three main charac-teristics of tracers are relevant to leakagestudies: size, type and penetrating ability. How-ever, no tracer can mimic the clinical conditionsand the presence of mixed flora precisely. Thevarious tracers used in endodontics are not ofconstant size, type or shape, yet one can gener-ally conclude that the larger the tracer, thesmaller the anticipated leakage.10 Most studies inwhich researchers used dye tracers, such asmethylene blue or India ink, could show only theleakage filling spaces along the root canal. Otherresearchers resorted to use of radioactive tracers,such as sodium 22 (22Na),11 to demonstrate themicroleakage.

In the 1990s, investigators used bacteria orbacterial particles of known size and pene-trating ability as a tracer for microleakage. Themain limitation of the bacterial model is theability to mimic clinically only leakage of bac-teria of the same size. Torabinejad and col-leagues,12 using a bacterial coronal leakagemodel of single-rooted root-filled teeth to eval-uate the rate of leakage, found that one-half ofthe teeth were contaminated along the entirelength of the root after 19 days (motile bacteria)

or 42 days (nonmotile bacteria). The penetrationof Proteus vulgaris, a motile bacterium, wasslower than that of Staphylococcus epidermidis,although the latter is nonmotile. Malone andDonnelly13 failed to demonstrate the penetrationof any bacterium from fresh human salivathrough an apical foramen sealer, even whentested with single-cone gutta-percha during a60-day period. Investigators in other studiesattempted to detect microleakage by means ofbacterial component, which is known to causeperiapical disease. Alves and colleagues14

showed that purified andotoxin penetrated root-filled teeth faster than did bacteria, whereasCarratù and colleagues15 did not find evidence of such penetration. The unclear clinical impor-tance of these bacterial models also may berelated to the fact that endodontic infection isbased on the mixed size and shape of micro -organisms and on biofilm development,16 neitherof which a tracer can mimic.

Measurement methods. Several methodsexist for measuring leakage, most of them quali-tative. Leakage commonly is determined by depthof marker penetration,17 turbidity (as assessed bymeans of spectrophotometry),12 fluid transport,18

glucose penetration18 and radioactivity.11

Experimental conditions. Most studies2,11,17

have dealt with the existence of positive or neg-ative pressure, yet far fewer involved the use ofthermocycling19,20 and repeated loading.21 Theseimportant parameters actually mimic conditionsin the mouth that cause degradation of coronalrestorations in general and especially tempo-rary ones.22

Measurement time. The time elapsedbetween the start of the experiment and thefirst evidence of leakage is a critical parameterfor demonstrating the presence of leakage.17 Onecan assume that a longer observation periodwill result in a greater potential for leakage.However, this is not always the case, asShemesh and colleagues18 showed in a fluidtransport model. Magura and colleagues23

demonstrated that salivary penetration wasgreater after three months than that observedafter shorter periods. Their results indicatedthat secondary endodontic treatment should beundertaken if obturated root canals wereexposed for at least three months. However,researchers have demonstrated contaminationof the root canal even within 30 days, regardlessof obturation technique.24 Friedman and col-leagues,11 using a 22Na radiotracer, found thattemporary fillings were effective for only up to


ABBREVIATION KEY. 22Na: Sodium 22.


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three weeks. It is not irrational to assume thata prudent dentist will not carry out secondaryendodontic treatment in patients with a three-week-old temporary restoration, even though itis clear that leakage may occur. Becauseleakage can occur at any time, as shown invarious in vitro studies,11,12 the recommendationfor re-treatment undertaken solely because ofsuspected microleakage is not evidence based.

Coronal restoration dimensions. Thedimensions of the coronal restoration are of greatimportance, because the physical barrier againstleakage increases with filling size and becausedye penetration also can be demonstrated in sev-eral temporary materials.25 Barthel and col-leagues26 used a 3 × 2.5 × 4-cubic millimeterfilling size, whereas Liberman and colleagues21

used a 6 × 3 × 7-mm3 filling size. The inconsistentdimensions of the temporary coronal restorationsin microleakage studies, and especially in clinicalpractice, illustrate the difficulty in evaluatingsealing efficiency, particularly in relation toelapsed time.

EPIDEMIOLOGIC STUDIESInvestigators in several studies have tried toevaluate the influence of the quality of coronalrestoration on the tooth’s clinical and radiographic periapical status. Safavi and colleagues27

found a higher success rate of complete peri-radicular healing in teeth with permanentcoronal restorations than in those with tempo-rary restorations. However, this difference wasinsignificant despite the fact that the investiga-tors observed the former teeth longer than theydid the latter teeth. Ray and Trope28 conducted across-sectional study of 1,010 periapical radio-graphs of endodontically treated teeth to eval-uate the teeth’s periapical status in relation tothe quality of the restoration or of the endo-dontic treatment. Although it is problematic toevaluate the quality of coronal restoration byusing only radiographs, the authors concludedthat the quality of the coronal restoration wassubstantially more important than that of theendodontic treatment. Kirkevang and col-leagues,29 also by using radiographic criteria,found that adequate coronal restorations wereassociated with a better periapical status thanwere inadequate restorations (48.0 percent ofteeth had apical periodontitis versus 63.9 per-cent, respectively). Hommez and colleagues,30 ina similar study, found that the radiographicappearance of the coronal restoration and thehomogeneity of the root fillings were equallyimportant, indicating an equivalent effect on theperiapical condition. They found that teeth

restored with resin-based composite exhibitedmore apical periodontitis (40.5 percent of thecases) than did amalgam-restored teeth (28.4percent of the cases), whereas marginal decaydid not influence the periapical status.

Siqueira and colleagues31 evaluated 2,051 radio-graphs of endodontically filled teeth and found ahigh prevalence of periradicular lesions. Coronalrestoration had an effect on the periradicularstatus, albeit the researchers found the quality ofthe root canal filling to be the most critical factor.Tronstad and colleagues,32 Segura-Egea andcolleagues33 and Tavares and colleagues34 foundthat the quality of the endodontic treatment hada greater effect on the periapical status ofendodontically treated teeth than did the coronalrestorations. Ricucci and colleagues6 examinedthe periapical status of endodontically filledteeth exposed to the oral environment because ofcaries or the absence of coronal restorations.They concluded that coronal leakage may not beof great clinical importance, as deduced fromnumerous in vitro studies, provided instrumenta-tion and placement of root fillings were per-formed carefully. Therefore, it is not surprising toread a case report regarding periradicularhealing in endodontically treated teeth despitethe patient’s having had temporary restorationsfor more than 2.5 years.35 Furthermore, it isobvious that a new tight coronal seal entombsmicroorganisms and nutrients and prevents theirreentry from the oral cavity, thereby preventingthe development of periradicular disease.

The explanation for the differences betweenthe results of these studies also may be related tostudy design. In analyzing aggregate data,Chugal and colleagues36 found that teeth with apermanent coronal restoration had a success ratehigher than that of nonrestored teeth (80 percentversus 60 percent). However, the results of astratified analysis of a key confounding factor(preoperative periapical diagnosis) showed thatthere was no significant association between per-manent restoration and endodontic outcome.36

The inconsistent conclusions regarding theclinical relevance of coronal restoration qualityto endodontic success, especially in casesinvolving high-quality endodontic treatment, donot lessen the need for high-quality coronal res-toration. However, they further reinforce theimportance of high-quality endodontic treat-ment with a tight seal. The opposite results ofsome of these studies28,32 may be explained bythe fact that teeth categorized as having goodcoronal or apical sealing according to radio-graphic and clinical means actually had amicroscopically inadequate seal.



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OUTCOME AND COMPLICATIONS OF SECONDARY ENDODONTIC TREATMENT

Satisfactory coronal restoration clearly is amongthe factors that may positively influence theoutcome of endodontic treatment.37 In a studyinvolving dogs, Yamauchi and colleagues38 alsoshowed the importance of a good coronal sealwith regard to teeth’s apical status. However,we did not find any study results showing ahigher success rate after completion of sec-ondary endodontic treatment in asymptomaticcases involving properly obturated root canalsand compromised coronal restoration, carriedout solely because of suspicion of microleakage.The finding by Hommez and colleagues30 thatmarginal decay did not influence the periapicalstatus may be explained by the differencesbetween the flora causing dental caries andthose causing endodontic disease.

Endodontic re-treatment is a straightforwardprocedure with a high success rate, especiallywhen it involves the use of modern endodontic

techniques. Yet, it also is important to bear inmind the risks of complications in the course ofendodontic treatment, although they are rare. (Inother words, “First, do no harm.”) Secondaryendodontic treatment carries with it the risk offurther loss of the residual dentin width of theroot canal walls, along with the risk of intro-ducing defects into the root canal walls.39,40 Thesedefects may propagate into vertical root frac-tures, leading to tooth loss.40 Other complicationsinclude canal blockage,41 instrument separation,42

canal transportation,43 root perforation44,45 andinfection developing during or between appoint-ments.46 Those aspects may support the findingby Van Nieuwenhuysen and colleagues47 thatradiographic monitoring alone revealed nochange or even a healing process in 97.2 percentof the canals studied, whereas the success rate ofsecondary endodontic treatment was as high as91 percent. This finding encourages the prudentclinician to be sure before beginning treatmentthat endodontic re-treatment is more likely to


Figure. Flowchart to guide the clinician’s decision making regarding secondary endodontic treatment of asymptomatic teeth. * Quality of obturation is evaluated clinically (whether gutta-percha is pinkish and firm) and according to radiographic assessment ofthe filling’s homogeneity, size and length.

Decision-Making Flowchart:

Asymptomatic Endodontically Treated Tooth

Well-Obturated Root Canal* Poorly Obturated Root Canal*

Compromised coronal restorationin place < 3 months

Compromised coronal restorationin place > 3 months to 1 year

Compromised coronal restorationin place > 1 year

Periradicular radiolucency present? Periradicular radiolucency present? Periradicular radiolucency present?

No No No YesYesYes

Previous radiograph

Same orimproved

3-6 months’ follow-up

Periradicular statussame or improved

Periradicular statusdeteriorated Endodontic

Re-treatment

Coronal Buildup

FinalProsthesis


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succeed than is merely replacing the coronal resto-ration. By removing the compromised coronal res-toration, the clinician may be able to verify thatthe gutta-percha is pinkish and firmly condensed.Furthermore, in questionable cases, the use ofcone-beam computed tomography to verify thestatus of the periradicular tissue may be helpful.48

Is there any justification for remaking acrown or bridge, removing a post and core ortaking the risk of losing a clinically good abut-ment tooth with no symptoms when there is achance of future failure owing to microleakage?There is no clear answer, and one has to con-sider the history of the treatment, the possi-bility of monitoring and follow-up and theoption of apical surgery in those few casesinvolving late failure of endodontic treatment.

To help the clinician make decisions in casesinvolving asymptomatic teeth, the flowchart(Figure) may prove useful.

CONCLUSIONSThe literature review presented here empha-sizes the importance of good permanent coronalrestoration. In the absence of clear scientific evi-dence, in cases involving high-qualityendodontic treatment but also a compromisedcoronal restoration of more than three months’duration, it may be prudent to resort to a per-manent coronal restoration.

Because radiographs are of limited value inassessing the quality of root canal obturation, itis important to verify clinically that the gutta-percha is pinkish and firmly condensed. The useof cone-beam computed tomography may behelpful in patients with an unclear periradic-ular status. If the periradicular status is notclear, it is important to inform the patient of theuncertain prognosis and to monitor the tooth forat least three months before proceeding withthe permanent crown. The clinician must bearin mind the option of future secondaryendodontic treatment or apical surgery.

Further prospective epidemiologic studiesregarding the success rate of endodontic treat-ment in teeth with replaced compromisedcoronal restoration versus that in similar casesinvolving re-treatment may be helpful. ■

Disclosure. None of the authors reported any disclosures.

The authors thank Dr. John Whitworth for his remarks and advice.

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