Determining the Optimal Obturation Length: A …

1 Determining the Optimal Obturation Length: A Meta-Analysis of LiteratureMichelle A. Schaeffer, DDS, MPH, Robert R. White, DMD, and Richard E. Walton, DMD, MSAbstractThe purpose was to aid in Determining termination ofinstrumentation and Obturation . A meta-analysis wasconducted as to success/failure of different obturationlengths. Inclusion criteria were (a) minimum follow-upof 2 yr, (b) data on Obturation length , (c) definition ofsuccess/failure, (d) available data on success/failure, (e)radiographic evaluation. Correlations were made as tosuccess/failure as related to length of Obturation fromthe apex. When comparing group A (obturated 0 1 mmfrom apex) versus group C (obturated past apex) usingthe DerSimonian and Laird estimates, group A showeda marginally better (p ) success rate than groupC by Group A had better success than group B(obturated 1 mm short); the difference was insignif-icant. The results were similar after controlling for studyquality using a single random effects regression conclusion, the meta-analysis indicated that a bettersuccess rate is achieved when treatment includes ob-turation short of the the Division of Endodontics, Director of EndodonticPrograms and Advanced Graduate Endodontics, HarvardSchool of Dental Medicine, Boston, MA and the University ofIowa College of Dentistry, Iowa City, request for reprints to Michelle A.

2 Schaeffer,DDS, MPH, 1450 28th St., West Des Moines, IA 50266;E-mail address: 2005 by the American Association ofEndodontistsThere has been disagreement where to terminate instrumentation and Obturation (1).Kuttler (2) believed termination should be to the apical constriction, when the apicalconstriction exists. Seltzer et al. (3) found that the reaction to tissues were milder wheninstrumenting short of the apex as compared to instrumenting beyond the apex. In asubsequent study, Seltzer et al. (4) concluded that optimum tissue repair was foundwhen canals were instrumented and filled short of the apex; material that was forcedinto the periapical tissues caused a chronic inflammatory response. Green (5, 6) Weine,(7) Frank (8), and Stein (9) advocated obturating short of the radiographic apex( mm). They based their arguments on Kuttler s microscopic analysis (2) or ontheir own studies. Walton and Torabinejad (10) and Weine (5) also agree with obtu-rating short of the radiographic apex, with the additional consideration that, in thepresence of root and/or bone resorption, preparation and Obturation should be to evenshorter lengths.

3 Alternatively, Schilder (11, 12) advocated debridement and obturationto the radiographic apex, which often results in material being extruded into perira-dicular the varying opinions on where to terminate, a meta-analysis of the literaturemay clarify this issue. Meta-analysis is a statistical procedure that combines the resultsof independent studies that are determined to be combinable (13). Assessment of thevalidity and quality of the independent studies is essential (14). Through a meta-anal-ysis, information is maximized when obtained from the available data; this would not bepossible from any single study. The goals of a meta-analysis include: (a) increasingstatistical power for comparing end-points and subgroups, (b) resolving uncertaintywhen reports disagree, (c) encouraging improvements in the quality of primary re-search, and (d) helping to plan for future research (15).The process of conducting a meta-analysis is similar to other research plans: first,formulate the problem to be addressed; next, collect and analyze the data; and finally,report the results.

4 A detailed research protocol that states the objectives, primaryendpoints for data analysis, the subgroups of interest, and the proposed methods andcriteria for identifying and selecting relevant studies must be documented a priori (16).The purpose of this meta-analysis of literature was to aid in assessing an optimalterminal point for root canal therapy to improve the prognosis. This was accomplishedby analyzing the English language literature on success and failure based on obturationlength. The hypothesis was that obturating materials confined to the canal space wouldcorrelate to a higher success and MethodsUsing the National Library of Medicine computerized bibliographic database MED-LINE, a search from January 1966 through June 2000 was conducted using a combi-nation of the following words: root canal , apical, prognosis, endodontic success,endodontic failure, apical third, endodontic, periapical, and root canal termina-tion. The combination of search words that produced the best results wasroot canal ,apical, and studies resulted from the three search words.

5 The abstractsor complete manuscripts as identified on MEDLINE were analyzed and screened. At thispreliminary phase, the selection criterion was broad. The study had to be on humans (invivo) and had to contain radiographic information on the terminal point of these criteria, 17 of the 60 studies fulfilled the criteria and were evaluated moreclosely. More stringent criteria were then applied. The inclusion criteria included: (a)a minimum follow-up of at least 2 yr; (b) data on termination of Obturation /instrumen-tation; (c) failures of treatment were defined adequately (with a minimum radiographicClinical ResearchJOE Volume 31, Number 4, April 2005 Determining the Optimal Obturation Length271evaluation for failure outlined and defined); (d) data available on suc-cess/failure of root canal therapy in relationship to the Obturation /instrumentation length ; and (e) presence or absence of out of the 17 studies met these criteria (17 21)A2yrrecall ratewas selected based on a study by Bender et al.

6 (22) They pointed out thatthe majority of unsuccessful cases were identifiable within 2 yr of cover the probability that more studies existed on the topic thanwere found on the computer search, the references from these fivearticles were evaluated using the broad criteria stated above. Thirty-eight more studies (covering the years of 1956 2000) were the more stringent eligibility list, seven of these studies met thecriteria. This resulted in a total of 12 studies (17 21, 23 29). Thismeta-analysis considered three categories of Obturation length from theradiographic apex: (a) 0 1 mm (group A), (b) 1 mm but 3mm(group B), (c) obturated past the radiographic apex, including sealer(group C). From the remaining 12 studies, only four studies includeddata that could be placed into the three categories of lengths (23 26)(see Table 1). This gave a total of four studies for final analysis andpooling of data, which included a total of 2178 to the principles and procedures of a meta-analysis(14), the four remaining studies were then scored for quality by twoindependent readers.

7 To asses the quality of the studies used in themeta-analysis, the study protocol and data analysis were evaluated. Thereaders were blinded to the names of the authors and their institutions,names of the journals, sources of funding, and acknowledgments. Thestudies were read in opposite order to avoid any systematic errorsbecause of learning through the reading process. The criteria for qualitywas based on the following: number of teeth in the study, the loss of teethto follow-up, who read the radiographs (student versus trained individ-ual), and if statistical analysis of methods were specified and given, andfinally if the exam of the patient was both clinical and radiographic. Thescores ranged from 0 to 2. The studies with the higher scores wereweighted more when the statistical analyses were performed (see Table2).Statistical analyses were done using the DerSimonian and Laird(30) estimates. After scoring the four studies for quality, the scores wereused in a single random effects regression model (31).

8 The estimateddifference in success rate were compared between groups A and B andbetween groups A and C (see Table 3).After the four studies were scored for quality, the scores were usedin a single random effects regression model to evaluate the relationbetween quality and the magnitude of the difference in success. In thisanalysis, significant heterogeneity was observed (tau squared )among the study results. Heterogeneity may exist, for example, whenstudy populations differ or when statistical methods have of the four studies that were used in the meta-analysisStudyMethodParticipants# of teethTreated byResultsHarty et al,1970 Does not state whoread studyAll patients accepted forRCT on upper andlower incisor andcanine teeth between1954 1963 at theDepartment ofConservative Dentistry,Institute of DentalSurgery (London,England).1025 teethPost-graduatestudents andstaff at theDepartment ofConservativeDentistry,Institute teeth obturated between0 1 mm (acceptable) weremore successful ( )than short ( ) or long( ).

9 Kerekes etal,1979 Interpretation of theradiographs weredoneindependently bytwo patients accepted forRCT and treated byundergraduatestudents at theUniversity of Oslo(Norway) in 1971 andwho participated inregular clinical andradiographic of 647 teeth at theUniversity ofOslo (Norway).In vital teeth, roots that wereshort of the apex 1mmhad a higher success rate(96%) than at the apex) (0 1 mm) (92%). In necroticteeth, roots that were shortof the apex 1 mm had alower success rate (85%)than those at the apex(93%).Matsumotoet al,1987 Does not state whoread loss tofollow-up (85 of223 evaluated).Patients were treated atthe School of Dentistry,AichiGakuin Universityin Nagoya, of 223 teeth wereeval for theminimum 2 3 yearfollow-up examMembers of theendodonticstaff at teeth obturated mm underextended(100%) were moresuccessful than mmunderextended (88%) or0 mm underextended( ) or overextended(40%)Kerekes etal,1978 The interpretation ofthe radiographswere doneindependently bytwo retrospective studieswere done.

10 The firstsurvey evaluated 188root canals treated byundergraduatestudents (US) at the Uof Oslo in 1969 and hadbeen followed for 3 5years. The secondsurvey consisted of 379root canals treated bygeneral dentists (GP).188 teeth done byundergrads at U ofOslo and 379 teethdone by generaldentists (GP) done byUndergraduatestudents at theUniversity ofOslo (Norway)in 1969. 2ndgroup of RCTdone bygeneraldentists (GP) inNorway root canals done by USshort of apex 1 3 mm weremore successful (88%) thanat apex 0 1 mm (84%), thanoverfilled (79%) than shortof apex 3 mm (79%).Those root canals done byGP at apex (0 1 mm) weremore successful (73%) thanshort of apex 1 3 mm (71%)than short of apex 3mm(54%) than overfilled (44%).Clinical Research272 Schaeffer et Volume 31, Number 4, April 2005 RsultsIn terms of percentage rates of success, the meta-analysis showedthat Obturation 0 to 1 mm short of the apex (group A) was better thanobturation 1 to 3 mm short of the apex (group B); both were superiorto Obturation beyond the apex (group C).