Effect of Different Apical Preparation Sizes on Outcome of Primary Endodontic Treatment: A Randomized Controlled Trial

Introduction: The study was designed as a randomized controlled trial to evaluate the effect of the apical preparation size in relation to the first apical binding file (FABF) on the outcome of primary endodontic treatment in mandibular first molars. Methods: One hundred sixty-seven patients met the inclusion criteria. They were randomly allocated to 5 different endodontic treatment groups (ie, A, B, C, D, and E) in which canals were enlarged to 2, 3, 4, 5, and 6 sizes larger than the FABF, respectively. One hundred twenty-nine patients were evaluated at the 12-month follow-up. The primary outcome measure was the change in periapical radiolucency as assessed by periapical index (PAI) scores. The clinical finding constituted the secondary outcome measure. Results: A statistically significant reduction in PAI scores was observed in all groups (P < .001). The proportion of successfully healed cases increased with an increase in the apical preparation size with 48%, 71.43%, 80%, 84.61%, and 92% successful healing observed in groups A to E, respectively. However, statistical analysis revealed that only group A showed significantly less improvement than other groups (P < .05). No significant difference was observed between the rest of the groups. Regression analysis revealed a significant and positive association between the master apical preparation size and an improvement in PAI scores (beta = 0.037, P = .001). Conclusions: The enlargement of the canal to 3 sizes larger than the FABF is adequate, and further enlargement does not provide any additional benefit during endodontic treatment. (J Endod 2012;38:1309-1315)