Abstract:

  Background and Aim : One of the problems encountered during a root canal preparations is preserving the minimum thickness of the canal walls. This study is aimed to evaluate the effect of final apical file size on residual dentin thickness of apical third of canal.

  Materials and Methods: In this experimental study, the initial images of the mesiobuccal canal of 40 extracted mandibular first molars were provided and measured at the levels of 1, 2.5, 4mm from the apex by CT cone beam. The specimens were divided in to 4 groups and canal preparations were done by RaCe rotary system. Master apical file size was selected based on #25, #30, #35 or #40(taper 0.04) in each group. Then, post preparation images were obtained at the previously mentioned positions. The initial and residual dentin thickness, also the amount of dentin removal were evaluated and analyzed statistically by ANOVA and TUKEY’S post hoc test.

  Results: In intergroup and intragroup evaluation there were no significant differences in the amount of initial and residual dentin thicknesses also in dentin removal at any levels. There was a significant statistical difference in the amount of dentin removal at 1mm level for mesial surface (p=0,026). The least residual dentin thickness were found in mesial surface which at 1,2.5 and 4 mm levels from the apex were 0.43±0.17, 0.52±0.16, 0.57±0.16 mm respectively.

  Conclusion: Based on this study the file size #35 and #40(taper 0.04) with no significant canal transportation can be used as a master apical file in canals with 20-35 degree curvature.