In Vitro Comparative Study of the Influence of Instrument Taper on the Fracture Resistance of Endodontically Treated Teeth: An Integrative Approach–based Analysis

Abstract

IntroductionThe objective of this study was to examine the influence of instrument taper on the fracture resistance of endodontically treated roots under in vitro experimental conditions. MethodsIn total, 58 maxillary canines complying with the inclusion criteria were sectioned at approximately 13 mm from the apex. The roots were standardized with respect to the buccolingual-mesiodistal diameter and weight before being randomly distributed into 3 experimental groups (n = 14) and 1 control group (n = 16). The roots in group 1 were instrumented with hand files up to file 40/.02 and groups 2 and 3 with Mtwo (VDW, Munich, Germany) rotary files up to files 40/.04 and 40/.06, respectively. After mechanical preparation, the roots were obturated with gutta-percha and sealer. Roots in group 4 acted as uninstrumented controls. A vertical load was applied to each specimen using a universal testing machine until the roots fractured. Data were statistically analyzed by introducing an innovative approach integrating 1-way analysis of variance, confirmatory factor analysis, and regression analysis. ResultsThe mean fracture load was 357.47 ± 110.54 N for the control group, 338.86 ± 105.23 N for group 1, 297.74 ± 77.31 N for group 2, and 280.10 ± 68.51 N for group 3. However, only the difference between group 3 and the control group was statistically significant (P < .05). ConclusionsAfter instrumentation using hand files up to file 40/.02 and rotary files up to files 40/.04 and 40/.06, only the last appeared to change the fracture resistance of endodontically treated roots.