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

Introduction: The 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. Methods: In 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. Results: The 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). Conclusions: After 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.