LAUSR

Introduction: The aim of the present study was to evaluate the frequency of dentinal microcracks observed after root canal preparation with ProTaper Universal (PTU; Dentsply Tulsa Dental Specialties, Tulsa, OK), ProTaper Gold (PTG; Dentsply Tulsa Dental Specialties), Self‐Adjusting File (SAF; ReDent Nova, Ra'anana, Israel), and XP‐endo Shaper (XP; FKG Dentaire, La Chaux‐de‐Fonds, Switzerland) instruments using micro–computed tomographic (CT) analysis. Methods: Forty extracted human mandibular premolars having single‐canal and straight root were randomly assigned to 4 experimental groups (n = 10) according to the different nickel‐titanium systems used for root canal preparation: PTU, PTG, SAF, and XP. In the SAF and XP groups, the canals were first prepared with a K‐file until #25 at the working length, and then the SAF or XP files were used. The specimens were scanned using high‐resolution micro–computed tomographic imaging before and after root canal preparation. Afterward, preoperative and postoperative cross‐sectional images of the teeth were screened to identify the presence of dentinal defects. For each group, the number of microcracks was determined as a percentage rate. The McNemar test was used to determine significant differences before and after instrumentation. The level of significance was set at P ≤ .05. Results: The PTU system significantly increased the percentage rate of microcracks compared with preoperative specimens (P < .05). No new dentinal microcracks were observed in the PTG, SAF, or XP groups. Conclusions: Root canal preparations with the PTG, SAF, and XP systems did not induce the formation of new dentinal microcracks on straight root canals of mandibular premolars. HighlightsMicro–computed tomography was used in the present study to evaluate the presence of dentin defects before and after root canal preparation with new nickel‐titanium rotary systems, precluding the need for cutting the specimens.Root canal preparation with ProTaper Gold, SAF, and XP‐endo Shaper systems did not induce the formation of new dentinal microcracks.However, new microcracks were observed only after root canal preparation with the ProTaper Universal rotary system.