Dentinal Microcrack Formation during Root Canal Preparations by Different NiTi Rotary Instruments and the Self-Adjusting File

Introduction: The purpose of this study was to compare dentinal microcrack formation while using hand files (HFs), 4 brands of nickel-titanium (NiTi) rotary files and the self-adjusting file. Methods: One hundred forty mandibular first molars were selected: 20 teeth were left unprepared and served as control, and the remaining 120 teeth were divided into 6 groups. HFs, HERO Shaper (HS; Micro-Mega, Besancon, France), Revo-S (RS, Micro-Mega), Twisted File (TF; SybronEndo, Orange, CA), ProTaper (PT, Dentsply Maillefer), and SAFs were used to prepare the 2 mesial canals. Roots were then sectioned 3, 6, and 9 mm from the apex, and the cut surface was observed under a microscope and checked for the presence of dentinal microcracks. Results: The control, HF, and SAF groups did not show any microcracks. In roots prepared with the HS, RS, TF, and PT, dentinal microcracks were observed in 60%, 25%, 44%, and 30% of teeth, respectively. There was a significant difference between the control/HF/SAF group and the 4 NiTi rotary instrument groups (P < .0001). However, no significant difference was found among the 4 NiTi rotary instruments (P > .005). Conclusions: All rotary files created microcracks in the root dentin, whereas the SAF file and hand instrumentation presented with satisfactory results with no dentinal microcracks. (J Endod 2012;38:232-235)