Comparative Evaluation of Dentinal Microcrack Formation before and after Root Canal Preparation Using Rotary, Reciprocating, and Adaptive Instruments at Different Working Lengths-A Micro- computed Tomographic Study

Introduction: This study aimed to compare root dentinal microcrack formation after root canal shaping using rotary, reciprocating, and adaptive instruments at different working lengths using micro-computed tomographic imaging. Methods: One hundred eighty extracted mature mandibular molar mesial roots with 2 separate canals were selected. The mesial roots were resected at the cementoenamel junction and randomly divided into 4 groups (n = 45) based on the nickel-titanium file system used: ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper Gold (Dentsply Maillefer), Twisted File Adaptive (SybronEndo, Orange, CA), and Reciproc Blue (VDW, Munich, Germany). Each of the 4 groups were then subdivided into 3 groups (n = 15) depending on the working length used for root canal preparation (ie, instrumentation 1 mm short, flush, and 1 mm beyond the major apical foramen). The roots were imaged with micro-computed tomographic scanning before and after root canal preparation. The cross-sectional images generated were screened to detect the presence of new microcracks. Results: The ProTaper Universal system significantly increased the number of postinstrumentation microcracks at all working lengths (P < .05). No significant increase (P . .05) in postinstrumentation microcracks was observed in the ProTaper Gold, Twisted File Adaptive, or Reciproc Blue groups. Conclusions: Rotary instrumentation induced a higher number of dentinal microcracks compared with reciprocating and adaptive instruments. Instrumentation at different working lengths did not significantly influence the formation of dentinal microcracks. (J Endod 2021;47:1314-1320.)