Micro-CT evaluation of dentinal microcrack formation in mesiobuccal canals of maxillary molars following instrumentation with heat-treated rotary and reciprocating systems

Background The goal of root canal preparation is to eliminate microorganisms and debris from the root canal system, while providing space for the placement of root filling materials. However, the process can lead to the formation of dentin microcracks, increasing the risk of vertical root fractures. This study used micro-CT to evaluate the formation of dentinal microcracks following instrumentation with One Curve, EdgeOne Fire, and VDW.ROTATE systems. Methods Thirty-three extracted maxillary molars with non-calcified Vertucci type 4 second mesiobuccal canals were included. After pre-instrumentation micro-CT scans, a single endodontist prepared the canals with three aforementioned rotary systems. Post-instrumentation scans were conducted and axial sections from both the pre- and post-preparation scans were analyzed by two blinded observers to identify newly formed microcracks. Cohen’s Kappa coefficient assessed interobserver agreement and dentinal microcracks were evaluated using ANOVA, ANCOVA, Kruskal-Wallis, and McNemar’s test ( P  < 0.05). Results All three rotary systems led to significant increases in dentinal microcracks post-instrumentation. While the VDW.ROTATE group showed a slightly higher percentage of cracked sections (72%), statistical analysis showed no significant difference between the groups ( P  = 0.35). Conclusion Preparation of maxillary molar root canals using different rotary systems resulted in the formation of dentin microcracks, with no significant correlation to the specific system used.