The Influence of Brushing Motion on the Cutting Efficiency of Two Heat-Treated Endodontic Files: An In-Vitro Micro Computed Tomography Study

Background: To assess the cutting efficiency of two heat-treated endodontic files with a brushing motion in oval-shaped canals. Methods: A total of 10 intact lower molars with a single oval distal canal were selected and randomly divided into two groups according to the system used for shaping: 2Shape and Hyflex CM. The instrumentation was performed in two parts: a first shaping according to the manufacturer’s instructions and final shaping using 5 brushing motions on the distal, lingual, and buccal walls, avoiding the danger zones. Micro computed tomography (micro-CT) scans before and after the brushing motion were superimposed at all three levels: coronal, middle, and apical. Canal changes in buccolingual (ΔBL) and mesiodistal (ΔMD) dimensions were measured. Data were statistically analyzed by repeated-measures analyses of variance and the student t-test (p < 0.05). Results: For ΔMD, no significant difference emerged between the 2Shape and Hyflex CM in the apical and coronal thirds. However, the cutting efficiency was significantly greater with the 2Shape in the middle third (p < 0.05). Regarding ΔBL, no statistically significant difference was detected between 2Shape and Hyflex CM comparing the anatomical thirds, while 2Shape had a significant higher cutting efficiency considering the total BL diameter (p < 0.05). Conclusions: Under the limits of a vitro study, the shaping procedure with 2Shape and brushing motion was more efficient than the Hyflex CM in the midroot levels in terms of ΔMD, and in total canal space for ΔBL. Both files ensured an effective mechanical preparation.