Evaluation Of Shaping Characteristics Between Progressive And Constant Tapered Files

This study used micro-computed tomography to evaluate the shaping characteristics of progressive and constant tapered rotary file systems in terms of volume changes, canal transportation, and centering ratio. Ten mandibular molars with two separate mesial canals (curvature: 10°- 30°) were randomly assigned to two groups (n = 10 per group): progressive or constant. Canals were scanned pre- and post-instrumentation using micro-computed tomography (SkyScan 1174v2; Bruker-microCT, Kontich, Belgium) with a voxel size of 17.85 µm. Coregistered images were analyzed for three-dimensional morphometric changes, including absolute and percentage volume changes, canal transportation, and centering ability. Independent samples t-tests were used for statistical analysis (p < 0.05). The progressive group showed significantly greater absolute and percentage volume changes than the constant group (p < 0.05). Canal transportation was also significantly higher in the coronal third for the progressive system (p < 0.05). No significant differences were found in the centering ratio or transportation at the middle and apical thirds (p > 0.05). The progressive system resulted in more remarkable volume changes and coronal transportation than the constant system. Both systems maintained centering ability and showed minimal transportation in the middle and apical thirds. These findings suggest that both systems can effectively instrument moderately curved mesial canals of mandibular molars without significant errors, except that the progressive system may lead to greater coronal transportation.