A micro-CT comparison of the latest ProTaper Ultimate file system with ProTaper Next file system for apical transportation and centering ability

Aim: The aim of this study was to assess the apical transportation and centering efficacy of ProTaper Ultimate (PTU) and ProTaper Next (PTN) by micro-computed tomography (micro-CT) analysis. Methods: A comparative in vitro study was conducted on excised human mandibular premolars with negligible canal curvature. Fifty single-rooted human mandibular premolars with slight curvature were extracted and decoronated. The teeth were randomly assigned to two groups ( n = 25). Group A received PTU treatment until Finishing 2 (F2) without glide path files, whereas Group B was shaped using PTN up to X2 following the establishment of a glide path. Samples were examined using micro-CT before and following instrumentation. Apical transportation and centering ratios were evaluated at distances of 3, 6, and 9 mm from the apex. The unpaired t -test was employed for statistical analysis. Results: PTU demonstrated significantly diminished apical transportation and enhanced centering ability versus PTN across all evaluated levels ( P < 0.05). Conclusion: PTU exhibited superior shaping accuracy in curved canals, likely attributable to its controlled memory alloy and progressive taper design. These features may enhance procedural safety and clinical predictability in endodontic practices.