Torque and force induced by ProTaper universal and ProTaper next during shaping of large and small root canals in extracted teeth.

INTRODUCTION: The purpose of this study was to compare peak torque and force between ProTaper Universal (PTU) and ProTaper Next (PTN) instruments during the preparation of large and small root canals in extracted teeth. METHODS: Twelve maxillary incisors and each independent canal of 6 mesial roots of mandibular molars were randomly assigned to be prepared with a new set of either PTU or PTN instruments after a glide path was achieved. A total of 12 new sets of each instrument system were used. The tests were run in a standardized fashion in a torque-testing platform. Peak torques (Ncm) and force (N) were registered; analysis of variance and Tukey post hoc tests were then applied. RESULTS: Among instruments in the same sequence, no significant differences in peak torque and force were found among PTN instruments when shaping small or large root canals, but some PTU instruments showed statistically lower peak torque and force (P \u3c .01) than others for both types of canals. Whereas PTU instruments showed significant differences in peak torque and force (P \u3c .05) between large and small root canals, PTN instruments showed significantly lower force (P \u3c .04) in large canals, but peak torque was not significantly different for upper central incisors or mesial mandibular root canals. CONCLUSIONS: Under the conditions of this study, instruments in ProTaper Next set showed greater regularity in peak torque for small and large canals than ProTaper Universal instruments