Torsional profiles of new and used revo-s rotary instruments: an in vitro study.

INTRODUCTION This study investigated the torsional properties of new and used Revo-S Shaping Universal (SU) endodontic instruments. METHODS Torsional profiles were established following the American National Standards Institute/American Dental Association Specification No. 28. Unused SU instruments (group 1, control; n = 30) and instruments used in simulated root canals twice (group 2, n = 30) or six times (group 3, n = 30) were tested. Analysis of variance with the Bonferroni/Dunn post hoc test (α = 0.05) was used to analyze the torque and angle of rotation at fracture. RESULTS The maximum torque at fracture did not differ significantly among instruments in group 1 and groups 2 and 3. The angle of rotation at fracture decreased significantly (P < .01) from group 1 to groups 2 and 3. CONCLUSIONS The repeated use of the SU rotary instruments significantly reduced the angle of rotation at fracture but did not reduce the torque at fracture.