Differences in torsional performance of single- and multiple-instrument rotary systems for glide path preparation.

A new rotary instrument has been developed to simplify the glide path preparation in root canals before shaping procedures. The purpose of this study was to compare the peak torque and force induced by nickel-titanium PathFile multiple-instrument system and the recently developed M-Wire ProGlider single instrument during glide path preparation of mesial root canals in extracted mandibular molars. Each independent canal of eight mesial roots of mandibular molars was randomly assigned to achieve a reproducible glide path with a new set of either PathFile #1 and #2 or ProGlider after negotiation with a 10 K-file. Tests were run in a standardized fashion using a torque-testing platform. Peak torque (N cm) and force (N) were registered and analysis of variance and Tukey post-hoc tests were applied. Preliminary data for stationary torque at failure were also obtained and compared with peak torque for each instrument. PathFile #1 and #2 instruments showed statistically lower peak torque (p = 0.001) and peak force (p = 0.008) than ProGlider. Torque at failure according to ADA No. 28/ISO 36030-1 was not significantly different from peak torque during glide path preparation for ProGlider instruments while it was significantly higher for PathFile #1 and #2 (p < 0.001). Under the conditions of this study, PathFile instruments developed significant lower peak torque and force during glide path preparation compared to ProGlider, which is possibly subjected to a greater contact with the canal walls due to the increase in its flute diameter at middle and coronal levels.