Effect of nickel-titanium engine-driven instrument rotational speed on root canal morphology.

Thirty-six mesial canals in 18 extracted human mandibular molars were randomly allocated to three experimental groups. Specimens were prepared and evaluated using a modified Bramante technique. Teeth were sectioned at the midroot and apical regions. Canals were prepared with the Lightspeed instruments rotating at 750, 1300, or 2000 rpm. Digitized uninstrumented and instrumented canal images were compared via subtraction software. There was no significant difference (p <0.05) among the three experimental groups in the amount of dentin removed, canal transportation, or the ability of the instrument to remain centered in the canal.