Canal wall planning by engine-driven nickel-titanium instruments, compared with stainless-steel hand instrumentation.

Twenty-two mesial roots of extracted human mandibular molars were divided into two groups based on root curvature and length. The mesiolingual canals were instrumented using either Flexofiles in a step-back anticurvature filing method, or they were instrumented with engine-driven 0.02 taper nickel-titanium files. Ground sections were prepared at 1-, 2.5-, and 5-mm levels from the working length. The mesiobuccal canal was used as an uninstrumented control for predentin character. Digitizing software was used to calculate the instrumented portion as a percentage of the total canal perimeter. The results indicated no significant difference in overall canal wall planning between the two groups and no significant difference at each of the three levels.