The systems tested in this study were effective in shaping curved canals in extracted teeth.

This study analyzed the abilities of ProTaper and GT Rotary files to shape the curved canals of extracted mandibular molars. Twenty mesial canals with curvatures ranging from 23 to 54 degrees (Weine analysis) were radiographically selected from a group of 58 molars. The specimens, divided into two groups, were instrumented using the two systems according to the manufacturer's guidelines. Using a radiographic platform and a contrast medium, reproducible preinstrumentation and postinstrumentation radiographs were taken. A computer analysis allowed magnification and superimposition of the images to measure the preparation asymmetry and the linear amount of dentin removal at five points along the canals and to detect canal aberrations. Instrument failures, working time, and working length changes were recorded. The dentin removal and the mean asymmetry showed no significant differences between the two systems. Neither aberrations nor significant changes in working length resulted, but two instruments separated in each group. Working time was shorter for ProTaper files (p < 0.05).