Background The purpose of this study was to evaluate the shaping advantage of M-wire NiTi ProTaper NEXT (PTN) compared with a conventional NiTi ProTaper Universal (PTU) file in heavy curvature canal. The shaping ability was measured by the amount of canal cutting and transportation between the PTN and conventional PTU. Methods Root canal shaping by the PTN and conventional PTU was classified into two experimental groups according to the final tip size, ISO #25 or ISO #40. Eighty-four J-shaped root canals (10°, 20°, 30° apical curvature) in resin block were used. Results After adjusting for the level and canal wall side, the mean transportation did not significantly decrease between the PTN and PTU with ISO #25. Significantly less deviation occurred with the PTN and PTU between 10° and 30° using ISO #40. Conclusions The M-Wire NiTi PTN improves file flexibility and enables accurate canal shaping for heavy curvature canals.
