Abstract: [Abstract] Objective The aim of this study was to evaluate the amount of apically extruded debris and efficiency during curved root canal preparation using ProTaper Gold(PTG) and ProTaper for hand use(PTH). Methods The canals were divided into 2 groups according to the curvature of canals(＜15°, 20-35°). Then each group was divided into 2 subgroups according to the Ni-Ti instruments(PTG, PTH)(n=15). The apically extruded debris of each group was collected into pre-weighed Eppendorf tubes. Then the tubes were stored in an incubator at 68 °C for 5 days and weighed using an electronic balance. Meanwhile, the time of root canal preparation was also recorded. Results No significant differences of the amount of apical debris were found among two Ni-Ti instruments when preparing curved root canals (P > 0.05). The time of root canal preparation with PTG showed significantly shorter than PTH (P < 0.05). Conclusions Two Ni-Ti instruments caused apical debris extrusion. And Root canal preparation with PTG was faster than PTH.

Key words: Keywords: Ni-Ti instruments, Curvature of root canal, Extruded debris, Efficiency of root canal preparation