Objective To compare the clinical efficacy of root canal preparation between the techniques of using ProTaper nickel- titanium hand- file and the standard hand stainless steel H file. Methods 120 teeth of 100 cases of pulpitis and periapical periodontitis were randomly divided into two groups, 60 teeth in each. 60 teeth of group 1 were used standard hand stainless steel H file and step- back technique. 60 teeth of group 2 were used ProTaper nickel- titanium hand- file preparation and crown- downward technique. The clinical efficacy was observed for three months after root canal therapy completed. Results After the root canal therapy completed, the clinical efficacy of group 2 was superior to that of group 1（P
