Abstract:Ojective To evaluate the effect of WaveOne nickel-titanium instruments on the treatment of curved root canal and compare WaveOne with stainless steel K-file and ProTaper nickel-titanium instruments. Methods With curvature ranging from 20-40o, 60 isolated premolars with single root canal were chosen and randomly divided into A, B and C three groups with 20 teeth in each. The teeth in the groups A, B and C were shaped by Crown-down technique with WaveOne nickel-titanium rotary instruments, modified step-back technique with stainless steel K -file and Crown -down technique with ProTaper nickel -titanium rotary instruments respectively. All the teeth underwent cone-beam computed tomography (cone-beam CT, CBCT)imaging before and after instrumentation. All the 60 teeth in three groups were treated with cold gutta-percha lateral condensation after root canal preparation. Then the time taking for root canal preparation and root canal filling was recorded. The apical transportation and centering ability at 2, 4 and 6 mm from the apical foramen were analyzed. All these results were statistically analyzed. Results The time taking for root canal preparation in the group A was obviously shorter than that in the groups B and C. The time taking for root canal filling was not significantly different between the group A and the group C (p > 0.05), but was significantly shorter in the group A than in the group B (p < 0.05). There were statistical differences between the group A and the group B in terms of apical transportation and centering ability at 2, 4 and 6 mm from the apical foramen (p < 0.05); however, the differences between the group A and the group C were not significant (p > 0.05). Conclusions WaveOne has advantages of high efficiency, favorbale effect of root canal shaping as compared to stainless steel K-file and ProTaper. So, it can be widely applied to the treatment of curved root canal in clinical practice.