Apical and cervical displacement produced by hand and engine-driven stainless steel and nickel-titanium instruments in simulated curved root canal

Aim: The purpose of this study was evaluate the occurrence of displacement on the apical and cervical thirds of artificial curved root canals with 30° of curvature,comparing the use of stainless steel hand and oscillatory files with nickel-titanium(NI-TI) hand, rotary and oscillatory files.
Methods: Seventy artificial curved root canals were divided into 7 groups (n=10). All canals were prepared with sizes 15 to 40 instruments at the working length according to a crown-down technique.The amount of material removed in the curved portion of the simulated canals at 2 mm level outside and 11 mm inside was measured. Data were analyzed statistically by ANOVA and Tukey’s test (p<0.05).
Results: There was statistically significant differences (p<0.05) at 2 mm level between NI-TI and steel stainless groups. At 11 mm, statistically significant differences (p<0.05) were observed between the groups that used rotary systems (5 and 6) and the remaining groups. The most centered preparations were those belonging to groups 5 and 6, at both levels. Root canal preparation with NI-TI files yielded better results than the stainless steel files especially when mechanically activated.