Cyclic Fatigue Resistance of One Curve, 2Shape, ProFile Vortex, Vortex Blue, and RaCe Nickel-Titanium Rotary Instruments in Single and Double Curvature Canals

Introduction: The aim of this study was to evaluate and compare the resistance to cyclic fatigue of the new One Curve (OC) instrument in double (S-shaped) and single curvature canals compared with other nickel-titanium rotary instruments. Methods: Size 25/.06 of OC, 2Shape (75), Vortex Blue (VB), ProFile Vortex (PV), and RaCe (RC) instruments were tested inside artificial canals with a single curvature (60 degrees curvature, 5 mm radius) and double curvature (corona) curve, 60 degrees curvature, 5 mm radius; and apical curve, 70 degrees curvature and 2 mm radius) while immersed in saline at 37 degrees C +/- 1 degrees C. The number of cycles to failure (NCF) was calculated, and the fracture surface was examined by using a scanning electron microscope. The data of NCF and fragment length were analyzed by using one-way analysis of variance and Tukey post hoc tests. The t test was performed between the data of fragment length in different curvatures. The level of significance was set at P < .05. Results: The VB instrument had a significantly higher NCF compared with the other instruments in double (S-shaped) and single curvature canals (P < .05). There was no significant difference between OC and TS in the NCF in single, apical, and coronal double curvature canals (P > .05). The lowest NCF values were recorded for RC instrument in all curvatures (P < .05). Conclusions: The fatigue resistance of VB was greater than that of other instruments. OC and TS instruments displayed superior cyclic fatigue resistance than PV and RC instruments.