Cyclic Fatigue Resistance and Force Generated by OneShape Instruments During Curved Canal Preparation

Objectives: To evaluate the cyclic fatigue resistance and the force generated by OneShape files during preparation of simulated curved canals. Methods: Six OneShape files (the test) and six ProTaper F2 files (the control) were subject to the bending ability test. Another thirty files of each type were used to prepare artificial canals (n=60), which were divided into 3 groups according to respective curvatures of the canals (30°, 60°, and 90°). The numbers of cycles to fatigue (NCF) as well as the positive and negative forces that were generated by files during canal preparation were recorded. The scanning electron microscopy was applied to detect the fracture surfaces. Results: Compared with ProTaper F2 files, the bending loads of OneShape files were significantly lower at deflections of 45°(P P P P P P P P P Conclusions：OneShape files possessed a reliable flexibility and cyclic fatigue resistance. According to the assessments of the forces generated by files, OneShape instruments performed in a more fatigue-resistant way during curved canal preparation, compared with the ProTaper F2 files.