Monotonic torsional resistance and fatigue resistance of novel SCOPE RS instruments.

To evaluate monotonic torsional resistance and fatigue resistance of novel SCOPE RS instruments and to compare ROTATE, Hyflex CM, OneCurve, and ProTaper Next instruments as a counterpart. The instrument groups were as follows: SCOPE RS; ROTATE; HyflexCM; OneCurve; ProTaperNext. The cyclic fatigue resistance of unused instruments was tested at both room and body temperatures (n = 10). The time to fracture, the mean number of cycles until failure, and the length of the fractured fragments were analyzed. The monotonic torsional resistance of new instruments was measured in accordingly American National Standards/American Dental Association No. 28 and International Organization for Standardization 3630-1:2008 specifications (n = 10). The maximum torque and angular deflection at break were recorded. The fractographic examination was performed by scanning electron microscope. Energy-dispersive X-ray spectroscopy was used to investigate the microstructure of NiTi instruments. One-way ANOVA with Games-Howell Post Hoc multiple comparisons tests were used (p < .05). The ROTATE had superior cyclic fatigue resistance than other groups in both temperature conditions (p < .01). However, it exhibited lower torsional resistance than SCOPE RS (p < .01). SCOPE RS had superior torsional resistance than other groups (p < .01). Micrographs revealed typical features of fatigue behaviors in all groups. Weight percentages of the Ni and Ti revealed similarity for all instruments. The novel SCOPE RS instruments presented superior monotonic torsional resistance but failed to show any improvement in the cyclic fatigue resistance compared with its counterparts, ROTATE, HyflexCM, and OneCurve.