Cyclic Fatigue Resistance of Various Nickel-titanium Rotary Endodontic Instruments at Body Temperature: An in Vitro Study

Abstract

Introduction: The purpose of this study was to compare the cyclic fatigue of different types of nickeltitanium rotary files at body temperature. Methods: Four types of rotary instruments with tip size 0.25 were used: HyFlex EDM (OneFile, variable taper, Colten/Whaledent), ProTaper Gold (F2, 0.08 taper, Dentsply), XP-endo Finisher (zero tapers, FKG Dentaire) and 2Shape (TS2, 0.06 taper, Micro-Mega). Ten files for each instrument were tested for cyclic fatigue at body temperature and rotated until fracture occurred in a simulated canal with an angle curvature of 60°, a radius curvature of 5 mm, and a canal width of 1.5 mm. Four groups were formed for all instruments (total number = 40). The number of cycles to fracture and the length of fractured fragment were recorded, and statistical analysis was completed using analysis of variance with significance at a (p-value < 0.05). Results: The cyclic fatigue resistance of the HyFlex EDM OneFile was significantly greater than the other instruments, while that of the 2Shape TS2 was significantly lower (p < 0.05). Conclusion: Within the limitations of this study, the HyFlex EDM OneFile was more resistant to cyclic fatigue than the XP-endo Finisher, ProTaper Gold F2 and 2Shape TS2 files.