Influence of surrounding temperature and angle of file access on cyclic fatigue resistance of two single file nickel-titanium instruments

The purpose of this study was to evaluate the influence of surrounding temperature and angle of file access on cyclic fatigue resistance of F6 SkyTaper (F6ST) and One Curve (OC). 120 new files #25.06 were tested at two insertion angles (0 degrees and 20 degrees) at room (20 degrees C +/- 1 degrees C) and body (35 degrees C +/- 1 degrees C) temperatures in a 16-mm stainless steel artificial canal (60 degrees curvature and 5-mm radius), using a customised device. Cyclic fatigue resistance was expressed as time to fracture (TtF) in seconds. Data were analysed statistically (P < 0.05). All instruments exhibited lower TtF at 35 degrees C (P < 0.05). An access of 20 degrees did not significantly influence the TtF of tested instruments, independently from the temperature. OC exhibited higher TtF of F6ST at 20 degrees C with a 20 degrees inclination (P < 0.05). Under the present conditions, F6ST and OC showed a significant reduction of cyclic fatigue resistance at body temperature. A file inclined insertion did not affect the cyclic fatigue resistance of tested instruments at both temperatures.

Automated summary

The study found that F6 SkyTaper and One Curve demonstrated significantly reduced cyclic fatigue resistance at body temperature, while inclined insertion did not significantly affect the TtF of the tested instruments.