Cyclic fatigue resistance and energy dispersive X-ray spectroscopy analysis of novel heat-treated nickel-titanium instruments at body temperature

The aim of this study was to evaluate the cyclic fatigue resistance of Dia-X, WaveOne Gold and One Curve files in a water bath at intracanal temperature (35 degrees C). Thirty-nine instruments Dia-X, WaveOne Gold, and One Curve systems (n= 13) were tested in an artificial canal with a curvature angle of 60 degrees and a radius of 3 mm. A water bath setup at a temperature of 35 degrees C was used to simulate the intracanal temperature and time to fracture (TTF) as seconds was recorded. The mean data were analyzed statistically using one-way ANOVA, and post hoc Tukey test (p= .05). The fractured surface of the instruments was examined with scanning electron microscopy (SEM) and chemical composition of the instruments were investigated with energy dispersive X-ray spectroscopy (EDS). Statistically significant differences were detected in TTF values of all the systems as follows: One Curve > WaveOne Gold > Dia-X (p < .05). One Curve instruments demonstrated the highest TTF values in all the tested instruments. The EDS microanalysis revealed similar NiTi composition of on the surface of One Curve, WaveOne Gold, and Dia-X instruments. The novel manufacturing process, including C-wire heat treatment and the variable cross-section of the One Curve files, could be the main factors affecting the fatigue life of the instruments.