Temperature-Dependent Effects on Cyclic Fatigue Resistance in Three Reciprocating Endodontic Systems: An In Vitro Study

This study aimed to analyze the effect of 1% sodium hypochlorite (NaOCl) solution at different temperatures on endodontic file resistance to cyclic fatigue. A total of 90 files, Reciproc NiTi M-Wire^® (REC) (n = 30), WaveOne Gold^® (WOG) (n = 30), and Reciproc Blue^® (RB) (n = 30) were activated under constant irrigation with 1% NaOCl at 5, 37, and 60 °C in a stainless-steel artificial canal (curvature angle = 60°; radius = 5 mm). The time to the fracture and the maximum and minimum load were recorded for each instrument, and data were subjected to statistical analysis. A higher number of cycles to fracture at 5 °C was observed between WOG and RB compared to the REC system (<i>p</i> < 0.05). The RB files were more resistant to cyclic fatigue fracture at 60 °C than WOG and REC (<i>p</i> < 0.05). No statistically significant differences were found between the mean values of the three file types used at 37 °C. The high temperature of NaOCl significantly affects the lifespan of endodontic files, making them more prone to fractures due to cyclic fatigue. The files manufactured with heat treatment showed a longer life than M-wire reciproc files.