Comparative evaluation of cyclic and torsional fatigue resistance of three thermally treated reciprocating NiTi systems.

Aims: The aim of this study was to evaluate the cyclic and torsional fatigue resistance of three thermally treated reciprocating instruments. Materials and Methods: A total of 60 reciprocating instruments were used to perform the cyclic and torsional fatigue tests: Reciproc Blue 25.08 (RB 25.08), CC One Blue File (CCO 25.08) and WaveOne Gold 25.07 (WOG 25.07) (n=20). The cyclic fatigue test was performed using an artificial stainless-steel canal with 60º angle of curvature and a 5-mm radius of curvature. The time to failure (TF) and number of cycles to failure (NCF) were evaluated. The torsional test was performed following the ISO 3630-1. Three millimeters of the instrument tip were fastened to a small load cell and the maximum torsional strength and angular deflection were recorded. The fractured surface of each instrument was assessed by scanning electron microscopy (SEM). The normality of the data distribution was analyzed using Shapiro-Wilk test, followed by ANOVA and Tukey’s test for Multiple comparisons at a significance level of 5%. Results: The cyclic fatigue tests demonstrated that RB 25.08 showed the highest TF and NCF values among the groups (P < 0.05). WOG 25.07 exhibited the lowest TF and NCF values (P > 0.05). Regarding the torsional test, CCO 25.08 had the highest torque among the groups (P < 0.05). Additionally, RB 25.08 exhibited the highest angular deflection values, followed by CCO 25.08 (P < 0.05). Conclusions: RB 25.08 demonstrated the highest TF, NCF and angular deflection among the tested instruments, while CCO 25.08 presented the highest torque to fracture.