The aim of the present study was to compare the effect of etidronic acid (HEBP), NaOCl, and EDTA solutions and their combinations on cyclic fatigue resistance of NiTi RPC Blue (RPC Blue), HyFlex EDM (HEDM), and WaveOne Gold (WOG) instruments having different metallurgic characteristics at the body temperature (37 °C). 100 WOG, 100 RPC Blue, and 100 HEDM NiTi files were randomly divided into 5 groups and immersed in the following solutions: group 1, distilled water; group 2, 6% NaOCl; group 3, 17% EDTA; group 4, 18% HEBP; group 5, 6% NaOCl and 18% HEBP. Then the instruments were rotated in an artificial canal until fracture occurred and the number of cycles to fracture was calculated. A univariate analysis of variance and post hoc Tukey tests were then performed for comparisons using SPSS 21.0 software with the significance level set at P < .05. In all the conditions, there was no difference between the cyclic fatigue resistance of WOG and RPC Blue files (P > .05). In the intragroup comparison, WOG, RPC Blue, and HEDM files showed significantly low cyclic fatigue resistance in group 5 compared to other groups (P < .05). Among the groups, there was no statistically significant difference in the fracture lengths (P > .05). EDTA, NaOCl and HEBP solutions did not affect the cyclic fatigue resistance of the tested files when used without combination. However, the combination of NaOCl and HEBP solutions significantly reduced the cyclic fatigue resistance of the tested files.
Keywords: Cyclic fatigue resistance; HyFlex EDM; Irrigating solution; Reciproc Blue; WaveOne Gold.