Evaluation of Cyclic Fatigue of Hyflex CM and M3-Pro Gold NiTi Rotary Endodontic Instruments in Artificial Curved Canals

Purpose: This study evaluated cyclic fatigue resistance of HyFlex CM and M3-Pro Gold NiTi rotary files.
Materials and methods: Two groups of endodontic rotary NiTi files were chosen (n = 20) based on file type (HyFlex CM and M3-Pro Gold). Files with tip size 25 and 4% taper were used in a customized model with a curvature angle of 60° and a 5 mm radius of curvature. Instruments failure were discovered by inspection via a clear glass and aided by a computer program. Total number of cycles to failure (NCF) has been calculated and the length of the fractured part (FL) was measured. The fracture surfaces of the split segments have been examined using SEM.
Results: Shapiro-Wilk test and Kolmogorov-Smirnov test were used to determine normality, and they indicated that the data came from normal data that was distributed in both groups. As a result, a comparison was made between different groups by independent-t-test and significance level was set at p ≤0.05. Comparison between HyFlex CM and M3-Pro Gold regarding fractured segment length (FL) revealed that, there was insignificant difference between HyFlex CM (4.02 ± 0.63) and M3-Pro Gold (3.98 ± 0.68) with (0.04) difference between them as P=0.84. Regarding NCF, HyFlex CM (2932.82 ± 646.35) was significantly higher than M3-Pro Gold (1422.1 ± 510.67) with (1511) difference between them as P=0.0001
Conclusion: HyFlex CM files showed higher cyclic fatigue resistance when compared to M3-Pro Gold.
Keywords: HyFlex CM, M3-Pro Gold, cyclic fatigue resistance