A comparative evaluation of cyclic fatigue resistance for different endodontic NiTi rotary files: An in-vitro study.

AIM: This in-vitro study evaluated and compared the flexural fatigue resistance for Hero Shapers, Hyflex CM, One Shape, Profile Vortex and Protaper Next rotary NiTi files.

METHOD AND MATERIALS: Total 25 rotary NiTi files allocated to each experimental group were tested in a simulated constructed apparatus with an angle of curvature 60° & radius of curvature 5 mm. Each experimental file was coated with EDTA gel and was placed in endodomotor handpiece with rubber stopper at support steel cylinder and its end between two shaping steel cylinders on the simulated apparatus. File was then rotated at 400 rpm, 2.5 N/cm torque and simultaneously digital stop watch was started. Time taken (in seconds) until the file got fractured was recorded.

RESULTS: Time taken to fracture ranged from 7 to 58 s in different groups. Analysis of variance show a statistically significant intergroup difference (p < 0.001). Tukey HSD test showed the significant differences. The Weibull modulus values ranged from 7.31 to 24.19.

CONCLUSION: Cyclic flexural fatigue resistance was observed highest for Grp IV (Hyflex CM) and lowest for Grp I (Hero Shapers).

CLINICAL SIGNIFICANCE: Hyflex CM rotary NiTi files can be used in curved root canals as they had superior resistance and long survival time which will be helpful in eliminating one of the reasons for file fracture (due to cyclic flexural fatigue) during the root canal treatment clinically where root canal possesses a sharp bend or curve.