Comparison of cyclic fatigue resistance of three different rotary NiTi systems – An in-vitro study

Abstract

Background: Nickel–titanium (NiTi) alloys created a revolution in the instrumentation of endodontics. However, they undergo unexpected fracture during the instrumentation of curved root canals due to cyclic fatigue. Hence, innumerable scientific and manufacturing researches are focused on fabricating NiTi rotary instruments with greater cutting efficiency and increased fatigue resistance. Aim: The aim of this study is to compare and evaluate the cyclic fatigue resistance of three different NiTi rotary file systems: Hyflex CM, Endostar E3, and Mani Silk. Materials and Methods: In this in-vitro study, 30 Hyflex CM (25/0.06), 30 Mani Silk (25/0.06), and 30 Endostar E3 (25/0.06) instruments were included. The static cyclic fatigue test was performed using a custom-made jig. The artificial canal was made of stainless-steel jig with an inner diameter of 1.5 mm, 45° angle of curvature, and radii of curvature of 5 mm. All the instruments were rotated according to the manufacturer's recommendations until failure occurred. The time taken to failure was recorded in seconds for each group using a digital chronometer. The data were analyzed statistically using the one-way analysis of variance, Post hoc test of Bonferroni was performed to identify pair-wise significance through SPSS 21.0 software (SPSS Inc, Chicago, IL, USA). The statistical significance was set at 5%. Results: Hyflex CM had the statistically highest fatigue resistance followed by Mani Silk and Endostar E3 (P < 0.05). Conclusion: Within the limitations of the present in vitro study, it was found that cyclic fatigue resistance of Hyflex CM files was higher than the cyclic fatigue resistance of Mani Silk and Endostar E3 files.