Numerical and experimental analysis in endodontic rotary files under cyclic fatigue or torsional stress

This study aims to analyze the mechanical behavior of two types of rotating endodontic instruments with different crosssections, both made by Coltene (Hyflex CM 40.04 of NiTi alloy and Hyflex EDM 40.04 of Heat-treated NiTi alloy), undercyclic fatigue or torsion. The study of the mechanical behavior combined the traditional approach, consisting in experimen-tal investigations, with a finite element analysis under similar bending and torque conditions. The non-linear superelasticbehavior of the NiTi alloy for fatigue and torsion, derived from experimental tests based on models in the scientific literature,was applied to the numerical analysis. A thermographic investigation was associated with the usual mechanical experimen-tal tests to assess the dependence of the temperature on the deformations undergone by the endodontic files under stress,especially near the breakage. The comparison between experimental and numerical results was in good agreement for bothtypes of files analyzed.