Comparison of the Mechanical Properties of Rotary Instruments Made of Conventional Nickel-Titanium Wire, M-Wire, or Nickel-Titanium Alloy in R-Phase

Abstract Introduction This study compared the mechanical properties of endodontic instruments made of conventional nickel-titanium (NiTi) wire (K3 and Revo-S SU), M-Wire (ProFile Vortex), or NiTi alloy in R-phase (K3 XF). Methods The test instruments were subjected to mechanical tests to evaluate resistance to bending (flexibility), cyclic fatigue, and torsional load in clockwise rotation. Data were statistically evaluated by the analysis of variance test and the Student-Newman-Keuls test for multiple comparisons. Results In the bending resistance test, flexibility decreased in the following order: K3 XF > Revo-S SU > ProFile Vortex > K3 . The ranking in the fatigue resistance test was the following: K3 XF > K3 > ProFile Vortex > Revo-S SU. In the torsional assay, the angular deflection at failure decreased in the following order: K3 XF > Revo-S SU > K3 > ProFile Vortex. For the maximum torque values, the ranking was K3 > K3 XF > ProFile Vortex > Revo-S SU. Conclusions The results showed that the K3 XF instrument, which is made of NiTi alloy in R-phase, had the overall best performance in terms of flexibility, angular deflection at failure, and cyclic fatigue resistance. In addition to the alloy from which the instrument is manufactured, the design and dimensions are important determinants of the mechanical performance of endodontic instruments.