Y. Gao, DENTSPLY Tulsa Dental Specialties, Tulsa, OK
Endodontic rotary files made of Nickel-Titanium shape memory alloys have become the most widely used engine-driven instruments for root canal shaping and cleaning. Intra-canal file separation due to cyclic fatigue within curved canals has remained as a major concern in the practice of endodontics even though there has been a considerable improvement in file design, manufacturing method, and preparation techniques. The purpose of this work is to understand the microstructural change of Nickel Titanium materials throughout the cyclic fatigue process in a simulated canal with controlled curvature. In this study, microstructural evolution of Nickel-Titanium wires (regular superelastic wire and M-wire that are used for endodontic rotary files manufactured by Dentsply Tulsa Dental Specialties) has been investigated by different characterization techniques and testing methods, including Differential Scanning Calorimetry (DSC), micro-hardness, bending test, and Transmission Electron Microscope (TEM) at four different stages (as-received state, 30%, 60%, and 90% of average fatigue life). The average fatigue life was calculated from 30 wire samples that were subjected to a strain-controlled (3% ~ 5%) rotating bend fatigue test at room temperature and rotational speed of 300 rpm.
Summary: In this study, microstructural evolution of Nickel-Titanium wires (regular superelastic wire and M-wire that are used for endodontic rotary files manufactured by Dentsply Tulsa Dental Specialties) has been investigated by different characterization techniques and testing methods.
