Comportamento termomecânico e fadiga de limas endodônticas de liga com memória de forma Ni-Ti: um estudo em flexão alternada usando analisador dinâmico mecânico (DMA).

Abstract

Endodontic therapy performed on curved root canals with stainless steel files can cause many iatrogenic accidents, resulting in problems such punctures the canal. In an attempt to overcome the limitations of the less flexible instruments, the alloy with shape memory and NiTi (Nickel-Titanium) for manufacturing endodontic instruments were developed. The use of the NiTi instruments modified methods of instrumentation of the root canal system, making them safer and faster. However, there is still little information on the thermomechanical behavior of more advanced instruments. In this context, the present work is done the thermal and mechanical characterization of three endodontic commercial LMF NiTi files: Protaper Next X2, Reciproc R25 and WaveOne Primmary were performed. For thermal characterization were performed differential scanning calorimetry (DSC) tests and electric resistance as a function of temperature (RET) for determining phase transformation temperatures of files, while the mechanical characterization consisted of static bending tests and dynamic regime (5 Hz frequency) at different temperatures and maximum deflections using a Dynamic Mechanical Analyzer (DMA) and finalizes with post fracture analysis with differential scanning calorimetry (DSC) and fractured surface analysis with an Electron Microscope. The results obtained with the three files showed that endodontic files are in phase known as Phase R, the quasi static tests revealed a strong dependence of the Required Force and the Temperature, the cyclic tests in alternating bending to impose deflections in the Range from ± 0.5 mm to ± 2.0 mm, the Reciproc R25 showed longer cycle life than the others, and with the test temperature rise from 35 °C to 45 °C, it was found that the force to impose the deflections were higher and the fatigue life of the limes reduced considerably.