Microstructural and mechanical characterizations of new Ni-Ti endodontic instruments

Abstract

NiTi alloys have been used for many years in dentistry, especially in endodontology. High flexibility of NiTi alloys, compared to the stainless steel one, has made of NiTi the alloy of choice for the new generation of shaping files. Despite the improvement of file design, endodontic NiTi instruments are not perfect and the risk of fracture during use is still a concern. In recent years, several new thermomechanical processes have been developed to optimize the structure of NiTi alloys, in particular, the development of treatments named "M-wire", "R phase" and "CM wire" technologies. According to the manufacturers, these innovative treatments may improve the flexibility and the fatigue life of endodontic instruments. In the present work, new generations of these files have been characterized using DSC and bending tests and compared to a conventional NiTi file. The new endodontic instruments seem to improve the instrument properties. Hypotheses on the microstructural modifications due to specific thermomechanical treatments are proposed.