An overview of the mechanical properties of nickeltitanium endodontic instruments

Differences in mechanical properties between endodontic instruments might be related to the chemical composition, phase constitution, or fabrication process of nickel–titanium (NiTi) endodontic instruments. An awareness and knowledge of the mechanical properties of NiTi endodontic files and their association with the metallurgical properties is useful for clinicians to understand the behavior of NiTi instruments in root canals and help them to make decisions regarding which instruments are appropriate for root canal therapy under certain clinical conditions. This review article summarizes the mechanical properties of NiTi endodontic instruments including the flexibility, torsional resistance, flexural resistance, and cyclic fatigue of the conventional superelastic NiTi instruments and the most recently developed novel NiTi instruments with martensite and R-phase. The influence of the metallurgical properties and the thermomechanical processing on the mechanical properties are discussed.