An Update on Nickel-Titanium Rotary Instruments in Endodontics: Mechanical Characteristics, Testing and Future Perspective-An Overview

Since the introduction of Nickel-Titanium alloy as the material of choice for the manufacturing of endodontic rotary instruments, the success rate of the root canal therapies has been significantly increased. This success mainly arises from the properties of the Nickel-Titanium alloy: the biocompatibility, the superelasticity and the shape memory effect. Those characteristics have led to a reduction in time of endodontic treatments, a simplification of instrumentation procedures and an increase of predictability and effectiveness of endodontic treatments. Nevertheless, the intracanal separation of Nickel-Titanium rotary instruments is still a major concern of endodontists, with a consequent possible reduction in the outcome rate. As thoroughly demonstrated, the two main causes of intracanal separation of endodontic instruments are the cyclic fatigue and the torsional loads. As results, in order to reduce the percentage of intracanal separation research and manufacturers have been focused on the parameters that directly or indirectly influence mechanical properties of endodontic rotary instruments. This review describes the current state of the art regarding the Nickel-Titanium alloy in endodontics, the mechanical behavior of endodontic rotary instruments and the relative stresses acting on them during intracanal instrumentation, highlighting the limitation of the current literature.

Automated summary

The success of root canal therapies has been significantly increased since the introduction of Nickel-Titanium alloy as the material for endodontic rotary instruments. The properties of Nickel-Titanium alloy, including biocompatibility, superelasticity, and shape memory effect, have led to a reduction in treatment time and increased predictability and effectiveness of endodontic treatments. However, intracanal separation of Nickel-Titanium rotary instruments remains a major concern for endodontists, with cyclic fatigue and torsional loads being the main causes. Researchers and manufacturers are focusing on parameters that influence the mechanical properties of endodontic rotary instruments in order to reduce the occurrence of intracanal separation.