Technological advancements achieved in recent years have enabled major progress in endodontic therapy. The introduction of nickel-titanium alloys and the automation of endodontic instrumentation was a huge leap forward, breaking the nearly 200-year paradigm of purely manual instrumentation. Nevertheless, the practice of root canal instrumentation has remained in a constant state of flux, whether due to development of new instruments with different designs or to further advances in Ni-Ti alloy treatments, continuously seeking to obtain more resilient and flexible systems. The objective of this book is to present and discuss the characteristics of the Ni-Ti alloys used in the major instrumentation systems available in the market, as well as the influence of the metallurgical and mechanical properties of Ni-Ti instruments and the movements that drive them, to enable more accurate and predictable planning of root canal preparation.