The nickel-titanium (Ni-Ti) alloys used in endodontics contain 56% Ni and 44% Ti. The 2 unique features related to clinical dentistry (i.e., shape memory effect and superelasticity) are due to the transition from austenite to martensite in Ni-Ti alloy. When a superelastic Ni-Ti alloy undergoes a low tensile loading, normal elastic behavior occurs. In fact, at higher tensile loads, the elastic s...