Nickel & Titanium

Ti–Ni alloy, consisting of nickel and titanium in nearly equiatomic proportions, is known for its unique mechanical properties of shape memory and superelasticity. These properties occur in association with thermoelastic martensitic transformation. Superelasticity is a phenomenon at a temperature above the reverse transformation temperature range, associated with stress-induced martensitic and reverse transformations. The alloy exhibits high flexibility owing to its wide recoverable strain range, in which the stress is kept low. Since Ti–Ni alloy shows high corrosion resistance and good biocompatibility, it has been applied in the medical and dental fields. This alloy was successfully introduced to orthodontic treatment as explained in the previous chapter.

In endodontics, the special flexibility of the Ti–Ni alloy is applied in instruments for root canal preparation. The first study on flexible Ti–Ni alloy for endodontic application was reported in 1988 by Walia et al.¹ Since the first Ti–Ni alloy root canal instrument was commercially available in the early 1990s, many manufacturers have developed Ti–Ni alloy root canal instruments with various designs and concepts.