6 - Nickel–titanium products in daily orthodontic practice

Abstract

The aim of this chapter is to present an overview of the clinical use and applications of the nickel-titanium (NiTi) alloys during the major stages of comprehensive orthodontic treatment. The stable and active nickel titanium alloys would seem to fulfill the ideal requirements of an ideal aligning archwire. Superelastic wires have clinical advantages over a flexible work-hardened NiTi wire only if the working point is on the plateau i.e. a narrow plateau starting at a high deflection level, may be clinically not useful. The forces exerted by superelastic NiTi archwires can be increased by removing and retying the same wire. Results from in vitro and in vivo studies evaluating the leveling/alignment phase are presented. The use of a continuous rectangular archwire during this treatment phase i.e. in an unlevelled dental arch, especially the insertion of rectangular austenitic NiTi’s should be avoided. During the main treatment stage, NiTi alloys may be used in form of archwires, open coil springs and closing loops. As a general rule, NiTi may result in decreased torque expression relative to stainless steel, due to its reduced modulus and stiffness. During the last stage of orthodontic treatment, preformed NiTi archwires should not be used, since individual tooth control is difficult, if not impossible, due to their poor formability. Lingual NiTi retainers have been individually constructed using computer-aided design and machining. However, further research is required to provide evidence of their effectiveness.