Properties of superelastic wires and their relevance to orthodontic treatment

In this study tools were developed to test and compare levelling archwires that the manufacturers claim to have superelastic properties. As the classic spring model and Hook's law cannot be applied, new parameters had to be found. It could be shown that three parameters are necessary to describe a superelastic archwire adequately: the distinctiveness of the pseudo-elastic plateau, the deflection at the beginning of the plateau, and the force level of the plateau. The results showed that many materials either did not show any pseudoelastic properties at all or that the wire parameters were such that they did not give any advantage over conventional work hardened NiTi materials. In many archwires the beginning of the plateau and thereby the desired characteristics began only when the archwire was displaced 1 mm or more. For many archwires the force level of this plateau also proved to be rather high with values often above 500 g.