Fifth European Symposium on Martensitic Transformations and Shape Memory Alloys

J. Phys. IV France 11 (2001) Pr8-577-Pr8-582
DOI: 10.1051/jp4:2001896

Mechanical characterisation of orthodontic superelastic Ni-Ti wires

M. Arrigoni¹, F. Auricchio², V. Cacciafesta³, L. Petrini² and R. Pietrabissa<sup>1

1</sup>  Laboratory of Biological Structure Mechanics, Department of Bioengineering, Politecnico di Milano, P.za Leonardo da Vinci 32, 20123 Milano, Italy
²  Department of Structural Mechanics, Università di Pavia, Via Ferrata 1, 27100 Pavia, Italy
³  IRCCS Policlinico S. Matteo, Department of Orthodontia, Università di Pavia, 27100 Pavia, Italy

Abstract
Nowadays, the orthodontic treatment is improving thanks to the introduction of Ni-Ti super-elastic alloy wires in the ordinary therapy. Indeed, laboratory tests performed in the last decade have shown that Ni-Ti superelastic wires are able to satisfy the ideal requirements for fixed arch-wire appliance : high flexibility, minimal distortion or plastic deformation, light constant force production over a wide range of displacements. On the other hand, many orthodontic companies produce Ni-Ti arch-wires, without giving detailed specifications on their superelastic characteristics. To improve the knowledge on real properties for these products, an experimental campaign on different commercial arch-wires has been started at the Laboratory of Biological Structure Mechanics (LABS) at the Politecnico di Milano (Italy). This work presents the first step of the research, concerning the comparison between the behaviour of four types of wires (two produced by ORMCO and two produced by 3M/Unitek) under monotonic and cyclic isothermal tensile tests. The results show significant differences between the products in terms of elastic modulus, stress values of the loading-unloading plateau, hysteresis amplitude, spring-back capacity, shape recovery capability, strain rate effect and fatigue behaviour.

© EDP Sciences 2001