Reduction of Ni release and improvement of the friction behaviour of NiTi orthodontic archwires by oxidation treatments.

This work studies NiTi orthodontic archwires that have been treated using a new oxidation treatment for obtaining Ni-free surfaces. The titanium oxide on the surface significantly improves corrosion resistance and decreases nickel ion release, while barely affecting transformation temperatures. This oxidation treatment avoids the allergic reactions or toxicity in the surrounding tissues produced by the chemical degradation of the NiTi. In the other hand, the lack of low friction coefficient for the NiTi superelastic archwires makes difficult the optimal use of these materials in Orthodontic applications. In this study, the decrease of this friction coefficient has been achieved by means of oxidation treatment. Transformation temperatures, friction coefficient and ion release have been determined.