Inhibition of Ni release from NiTi and NiTiCu orthodontic archwires by nitrogen diffusion treatment.

The effects of nickel (Ni) allergy from NiTi alloys were reduced due to the titanium nitrided coating obtained by nitrogen gas diffusion at different temperatures. The samples were immersed in artificial saliva at 37 degrees C for different periods demonstrating that the titanium nitride coating prevents biodegradation. In addition, the lack of low friction coefficient for the NiTi super-elastic archwires makes the optimal use of these materials in orthodontic applications difficult. In this study, the reduction in this friction coefficient was achieved by nitrogen diffusion heat treatments. (Journal of Applied Biomaterials & Biomechanics 2004; 2: 151-5).