Titanium nitride plating reduces nickel ion release from orthodontic wire

The leaching of metal ions from orthodontic appliances is a problem for their use in patients with metal allergies. Despite the development of a number of non-metal orthodontic appliances, including brackets, non-metal wires are not yet available. Therefore, it is necessary to modify the surfaces of orthodontic wires to prevent the leaching of metal ions into the oral environment for use in such patients. This study was performed to examine whether plating of orthodontic wire with titanium nitride (TiN), which does not impair its mechanical properties, could prevent the leaching of metal ions from the wire on immersion in acid. To investigate the acid corrosion resistance of the wire, the amount of metal ions eluted from the wire immersed in acid was measured by using inductively coupled plasma mass spectrometry (ICP-MS) and the dimethylglyoxime (DMG) test, the properties of the wire surface were examined by stereomicroscopy and scanning electron micros-copy, and the surface roughness was measured using a surface roughness tester. The results indicated that TiN plating of orthodontic wire significantly suppressed the elution of metal ions on immersion in acid.