Analysis of the corrosion resistance of titanium nitride coating on orthodontic wires

Objectives: Allergic diseases which have been thought to be caused by dental metals have recently become problems. Orthodontic materials also contain metals that can be a cause of metal allergy; therefore, attention should be paid to the treatment of patients with metal allergy. Ion plating is one of the most advanced surface finishing processes. Advantages of ion plating are chemically stable, high attachment strength, low coefficient of friction, and thin layer. The purpose of this study is that orthodontic wires are improved to have high corrosion resistance by titanium nitride (TiN) coating using ion plating method.
Methods: The orthodontic wires, which are Ni-Ti wire and stainless steel wire, were coated TiN by using ion plating method. This process was treated at 220℃, and TiN layer was created with 0.3μm on an orthodontic wires. Non-coated and TiN coated wires were separately immersed in plastic dish containing 10ml of various solutions. Each wire was kept at 37℃ for 30 minutes, 1 hour, and 24 hours. The quantity metal elution was measured using the inductively coupled plasma mass spectrometry (ICP-MS). Furthermore, the corrosion resistance of TiN coated orthodontic wires were evaluated by using anodic polarization tests. The anodic polarization test was measured the breakdown potential and corrosion potential with a potentiostat.
Results: The quantity of metal elution from coated Ni-Ti wire and stainless steel wire were lower than that from non-coated wires in hydrochloric acid. The breakdown potential and corrosion potential of coated Ni-Ti wire and stainless steel wire were higher than those of non-coated wires, respectively.
Conclusions: These results indicate that the corrosion resistance of the orthodontic wire is improved by TiN coating. Therefore, TiN coating by ion plating to orthodontic wires is to be useful in the patient with metal allergy.