| The magnetic materials used in orthodontics at present are rare earth neodymium-iron-boron, which are easily oxidized and corroded because of containing iron and neodymium when they are used intra-orally. These lead to the disintegration of the magnets and the decay of the magnetic force and limit their application and popularization in orthodontics.In recent years, titanium nitride (TiN) is increasingly important in industry. The anticorrosion and physio-chemical properties of TiN are excellent and thin TiN coating is able to improve the properties of metallic materials. In this study, TiN coating was deposited by direct current pulse plasma enhanced chemical vapor deposition (PCVD) and the physio-mechanical properties of the magnets with TiN coating were tested. Then the corrosion resistance of the magnets with TiN coating was qualitatively and quantitatively studied by immersing into the artificial saliva and by electrochemical test. Moreover, according to ISO standard, the biocompatibilities of magnets coated TiN were evaluated by cytotoxicity test using L-929 mouse fibroblasts with 3-(4,5-dimetnyltniazol-2-yl)-2,5-dipnenyltetra-zoliumbromide (MTT) method and by oral mucous irritation testin Japanese white rabbit.Results: Coating TiN film on the surface of the orthodontic magnets does not change magnetic force of the magnets and greatly improves the anticorrosion resistance of the magnets and the biocompatibilities of the magnets coating TiN are excellent.Conclusion: (1) Direct current PCVD is a desirable method and can be employed to coat the magnets used in orthodontics. (2) Magnetic force of the magnets with TiN film does not be changed. (3) The anticorrosion resistance of the magnets with TiN coating is significantly strengthened. (4) The biocompatibilities of the magnets with TiN film are excellent. (5) Coating TiN film on the surface of the orthodontic magnets has the worth of popularization and application.
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