Study Of The Coating To Cast Pure Titanium By Ion Nitriding/TiN-coated Compound Treatment

As a newly rising biomaterial, titanium is widely used as removable denture framework. But there are still several problems about titanium frameworks, such as inelegant color, low wear resistance and poor corrosion resistance with fluorid.et al.Plasma ion nitriding combined pulsed bias arc ion (compound nitriding) was treated to cast pure titanium(PT) as a kind of medical and dental materials in order to improve the surface properties and better the color stability. Surface properties, biosafety, fungi adherency and clinical application were studied in our work.Part 1. Microstructure and properties of the coating to cast pure titanium by compound nitridingCompound nitriding(CN) with different nitriding temperatures were treated to PT. The chemical composition and microstructure of the modified layer were analyzed using XRD (X-ray diffraction) and SEM (scanning electron microscopy). The contact angle and color of the samples were studied after CN treatment by EasyDrop Standard and spectraphotometer, respectively. It shows by results that a compound gradient coating which is uniform, stable and dense is formed by CN. The surface energy of samples treated by CN is obviously higher than the untreated PT samples. And the color of CN samples which appears L*:61.22±0.455,a*:1.84±0.055,b*:25.66±0.219 in CIE-1976-L*a*b* colorrange system is bright and golden. A compound nitriding layer containing TiN and Ti2N formed on the specimen surface is tested by XRD.Part 2. Biological safety of the coating on cast pure titanium by compound nitridingCytotoxicity test, hemolytic test, acute systemic toxicity test and oral mucosa irritantion test were carried out according to international standard ISO10993 and YY/T 0268:2001. Cytotoxicity test results showed that the samples of CN had no cytotoxicity. The result of hemolytic test indicated that CN samples had a good hemocompatibility and the hemolytic rate was 0.45%. In addition, the acute systemic toxicity test showed CN samples had no acute systemic toxicity and no mucous membrane irritation in oral mucous irritation test. To concludde, this new coating on cast pure titanium by compound nitriding has good biological safety.Part 3. Fungi adherency to titanium before and after CN coating. This part is mainly about Candida albicans. Cells count assay and XTT reduction assay were used to analysis the amount of Candida albicans to samples with different treatments while SEM and LCSM were applied to study the microstructure of Candida albicans on different samples.. We found the amount of Candida albicans adherency to CN decreased significantly compared with other treatments. SEM and LCSM results show that hyphal forms of Candida albicans were scarcely observed on the surface of CN samples compared with PT.Part4. Clinical research on titamiun framework with CN coatingA prospective clinical trail was carried out to evaluate the clinical effect of CN coating. 40 patients needing removable detures were randomized into 2 groups: PT framework before and after CN coating. With a 1-year follow-up,△E of CN frameworks was lower than PT frameworks. According to questionnaire, the degree of satisfaction is high with the low expulsion rate and there is no allergy and abnormal flavour complaint. So, CN coating has a color stability and aesthetic effect.The four parts experiments metioned above suggest that the coating to PT by ion nitriding/TiN-coated compound treatment can enhance the surface quality and aesthetic effect with a stable clinical effect .