The Study Of Nano Nitrogen-doped DLC Coating On Pure Titanium Bracket

Pure titanium was wildy used in prosthdontics as perfect dental materials. However, some defects such as pore by casting, weak attrition resistance and corrosion by fluoride need to be solved by surface modification. Diamond like carbon(DLC) coating was widly used in industry as rising material, contrary, it seldom used in prosthdontics because of weak tenacity, single color and poor adhesion to pure titanium. This study aimed at developing Nitrogen-doped DLC coating to improve capability of pure titanium bracket; satisfacting clinical need. Method: 1. applying multi impulse arc plasma plating machine to produce TiN coatings on pure titanium in nitrogen atmosphere, then filming with DLC on TiN in methane; 2. using tooth brushing machine to test the friction of DLC (compared with TiN, Anodizing); SEM to analyse the surface morphology and content in DLC film; wetting detective apparatus to measure wettibility; comparing adhering of candida albicans on DLC and evaluating cytotoxicity of DLC; 3.observing the effect of clinical use. Result: 1.Affirming technical parameter of filming DLC⑴①Influence of voltage on the DLC uniformity: When the voltage was 300V,200V and 100V,the relative error of uniformity was 36.23%,35.48% and 34.67%. 200V should be the best choice.②When the frequency was 1Hz,3Hz and 5Hz,the relative error of uniformity was 39.76%,39.39% and 42.94%.3Hz should be the best choice.③When the distance between cathode and samples was 240mm,270mm and 300mm,the relative error of uniformity was 23.53%,11.63% and 11.76%.270mm should be the best choice.⑵Influence of angle of incidence on the DLC uniformity and hardness: When the angle of incidence was within 45°, the hardness was higher than other angles. However, the uniformity changed obviously if the angle was beyond 30°Within 30°should be the best choice.⑶①Surface morphology of 4 samples with different content nitrogen (SEM). From A to D showed that dense of crystals formed in DLC films become more compact which improve that Nitrogen can induce the crystal growing up under special pressure and temperature.②Transect of 4 samples with different content nitrogen (SEM) . From A to D showed that the thickness of DLC films become more thicker which improve that Nitrogen can induce titanium element from transition layer (TiN) diffused into DLC films③SEM and XPS show CNx bond appearing in DLC film④DLC/CNx decrease the stress in DLC , enhance the binding strength between pure titanium and DLC. 2.Testing the capability of DLC film⑴The change of roughness, reflectivity and color difference in DLC was the lowest compared with Tin, Anodizing and Uncoated. The color difference in DLC was the lowest either. DLC coating may improve quality of titanium denture.⑵Corrosion test manifest DLC have the best corrosion resistance than Tin, Anodizing and Uncoated pure titanium.⑶The resin bonding strength and surface energy of DLC group was lower than Tin, Anodizing and Uncoated pure titanium The wettability and resin bonding strength have been increased after coating with H-DLC which can used in denture repair.⑷Comparing adhering of candida albicans on four kinds of surface (DLC, TiN, Anodizing, Uncoated pure titanium)after used in clinical patients, DLC show the best ability of anti- candida albicans.⑸When changing the time of deposition , DLC surface show different color. Golden yellow was present when time of deposition was 30min.⑹The results of cell toxicity tests reveal no cytotoxicity finding with DLC,it was safe to L-929 cell.It can be conclude that DLC was safe to use in human body.3.Nitrogen-doped DLC coating on pure titanium bracket applying in human in vivoNitrogen-doped DLC coating on pure titanium bracket was received by patients after applying in vivo; comparing with uncoated titanium brackets, titanium brackets filming with DLC decreased the aggradient of color, improved feeling of chewing.On the base of the above results of this study, it can be concluded that:Nitrogen-doped DLC can filming on denture repair with complex shape after ameliorate working conditions; improving the wear ability of titanium denture repair; enhancing corrosion resistence of titanium denture repair; keeping favourable wettibility and comfort for patient use with no influence on binding strength between resin and bracket; When changing the time of deposition , DLC surface show the color of golden yellow which promote aesthetic feeling; after used in clinical patients, DLC show the best ability of anti-candida albicans. The results of cell toxicity tests reveal no cytotoxicity finding with DLC, it was safe to L-929 cell.It can be conclude that DLC was safe to use in human body; Nitrogen-doped DLC coating on pure titanium bracket was received by patients after applying in vivo; Comparing with uncoated titanium brackets, titanium brackets filming with DLC decreased the aggradient of color, improved feeling of chewing.