Effect On The Properties For The Medical Ni-Cr Alloy With Gold-plated Layer Treatment

Objective:In this study, a new Non-cyanogen gold-plating technique was employed for Ni-Cr alloy surface treatment. Physical, chemical as well as cell biology research methods were used to comprehensively evaluate surface structure, physicochemical property, antibacterial property and biological property of gold-plated Ni-Cr alloy.The purpose of this study was to further promote safer and wider application of medical Ni-Cr alloys,which was electrop lated with non-cyanogen gold coating treatment in vitroMethods:1.A layer of Non-cyanogen gold film was deposited uniformly on the surface of dental medical Ni-Cr alloy using new Non-cyanogen gold-plating technique.2.The surface morphology, crystal structure, phase composition, bond stgrength of film-substrate interface,carrying capacity as well as thickness of Non-cyanogen gold film was measured by SEM,XRD and electronic universal testing machine,respectively.3. Trying blasting Ni-Cr alloy and alloy after cyanide-free gold-plated in PH 6.8 normal enviroment or the PH 4.8 acid environment, using AA-240 atomic absorption spectronphotometer detects soaked the solution of the precipitation Ni.4. Trying blasting Ni-Cr alloy and alloy after cyanide-free gold-plated in Candida albians, Streptococcus mutans fluid, respectively. After incubation for a certain time,the amount of bacterial adhered on the surface of material was compared by electron microscope and colony-forming unit counting method.5.The primary human gingival fibroblasts were cultured with improved tissue explants method. Morphological and immunocytochemical methods were used to identify cell origin and to evaluate the efficiency of primary culture.6.The effect of surface nitriding on proliferation rate, cell cycle and apoptosis of human gingival fibroblast was evaluated comprehensively by MTT assay and cells adheretion.Results:1,After surface Non-cyanogen gold-plating, the structure of Ni-Cr alloy was quite compact, without defect such as bubble and crack, although there are some pores in some areas. Modifying substance mainly existed in the form of Au. The value of bond strength was 37.6N, The thickness of film was 0.621μm.2,The amount of Ni2+ released from specimens coated with gold was much fewer than those from unplated specimens (P<0.05) in PH 6.8 normal enviroment or the PH 4.8 acid environment, the difference was significant(P<0.05).3,Trying blasting Ni-Cr alloy and gold-plated Ni-Cr alloy in Candida albians, Streptococcus mutans fluid, respectively for a certain time. The amount of viable organism on the surface of gold-plated Ni-Cr alloy was much fewer than those from unplated specimens by electron microscope.4,Improved tissue explants method successfully cultured human gingival fibroblast and identified cell origin.5,Compared with unplated group, cell proliferation rate in gold-plated Ni-Cr alloy group was significantly greater((P<0.05).Conclusions:A new Non-cyanogen gold-plating technique was employed for Ni-Cr alloy surface treatment, chemical corrosion resistance as well as surface stability. Gold-plated Ni-Cr alloy group displays the ability of suppressing bacterial adhesion and ideal biological property.