플라즈마 전해산화 공정을 통한 골유착성 및 항균성 임플란트 표면처리에 관한 연구

Abstract

Commercially pure titanium and its alloys are used widely for biomedical materials, such as dental and orthopedic implants due to its high specific strength, excellent corrosion resistance, and good biocompatibility. On the other hand, the naturally formed passive layer of titanium is bio-inert, which leads to the delayed adhesion of bone cells directly to the titanium implant surface after surgical implantations. Surface modification is essential for imposing the bioactivity on the titanium implant because the manipulated surface structure with a high surface roughness on titanium implants play a favorable role in promoting the osseointegration property. In addition, introduction of bioactive materials such as tricalcium phosphate and hydroxyapatite (HA) is also significant to enhance the osteoconduction and/or osteoinduction response. The plasma electrolytic oxidation (PEO) process, as a relatively new and eco-friendly surface modification method, could be a versatile technique for biologically enhancing the surface characteristics by controlling electrolyte, pH and electrical parameters. This study covers the formation of bioactive titanium implant via PEO process viz., investigation of i) optimum pore size on cell response, ii) effects of phosphate electrolytes on surface structures, iii) how ZrO2 nanoparticles affect coating properties, iv) the optimum concentration of Ag nanoparticles and v) how to deposit bioactive HA nanoparticles on titanium substrate. Because the porous biomaterials provide anchorage by favoring ingrowth of mineralized tissue and bone cells, how the pore size of the oxide surface influences the growth of osteoblast cells and their proliferation was investigated. Hereby, titanium oxide with optimum pore size could be formed in the potassium pyrophosphate electrolyte and biological influences of oxide characteristics on bone-forming ability and cell response were examined. Furthermore, high adhesive titanium oxide was fabricated in the electrolyte containing t-ZrO2 particles using their stress-induced transformation toughening property. By suspending Ag nanoparticles in the electrolyte, we fabricated porous titanium oxide exhibiting anti-bacterial activity as well as bioactivity. On the other hand, in order to overcome limitations of commercialized HA plasma spraying technique, how to deposit hydroxyapatite, which is one of the bioactive materials, on the titanium substrate via optimized PEO process was investigated and the deposition models were discussed.