Improvement of biocompatibility of metallic biomaterials by surface amorphization

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The biocompatibility is strongly affected by the physical and chemical properties of materials' surfaces. Metal carbides and nitrides are chemically stable compared to their original metals. Then, their biocompatibility are also same as or better than their original metals.Recently, high energy lasers are applied to the welding of metallic dental restoratives. The laser provides high energy into restricted area without contermination. The authors applied the dental laser welder for surface treatment of dental alloys. Various dental alloys are irradiated by laser with various atmosphere and laser power and their surface properties were estimated. The alloy phase and crystal stracture was changed by laser irradiation. Therefore, the laser heating was possible to provide the heat treatment effect in the restricted area. The laser radiation in the N2 atmosphere, nitride layer was formed on titanium surface and surface hardness was imporoved. Thus, the surface treatment of aimed area was possible by laser irradiation.To evaluate the biocompatibility, X-ray absorption fine structure (XAFS) analysis was applied for the analysis of titanium (Ti) in the human oral mucosa in contact with Ti dental implants from two different patients. Metallic Ti and an oxide (anatase) were detected. The metallic Ti was distributed in particulate form, which would be debris formed by the abrasion during the operation of implantation. The derivation of titanium oxides were assumed that the dissolved titanium was oxidized in the tissue and titanium dioxide was formed. The possibility of using XAFS for the analysis of the chemical state of rarely contained elements in biological tissue was suggested.