Improvement of biocompatibility of metallic biomaterials by surface amorphization

材料表面的物理和化学性质对生物相容性有很大影响。金属碳化物和氮化物与其原始金属相比化学稳定。近年来，高能激光被应用于金属牙科修复材料的焊接。激光器提供高能量进入限制区域而没有污染。作者将牙科激光焊接机应用于牙科合金的表面处理。用不同气氛和激光功率的激光辐照牙科合金，并对其表面性能进行评价。激光辐照改变了合金相和晶体结构。因此，激光加热可以在受限区域中提供热处理效果。在N_2气氛中激光辐照，钛表面形成氮化层，提高了表面硬度。为了评价激光照射后的生物相容性，采用X射线吸收精细结构（XAFS）分析技术对两个不同患者口腔粘膜中与钛种植体接触的钛进行了分析。检测到金属Ti和氧化物（Ti）。金属钛以颗粒形式分布，这可能是植入手术过程中磨损形成的碎屑。钛氧化物的衍生假设是溶解的钛在组织中氧化并形成二氧化钛。提出了用XAFS分析生物组织中稀有元素化学状态的可能性。

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.