Development of low-allergenic alloys with corrosion resistance substituted for conventional Ag-Pd-Au-Cu based alloys

本研究的目的是阐明比传统Ag-Pd-Au-Cu合金具有更多Au和更少Pd的合金的成分，以确保耐腐蚀性和安全性，并将其应用于实践。首先，进行抗硫化物腐蚀试验，并通过XPS从硫化物层的厚度估计合金的抗硫化物腐蚀性。其次，对合金的力学性能进行了测试。结果如下：1.即使合金中Pd含量降低，随着Au含量的增加，合金的抗硫化物腐蚀性能保持或提高.即使合金中贵金属含量相同，硫化层厚度也有随Cu含量增加而增加的趋势。为了证实这一预测，对经过酸洗、加热和抛光等表面处理后的试样进行了耐腐蚀性试验。结果表明，铜含量高的合金经固溶热处理和抛光后的硫化物层厚度大于铜含量低的合金经酸洗后的硫化物层厚度。Cu含量与合金的硫化有关.结果表明，即使降低铜含量以提高耐腐蚀性的合金也具有与传统Ag-Pd-Au-Cu合金相当的机械强度。从这些结果来看，含更多Au和更少Pd的Ag-Pd-Au-Cu合金的耐硫腐蚀性和机械性能并不劣于传统合金。未来，假设假体在口腔中长期存在，考虑到由于溶解离子引起的过敏，将进行合金的生物学评价，并将估计实际合金的潜力。

The aim of this study is to clarify composition of the alloys with more Au and less Pd than conventional Ag-Pd-Au-Cu alloys to secure corrosion resistance and safety and to come in practice. First, the test for sulfide corrosion resistance was carried out and estimated sulfide corrosion resistance of the alloys from the thickness of sulfide layer by XPS. Second, the jests for mechanical properties of the alloys were performed. The results were as follows:1. Even if Pd content in the alloys was decreased, sulfide corrosion resistance was maintained or improved as Au content was increased.2. Even if the contents of noble metals in the alloys were the same, the sulfide layer thickness tended to increase with Cu content. To confirm this forecast, the tests for corrosion resistance of the specimens which surface composition was changed by surface treatments including pickling, heating and polishing were conducted. As a result, the sulfide layer thickness of the alloys after solution heat treatment and polishing, with high Cu content, was thicker than that of after pickling, with low Cu content. Cu content was related to sulfuration of the alloys.3. It was revealed that even the alloys which Cu content was reduced to improve the corrosion resistance had mechanical strength corresponding to conventional Ag-Pd-Au-Cu alloys.From these results, sulfide corrosion resistance and mechanical properties of the Ag-Pd-Au-Cu alloys with more Au and less Pd proved to be not inferior to conventional alloys.In future, assuming that prosthesis exists in oral cavity for a long time, biological evaluation of the alloys in consideration of allergy due to dissolution ions will be carried out and the potential for practical alloy will be estimated.