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与传统的Ag-Pd-Au-Cu合金相比，多Au、少Pd的合金的成分，以确保耐蚀性和安全性，并走向实用。首先，进行了耐硫化物腐蚀试验，并用XPS从硫化物层厚度估算了合金的耐硫化物腐蚀性能。其次，对合金的力学性能进行了测试。研究结果如下：1.即使合金中的Pd含量减少，但随着Au含量的增加，合金的硫化物耐蚀性仍保持或提高。即使在合金中贵金属含量相同的情况下，随着铜含量的增加，硫化层厚度也有增加的趋势。为了验证这一预测，对经酸洗、加热和抛光等表面处理改变了表面成分的试件进行了耐蚀性试验。结果表明，铜含量较高的合金固溶处理和抛光后的硫化层厚度比酸洗后的厚，而铜含量较低。铜含量与合金的硫化程度有关。结果表明，即使是降低了铜含量以提高耐腐蚀性的合金，其机械强度也与传统的Ag-Pd-Au-Cu合金相当。由此可见，含Au较多而Pd较少的Ag-Pd-Au-Cu合金的抗硫化物腐蚀性能和力学性能并不比常规合金差。未来，假设口腔假体长期存在于口腔中，将对合金进行考虑溶解离子过敏的生物学评价，并对其应用潜力进行评估。

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.