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

本研究的目的是澄清与传统的Ag-Pd-Au-Cu合金相比，含有更多Au和更少Pd的合金的成分，以确保耐腐蚀性和安全性，并进入实践。首先进行了耐硫化物腐蚀试验，利用XPS从合金的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。实验结果如下：1.实验结果表明：即使合金中Pd含量降低，但随着Au含量的增加，合金的抗硫化物腐蚀性能仍能保持或提高。即使合金中贵金属含量相同，硫化物层厚度也随Cu含量的增加而增加。为了证实这一预测，对经过酸洗、加热和抛光等表面处理改变表面成分的试样进行了耐蚀性试验。结果表明，Cu含量高的固溶热处理和抛光后合金的硫化物层厚度比Cu含量低的酸洗后合金的硫化物层厚度厚。Cu含量与合金的硫化程度有关。结果表明，通过降低Cu含量来提高合金的耐蚀性，合金的机械强度与传统的Ag-Pd-Au-Cu合金相当。结果表明，含金多、钯少的Ag-Pd-Au-Cu合金的抗硫化物腐蚀性能和力学性能均不低于常规合金。未来，假设假体在口腔内长期存在，将对合金进行考虑溶出离子过敏的生物学评价，并对合金的实用化潜力进行估计。

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.