A Clinical Study n Discoloration of the Dental Casting Alloys

本研究旨在评价牙科铸造金属在口腔抛光表面的变色和附着情况。结果表明，在体外，CH_3SH、H_2S的生成与Au-Ag-Pd合金变色有关。Au-Ag-Pd合金的变色也可能与牙周病、口臭、口腔护理等口腔疾病有关。Ag-Pd-Au合金(铜：10.0~20.0质量%，Au：12.0或20.0质量%)的组成对防止变色有影响。但以目前的成分对口腔腐蚀性较强的患者来说，市售的Ag-Pd-Au合金很难防止变色。铸造卡环通常使用Ag-20Pd-12Au合金铸造。铸造后按翼形方式进行热处理：1)在800℃下加热1h，在水中淬火。2)800℃加热1小时，风冷。作为对照，铸造卡环而不进行热处理。虽然两个热处理组和对照组的亮度有显著差异，但在分娩后的所有条件下，亮度都显著降低。对于变色率较高的受试者，热处理可能影响不大。3例患者采用纯钛和Ag-Pd-Cu-Au合金配合植入局部义齿，每副义齿照常使用2个月。变色后的试件表面被球状附着物覆盖。X射线光电子能谱分析表明，Ar离子腐蚀去除了钛的附着物，其厚度为0.3~0.5μm，而Ag-Pd-Cu-Au合金中的附着物由于被Ar离子腐蚀除去，其厚度无法估算。

The present study was to evaluate discoloration and accretion on the polished surface of dental cast metal in the oral cavity.1. The findings indicated in vitro that the production of CH_3SH, H_2S was related to the discoloration of Au-Ag-Pd alloy. The dicoloration of Au-Ag-Pd alloy may also be related to the oral conditions such as periodontics, halitosis and oral care.2. The prevention of discoloration was influenced by composition of Ag-Pd-Au alloys (Cu : 10.0〜20.0 mass%, Au 12.0 or 20.0 mass%). But it was difficult to prevent to the discoloration of commercially available Ag-Pd-Au alloys with the current compositions for patients having high corrosive influence on the mouth.3. Cast clasps ware conventionally cast using Ag-20Pd-12Au alloy. After casting, the heat treatment was performed as wing manners : 1) Heated at 800℃ for 1 hour and quenched in water. 2) Heated at 800℃ for 1 hour and air cooled. As a control, cast clasps without heat treatment. Although there are significant differences in the luminance among two heat treatment and control, the luminance was markedly decreased in all conditions after delivery. On the high discoloration subjects heat treatments might be little effect.4. The pure titanium and Ag-Pd-Cu-Au alloy were installed in the partial denture by cooperating in three patients and each denture was used as usual for two months. The surfaces of the discolored specimens were confirmed to be covered with the spherical accretion. The accretion of titanium was taken away by Argon ion etching in X-ray Photoelectron Spectroscopy and its thickness was confirmed to be 0.3〜0.5μm. However, the thickness of the accretion in Ag-Pd-Cu-Au alloy could not been estimated because it was taken away by Argon ion etching.