Patsurakos A, Moberg L E
Department of Prosthodontics, Karolinska Institute, Stockholm, Sweden.
Scand J Dent Res. 1988 Aug;96(4):376-83. doi: 10.1111/j.1600-0722.1988.tb01570.x.
The marginal microhardness of three different types of amalgam was tested after 2 months' immersion in an aqueous solution of NaCl (85 mM) and phosphates (Na2HPO4 100 mM and NaH2PO4 100 mM). Amalgams immersed in distilled water were used as controls. The microhardness tests were conducted at a distance of 50 micron from the margins and at the bulk of each specimen. The solutions were analyzed for Sn, Cu, Zn, Ag, and Hg by means of atomic absorption spectrophotometry (AAS). A statistically significant reduction in the marginal microhardness after immersion in the test solution was found for the conventional and the high-Cu single composition amalgam but not for the high-Cu blended amalgam. SEM-examination of cross-sections of the amalgams revealed small areas of subsurface grain boundary corrosion, no deeper than 10 micron for all the amalgams. The SEM-examination of the specimens and AAS analysis of the solutions indicated that the reduction in marginal microhardness was attributed mainly to corrosion of the Cu-rich phases for the high-Cu single composition amalgam and to corrosion of the gamma 2 phase for the conventional amalgam. The phosphates reduced the corrosion of the amalgams in the presence of NaCl. It is concluded that the marginal strength of dental amalgams in a corrosive environment is largely dependent upon their corrosion resistance.
将三种不同类型的汞合金浸泡在NaCl（85 mM）和磷酸盐（Na2HPO4 100 mM和NaH2PO4 100 mM）的水溶液中2个月后，测试其边缘显微硬度。浸泡在蒸馏水中的汞合金用作对照。显微硬度测试在距每个样品边缘50微米处和样品主体进行。通过原子吸收光谱法（AAS）分析溶液中的Sn、Cu、Zn、Ag和Hg。结果发现，对于传统型和高铜单组分汞合金，浸泡在测试溶液后边缘显微硬度有统计学意义的降低，但高铜混合型汞合金没有。对汞合金横截面的扫描电子显微镜（SEM）检查显示，所有汞合金的亚表面晶界腐蚀区域较小，深度不超过10微米。对样品的SEM检查和溶液的AAS分析表明，边缘显微硬度的降低主要归因于高铜单组分汞合金中富铜相的腐蚀以及传统汞合金中γ2相的腐蚀。磷酸盐在NaCl存在的情况下减少了汞合金的腐蚀。得出的结论是，在腐蚀性环境中，牙科汞合金的边缘强度很大程度上取决于其耐腐蚀性。
