Corrosion of amalgam in contact with gold

Abstract

In order to investigate the effect of the gold/amalgam contact, a spherical alloy amalgam was brought into contact with a Type III gold alloy, pure gold, or acrylic resin in the artificial saliva 8 minutes after the start of mixing, and the change was examined by the use of an optical microscope and an electron probe microanalyser periodically for a year. Findings were as follows: (1) The pure gold/amalgam contact produced an irregular silver-gray prominence containing gold, tin, mercury, and silver at the contact area of the gold and a slightly prominent silver-gray circle containing mercury and gold at the margins of the area after one hour. Outside the margin, a slight, diffuse, circular stain appeared by tin deposition after one week. (2) The type III gold alloy/amalgam contact produced a group of silver-colored prominences of a new gold amalgam phase that were a few microns in height and depth in the contact area. After one hour, there was no further change. Outside the contact area, no prominent circle caused by mercury diffusion appeared. There was only slight silver-colored stain by tin deposition. (3) The amalgam surfaces in the artificial saliva were covered with debris which increased with time. The change was less in the gold/amalgam contact than in the resin/amalgam contact and less on the unpolished amalgam surfaces than on the polished amalgam surfaces when in contact with gold. (4) The resin/amalgam contact produced no particular change on the amalgam surface, but the gold/amalgam contact produced a glossy spot of metallic luster in the contact area which did not change after one week. (5) The contacts produced no appreciable changes in roughness and metallurgical structure of the rest of the surface of amalgam.