In vitro corrosion of dental amalgams with different Cu content

Both Cu amalgam and Sn-containing Ag amalgam alloys with Cu contents ranging from 2 to 30% were used in the investigation. The amalgams were placed in artificial saliva and the content of the dissolved Cu was determined after 1 month. The amalgam remained in the saliva for another 5 months. After the amalgams were removed from the solution, metallographic and microprobe examinations were made. The Cu amalgam released about 10 times more Cu to the artificial saliva than any of the other amalgams. The dispersion type amalgams showed a relatively large dissolution of Cu, while a smaller release was found from amalgam made of powder with one composition. The phases that appeared to be corroded first were gamma2 and Cu-Sn phases. In dispersion type amalgams the gamma phase appeared to be attacked. Most of the corrosion products remained inside the amalgam and were identified to be tin oxide chlorides.