[In vitro study on the corrosion behavior of two amalgams in direct contact to different cast metal alloys].

The direct contact between amalgam and cast metal may enhance electrochemical reactions. In a study to determine the amount of mercury released in these reactions, six cast metal alloys with increasing precious metal contents were placed in immediate contact (contact area 10 mm2) to two non-gamma 2-amalgams (Amalcap, Valiant) and incubated with artificial saliva at 37 degrees C for up to 8 weeks; then the salivary mercury concentrations were measured. After the end of the incubation period the case metal surfaces were analyzed by ESCA for metal appositions. The results showed that direct contact between amalgam and cast metal after storage in artificial saliva for 8 weeks resulted in a minor release of mercury (22.7 +/- 10.63 ng/ml Hg). On the cast metal plates themselves only smallest mercury concentrations could be demonstrated. These in vitro tests have shown again that, although charge transfers do occur when different metals are in direct contact, they do so only to a minor degree, because of the passivation processes involved.