Corrosion of five different dental amalgams.

The purpose of this study was to determine the gamma-2 presence in two South African amalgams (Amalgaphase and Silvalloy) and to compare this data with that obtained from tests on a well-known gamma-2 containing amalgam (Amalcap) and on two products with a reportedly low gamma-2 content (Dispersalloy and Permite-C). Samples were prepared according to standard ISO procedures in special sample holders. The rotating disc electrode technique (similar to the technique described by Gal-Or, Bruckenstein and Carter, 1978) was used to determine the presence of gamma-2. All samples were evaluated after one and again after nine days. Results indicated that only Dispersalloy displayed no reaction at day one; in other words no gamma-2 could be detected after 24 hours. All other amalgams showed a definite peak on the polarization plot between -200 and -250 mV indicating electrochemical activity (corrosion) in that region. On day nine, only Amalcap (the gamma-2 containing amalgam) still exhibited a reaction peak. Thorough clinical studies will have to be undertaken to evaluate the durability of the South African products.