Journal of Dental Research, Vol 69, 1167-1174, Copyright © 1990 by International & American Associations for Dental Research Online Journals
The release of mercury from dental amalgam: the mechanism and in vitro testing
M. Marek
School of Materials Engineering, Georgia Institute of Technology, Atlanta 30332-0245.
Dissolution of mercury from the Ag-Hg matrix phase of dental amalgam is
distilled water and synthetic saliva, and the mercury evaporation from the
solutions, were studied in vitro. The main objectives of the study were to
evaluate the factors that affect the results of the mercury release tests,
and to consider the possible mechanisms of the release in vivo. Specimens
were exposed to the liquids in open or closed bottles, and the changes in
the mercury concentration were determined by cold-vapor Atomic Absorption
Spectrophotometry. Concentration vs. time tests showed the dissolution rate
decreasing with time. Tests involving sequences of short and long exposures
with solution changes showed higher average rates for short-term
dissolution into the fresh solution than for the longer preceding
exposures. The differences were attributed to a stifling effect of the
concentration of elemental mercury on the dissolution. It is believed that
mercury dissolved mainly in the elemental form and that a continuous
increase in the concentration was made possible by oxidation in the
solution. In open cells, some of the mercury was lost by evaporation. The
analysis showed that the results of mercury dissolution tests depend on
many test variables, such as time, solution volume, oxidation and
evaporation conditions, etc. Evaporation, dissolution, and
evaporation/dissolution mechanisms of the mercury release in vivo were
considered. It was concluded that the dissolution/evaporation model best
described the mercury release from dental amalgam restorations.
