University of Washington and Universidad de Lisboa have published a study on dental amalgams. The study was in the October 2007 issue of Environmental Health Perspectives.  "Silver" amalgams are made with mercury.

The conclusion states: "Urinary mercury concentrations are highly correlated with both number of amalgam fillings and time since placement in children. Girls excrete significantly higher concentrations of mercury in the urine than boys with comparable treatment, suggesting possible sex-related differences in mercury handling and susceptibility to mercury toxicity."

Here's a link to the full report in a PDF FILE.