Dental amalgam is a material used in a variety of dental restorations including most fillings, crowns and bridges. It is the end result of mixing approximately equal parts of elemental liquid mercury (43-54%) and an alloy powder (57-46%) composed of silver, tin, copper and sometimes smaller amounts of zinc, palladium, or indium

Since millions of dental patients in California were being regularly exposed to levels of mercury requiring a warning under Proposition 65, As You Sow initiated actions in 2001 against large dental offices around the state over the use and implementation of dental amalgam restorations.

In 2003, the California Dental Association (CDA) negotiated an agreement with As You Sow on behalf of its members and the dental health community. The CDA agreed to provide a warning package to licensed practitioners, laboratories and educational organizations in the dental field. Such entities would be extended an opportunity to join the agreement whereby they would agree to post an agreed upon warning in waiting rooms or other locations likely to be seen by dental patients prior to treatment. Dentists, dental laboratories and dental educational organizations throughout California have joined the settlement and are now providing As You Sow-drafted warnings to patients in advance of treatment.

Both the Center for Disease Control and the U.S. Food and Drug Administration since have published information regarding mercury and the use of dental amalgam.