The most common use of mercury in dental operations is the dental amalgam. Dental amalgam is a direct filling material used in restoring teeth. It is made up of approximately 40-50% mercury, 25% silver and 25-35% a mixture of copper, zinc and tin. The total amount of mercury per amalgam can range from 327-982 mg depending on the size of the amalgam. The U.S. Department of the Interior estimated that 31 metric tons of mercury was purchased in the U.S. for use in dental equipment and supplies in 1996. A 1998 survey by the Metropolitan Council Environmental Services (the Publicly-Owned Treatment Works facility for Minneapolis-St. Paul) revealed that 83% of the 1069 dentists surveyed use amalgam.

Amalgam particles enter the wastewater from dental offices when dentists remove old amalgam fillings or place new fillings. Estimates of the contribution of mercury in wastewater from dentists to publicly-owned treatment works range from 11% (San Francisco) to 14% (King County, WA) to 76-80% (Minneapolis) of the total mercury load. In its "Mercury Study: Report to Congress," the U.S. Environmental Protection Agency estimated that 0.7 tons of mercury per year are emitted to the environment from "dental preparations."

In order to reduce the amount of mercury emitted from dental facilities, many states in the U.S. are implementing voluntary educational and mercury collection programs. Some dental associations have assisted in these efforts, favoring voluntary programs over additional regulation.

Sources: Water Environment Federation, "Controlling Dental Facility Discharges in Wastewater: How to Develop and Administer a Source Control Program," 1999; U.S. Environmental Protection Agency, "Mercury Study: Report to Congress, Volume I, Executive Summary," 1997.