Amalgam fillings are durable and long-lasting. They are made of mercury, silver, copper and tin, and sometimes include a small amount of other metals such as zinc and indium. Amalgam fillings generally cost less than tooth-colored composite fillings, which are made with a type of plastic resin and glass.

About half of dental amalgam is liquid mercury, which is used to bind the metal particles together into a hard, strong filling. Over time, amalgams can release a very low level of mercury vapor, but extensive research shows amalgam fillings are safe and not harmful to the health of the large majority of people. This has been verified by the U.S. Food and Drug Administration (FDA), Centers for Disease Control and Prevention, World Health Organization and American Dental Association. The FDA also does not recommend removing existing silver fillings, unless medically necessary.

Certain groups who may face greater health risks from exposure to even small amounts of mercury should avoid amalgam if possible, according to the FDA. These include women who are pregnant or nursing; children under 6; people with impaired kidney function or neurological diseases such as multiple sclerosis, Alzheimer's disease or Parkinson's disease; and those allergic to mercury or other metals in amalgam.