Once decay is removed, a filling is placed inside the cut-out area to retain the tooth's shape and function, including chewing. A variety of filling materials is available.
One of the oldest and most commonly used filling is amalgam, a metal alloy of silver, tin, copper, and sometimes indium, palladium and zinc that is mixed with about an equal amount of mercury. FDA regulates amalgam alloy as a medical device.
According to a 11-98 article in the Journal of the American Dental Association, dentists continue to use amalgam primarily because it is inexpensive and durable and withstands the tremendous forces of chewing. A 1993 U.S. Public Health Service report on dental amalgam said that amalgam typically lasts from 8 to 12 years. Only gold alloy and metal-ceramic crowns last longer up to 18 years.
Amalgam has drawn controversy in the past 10 years because its critics contend that the mercury emits minute amounts of vapor, causing a variety of health problems ranging from multiple sclerosis and arthritis to mental disorders. However, several investigations by the federal government and others have not borne this out, and the use of amalgam is supported by FDA, the National Institute on Dental and Craniofacial Research, the American Dental Association, and other professional organizations.
In a scientific literature review published in the 11-98 Journal of the American Dental Association, professors of dentistry in the United States and China found that research has not yet shown that mercury vapors escaping amalgams are "in concentrations high enough to produce any detectable effect on the body." The authors concluded that, contrary to some dentists' current practice, "dentists cannot ethically tell patients that amalgam is a health hazard and that removal of restorations will benefit their health."
While amalgam remains the most commonly used dental filling, its use does appear to be declining. According to the dental association's journal article, the use of amalgam for filling back teeth has dropped from 85% in 1988 to 58% in 1997. "The use of amalgam will likely continue to diminish, and it will eventually disappear from the scene," the journal article said.
One reason for the decline is the introduction of new materials that afford similar durability and strength as amalgam and, unlike the silver-colored fillings, can be made to match the color of a patient's teeth. "The aesthetics' side of it is very important to many patients," Runner says. However, using these materials -- composites, glass ionomers, and metal-ceramic crowns -- can cost a patient from 1.5 times to 8 times the cost of an amalgam restoration.