Amalgam deemed safe in dental fillings

Healthfacts, Feb, 1988

AMALGAM DEEMED SAFE IN DENTAL FILLINGS

The public's concern over the toxicity of mercury vapors from the most commonly used dental fillings prompted the recent report by Dan C. Langan, D.D.S., and colleagues for the American Dental Association's Council on Dental Therapeutics in the Journal of the American Dental Association (December 1987). After reviewing all studies in the recent scientific literature relevant to the safety and use of mercury in dentistry, they concluded that there are no adverse health effects except to a tiny minority with mercury hypersensitivity.

The greater danger involves inhaling mercury vapor as the filling is being inserted, but this is potentially more of a hazard to dental personnel rather than to the clients. Several recent studies showed that a significant number of dental personnel are exposed to levels of mercury vapor in excess of safety limits; yet the investigators report that toxicity symptoms are rare. The ADA reached a similar conclusion the last time it published a position paper in 1983.

Chronic exposure to mercury vapor primarily causes neurological effects. Symptoms of low level exposure include weakness, fatigue, anorexia, weight loss, and gastrointestinal disturbances; symptoms of increasing exposure include fine trembling of muscles interrupted by coarse shaking movements. We are exposed to mercury in a variety of ways ranging from its presence in the environment as a naturally occurring element to eating large fish, such as tuna and swordfish, from waters contaminated by industrial wastes.

As for dental exposure, the amalgam or silver filling remains the most commonly used material because it is less expensive than gold inlay and more durable than the tooth-colored plastic composite filling normally reserved for the front teeth. The safety of amalgams became a public issue several years ago when Carl W. Svare, D.D.S, and colleagues at the University of Iowa College of Dentistry, reported the first study not only to show that measurable amounts of mercury could be detected in the blood but they could also be directly attributed to amalgam fillings (see "Saving Your Teeth," HEALTHFACTS, May 1983). The six participants were given blood tests before and after the removal of fillings that were approximately two years old. Mercury concentrations in the blood of all participants were reduced after removal of the amalgam fillings. These preliminary results were announced at a meeting of the International Association for Dental Research and widely reported in the lay media (published several years later in the 1986 Journal of Dental Research, Vol. 65, Abstracts No. 1276).

In a telephone interview, Daniel Boyer, D.D.S, a co-investigator with the late Dr. Svare, told HEALTHFACTS that their study was not designed to determine the health effects of amalgam fillings. While no such study has been conducted, Dr. Boyer, an associate professor of operative dentistry at the University of Iowa College of Dentistry, said that he was satisfied with the conclusions drawn by the ADA reviewers. The levels of mercury from amalgam fillings were always found to be well within the limits of safety as determined by tests conducted on workers in industries where exposure to mercury is extremely high, according to Dr. Boyer.

Should pregnant women take any special precautions, given the fact that the ADA review acknowledged an increase in mercury vapor at the time an amalgam filling is inserted? P.L. Fan, Ph.D., co-author of the ADA review, said in a telephone interview, "We did not address it [safety of amalgam fillings to pregnant women] because there is no information on the topic."

Atiny minority of the population--less than one percent--is believed to have mercury hypersensitivity, a condition that would manifest itself as a skin reaction. Anyone considering a patch test should be certain it is administered by a physician or dentist with special training in allergic reactions, said Dr. Fan who is the associate secretary of the ADA's Council on Dental Materials, Instruments, and Equipment. The ADA review found patch testing to be generally unreliable with one exception. The test using one percent ammoniated mercury in petrolatum was recommended by the North American Contact Dermatitis Group, which consists of physicians who specialize in allergies.

Since dental personnel were singled out in the review as a group at some risk, they were offered specific ways to minimized mercury exposure with techniques, such as high vacuum evacuation, water spraying the work area, and good ventilation. The patient is also protected by these measures along with the use of the "rubber dam," which serves as a barrier around the tooth.