Health Effects of Dental Fillings in Children

Dentists have used silver-colored amalgam to fill cavities for more than 150 years. It's made from a mix of silver, copper, zinc, and other metals held together like glue by mercury, which comprises about half the total weight of a filling. Worries about the safety of mercury have led 2 groups of scientists, supported by NIH's National Institute of Dental and Craniofacial Research, to conduct the first-ever randomized clinical trials to evaluate the safety of amalgam fillings in children's teeth. Both studies — one conducted in Europe, the other in the U.S. — independently reached the conclusion that the dental amalgam caused no health problems during the 5-7 years the children were followed.

For decades, researchers believed that you were really only exposed to the mercury in amalgam while the dentist packed the filling into your tooth. But with the arrival of more sensitive laboratory tools in the late 1970s and early 1980s, scientists showed that dental amalgam continuously releases a mercury vapor into your mouth that is inhaled and absorbed by the body. That raised concerns about the possible toxic effects of chronic low-level exposure to mercury from dental amalgam. Exposure to the element at higher levels can cause irritability, memory loss, tremors, poor physical coordination, insomnia, kidney failure and anorexia. Nearly all of the available information on mercury exposure, however, involved adults working in places where they get relatively large doses, such as dental offices.

The two studies each enrolled over 500 children who had existing untreated decay in their back teeth and no previously placed amalgam fillings. Each child was randomly assigned to receive either amalgam or composite resin (tooth colored) fillings. All were evaluated for several years to see if any health changes occurred. The U.S. study focused on IQ changes, while the European study focused on memory, concentration and coordination.

The findings, reported in the April 19 issue of the Journal of the American Medical Association, were that there was no detectable loss of intelligence, memory, coordination, concentration or kidney function during the 5-7 years the children were followed. The authors noted that children in both studies who received amalgam had slightly higher but still very low levels of mercury in their urine. After several years of analysis, they found that the mercury levels remained quite low and weren't related to IQ loss or other measures of brain and kidney function.

Dr. Sonja McKinlay, the principal investigator of the American study, said, "Given the rigorous nature of the study designs and that both clinical trials confirmed the other's results, I think these findings should be reassuring for parents, children, and dental professionals."