THURSDAY, June 29 (Health Day News) -- Traditional amalgam dental fillings containing mercury are safe for school-age children, two new studies find.
The safety of such materials has long been debated, and the two studies are significant because they are the first-ever randomized clinical trials to evaluate the fillings' safety in a head-to-head comparison with resin (tooth-colored) fillings, which do not contain mercury. They were to be presented at the International Association for Dental Research's annual meeting, which opened Wednesday in Brisbane, Australia.
One study, first published earlier this year in the Journal of the American Medical Association, was conducted in the United States and the other in Europe. Both reached the same conclusion: Amalgam fillings, which contain mercury, are not associated with neurological or kidney problems as children age.
But the studies still leave unanswered the safety of dental fillings in children younger than age 6, because those studied were all age 6 years or older when the follow-up began, said the experts.
Still, the findings are as solid an answer as parents are likely to get for a while, said one researcher.
"I would say to include amalgam as one of the materials to consider for restoring large cavities in molars," said Tim DeRouen, director of the Comprehensive Center for Oral Health Research at the University of Washington, Seattle, and the lead author of the Portugal-based study. "Unless you have reason to believe that you have an unusual reaction to mercury, you should not have to worry about health risks from the small amount of mercury exposure from dental amalgam," he said.
The U.S.-based study was led by David C. Bellinger, a professor of neurology at Harvard Medical School in Boston. His team followed the health of 534 children, ages 6 to 10 years at the start of the study. Half of the children got an amalgam filling, and the other half received resin composite fillings. The researchers tracked five-year changes in full-scale IQ scores as the primary outcome of the study. The children had a mean of 15 tooth surfaces restored during the five-year follow-up.
In the Portugal study, conducted for seven years in Lisbon, the researchers tracked 507 children, aged 8 to 10 years at the beginning of the trial. Again, the researchers assigned half to the amalgam and half to the resin composite filling group. They focused on tests of memory, concentration, coordination and attention. The children had a mean of 18.7 tooth surfaces restored in the amalgam group and 21.3 in the composite group.
In both studies, researchers found no significant differences between the amalgam and resin groups in terms of detectable loss of intelligence, memory, coordination or concentration. The U.S. trial also compared kidney function between the two groups and found no differences.
DeRouen said the new data "represents the only evidence about the issue to come from randomized clinical trials, the highest-quality research design that can be used to address the issue. They are expensive and take years to complete, so it isn't like there will be more [of the same type of studies] in the foreseeable future."
DeRouen said that fillings that contain mercury could pose a problem for people allergic to mercury. However, according to the American Dental Association (ADA), fewer than 100 cases of such allergies have ever been reported.
Bellinger acknowledged that the two studies don't include children under 6 years of age. "As far as I am aware, there are not studies of the effects of dental amalgam in children younger than six," he said.
"These are both important, controlled trials," said Dr. James Crall, chairman of pediatric dentistry at the University of California, Los Angeles, School of Dentistry. "The results are consistent across both studies. They both showed some slight elevation in mercury levels [in the urine of the amalgram groups] over the seven years of the study but no significant differences in outcome measurements that related to neuropsychological outcomes [such as memory, concentration and other skills]."
While he, too, is not aware of any published studies of amalgam fillings in children under age six, in baby teeth, he said the exposure is short term by definition, as the baby teeth drop out by age 8 or 9.
The DeRouen study was first published in JAMA in April, along with another trial that found no kidney problems in children who received amalgam fillings.
At the time, the ADA issued a statement to consumers, saying, "Dental amalgam remains among several safe, effective options for treating dental decay." The ADA also noted that the best option is to prevent dental decay and other disease by conscientious brushing, flossing and dental visits for examinations.
For more on good dental care, head to the American Dental Association.