A much anticipated study of the health impacts of dental fillings containing mercury has ended. Researchers in Maine and Massachusetts monitored more than 530 school-age children – including about 250 in Farmington – over five years and have concluded that the silver-colored amalgam material has no negative effect on children’s neurological functioning.

The study report appears in the current issue of the Journal of the American Medical Association. A study conducted in Portugal reports similar findings in the same issue.

Exposure to mercury in the environment is associated with behavioral changes, reduced IQ, learning problems and other disorders – including, at high levels, convulsions, coma and death. Autism also is suspected of being related. Some consumer groups, including some here in Maine, have recently advocated for laws prohibiting the use of mercury amalgam fillings, especially in young children and pregnant women, who are especially at risk.

Most dentists and public health officials, however, have argued that the mercury in dental fillings is so tightly bound to the tin and silver also contained in the material that only minute amounts of vapor are released harmlessly. They say eliminating amalgam fillings ultimately would harm children’s dental health, because many public and private payers won’t pay for the more expensive white fillings consumer groups advocate for. Additionally, many dentists prefer to use the amalgam because it is more durable and easier to handle, especially in younger children or those with special needs who find it difficult or impossible to cooperate in the dentist’s chair.

In response to the growing debate over the safety of mercury amalgam fillings, researchers from the New England Research Institutes, the Forsythe Institute, Children’s Hospital in Boston and the University of Rochester School of Medicine designed the New England Children’s Amalgam Trial. They recruited children 6 to 10 years old from the Farmington area and from the Boston vicinity. The children were eligible to participate in the study – and to receive free dental care – if they were fluent in English, had no known prior or existing amalgam fillings, had at least two back teeth with existing cavities, and, by their parents’ report, had no diagnosed psychological, behavioral or neurological disorders. They also were required to have a healthy immune system and healthy kidneys.

The children received a comprehensive examination at the outset of the study, including urine tests and a battery of assessments designed to measure their IQ, memory and eye-hand coordination. They then were randomly assigned to receive either mercury amalgam fillings or a white, resin-based filling in any cavities that developed during the study. They were seen twice each year for dental care, more often if dental problems arose.

Researchers in Massachusetts and Maine readministered the neurological exams at the end of the first, second and fourth year to measure whether the children were showing any damage. They also monitored kidney function for changes that might be attributable to mercury exposure. The study found no statistically significant differences between the two groups of children.

“These findings suggest that the health effects of amalgam restorations in children need not be the basis of treatment decisions when choosing restorative dental materials,” the report states.

Reactions to the report in Maine were mixed this week. John Bastey of the Maine Dental Association said the results were not unexpected. While consumers’ concerns make sense on one level, he said, dentists have believed for years that mercury binds so tightly to the other materials in the amalgam that only tiny amounts are released, not enough to cause any harm. Bastey said many dentists prefer amalgam because it is longer-lasting, easier to place and less expensive than white composite fillings.

Pediatric dentist Jonathan Shenkin of Bangor said younger dentists are using less of the amalgam in response to consumer demand for the more visually pleasing white composite fillings. Though he uses amalgam only rarely, he said restricting its use ultimately would be detrimental to children’s dental health. The best solution, though, is better prevention so children don’t need fillings at all, he said.

Jon Hinck of the Natural Resources Counsel of Maine said it’s only logical for consumers to be worried about the health implications of filling their children’s teeth with a known toxin such as mercury. While the study may be reassuring on that count, he said NRCM continues to focus on the environmental impact of mercury and pointed out that “a healthy percentage of what goes into teeth ends up in the environment.”

Efforts this week to reach Pam Anderson and her dentist husband, Thomas Anderson, of Houlton, persistent advocates of mercury-free dentistry, were unsuccessful. But Maine Sen. Dennis Damon, D-Trenton, sponsor of a measure during the last session that would have phased out dental mercury, said Monday that he remains skeptical. Common-sense concerns and anecdotal accounts of neurological changes associated with mercury amalgam fillings will keep the debate alive, he predicted, even though the study may allay some fears.

A spokesman from the New England Research Institute said the studies in New England and Portugal, taken together, make a powerful argument for the safety of dental amalgam.

“From a scientific point of view, it gives us the confidence that these findings are not equivocal, and the similarity suggests that the results are real,” said Dushanka Kleinman, the institute’s deputy director.

Charlie Brown, counsel for Consumers for Dental Choice, an advocacy group pushing to end the use of mercury in dental fillings, said both studies ignore research that indicates mercury causes a host of physical and mental problems. Brown blasted the studies as unethical, saying that children or their guardians were never told of the potential risks of the mercury fillings.

Authors of both studies disputed that contention, saying they disclosed what they were doing and why. Dr. Timothy DeRouen, who led the study in Portugal, said, “We weren’t doing anything experimental. We were giving standard dental treatment.”

DeRouen said a review board at the University of Washington found the allegations to be unfounded.

An anti-amalgam group called the International Academy of Oral Medicine and Toxicology announced it was filing ethics complaints with institutions that took part in what it characterized as “outrageous” experimentation on children.

The National Institute of Dental and Craniofacial Research funded both the studies.

The Associated Press contributed to this report.