CHICAGO -- Two long-awaited, government-funded studies found no evidence that dental fillings containing mercury can cause IQ-lowering brain damage or other neurological problems in children. Children with such fillings were no more likely than other youngsters to suffer such problems, the researchers found.
Some specialists found the findings reassuring. But the studies are unlikely to end the fierce debate over the long-term effects of what are known as amalgam fillings, and some advocates accused the researchers of conducting unethical experiments on children.
Amalgam fillings, also called silver fillings, are made of mercury and other metals and have been used by dentists for more than a century. But their use has dropped in recent years as more dentists switch to resin composite fillings, which are considered more appealing because they are white.
Some advocacy groups and dentists have long contended that the mercury in fillings can leach into the body and cause harmful neurological effects, including autism.
The latest studies were published today in the Journal of the American Medical Association.
''We didn't see any indications of harm to these kids," said Dr. Timothy DeRouen, a University of Washington professor of biostatistics and dental public health sciences, who led a study of 507 children, ages 8 to 10, in Portugal to determine whether mercury fillings had any neurological effects. ''And we tested them repeatedly over seven years."
The other study, led by Dr. Sonja McKinlay of the New England Research Institutes, looked at the effect on intelligence, memory and other mental functions, and kidney function. It involved 534 children in New England, ages 6 to 10.
McKinlay said she is confident that such fillings are safe for children in this age group, in large part because the youngsters were given far more amalgam than the average American child gets.
''If there was no sign of any health problems from this study in these kids with all this amalgam in their mouths . . . you know it is going to be safe for kids in the same age group in the rest of the country because they are getting much less exposure," she said.
McKinlay also said that while the study revealed children with the mercury fillings had higher mercury levels in their urine, there was no evidence they had a higher incidence of kidney damage.
Neither study examined autism. Dr. David Bellinger, an author of the New England study, said that autism is so rare that it wouldn't be expected to be found among the number of children studied. Also, any children with autism would have been eliminated from the study, as would other children with prior neurological disorders.
The National Institute of Dental and Craniofacial Research funded the studies.