Mercury-containing amalgam used to fill cavities in kids’ teeth appears to have no adverse intellectual, neurological, or behavioral effects, according to two reports in this week’s Journal of the American Medical Association.

For the first paper, Dr. Sonja M. McKinlay, from the New England Research Institute in Watertown, Massachusetts, and associates enrolled 534 children ages 6 to 10 with two or more teeth with caries. The subjects were randomly assigned to fillings with amalgam or resin composite materials (267 in each group).

After 5 years, neuropsychological function - including full-scale IQ and general memory scores - did not differ significantly between the two groups, although McKinlay’s team points out that the slight differences “favored the amalgam group.”

“Under the conditions of use represented in this trial, there is no reason to discontinue use of mercury amalgam as the standard of care for caries in posterior teeth,” McKinlay and her associates write.

In another study, Dr. Timothy A. DeRouen at the University of Washington in Seattle, and colleagues there and in Lisbon, Portugal, conducted a similar analysis in a group of 507 children, 8 to 10 years old, with at least one cavity on a permanent tooth and no previous exposure to amalgam. Subjects were randomly assigned to amalgam or resin treatment and were assessed annually.

During the 7-year follow-up, at each assessment, there were no significant differences between groups in IQ, memory, visual-motor skill, attention/concentration, or nerve conduction tests.

DeRouen’s team agrees with McKinlay’s group that “amalgam should remain a viable clinical option in dental restorative treatment.”

However, “to assert that use of mercury amalgam in dentistry is risk-free… would be unfortunate and unscientific,” writes Dr. Herbert L. Needleman in an accompanying editorial.

Needleman, from the University of Pittsburgh, calls the studies “thoughtful and important contributions” but told Reuters Health that “good evidence is emerging that early exposure reprograms genetic resistance to toxins later in life.”

More than 50 million children in the US “have mercury in their mouths,” he said, “so this is a very important issue.”

He recommends studies with much larger sample sizes and extensive follow-up, “and other sensitive measures of physiologic function should be employed, such as tremor and balance.”

Asked if he would allow mercury amalgam to be used in young children of his own, Needleman answered, “Absolutely not.”

SOURCE: Journal of the American Medical Association, April 19, 2006.