A new study is linking white, composite dental fillings with possible long-term behavioural problems in children. But members of the Canadian Dental Association say the study is badly flawed and that few conclusions can be drawn from it.

The study, which appears in the medical journal Pediatrics, looked at 534 kids, age six to 10, who had at least two cavities filled and then examined their social skills before and five years after getting the fillings.

Some of the kids got the silvery fillings called amalgam, while others got one of two types of white composite fillings: ones made with bisGMA, a plastic derived from bisphenol A or BPA; or those made with urethane.

The two kinds of composite fillings have been the norm for treating children's cavities since the mid-1990s, when amalgam fillings were set aside over now-disputed concerns grew about the effect of mercury in the fillings.

The researchers in this study found that those kids who had composite fillings made using BPA scored two to six points worse on 100-point scale of behaviour measurement than those who had none of those fillings. The longer they had the fillings, the worse they scored on the tests.

The behaviour problems included anxiety, depression and stress. All the behaviour symptoms were self-reported or noted in parents’ questionnaires.

Among those kids with the most bisGMA-based fillings, 16 per cent were at risk for having a behavior problem, compared with only 6 per cent of children who had the fewest of those types of fillings.

No differences in emotional problems were seen in kids with the most amalgam fillings compared to the fewest, or who had the most urethane-based fillings compared to those with the fewest.

The study could only draw a link between resin fillings and behaviour problems; it couldn’t prove cause and effect. The study did not measure how much BPA were in the kids’ bodies overall, nor did it look at other ways the kids might have been exposed to BPA.

Benoit Soucy, the director of clinical and scientific affairs at the Canadian Dental Association tells CTV’s Canada AM that after his group reviewed the study, they realized that the behaviour effects seen in the study were “very, very” small.

“That small change is not clinical in almost all of the cases,” he said, meaning the differences wouldn’t be noticeable.

“We do not know if it something that is real or if it’s just an experimental error and just something that come up during the study by accident,” he added.

The study authors concede that on average, the difference in behavior scores were small and likely would not be noticed in any one child. But they say across a large group of children, the differences would be more noticeable.

Soucy says a major problem with the study is that it’s actually a re-evaluation of a previous study intended to look at the health effects of amalgam. That meant that the researchers were not able to analyze the fillings themselves to look for what components might have been causing problems.

He says there are many brands of amalgam and each one contains different ingredients. So he says a larger and better study is needed to look at exactly what component --- if any -- in the fillings might be linked to behaviour problems.

Soucy adds it’s important to note that bisGMA fillings do not actually contain BPA.

“They contain materials that are derived form BPA, and those materials do not revert to BPA,” he said.

Composite fillings have been used for 25 years and no major health problems have ever been noticed, Soucy adds. While he encourages further study to see if the fillings are a problem for certain children, he fells assured of their safety.

“Composite fillings are absolutely safe for children,” he said.