Deconstructing the arguments against BPA

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The case against bisphenol A (BPA) as an estrogen-mimetic toxin is weakening, according to a presentation last week at the Rocky Mountain Dental Convention in Denver.

The most recent statement justifying acceptance of the compound at low levels in dental sealants and composites was issued in July 2010 by the ADA, Sheldon Newman, DDS, an associate professor at the University of Colorado School of Dental Medicine, said January 13.

Dr. Newman, who serves on the ADA Standards Committee on Dental Products, said the ADA believes that BPA poses "no known threat."

Still, fear persists over claims that the polycarbonate manufacturing compound is dangerous in dental materials and responsible for complications as far reaching as male sexual performance, early onset of puberty in females, diabetes, and obesity. Thus, dentists should continue making every effort to clarify the issue for worried patients, Dr. Newman urged.

Specifically, dentists should make clear that residual BPA in dental materials is usually undetectable and typically present at levels lower than regulatory or scientific recommendations.

Dentists should also keep their eyes peeled for future products that can guarantee BPA-free content, he said -- something many patients are looking forward to as well.

"They're not out there yet, but they're coming," Dr. Newman said.

Wrong monomer?

In a slide presentation, Dr. Newman deconstructed the controversy over BPA that has gestated in the public consciousness since a 1996 Environmental Health Perspectives article (March 1996, Vol. 104:3, pp. 298-305) on resin-based dental composite tests cautioned against a dental monomer called bisphenol A glycidyl methacrylate (bis-GMA). The authors claimed that bis-GMA is a xenoestrogen, capable of facilitating an estrogenic-like effect in humans. But Dr. Newman explained that it is another dental monomer, bisphenol A dimethacrylate (bis-DMA), that has displayed this propensity to a certain degree.

“It's used in the lining of cans and we're worried about dental fillings?”
— Sheldon Newman, DDS, University of

Tests confirm that BPA itself is a xenoestrogen. But it is not actually a direct ingredient of dental sealants and composites, Dr. Newman said. Something closer to the truth, he said, can be found in a study published in October 2010 in Pediatrics (Vol. 126:4, pp. 760-768), which explained that many dental materials contain compounds that turn into BPA only upon contact with saliva.

Additional fallacies have been dispensed in recent years by mainstream media and alarmists who claim that lobbyists are preventing a full-fledged ban of the compound, he added.

BPA is most commonly used in polycarbonate synthesis, epoxies, flame retardants, and carbonless copy paper. It also has been used in the production of water bottles, baby bottles, and soft drink cans.

The latter use drew a scoff from Dr. Newman. "It's used in the lining of cans and we're worried about dental fillings? Let's put this into perspective," he said.

Peer-reviewed studies

Various studies and websites have listed deleterious effects of BPA related to thyroid function, cancer, endocrine disruption, cardiovascular disease, hyperactivity, and other complications. And some U.S. states -- including Connecticut and Minnesota -- as well as Canada and the European Union have banned use of BPA in baby bottles, Dr. Newman noted.

In addition, the U.S. National Toxicology Program (NTP) drew from data reported by agencies associated with the National Institutes of Health, Centers for Disease Control and Prevention, and U.S. Food and Drug Administration (FDA) to review the issue and published a monograph on its findings in 2008. That report suggested that some concern is warranted over potential BPA effects on the brain or prostate glands of fetuses, infants, and children who are exposed to normal levels of the compound.

However, evaluations of BPA's impact on mammary gland health, early female puberty, neonatal mortality, birth defects, reduced birth weight, and reproductive health were reported as either "minimal" or "negligible" by the NTP.

Dr. Newman cited eight peer-reviewed studies that appear to refute most of the BPA toxicity claims that have been made in recent years.

Still, a certain level of reservation remains, he said. The FDA has expressed its support of an end to BPA use in baby bottle manufacturing, as well as in the linings of infant formula cans and other types of food cans.

Copyright © 2011

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