Do resins in sealants pose a long-term health issue?

By Tony Edwards, editor in chief

January 3, 2018 -- Dental sealants have been shown to be effective in preventing tooth decay. But do resins in sealants available in the U.S. contain chemicals that may cause long-term health problems if children and adults are exposed to them? A new study looked into this question.

Researchers studied the composition of 70 different dental resins available in the U.S. and found that 65 of them contained bisphenol A (BPA) or bisphenol A diglycidyl ether (BADGE), chemicals that may cause long-term health problems (Environmental Research, December 22, 2017).

New resins are needed for dental sealants, corresponding author Kurunthachalam Kannan, PhD, told by email.

"Regulations are needed to stop using BPA/BADGE-based resins as dental sealants," he said.

Kannan is deputy director of the Division of Environmental Health Sciences at the New York State Department of Health's Wadsworth Center, as well as a professor at the University at Albany School of Public Health.

Destructive effects?

While dental sealants are widely used in the U.S., especially in children, there have been few, if any, studies on the composition of these sealants and whether exposure to these chemicals could be harmful to adults and children.

“Regulations are needed to stop using BPA/BADGE-based resins as dental sealants.”
— Kurunthachalam Kannan, PhD

Previous studies have shown that incomplete polymerization and secondary decomposition of sealants can lead to exposure to epoxy resins widely used in these sealants, such as BPA and BADGE. Kannan and colleagues wanted to investigate how many widely available sealants contain these resins and to assess the exposure of adults and children to bisphenol and BADGE through sealant application.

Exposure-mitigation strategies cannot be formed until the level of human exposure is known, the researchers noted.

While some information indicates that dental sealants contain BPA, no one has measured bisphenol and BADGE in these sealants, Kannan said.

"Bisphenols are endocrine disruptors, and there is an interest in understanding exposures," he said. "This study shows that dental sealants are a source of exposure to bisphenols."

The researchers purchased 70 different dental sealants from online vendors and distributors from June to August 2015. The dental sealants represented 15 manufacturers/distributors and 19 popular brands available in the U.S. Various shades of sealants (opaque, clear, ultraclear, natural, and off-white) and types of cure (light and self-cure) were included.

The researchers extracted bisphenols and BADGEs from the sealants. They found that 65 of the 70 sealants contained at least one of eight bisphenol analogues. Among these analogues, BPA was the most abundant (46%), at concentrations that ranged from below quantification levels to 1,070 µg/g. The group noted that unpolymerized BPA-based monomers can leach into saliva, followed by systemic absorption into the bloodstream.

Bisphenol F was the second most abundant bisphenol found, with a detection rate of 24% and concentrations ranging from below quantification levels to 374 ng/g. Other bisphenols were less frequently detected.

The geometric mean concentration of total BADGEs was 47.8 µg/g, which was two to three orders of magnitude higher than the concentration of total bisphenols (539 ng/g).

The researchers also conducted an exposure assessment on the concentrations of bisphenol and BADGE measured in sealants and their application rates in dentistry. The worst-case exposure scenario with the highest measured concentration of total bisphenol and BADGE and application on eight teeth at 8 mg each yielded an estimated daily intake of 1,670 and 5,850 ng/kg·bw/day for adults (70 kg) and children (20 kg), respectively.

Kannan and colleagues noted that their estimate is based on the concentrations of extracted bisphenol and BADGE, and that it's likely that a smaller amount would seep into body.

"Nevertheless, the results of this study provide evidence that dental sealants can be a source of exposure to [bisphenol analogues] and BADGEs, especially in children," they wrote.

Ideal outcome

While the researchers did not list any study limitations, they did note that further studies are needed to establish the permissible levels of bisphenol and BADGE in sealants.

Kannan said he and his fellow researchers would like to see additional sealant options on the market.

"It would be ideal to have BPA/BADGE-free dental sealant to avoid exposures in people who receive sealants and dentists who apply sealants," he said.

Copyright © 2018

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