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Dental patients may ask about a widely reported article on exposure to bisphenol-A (BPA) from sealants and composite materials, which was published on September 7th in the journal Pediatrics and will appear in the October print edition.1 News coverage on the article has raised several common questions about the relationship between BPA, a synthetic chemical resin, and dental materials. This "Science in the News" provides analysis based on the current body of knowledge on sealants and composites that contain BPA derivatives (monomers derived from BPA).

In recent years, widespread media attention has focused on environmental exposure to BPA in consumer products (e.g., plastic bottles and canned foods), citing public health concerns and persistent debates about BPA's safety, its reported estrogenic properties, and potential adverse health effects. Of relevance to dentistry, BPA has often been publicized as a chemical that was "found in" or "released from" dental materials, which has generated some misperceptions and inaccurate information about health risks related to potential BPA exposure from dental materials. Many questions have also been raised about the presence of BPA as a starting ingredient in the formation of two monomers that are widely used in resin-based materials: bis-DMA and bis-GMA. 

In the vast majority of dental materials, bisphenol-A is not used directly in the manufacturing process. Resin-based materials are commonly made with bis-GMA, and research has shown that bis-GMA does not hydrolyze into BPA.2 For these reasons, previous studies have not identified significant amounts of BPA in dental sealants or composites. 

Table 1 in the Pediatrics article provides a list of dental sealants representing over 90% of the U.S. market share, and none identify BPA as a starting raw chemical. While dental sealants can be manufactured with bis-DMA or bis-GMA, which are both derived from BPA, the identified sealants do not use pure BPA as an initial chemical compound. 

It should be noted that sealants and composite resins developed with bis-DMA and/or bis-GMA may contain trace amounts of BPA as a byproduct of the manufacturing process. However, as noted in the Pediatrics article, resin-based dental materials containing bis-DMA can break down into BPA after coming in contact with enzymes in saliva, but materials made with bis-GMA do not undergo this reaction. 

Importantly, BPA exposure from dental sealants is only detectable in human saliva as a transient, low-level exposure, and the exposure has only been identified in dental materials that contain bis-DMA. Further, the amount or extent of BPA absorption by the body, and whether this poses a significant risk for adverse effects on human health, is not known. Previous research found that only one out of 10 dental sealants produced any level of BPA, and for that sole sealant, only trace levels of BPA were detectable in saliva (not in serum) up to 3 hours after placement.3 Previous research also confirmed that dental materials with bis-DMA can release trace quantities of BPA because it is subject to degradation by salivary enzymes. Although bis-DMA is not commonly used as a primary resin in dental materials today, dentists can confirm whether their dental materials contain bis-DMA or bis-GMA by checking the material safety data sheet(s) or by contacting the product manufacturer. 

Based on the well-established effectiveness of sealants in preventing dental caries, the pediatric authors recommend the continued usage of dental sealants and composites in clinical practice and in school-based sealant programs. They conclude that the benefits of dental sealants outweigh the risk of brief BPA exposure following sealant application or composite placement. This conclusion is supported by current scientific evidence, which confirms that dental materials are far less likely to cause BPA exposure than other consumer goods such as beverage containers made with polycarbonate plastic or food cans lined with epoxy resin. 

The authors also offer two precautionary recommendations for minimizing exposure to BPA, despite an absence of documented adverse health risks related to dental materials: (1) precautionary application techniques to remove residual monomer in the oxygen-inhibited surface layer after sealant/composite placement (e.g., wiping/rubbing the monomer layer with pumice on a cotton roll; asking the patient to rinse/gargle with water); and (2) minimizing elective use of resin-based materials during pregnancy. These recommendations can be considered advisory in nature, since only minute amounts of monomer have been detected in saliva and urine of patients after placement of resin-based materials, and there are no data indicating human systemic toxicity. It is considered advisable that dentists adequately cure resin-based materials according to the manufacturer's directions, since the amount of leachable components decreases with more extensive degree of cure of these materials. 

Dentists can reassure patients who may be concerned about BPA exposure that the ADA Council on Scientific Affairs has not identified evidence to suggest that the use of resin-based dental sealants or composite resin restorative materials is linked to adverse health effects from BPA exposure.4 As recently reported by The New York Times,5 the National Institutes of Health are funding several human and animal studies that will continue to investigate various adverse health effects that may potentially be associated with low-dose oral exposure to BPA.  The ADA will continue to monitor the peer-reviewed, scientific literature for documented evidence of any adverse health effect related to dental materials and/or their components. The following resources on bisphenol-A and dental materials are also available for more information:

Footnotes

1. Fleisch AF, Sheffield PE, Chinn C, Edelstein BL, Landrigan PJ. Bisphenol A and related compounds in dental materials. Pediatrics 126(4), October 2010, 760-68. Available at: "http://pediatrics.aappublications.org/cgi/reprint/peds.2009-2693v1". Accessed September 10, 2010.

2. Schmalz G, Preiss A, Arenholdt-Bindslev D. Bisphenol-A content of resin monomers and related degradation products. Clin Oral Investig 1999;3(3):114-9.

3. Fung EY, Ewoldsen NO, St Germain HA, Fr. et al. Pharmacokinetics of bisphenol A released from a dental sealant. JADA 2000;131(1):51-8. 

4. American Dental Association Council on Scientific Affairs. Statement on Bisphenol A and Dental Materials.  July 2010. Available at: "http://www.ada.org/1766.aspx". Accessed September 10, 2010.

5. Grady D. In feast of data on BPA plastic, no final answer. The New York Times, September 7, 2010.  Available at: "www.nytimes.com/2010/09/07/science/07bpa.html". Accessed September 10, 2010.

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Science in the News is a service by the American Dental Association (ADA) to present current information about science topics in the news. The ADA is a professional association of dentists committed to the public's oral health, ethics, science and professional advancement; leading a unified profession through initiatives in advocacy, education, research and the development of standards. As a science-based organization, the ADA's evaluation of the scientific evidence may change as more information becomes available. Your thoughts would be greatly appreciated.

Document Posted September 2010