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Overview
Recent news articles1-4 have presented findings from a new study  , published in the June 2006 Cancer Research, which concluded that laboratory rats exposed to bisphenol A, an environmental estrogen, and estradiol, a naturally occurring form of the hormone estrogen, had increased susceptibility to precancerous prostate lesions.
As previous studies have noted, people may be exposed to bisphenol A (BPA) in the environment through contact with food and beverage containers that are made with polycarbonate plastics and epoxy resins. While the study determined that early exposure to low-dose bisphenol A could predispose laboratory rats to precancerous prostate lesions, bisphenol A alone was not sufficient to create the lesions. Subsequent exposure to prolonged elevated levels of both estradiol and testosterone in the adult rat was required to see the increased incidence of the precancerous lesion. This was correlated with changes in gene expression. Exposure to “environmentally relevant” levels of bisphenol A alone did not increase the incidence of precancerous lesions. Furthermore, the bisphenol A was administered subcutaneously to the laboratory rats rather than orally, thus bypassing normal metabolic defense mechanisms and likely exaggerating an estrogenic effect.
A common misperception in dentistry is that bisphenol A is present in dental sealants, which are frequently placed on teeth for caries prevention. In fact, bisphenol A is not used as an ingredient in the manufacture of resin-based dental sealants. Among the many manufacturers of dental sealants, only one product may result in trace levels of bisphenol A (detectable only in saliva, not in serum) up to 3 hours after a sealant is placed. 5 This is due to the hydrolysis and salivary esterase conversion of BisDMA, an ingredient not used in sealants made by other manufacturers. Researchers have concluded that there is no systemic bisphenol A detectable when this sealant product is used and the concern about potential estrogenicity may be unfounded. 5
As noted in a 1999 report from the ADA Council on Scientific Affairs, “there is no evidence to suggest a link between any adverse health condition and bisphenol A leached out of dental sealants.” The same report also evaluated blood samples of dentists (with and without sealants on their teeth), and found no BPA in the blood samples of either group of dentists.
While the new study demonstrated low-dose effects on laboratory rats, further research still is required. Based on the collective body of current scientific evidence, there are no adverse health risks, including prostate cancer, that are known to result from dental sealants. Further information on prostate cancer is available from the National Cancer Institute .
Footnotes
1 Cone M. Chemical in plastics is tied to prostate cancer. Los Angeles Times, June 1, 2006. Available at: http://www.latimes.com/news/nationworld/nation/la-na-prostate1jun01,1,774 2836.story?coll=la-headlines-nation&ctrack=1&cset=true . Accessed June 4, 2006.
2 Fischer D. Scientists find new link between plastic, cancer. Oakland Tribune, June 1, 2006. Available at: http://www.insidebayarea.com/oaklandtribune/ci_3887148 . Accessed June 4, 2006.
3 Early estrogen exposure tied to cancer. United Press International, June 1, 2006. Available at: http://www.upi.com/HealthBusiness/view.php?StoryID=20060601-112643-8344r. Accessed June 4, 2006.
4 Smith M. Neonatal Estrogen Exposure Leads to Prostate Cancer in Rats. MedPageToday, June 1, 2006. Available at: http://www.medpagetoday.com/HematologyOncology/ ProstateCancer/tb/3443 . Accessed June 8, 2006.
5 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.
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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 December 2005
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