Science You Can Sink Your Teeth Into
Sealants and Amalgam
February is National Children’s Dental Health Month—a good time to make sure your kids have regular checkups and are brushing two to three times a day. Here’s the latest research on some rather toothy topics: dental sealants and mercury fillings.
Don't Swallow Sealants
Dental sealants, plastic coatings that can protect teeth from cavity-causing bacteria, may release the estrogenic chemical bisphenol A (BPA), which is linked in animal studies to decreased sperm production, early puberty and miscarriage. Recently, BPA was also linked to prostate cancer, according to a study in the June 1, 2006 Journal of Cancer Research. Dentists commonly apply sealants to hard-toclean molars, using them on 32 percent of U.S. children, according to the Centers for Disease Control and Prevention (CDC).
Some sealants contain BPA and can release it into the body during application, according to a study in the March 2006 Journal of the American Dental Association. Researchers tested 14 volunteers immediately after sealant application and found that patients who received Delton Light Cure (LC) Opaque brand absorbed about 110 micrograms of BPA, 20 times that absorbed by recipients of another brand, Helioseal F (5.5 micrograms). Delton Light Cure (LC) leached amounts similar to those that caused developmental toxicity in rodent studies and, at 42.8 parts per billion (ppb), are higher than the highest amount found in canned food (38 ppb).
“We believe this is because there is incomplete curing of the sealant,” says Dana Barr, Ph.D., a research chemist at the CDC. “If the patient doesn’t spit it out, he or she will likely swallow it.” The American Dental Association’s position on BPA states, “there is no evidence to suggest a link between any adverse health condition and BPA leached out of dental sealants.”
Composite versus Amalgam
If you do get a cavity, should you fill it with a plastic composite that may leach BPA? Or opt for a silver-colored amalgam filling, containing about 50 percent mercury, a heavy metal linked to lowered IQ and attention problems?
Approximately 50 million U.S. children have amalgam fillings. Recently two publicly funded studies in the U.S. and Portugal followed 500 children ages six to 10 that randomly received composite or amalgam fillings. Both found that mercury-silver amalgam fillings do not pose a risk of lowered IQ, attention deficit or problems with motor skills or coordination in children, as published in the April 19 issue of the Journal of the American Medical Association (JAMA).
These studies don’t give mercury a clean bill of health, warns Herbert L. Needleman, M.D., a pediatric psychiatrist at the University of Pittsburgh, in an accompanying editorial. The researchers may have overlooked subtle effects on brain function, and the seven-year maximum follow-up period may miss mercury’s effects later in life, Needleman says, adding, “evidence is piling up to support that dental amalgam is a risk for children’s brain function.”
Previous studies have found that amalgam fillings do release mercury into the body, and dental clinics release it into wastewater that pollutes lakes and streams. Noting that mercury is hazardous waste elsewhere, Michael Bender, executive director of the Mercury Policy Project, asks, “why don’t we consider it hazardous waste when it is in somebody’s mouth?”
What You Can Do
■ Prevent cavities by brushing twice daily with fluoride toothpaste, flossing daily, limiting sugary snacks and having regular dental check-ups. To prevent fluorosis, children under six should not use fluoridated mouthwashes. To help prevent early childhood tooth decay, see the ADA’s tips at www.ada.org.
■ If a dentist suggests sealants for you or your child, ask why, whether it’s necessary on baby teeth and whether decay may be avoided by improving diet and hygiene first.
■ If you are considering sealants, ask your dentist or call the manufacturer to check for BPA. Composite fillings can also contain this chemical.
■ To limit childhood exposures, ask your dentist to help you find BPA-free sealants.
■ If you decide on sealants, immediately after the sealant is applied, chew on a cotton pad to induce saliva and then spit out as much as you can into the sink.
■ If you need a filling, choose a composite: BPA exposures are low and not released continually, as mercury is.
Reprinted with permission from the July/Aug 2006 issue of The Green Guide. For subscription information, see thegreenguide.com