After decades of touting the importance of fluoride, federal officials now say that many Americans may be getting too much of a good thing.
For years, parents have heeded their dentists' warnings and had their children take fluoride supplements or use fluoride toothpaste, in addition to whatever amount of the mineral they received from their tap water.
But today the U.S. Department of Health and Human Services and the U.S. Environmental Protection Agency announced that too much fluoride can cause fluorisis, a hypermineralization of tooth enamel that can result in the staining or pitting of teeth.
"In the vast majority of those affected, it's barely noticeable, even by dentists and oral health professionals," said Dr. Howard Koh, assistant secretary for health at HHS, "and that's why we believe making this adjustment now will promote health, improve oral health and reduce rates of fluorosis going forward."
HHS has proposed that the current recommendation be set at 0.7 milligrams of fluoride per liter of water, lowered from the previously recommended range of 0.7 to 1.2 milligrams.
Fluoride, when taken in moderate amounts, can help prevent cavities. The mineral has been added to toothpaste and to water to improve dental health. But some parts of the country, where the water is already rich in fluoride, have reported cases of fluorosis.
Dr. Griffin Cole, a dentist in Austin, Texas, said he has seen several cases of mild to severe fluorosis in his practice.
While he applauded the feds' proposal, he'd like to see the recommendations go even lower.
"I still don't think it's enough, honestly," he said. "I don't think there should be fluoride in the water at all.
"I think it's a nice move in the right direction," he said.
Cole said he began his dentistry career in the early 1990s, working for a dentist who was openminded about fluoride use and believed that his patients were getting too much. Cole said he had never once prescribed fluoride supplements to his patients.
He cited studies from the past decade that have linked excess fluoride to not only fluorosis but to higher instances of bone cancer in the test subjects. He also said osteoporosis was an additional concern, since ingested fluoride is known to sit in a person's bones.
"Ingesting fluoride in any form does nothing for your teeth," he said. In cases of "rampant" tooth decay, applying a topical fluoride can improve dental health, but only minimally.
Fluoride, Cole said, molds to the tooth's enamel. So while it will aid in preventing decay, it can also make teeth brittle.
"When you see a case of somebody coming in with bad fluorosis, to restore those teeth you either have to crown them completely or at least do a veneer," he said. "So it's a very costly thing to fix."
Depending on the dentist and the region of the country, restoration could cost between $900 and $1,600 a tooth.
Koh said that in recognition of the multiple sources of fluoride available, HHS and the EPA also recommend that municipalities lower the levels of fluoride in their drinking water.
"The main issue of the very mild dental fluorosis in children is what we're addressing right now," he said, "and what we anticipate is that with this adjustment, we're going to lower that."