Fluoride

Fluoride is the term used for the form of fluorine that appears in drinking water and in the body. In children, fluoride strengthens the mineral composition of the developing teeth, so they resist the formation of dental cavities, and it also strengthens bone. In adults, fluoride helps teeth by decreasing the activity of the bacteria in your mouth that cause dental caries.

• Fluoride— The form of fluorine that appears in drinking water and in the body.

The major source of fluoride is drinking water, although fish and most teas contain fluoride as well. Some water supplies are naturally fluoridated, and many supplies have fluoride added, usually at a concentration of one part fluoride to a million parts water. Fluoride levels in water are stated in concentrations of parts per million (ppm). About 1 ppm is ideal. Less than 0.7 ppm isn't adequate to protect developing teeth. More than about 1.5 to 2.0 ppm can lead to mild fluorosis, a condition that causes small, white, virtually invisible opaque areas on teeth. In its most severe form, fluorosis causes a distinct brownish mottling or discoloring. Fluorosis can occur only during tooth development. To prevent fluorosis, children should be advised to use small amounts of fluoride toothpaste and not to swallow it. Also, monitor the fluoride content of your local water supply and use fluoride supplements as directed by your doctor.

• Fluorosis— A condition in which the teeth become mottled and disordered due to high fluoride ingestion.

Only fluoride taken internally, whether in drinking water or dietary supplements, can strengthen babies' and children's developing teeth to resist decay. Once the teeth have erupted, they are beyond help from ingested fluoride. Supplements are often prescribed for the approximately 40 percent of Americans who do not have adequately fluoridated water supplies.

For both children and adults, fluoride applied to the surface of the teeth can nonetheless add protection, at least to the outer layer of enamel, where it plays a role in reducing decay. The most familiar form, of course, is fluoride-containing toothpaste, introduced in the early 1960s. Fluoride rinses are also available, as are applications by dental professionals. They are considered effective adjuncts to ingested fluoride and are the only useful sources of tooth-strengthening fluoride for teenagers and adults.