The trace element fluorine is present in the body almost entirely in bone and teeth. Because of its high reactivity, fluorine exists as its anion fluoride. Fluoride’s best known effect is to serve as a catalyst for both the mineralization of developing tooth enamel prior to tooth eruption and for remineralization of surface enamel. The combination of these fluoride effects greatly reduces occurrence of dental decay (caries). Denotal caries is an infectious disease caused by bacteria. When food is ingested, oral bacteria multiply within their home (plaque) and produce organic acids. Loss of tooth enamel accelerates as long as plaque pH is less than 5.5. The presence of fluoride changes some of the tooth crystal into a less acid-soluble crystal known as fluoropatite.
The Food and Nutrition Board of the National Academy of Sciences has concluded that a fluoride intake of 0.05 mg/kg body weight, after the age of 6 months, provides an adequate fluoride intake to reduce risk of dental decay. It is assumed that this fluoride will come from a combination of food and water sources.
The major source of fluoride is drinking water. Seafood, some teas, and foods made with mechanically separated chicken (baby food, canned meats, luncheon meats, and frankfurters) contribute to total fluoride intake. Otherwise, most foods are very low in fluoride.
Regular comsumption of fluoride from a community water supply plus regular use of fluoridated toothpaste can significantly decrease prevalence of dental decay. Dietary fluoride supplements are only recommended for children when the water supplies fluoride at less than 0.3 mg/L. In this case, fluoride supplements of 0.25 mg/day for ages 0.5-3 years, 0.5 mg/day for ages 3-6 years, and 1 mg/day for ages 6-16 years can be recommended. No dietary fluoride supplement is recommended when water supplies fluoride at greater than 0.6 mg/L.
Under controlled experimental conditions, slow release administration of fluoride (23 mg/day) plus calcium has been shown to stimulate new bone formation in some individuals.
Children less than 8 years of age can develop mottled tooth enamel (white horizontal lines with hypo-mineralized areas susceptable to decay in extreme cases) if they ingest several times more fluoride than recommended during tooth enamel formation. Swallowing of fluoridated toothpaste by young children has been shown to be the most prevalent cause of this problem.