Fluoride therapy is the use of fluoride for medical purposes. Fluoride supplements are recommended to prevent tooth decay in children older than six months in areas where the drinking water is low in fluoride. It is typically used as a liquid, pill, or paste by mouth. Fluoride has also been used to treat a number of bone diseases.
Relatively high ingestion of fluoride by babies and children may result in white marks on the teeth known as fluorosis. Excessive ingestion by babies and children can also result in severe dental fluorosis, indicated by a brown or yellow coloring and weakness/brittleness of the teeth, or in severe cases, acute toxicity. Fluoride therapy typically uses the sodium fluoride form, though stannous fluoride may also be used. Fluoride decreases breakdown of teeth by acids, promotes remineralisation, and decreases the activity of bacteria. It is believed to work primarily through direct contact with the teeth in the mouth after they have emerged from the gums.
Fluoride came into use to prevent tooth decay in the 1940s. Fluoride is on the World Health Organization's List of Essential Medicines. In 2020, it was the 265th most commonly prescribed medication in the United States, with more than 1million prescriptions.
Medical uses
Dental caries
Fluoride therapy has been proven to have a beneficial effect on the prevention of dental caries. Robust evidence supports the use of fluoride toothpaste (with concentrations of 1000 ppm and above) to reduce the risk of dental caries in school-aged children and adolescents. The ingestion of fluoride as primary teeth are being developed has shown that the teeth have formed stronger and more resistant for caries, though increases the risk of dental fluorosis. Water and milk fluoridation are two forms of systemic fluoride therapy that have been demonstrated to be effective at preventing dental cavities.
Osteoporosis
Fluoride supplementation has been extensively studied for the treatment of postmenopausal osteoporosis. This supplementation does not appear to be effective; even though sodium fluoride increases bone density, it does not decrease the risk of fractures.
Side effects
Fluorosis
See main article Dental fluorosis. The use of fluoride toothpaste (with concentrations of 1000 ppm and above) and fluoride supplements in children below the age of six years, and especially within the first three years of life, is associated with a greater risk of dental fluorosis. However, the use of fluoride supplements during the last six months of pregnancy has no significant impact on the incidence of fluorosis in children. It has also been estimated that optimal water fluoridation for the prevention of dental caries increases the prevalence of dental fluorosis by 4 to 5%. The observed effects are mild to moderate, usually of minimal aesthetic concern.
Other risks
Reports have claimed that water fluoridation can be linked to the development of osteoporosis and various cancers; however, a recent systematic review has found no evidence to support these claims.
Overdose
Consumption of large amounts of fluoride can lead to fluoride poisoning and death; the lethal dose for most adult humans is estimated at 5 to 10 g (which is equivalent to 32 to 64 mg elemental fluoride/kg body weight). Ingestion of fluoride can produce gastrointestinal discomfort at doses at least 15 to 20 times lower (0.2–0.3 mg/kg) than lethal doses. Chronic intake and topical exposure may cause dental fluorosis, and excess systematic exposure can lead to systemic effects such as skeletal fluorosis. Young children are at risk for receiving excess fluoride, and the American Dental Association (ADA) has recently issued an interim guidance on their fluoride consumption.
In 1974 a three-year-old child swallowed 45 milliliters of 2% fluoride solution, estimated to be triple the fatal amount, and then died. The fluoride was administered during his first visit to the dentist, and the dental office was later found liable for the death.
Mechanism
Strictly speaking, fluoride therapy repairs rather than prevents damage to the teeth, causing the mineral fluorapatite to be incorporated into damaged tooth enamel. Fluorapatite is not a natural component of human teeth, although it is found in the teeth of sharks. The main mineral found in natural tooth enamel is hydroxyapatite rather than the fluorapatite created in the presence of fluoride. Even without fluoride, teeth experience alternating increases and decreases in mineral content, depending upon how acidic or alkaline the mouth is, and depending upon the concentration of other substances in the mouth, such as phosphate and calcium.