Fluoride therapy

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. Fluoride decreases breakdown of teeth by acids, promotes remineralisation, and decreases the activity of bacteria. Fluoride is on the World Health Organization's List of Essential Medicines. In 2021, it was the 291st most commonly prescribed medication in the United States, with more than 600,000 prescriptions.

Medical uses

Dental caries

Fluoride therapy has a beneficial effect on the prevention of dental caries. Fluoride toothpaste, with concentrations of 1000 ppm and above, reduces the risk of dental caries in school-aged children and adolescents. Water and milk fluoridation are two forms of systemic fluoride therapy that are effective at preventing dental cavities.

Osteoporosis

Fluoride supplementation has been studied for the treatment of postmenopausal osteoporosis, for which it does not appear to be effective. Even though sodium fluoride increases bone density, it does not decrease the risk of fractures.

Side effects

Fluorosis

The use of fluoride toothpaste (with concentrations of 1000 ppm and above) and fluoride supplements in children below the age of six years, especially within the first three years of life, is associated with a greater risk of dental fluorosis. Optimal water fluoridation for the prevention of dental caries increases the prevalence of dental fluorosis by 4 to 5%. Ingestion of fluoride can produce gastrointestinal discomfort at doses as low as 0.2 mg/kg, 20 times lower than lethal doses. Chronic intake and topical exposure may cause dental fluorosis, and excess systematic exposure can lead to skeletal fluorosis. The American Dental Association (ADA) recommends infants primarily consume human milk to reduce fluoride intake and prevent infants developing fluorosis.

In 1974, a three-year-old child swallowed 45 milliliters of 2% fluoride solution, triple the fatal amount, and 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.

Fluoride reduces the decay of tooth enamel by the formation of fluorapatite and its incorporation into the dental enamel. The fluoride ions reduce the rate of tooth enamel demineralization and increase the rate of remineralization of teeth at the early stages of cavities. Fluoride exerts these effects by the demineralization and remineralization cycle. The remineralization cycle, critical to decay prevention, occurs when fluoride is present in the oral cavity. After fluoride is swallowed it has a minimal effect.

Fluoride ions are involved in three principal reactions of remineralization:

Fluoride can be delivered by many chemical methods (sodium fluoride, stannous fluoride, amine fluoride, monofluorophosphate, and more). The anti-caries performance differences between them have been shown to have less effect than variations in behavior shown by individuals in brushing, using fluoride products and post use behavior. Often the chemical form of fluoride is driven by compatibility with the other elements mixed with, price, and such. Fluoride does not prevent cavities but rather controls the rate at which they develop, and so repeated exposure throughout the day is essential for its effective function. Its use in the U.S. began in the 1940s, following studies of children in a region where water is naturally fluoridated. In 1945, Grand Rapids, Michigan became the first city in the world to fluoridate its drinking water. The Grand Rapids water fluoridation study was originally sponsored by the U.S. Surgeon General, but was taken over by the NIDR shortly after the institute's inception in 1948. Fluoridation is now used for about two-thirds of the U.S. population on public water systems and for about 5.7% of people worldwide. Although the best available evidence shows no association with adverse effects other than fluorosis, most of which is mild, Water fluoridation is the most cost-effective way to induce fluoride, with an estimated cost between US$0.50 and $3.00 per person per year, depending on the size of the community involved.

Toothpaste

Most toothpastes contains between 0.22% (1,000 ppm) and 0.312% (1,450 ppm) fluoride, usually in the form of sodium fluoride, stannous fluoride, or sodium monofluorophosphate (MFP).

Frequent use of toothpaste with 1,100 ppm fluoride content enhances the remineralization of enamel and inhibits the demineralization of enamel and root surfaces.

Most toothpastes with fluoride contain mild abrasives in order to remove heavier debris and light surface staining. These abrasives include calcium carbonate, silica gels, magnesium carbonates and phosphate salts. Second, it is available as profluoride compounds which can precipitate in the mouth during toothbrushing and release ionic fluoride.

Fluoridated toothpaste is also available in the form of 0.454% stannous fluoride (SnF<sub>2</sub> with fluoride concentration 1,100 ppm). When combined with the stannous ion (Sn<sup>2+</sup>), fluoride in toothpaste appears to have a wide range of benefits to oral health.

Toothpastes containing stannous fluoride have been shown to be more effective than other fluoride toothpastes for reducing dental decay, dental erosion, gingivitis, tooth hypersensitivity, dental plaque, and stains.

Anti-sensitivity toothpastes with fluoride are also available for those who have sensitive teeth. Some anti-sensitivity toothpastes with fluoride on the market contain the ingredients called strontium chloride or potassium nitrate which help to alleviate tooth sensitivity. The fluoride rinse with a 0.05% fluoride content is used for daily rinsing, while the rinse with 0.2% fluoride content is used for weekly rinsing and in school-based weekly rinsing programs. Fluoride at these concentrations is not strong enough for people at high risk for tooth decay. Regular use of a daily (230 ppm) or weekly (900 ppm) fluoride mouth rinse under supervision results into a reduction of tooth decay in children's permanent teeth. After a fluoride mouthrinse treatment, the fluoride in the mouthrinse is retained in the saliva which helps prevent tooth decay. They are not recommended if a person is drinking water that already contains sufficient fluoride.

Professionally applied fluoride gel or foam is applied through the use of a foam mouth tray which is held in the mouth by gently biting down. The application usually lasts for approximately four minutes, and patients should not rinse, eat, smoke, or drink for 30 minutes after application. The reason for this is to allow the teeth to absorb the fluoride into the tooth structure when it is at its highest concentration, without being interrupted. This aids in the repair of microscopic dental decay. There is no clinical evidence on the effectiveness of one-minute fluoride gel/foam applications. A specific benefit when using foam is that less product is required during application, which results in a lower fluoride dose and lessens the risk of accidental ingestion.

More research is required regarding the efficacy of fluoride gels in treating initial dental decay lesions.

Varnish

Fluoride varnish has practical advantages over gels in ease of application and use of smaller volume of fluoride than required for gel applications. The principle of fluoride varnish is to apply fluoride salt in a very high concentration (approximately 50,000 ppm) onto the surface of the teeth. A 2018 Cochrane review found insufficient evidence to determine the effect of slow-release fluoride glass beads in caries-inhibiting when compared to other types of fluoride therapy.

Lozenges

Fluoridated lozenges may contain about 1 mg fluoride each, and are meant to be held in the mouth and sucked. The dissolved lozenge is swallowed slowly, so the use of lozenges is both a topical and a systemic therapy. A 1955 study comparing the effects of fluoride lozenges and fluoride pills provided clear evidence early that fluoride acts topically.

Medical supplements

Medical fluoride supplements in the form of tablets, lozenges, or liquids (including fluoride-vitamin preparations) are used primarily for children in areas without fluoridated drinking water. The evidence supporting the effectiveness of this treatment for primary teeth is weak. The supplements prevent cavities in permanent teeth. A significant side effect is mild to moderate dental fluorosis.