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.
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 result in severe dental fluorosis, indicated by a brown or yellow coloring, weakening and 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. Fluoride works primarily through direct contact with teeth.
Fluoride came into use to prevent tooth decay in the 1940s. 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. As primary teeth are being developed, the ingestion of fluoride causes the teeth to form stronger and more resistant to cavities, although this increases the risk of dental fluorosis. 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 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. The use of fluoride supplements during the last six months of pregnancy has no significant impact on the incidence of fluorosis in children. 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
Water fluoridation is not linked to the development of osteoporosis or cancer.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 grams, equivalent to 32 to 64 mg elemental fluoride per kg of body weight. 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 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:
- Iso-ionic exchange of F− for OH− in apatite: Ca1062 + 2F− → Ca106F2 + 2OH−
- Crystal growth of fluorapatite from a supersaturated solution: 10 Ca2+ + 6PO43− + 2F− → Ca106F2
- Apatite dissolution with CaF2 formation: Ca1062 + 2F− → 10 CaF2 + 6PO43− + 2OH−
Fluoride's effect on oral microflora and the significance of this effect on fluoride's overall effectiveness against cavities does not currently have a consensus. Many studies on bacterial cells in laboratories have shown the fluoride has many effects on them as an antimicrobial agent. The antimicrobial effects require concentrations of fluoride at least 10 ppm F, which only occurs briefly in the mouth with oral fluoride-containing products. A study looked at fluoride's effects on oral microflora and concluded that fluoride may not solely interact as an antimicrobial agent, acting additionally to reduce bacterial adhesion to teeth, along with the primary action of decreasing demineralization. Further investigation will need to be done to verify these claims.
Fluoride can be delivered by many chemical methods. 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.
All fluoridation methods provide low concentrations of fluoride ions in saliva, thus exerting a topical effect on the plaque fluid. 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. The more constant the supply the more beneficial fluoride will be in cavity prevention.
Delivery
Water fluoridation
Water fluoridation is the controlled addition of fluoride to a public water supply in order to reduce tooth decay. 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 has been contentious and opposition to water fluoridation exists despite its support by public health organizations. 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. A dollar spent on fluoridating water is estimated to save $7–42 on dental treatment.Toothpaste
Most toothpastes contains between 0.22% and 0.312% fluoride, usually in the form of sodium fluoride, stannous fluoride, or sodium monofluorophosphate.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.
Fluoride is available in three forms during toothbrushing. First, it is available as a free ionic fluoride which can react with the tooth structure, interfere with the metabolism of bacteria in plaque, or absorb to the oral mucosa. Second, it is available as profluoride compounds which can precipitate in the mouth during toothbrushing and release ionic fluoride. Lastly, fluoride in toothpaste can exist as unavailable fluoride compounds which do not release fluoride ions. This is due to the fluoride ions being swallowed or expelled when spitting.
High-fluoride content toothpaste generally contains 1.1% sodium fluoride toothpaste. This type of toothpaste is used in the same manner as regular toothpaste. The application of high-fluoride content toothpaste in adults twice daily improves the surface hardness of untreated root decay when compared to toothpaste with regular fluoride content.
Fluoridated toothpaste is also available in the form of 0.454% stannous fluoride. When combined with the stannous ion, 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, calculus and stains. A systematic review revealed stabilised stannous fluoride-containing toothpastes caused a reduction of plaque, gingivitis and staining in clinical trials, with a significant reduction in calculus and halitosis compared to other toothpastes.
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.