Fluoride therapy is the delivery of fluoride to the teeth topically or systemically in order to prevent tooth decay (dental caries) which results in cavities. Most commonly, fluoride is applied topically to the teeth using gels, varnishes, toothpaste/dentifrices or mouth rinse. Systemic delivery involves fluoride supplementation using water, salt, tablets or drops which are swallowed. Tablets or drops are rarely used where public water supplies are fluoridated.
Fluoridation is widely, but not universally, accepted by dentists and other medical professionals as being useful in preventing tooth decay. The U.S. Center for Disease Control lists water fluoridation as one of the "ten greatest public health achievements of the 20th century." It is therefore understandable that fluoride therapy would be commonly practiced and in many modalities. Many types of fluoride therapies are known, ranging from use of fluoridated toothpaste at-home to professionally administered topical fluorides provided by dental offices, to publicly sponsored fluoridation of water or other commonly ingested materials such as salt. At-home therapies can be further divided into over-the-counter (OTC) and prescription strengths. The fluoride therapies, whether OTC or PATF, are categorized by application – dentifrices, mouth rinses, gels/foams, varnishes, dietary fluoride supplements, and water fluoridation.
All fluoridation methods provide low concentrations of fluoride ions in saliva, thus exerting a topical effect on the plaque fluid. Fluoride combats the decay primarily by the formation of fluorapatite via remineralization of enamel. The fluoride ions reduce the rate of tooth enamel demineralization and increase the rate of remineralization of the early stages of cavities. Fluoride exerts its major effect by this demineralization and remineralization cycle. Fluoride also affects the physiology of dental bacteria, although its effect on bacterial growth does not seem to be relevant to cavity prevention. Fluoride has minimal effect on cavities after it is swallowed. Technically, fluoride does not prevent cavities but rather controls the rate at which they develop. Although fluoride is the only well-documented agent with this property, it has been suggested that also adding some calcium to the water would reduce cavities further.
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. It 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 for ethical, safety, and efficacy reasons, and opposition to water fluoridation exists despite its support by public health organizations. As mentioned, fluoride primarily only helps teeth when it is in the mouth. After it is swallowed, it has minimal effect.
A 2000 systematic review of water fluoridation's effectiveness found that fluoridation was associated with a decreased proportion of children with cavities (the median of mean decreases was 14.6%, the range −5% to 64%), and with a decrease in decayed, missing, and filled primary teeth (the median of mean decreases was 2.25 teeth, the range 0.5 to 4.4 teeth). A more comprehensive 2007 review which used the 2000 review for its water fluoridation efficacy conclusions affirmed this result.
Most toothpaste today contains between 0.22 percent (1000 ppm) and 0.312 percent (1450 ppm) fluoride, usually in the form of sodium fluoride or sodium monofluorophosphate (MFP); 100 g of toothpaste containing 0.76 g MFP equates to 0.1 g fluoride.
Prescription strength fluoride toothpaste generally contains 1.1% (5,000 ppm) sodium fluoride toothpaste. This type of toothpaste is used in the same manner as regular toothpaste. It is well established that 1.1% sodium fluoride is safe and effective as a prevention of cavities. This prescription dental cream is used up to three times daily in place of regular toothpaste.
Mouth rinses 
The most common fluoride compound used in mouth rinse is sodium fluoride. Over-the-counter solutions of 0.05% sodium fluoride (225 ppm fluoride) for daily rinsing are available for use. Fluoride at this concentration is not strong enough for people at high risk for cavities.
Prescription mouth rinses are more effective for those at high risk for cavities, but are usually contraindicated for children, especially in areas with fluoridated drinking water. However, in areas without fluoridated drinking water, these rinses are sometimes prescribed for children.
Gels and foams are used for individuals who are at high risk for caries, orthodontic patients, patients undergoing head and neck radiation, patients with decreased salivary flow, and children whose permanent molars should, but cannot, be sealed.
The gel or foam is applied through the use of a mouth tray, which contains the product. The tray is held in the mouth by biting. Application generally takes about four minutes, and patients should not rinse, eat, smoke, or drink for at least 30 minutes after application.
Some gels are made for home application, and are used in a manner similar to toothpaste. The concentration of fluoride in these gels is much lower than in professional products.
An imprint of a person's teeth can be made by a dentist, who then uses that to make well fitting trays to put over their teeth. The patient can then use this to hold a fluoride treatment against their teeth overnight.
Fluoride varnish has practical advantages over gels in ease of application, an unoffensive taste, and use of smaller amounts of fluoride than required for gel applications. Varnish is intended for the same group of patients as the gels and foams. There is also no published evidence yet that indicates that professionally applied fluoride varnish is a risk factor for enamel fluorosis. The varnish is applied with a brush and sets within seconds. Topical application of fluoride has shown better result than systemic fluoride application to a greater extent.
Slow-release devices 
Devices that slowly release fluoride can be implanted on the surface of a tooth, typically on the side of a molar where it is not visible and does not interfere with eating. The two main types are copolymer membrane and glass bead. These devices are effective in raising fluoride concentrations and in preventing cavities, but they have problems with retention rates, that is, the devices fall off too often.
Dietary supplements 
Dietary 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.
Indications for fluoride therapy 
The individual's risk factors and the reason for treatment will determine which method of fluoride delivery is used. Consult with a dentist before starting any treatment.
- White spots
- Moderate to high risk patients for developing decay
- Active decay
- Orthodontic treatment
- Additional protection if necessary for children in areas without fluoridated drinking water
- To reduce tooth sensitivity
- Protect root surface
- Decreased salivary flow
- Institutionalized patients
Health risks 
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/kg 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 ADA has recently issued an interim guidance on their fluoride consumption.
In 1974 a 3-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.
- See main article Dental fluorosis.
Most fluorosis is mild and cosmetic, but the chance of more severe fluorosis increases with exposure. A recent report by National Research Council (NRC) states that severe dental fluorosis can be considered a "toxic effect" which increases the prevalence of caries (106), but fluorosis this severe is not expected with the normal use of fluoride therapy.
Fluoride conversion chart 
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- New York Times. (1979). $750,000 Given in Child's Death in Fluoride Case: Boy, 3, Was in City Clinic for Routine Cleaning. NYT archive, free full-text available at NYT here.
Further reading 
- Committee on Fluoride in Drinking Water, National Research Council. (2006). Fluoride in Drinking Water: A Scientific Review of EPA's Standards. National Academies Press.
- government guidelines
- Fluoride History History of fluoride therapy including early patents
- Clark CD. Appropriate use of fluorides in the 1990s. J Canad Dent Assoc. 1993;59:272-279.
- Hawkins R, Locker D, Noble J, Kay EJ. Prevention. Part 7: Professionally applied topical fluorides for caries prevention. British Dental J. 2003: Vol. 195, No 6: 313-317.
- Moran R, Saemundsson S. Fluoride Varnish: An alternative to traditional topical fluoride therapy. Department of Pediatric Dentistry, University of North Carolina 1996
- Stookey GK. Review of fluorosis risk of self-applied topical fluorides: dentifrices, mouthrinses and gels. Community Dent Oral Epidemiol. 1994;22:282-286