Fluoride therapy is the delivery of fluoride to the teeth, topically or systemically, to protect them from dental caries (cavities). 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 basic the mouth is, and depending upon the concentration of other substances in the mouth, such as phosphate and calcium. Fluoride enhances and modifies the restoration of the mineral content of the teeth, and counteracts the breakdown of the teeth from lactic acid producing bacteria. The purpose of tooth-brushing is twofold: to mechanically remove plaque, and also to apply fluoride to the tooth surface, promoting re-mineralisation with fluorapatite.
In topical fluoride therapies, fluoride is applied directly to the surface of the teeth, most commonly by means of a fluoride toothpaste. Other topical fluoride therapies include fluoridated mouth rinses, lozenges, gels, foams, and varnishes.
In systemic fluoride therapies, fluoride is swallowed as an additive to drinking water, salt, or milk, or as an ingredient in tablets, lozenges, or drops. Where public water supplies are fluoridated, other systemic fluoride therapies are not recommended.
- 1 Benefits
- 2 Mechanism
- 3 Delivery
- 4 Health risks
- 5 Fluoride conversion chart
- 6 References
- 7 Further reading
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) and fluoride supplements, in the form of drops and tablets, to reduce the risk of dental caries in school-aged children and adolescents. The influence of fluoride toothpaste and fluoride supplements on preventing caries in primary teeth remains inconclusive. Water and milk fluoridation are two forms of systemic fluoride therapy that have been demonstrated to be effective at preventing dental caries.
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 as it applies to preventive methods is occurring when fluoride is present in the oral cavity. After fluoride is swallowed it has a minimal effect.
There are three principle reactions with fluoride ion for remineralization:
- Iso-ionic exchange of F− for OH− in apatite: Ca10(PO4)6(OH)2 + 2F− → Ca10(PO4)6F2 + 2OH−
- Crystal growth of fluorapatite from a supersaturated solution: 10 Ca2+ + 6PO43− + 2F− → Ca10(PO4)6F2
- Apatite dissolution with CaF2 formation: Ca10(PO4)6(OH)2 + 20F− → 10 CaF2 + 6PO43− + 2OH−
Iso-ionic exchange by the replacement of F- for OH¯ in apatite and crystal growth of fluorapatite from supersaturated solutions are able to occur during exposure to low levels of fluoride (0.01-10 ppm F) over long periods of time. Reaction of apatite dissolution with CaF2 formation occurs in higher levels of fluoride (100-10,000 ppm F) and the addition of CaF2 or a CaF2 containing compound.
Fluoride's effect on oral microflora and the role of its importance in fluoride's 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, rather additionally acting to reduce bacterial adhesion to teeth along with the primary action of decreasing of demineralization. Further investigation will need to be done to verify these claims.
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.
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.
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 and opposition to water fluoridation exists despite its support by public health organizations.
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.
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 people 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.
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.
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 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. Reasons for fluoride therapy include:
- 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
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.
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. It has 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.
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.
Fluoride conversion chart
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- government guidelines
- Fluoride History History of fluoride therapy including early patents
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