Fluoride therapy

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.

Benefits

Fluoridation is universally accepted by dentists and other medical professionals as being useful in preventing tooth decay. The U.S. Center for Disease Control lists fluoridating drinking water 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.

Mechanism

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:

1. Iso-ionic exchange of F⁻ for OH⁻ in apatite: Ca₁₀(PO₄)₆(OH)₂ + 2F⁻ → Ca₁₀(PO₄)₆F₂ + 2OH⁻
2. Crystal growth of fluorapatite from a supersaturated solution: 10 Ca²⁺ + 6PO₄³⁻ + 2F⁻ → Ca₁₀(PO₄)₆F₂
3. 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 is not seen as an important role in fluoride's effectiveness against cavities. 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 this study concluded that fluoride may not solely interact as an antimicrobial agent, rather additionally acting to reduce bacterial adhesion to teeth along with the 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.

Delivery

Water fluoridation

Main article: 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 and opposition to water fluoridation exists despite its support by public health organizations.

Toothpaste

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/foams

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.

Varnish

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.

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

Fluoride is sold in tablets for cavity prevention.

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

See also

• Amine Fluoride

Health risks

Overdose

Main article: Fluoride toxicity

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.

Fluorosis

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 (16), but fluorosis this severe is not expected with the normal use of fluoride therapy.

Fluoride conversion chart

APF (10)(%)(1000)	ppm
1.0%	10,000
1.23%	12,300
NaF (4.5)(%)(1000)	ppm
0.05%	225
0.20%	900
0.44%	1,980
1.0%	4,500
1.1%	4,950
2.0%	9,000
5.0%	22,500
SnF2 (2.4)(%)(1000)	ppm
0.40%	960
0.63%	1,512

References

12334

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