Leaflet: Fluoride (pdf)


Tooth decay (dental caries) is one of the most common chronic diseases worldwide. Although it is rarely life-threatening, tooth decay can cause pain and harm eating, speaking, impact facial appearance, and affect acceptance into society. It greatly influences the quality of life of children, and is particularly common in those of low social and financial status.

Harmful bacteria in the mouth produce organic acids when carbohydrates, especially sugar, are eaten. When enough acid is produced so that the pH (level) goes below 5.5, the acid dissolves hydroxyapatite, the main component of tooth enamel, in a process known as demineralization. After the sugar is gone, some of the mineral loss can be recovered—or remineralized—from the saliva. Cavities result when the rate of demineralization exceeds the rate of remineralization, usually in a process that requires many months or years.

How fluoride works.

paste-on-brushThe early sign of dental decay is dissolving of the enamel which can be reversed with careful cleaning, change in diet and fluoride treatment. Fluoride treatments (e.g. fluoride mouth rinses, varnishes, gels and foams) help to protect teeth against decay and also provide additional protection against acid attacks on the tooth enamel. In the mouth it creates low levels of fluoride in saliva, which reduces the rate at which tooth enamel demineralizes and increases the rate at which it remineralizes in the early stages of cavities. The fluoride becomes more concentrated in the dental plaque and thus reduces the change in dietary sugars into acid by plaque bacteria.

Fluoride works in 3 ways:

  • It slows down the development of decay by stopping demineralization.
  • It makes the enamel more resistant to acid attack and speeds up the remineralization with fluoride ions, making the tooth surface less soluble.
  • It can stop bacterial metabolism to produce less acid.

The fluoride does not prevent cavities but instead controls the rate at which they develop. When fluoride is present, a remineralized layer is formed over the remaining surface of the enamel; this layer is much stronger and more acid-resistant than the original mineral, and is formed more quickly than ordinary remineralized enamel would be.

paste-and-brushWater fluoridation is the most effective means of achieving fluoride coverage that is community-wide, but this is not available in Devon. Other fluoride therapies may be used which are also effective in preventing tooth decay; they include fluoride toothpaste, mouthwash, gel, and varnish, and fluoridation of salt and milk. Dental sealants are effective as well, with estimates of prevented cavities ranging from 33% to 86%, depending on age of sealant and type of study.

Fluoride toothpaste is the most widely used and thoroughly assessed fluoride treatment. Its introduction in the early 1970s is considered the main reason for the decline in tooth decay in industrialized countries. However, it relies on individual and family behaviour, and its use is less likely among lower economic classes; Fluoride toothpaste prevents about 25% of cavities in young permanent teeth, and its effectiveness is improved if higher concentrations of fluoride are used, or if the toothbrushing is supervised. Fluoride mouthwash and gel are about as effective as fluoride toothpaste; fluoride varnish prevents about 45% of cavities. By comparison, brushing with a nonfluoride toothpaste has little effect on cavities.


Children who have fluoride when their teeth are developing tend to have shallower grooves in their teeth so plaque can be more easily removed. Plaque is a thin, sticky film of bacteria that constantly forms on your teeth. Children living in poorer areas where the water supplies are not fluoridated can have 5 times more decay than children living in better-off or fluoridated areas.

A dentist or dental hygienist can apply fluoride to the teeth. These come as gels or varnishes and are more concentrated than toothpaste, and therefore are not needed as often. Some adults can benefit from these applications. Fluoride gels can help to reduce root decay – especially in people with dry mouth and the elderly. Some people are more prone to tooth decay and the dentist may also advise using fluoride supplements, such as tablets, as well as fluoride toothpaste for extra protection. It is very important that fluoride supplements are only taken on the advice of a dentist, and that they are used in the way they say. Supplements are suitable for children from about 3 onwards and can help reduce decay.

What are the side effects?

teethAlthough there are very few side effects, especially at the concentration used in toothpaste and varnishes, dental fluorosis is caused by having too much fluoride when the teeth are developing. In its mildest form, dental fluorosis appears as very fine pearly white lines or flecking on the surface of the teeth. This mild fluorosis can often only be spotted by a dental expert. Severe fluorosis may lead to the enamel being pitted and discoloured. It can happen when children swallow toothpaste or when too much topical is applied. After many years the scientific conclusion is that fluoride toothpaste and correctly fluoridated water, salt and milk are of great benefit to dental health and help to reduce decay, and cause no harmful side effects to general health. Recent studies carried out for the government by the Medical Research Council have failed to find any evidence that fluoride added to water causes harmful side effects. Worldwide, over 300 million people drink fluoridated water supplies. Many millions more regularly use fluoridated toothpaste.

Leaflet: Fluoride (pdf)

Last updated: March 13, 2014

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