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Fluoridation is the addition of fluoride to water supplies to help prevent tooth decay .


The element fluorine is the seventeenth most abundant element in the earth's crust. It occurs as fluoride ion in combination with other elements such as sodium. Most water supplies naturally contain low levels of fluoride. In much of the United States, as well as in other parts of the world, fluoride is added to community water systems to bring fluoride levels up to the recommended amount for preventing teeth decay: 0.71.2 parts of fluoride to 1 million parts of water (parts per million or ppm). The levels of naturally occurring fluoride in fresh water range from less than 0.1 ppm to more than 13 ppm. Seawater contains about 1.5 ppm. As of 2000, about 162 million Americanstwo-thirds of the populationwere served by fluoridated water systems.

Mode of action

Systemic fluorides, including fluoridated water and prescription fluoride supplements supplied as tablets, drops, or lozenges, can be incorporated into the enamel of children's developing teeth. The enamel that covers the crown, the part of the tooth that is above the gum, is made of a substance called hydroxyapatite. When enough fluoride from water, supplements, food, or other sources enters the bloodstream and reaches the teeth while the enamel is forming, the fluoride can replace a piece of the hydroxyapatite molecule to form fluorapatite. Thus fluoride becomes part of the tooth enamel. Fluoride makes the tooth more resistant to acids produced by the bacteria that cause tooth decay. These acids dissolve the enamel, causing cavities. Fluoride in the enamel appears to do the following:

  • make the enamel less susceptible to bacterial acids
  • reduce the bacteria's ability to produce acid
  • reduce the number of bacteria in plaque deposits

It is unlikely that sufficient fluoride will be incorporated into the enamel throughout the years of crown formation. With optimally fluoridated water (1 ppm) as the primary source of fluoride, a child would have to drink two quarts of water every day for 12 to 14 years to incorporate fluoride into all of the baby and adult teeth as they form. The child would be ingesting about 2 mg. of fluoride daily.

Topical fluorides are applied directly to the surfaces of fully-formed teeth. Fluoridated water acts as a topicalas well as a systemicsource of fluoride. Other topical fluorides include fluoridated toothpastes and mouthwashes and fluoride gels that are applied to children's teeth at dental examinations. Topical fluoride is the most effective mineral for renewing or remineralizing the surface layers of enamel and dentin as they wear out and are eaten away by acids from food and bacteria. Fluoride remineralization makes the tooth surface more resistant to decay and reverses early decay processes. Thus topical fluorides help prevent decay in both children and adults. Systemic fluorides also can provide topical protection because they are incorporated into the saliva that bathes the teeth.

Sources of fluoride

Fluoridated water is a major source of fluoride. Most bottled water contains only trace amounts of fluoride. Filtered water and well water vary greatly in their fluoride content. Children who drink water that is low in fluoride may be given fluoride supplements.

Fluoride occurs in many different foods and is also added to some foods. Fruits and vegetables may contain more than 0.2 mg of fluoride per serving, depending on where they were grown and whether fluoridated water was used for irrigation and processing. Most seafood is high in fluoride. The amount of fluoride in beverages depends on the amount of fluoride in the water used to make them. Many vitamins and medicines also contain fluoride. Most baby food is made with nonfluoridated water.

Fluoridated toothpastes and mouthwashes contain high amounts of fluoride. A tube of fluoridated toothpaste may contain as much as 1 to 2 gm of fluoride. Nonprescription mouthwashes can contain up to 120 mg of fluoride. Children between the ages of two and six swallow about 33 percent of the toothpaste they use; children between seven and 15 swallow about 20 percent. The average child using the typical amount of fluoridated toothpaste will swallow or absorb 0.5 to 1.0 mg. of fluoride per brushing. Much of this fluoride is excreted.

It is believed that fluoridated water is between 20 and 60 percent effective in preventing cavities in children and adults. Early studies suggested that water fluoridation was eliminating tooth decay in children. However, other factors are recognized in the early 2000s as having contributed to the decline in dental cavities. The widespread use of fluoridated toothpastes and mouthwashes has increased children's sources of fluoride significantly. Furthermore, both children's and adults' knowledge about dental care and dental hygiene has improved in the last quarter of the twentieth century.

General use


In the early twentieth century a young dentist in Colorado Springs, Colorado, named Frederick McKay, noticed that many local residents had brown stains on their permanent teeth and that their teeth were surprisingly resistant to decay. McKay eventually discovered that this "mottling"as he called itresulted from high levels of naturally occurring fluoride in the drinking water.

The first fluoridation of a public water system took place in Grand Rapids, Michigan, in 1945. By the 1950s and 1960s increasing numbers of communities were fluoridating their water using by-products from the phosphate fertilizer industry. The practice became mired in controversy, and it remains so in the first decade of the twenty-first century. Since the decision to fluoridate usually is made at the local level, by public officials or a vote of the people, fluoridation has become a political as well as a scientific controversy.


Proponents of water fluoridation argue the following:

  • It significantly reduces tooth decay, both before and after tooth enamel has formed.
  • The fluoride levels used are completely safe.
  • The children of parents who are poorly informed about dental hygiene and cavity prevention or who cannot afford dental treatment are still protected against tooth decay.

Most government agencies and scientific and professional organizations agree that water fluoridation is safe and effective in preventing tooth decay and cost-effective in that it reduces the need for expensive dental treatment. Among the organizations that endorse fluoridation of water supplies are the following:

  • American Academy of Pediatric Dentistry
  • American Dental Association
  • American Medical Association
  • National Institute of Dental and Craniofacial Research
  • U.S. Centers for Disease Control and Prevention (CDC)
  • U.S. Public Health Service
  • World Health Organization (WHO)


Opponents of water fluoridation often use one or more of the following arguments:

  • Any fluoride above the naturally occurring (usually trace) amounts is unnecessary and possibly toxic.
  • An individual dose of fluoride cannot be controlled because it depends on the amount of fluoridated water that a child ingests each day.
  • Fluoridation of public water systems deprives people of freedom-of-choice as to what they ingest.
  • People can choose from a variety of fluoride-containing products that are just as effective as fluoridated water.
  • Where the water is not fluoridated, schools often provide fluoridation programs, and parents can choose whether their children participate.
  • Although fluoride may help prevent decay, good diet, good oral hygiene , and regular dental cleanings can be just as effective.
  • Fluoride can be toxic and even fatal at higher doses.
  • The difference between the amount of fluoride that is beneficial and the amount that can cause mottling is only two to four-fold.
  • People vary in their susceptibility to the effects of fluoride.
  • It is impossible to determine how much fluoride a child is ingesting because of the numerous sources of fluoride in food and products; a child may regularly drink water from sources with different fluoride levels.
  • Fluoride is ineffective against gum disease, the major destroyer of teeth.

Communities throughout the United States, as well as many countries, have chosen not to fluoridate their water. In the early 2000s a number of countries have discontinued fluoridation because of ongoing concerns about possible health effects.

Fluoride dosages

There is some disagreement as to whether fluoride is an essential mineral in humans. Relatively low levels of fluoride (2080 mg) are considered toxic. Less than 1 gm of fluoride can be fatal to a small child. The Food and Nutrition Board of the Institute of Medicine of the U.S. National Institutes of Health has determined an adequate daily intake of fluoride and a maximal safe daily intake, based on a child's weight:

  • infants up to six months of age or about 16 lb (7 kg): 0.01 mg is adequate and 0.7 mg is the maximum safe intake
  • infants between six and 12 months or about 20 lb (9 kg): 0.5 mg and 0.9 mg
  • children one to three years of age or about 29 lb (13 kg): 0.7 mg and 1.3 mg
  • children aged four to seven or about 48 lb (22 kg): 1.0 mg and 2.0 mg
  • children aged nine to 13 or about 88 lb (40 kg): 2.0 mg and 10 mg
  • children aged 14 to 19 or about 125166 lb (5776 kg): 3.0 mg and 10 mg

Fluoride supplements often are prescribed for children who drink nonfluorinated water and do not use fluoride toothpaste. Fluoride supplements should not be used if the drinking water contains more than 0.6 ppm of fluoride. One ppm of fluoride is equivalent to about 1 mg per quart (or liter) of water. Fluoride supplements should not be given to babies under six months of age regardless of the fluoride content of the water. Babies get adequate fluoride from breast milk or infant formula. Powdered or concentrated infant formula should be mixed with low-fluoride or fluoride-free water.

If the water supply contains 0.0 to 0.3 ppm fluoride, the recommended daily dosage of fluoride supplement is:

  • 0.25 mg for children aged six months to three years
  • 0.50 mg for children aged three to six years
  • 1 mg for children aged six to 16 years

If the water supply contains 0.3 to 0.6 ppm fluoride, the recommended daily dosage of fluoride supplement is:

  • 0.0 mg for babies aged six months to three years
  • 0.25 mg for children aged three to six years
  • 0.50 mg for children aged six to 16

Fluoride supplements usually come in the form of sodium fluoride: 2.2 mg of sodium fluoride supplies 1 mg of fluoride ion.


A child easily can swallow enough fluoridated toothpaste to exceed the recommended daily amount of fluoride by four-fold. A medium-sized toothpaste tube contains enough fluoride to make a child seriously ill or even cause death should the child eat it all. The flavorings added to toothpaste to encourage children to brush also can entice them into eating it. Toothpaste always should be stored out of the reach of children.

Side effects

As little as four to eight mg of fluoride ingested daily while the tooth enamel is forming can cause mottlingoften called fluorosisin children under age eight. Fluorosis only affects children whose teeth are still developing within the gums. Symptoms of fluorosis include:

  • teeth discoloration
  • white or brown chalky spots
  • brown enamel
  • pitting of teeth
  • excessive wear on the enamel
  • structural damage to the enamel
  • brittle teeth in which the enamel breaks easily

The extent of mottling depends on the following:

  • when the excess fluoride is ingested
  • how much is ingested
  • over how long of a period it is ingested
  • how much of the fluoride reaches the enamel

Most cases of fluorosis are very mild. Very mild to mild fluorosis has no effect on tooth function and may help prevent decay. Even severe fluorosis is not harmful. Fluorosis in children appears as of 2004 to be increasing; however, it is not known whether this is from water fluoridation, the excessive use of fluoride-containing products, or both.


No type of fluoridation can replace good dental care and hygiene, which are necessary for preventing gum disease as well as tooth decay. Weekly rinsing with a fluoride mouthwash can reduce decay in children by 2040 percent. Fluoride supplements can reduce decay in children by 40 percent, if administered at least 150 days of every year that enamel is forming.

Topical fluoride treatments given in a dentist's office have been proven to be 40 percent or more effective in preventing decay. These treatments include fluoride gels and foams and fluoride varnishes. Advantages of fluoride varnishes include the following:

  • They are more concentrated than other fluoride treatments and so are less likely to be ingested.
  • They are fast and easy to apply.
  • They continue to provide fluoride to the enamel for about 24 hours after application.

Varnishes may be particularly appropriate for young children and those with special needs since varnishes do not require the use of a fluoride tray.

Parental concerns

It is the parents' responsibility to monitor their child's fluoride intake. Pregnant and nursing mothers should pay close attention to how much fluoride they ingest. Children should:

  • be over two years of age before using a fluoridated toothpaste; younger children are likely to swallow most of their toothpaste
  • use a pea-sized amount of toothpaste or less
  • not use fluorinated mouthwashes until the age of six
  • be prevented from swallowing fluoridated toothpaste or mouthwash


Dentin The middle layer of a tooth, which makes up most of the tooth's mass.

Enamel The hard, outermost surface of a tooth.

Fluorapatite Fluoride-substituted hydroxyapatite.

Fluorosis Mottled discoloration of tooth enamel due to excessive systemic ingestion of fluoride during tooth development.

Mottling Fluorosis; spotting on the teeth due to excess fluoride as the tooth enamel is forming.

Plaque A deposit, usually of fatty material, on the inside wall of a blood vessel. Also refers to a small, round demyelinated area that develops in the brain and spinal cord of an individual with multiple sclerosis.

Remineralization Recalcification; the process by which minerals from saliva and food are added to the surface of the enamel or to the dentin.

Systemic absorption Any substance topical, inhaled, or ingested that is absorbed into the blood-stream and distributed throughout the body.

Topical Not ingested; applied to the outside of the body, for example to the skin, eye, or mouth.

See also Dental development.



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Bryson, Christopher. The Fluoride Deception. New York: Seven Stories Press, 2004.


"Anti-Fluoride Flood." Better Nutrition 65, no. 1 (January 2003): 301.

Gorman, Megan Othersen. "Got Enough Fluoride?" Prevention 54, no. 2 (February 2002): 48.

Mascarenhas, Ana Karina. "Risk Factors for Dental Fluorosis: A Review of the Recent Literature." Pediatric Dentistry 22, no. 4 (2000): 26977.

Motavalli, Jim. "Your Health: Facing up to Fluoride." E: the Environmental Magazine 12, no. 1 (January/February 2001): 401.

Pendrys, D. G. "Risk of Enamel Fluorosis in Nonfluoridated and Optimally Fluoridated Populations: Considerations for the Dental Professional." Journal of the American Dental Association 131 (2000): 74655.

Pratt, Edwin, Jr., et al. "Fluoridation at Fifty: What Have We Learned?" The Journal of Law, Medicine, and Ethics 30, no. 3 (Fall 2002): 11722.

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American Academy of Pediatric Dentistry. 211 East Chicago Avenue, Suite 700, Chicago, IL 606112663. Web site: <>.

American Dental Association. 211 East Chicago Avenue, Chicago, IL 606112678. Web site: <>.

Fluoride Action Network. PO Box 5111, Burlington, VT 05402. Web site: <>.

National Center for Fluoridation Policy and Research. Department of Oral Biology, School of Dental Medicine, State University of New York at Buffalo, Buffalo, NY 142143008. Web site: <>.


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Margaret Alic, PhD

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Fluoridation is the process of adding the chemical fluoride to a substance (often drinking water) to reduce tooth decay. In the human body, fluoride acts to prevent tooth decay by strengthening tooth enamel and inhibiting the growth of plaque-forming bacteria. Fluoridation was first introduced into the United States in the 1940s in an attempt to study its effect on the reduction of tooth decay. Since then many cities have added fluoride to their water supply systems.

Early fluoridation studies

In 1901, Frederick McKay (18741959), a dentist in Colorado Springs, Colorado, noticed that many of his patients had brown stains, called mottled enamel, on their teeth. After studying the cause of this staining for three decades, McKay concluded that it was due to high concentrations of fluoride in the patients' drinking water. McKay also observed that although unsightly, the stained teeth of his patients seemed to be more resistant to decay. After experimentation, he found that the ideal level of fluoride in water should be one part fluoride per million parts of water (or one ppm). That was enough to stop decay but too little to cause mottling.

The U.S. Public Health Service (USPHS) grew interested in fluoride and, following safety tests on animals, conducted field tests. In 1945, the public water systems of Newburgh, New York, and Grand Rapids, Michigan, became the first ever to be artificially fluoridated with sodium fluoride.

Results of these tests seemed to show that fluoridation reduced dental cavities by as much as two-thirds. Based on those results, the USPHS recommended in 1950 the fluoridation of all public water systems in the United States. Later that year, the American Dental Association added its endorsement, and the American Medical Association followed suit in 1951.

To fluoridate or not to fluoridate

Even though almost the entire dental, medical, and public health establishment favored fluoridation, the recommendation was immediately controversial, and has remained so. Opponents objected to fluoridation because of possible health risks (fluoride is toxic, or poisonous, in large amounts). They also objected to being deprived of the choice whether to consume a chemical. Despite the opposition, nearly 60 percent of people in the United States now drink fluoridated water. Fluoridation also is practiced in about 30 other countries.

Fluoridation today

Over the years, other ways of applying fluoride have been developed. In 1956, Procter & Gamble added fluoride to one of its brands of toothpaste, Crest. Four years later, the Council on Dental Therapeutics of the ADA gave Crest its seal of approval as "an effective decay-preventive dentifrice." The ADA now estimates that brushing with fluoride-containing toothpaste reduces tooth decay by as much as 20 to 30 percent.

By the 1990s, the initial claims that fluoridation in drinking water produced two-thirds less tooth decay had been modified to about 20 to 25 percent reduction. Researchers now believe that the overall reduction of tooth decay levels in the twentieth century has been brought about by the addition of fluoride to many items, including food, salt, toothpaste, and mouth rinses. Education and better dental hygiene also have played a part. In 1993, the National Research Council published a report stating the maximum recommended level of four ppm for fluoride in drinking water was appropriate. Since then, the scientific debate of the health benefits of fluoridation versus its possible health risks has continued. Both sides agree that further research into this area is needed.

Words to Know

Fluoride: A form of the element fluorine that is soluble in water. It is often added to drinking water to reduce tooth decay.

Parts per million (ppm): A way to express low concentrations of a substance in water. For example, 1 ppm of fluoride means 1 gram of fluoride is dissolved in 1 million grams of water.

[See also Poisons and toxins ]

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fluoridation (flŏŏr´Ĭdā´shən), process of adding a fluoride to the water supply of a community to preserve the teeth of the inhabitants. Tooth enamel ordinarily contains small amounts of fluorides and when the amount is augmented through the intake of fluoridated water, especially during the first eight years of childhood, tooth decay can be greatly reduced.

In the early 1900s, Frederick S. McKay, a Colorado dentist, discovered that an unknown substance in the local drinking water caused a mottling or staining of the teeth and that these teeth also showed fewer cavities. In 1931 the substance was identified as a fluoride. Later, in the 1930s, it was found that a fluoride level in drinking water of about one part per million was high enough to reduce tooth decay but low enough to prevent teeth from becoming mottled.

In some communities fluorides are a natural constituent of the water supply; other communities have added fluorides to their reservoirs. Such action has the support of the American Dental Association, the American Medical Association, and other scientific organizations. Although studies have proven that fluoridation at levels of one part per million is safe, attempts at fluoridation have met with resistance and controversy. Its opponents say that it constitutes compulsory medication, that the amount of fluorine taken into the body cannot be controlled, and that those who wish to prevent tooth decay through fluorides can do so individually by adding the compound to their beverages or by using toothpaste and other dental substances to which fluorides have been added. Despite such resistance, many Americans drink artificially fluoridated water, and fluoridation programs have been started in other countries as well.

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fluoridation The process of adding very small amounts of fluorine salts (e.g. sodium fluoride, NaF) to drinking water to prevent tooth decay. The fluoride becomes incorporated into the fluoroapatite (see apatite) of the growing teeth and reduces the incidence of dental caries. However, some argue that there is an accompanying risk of fluoride toxicity.

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fluoridation (floo-er-id-ay-shŏn) n. the addition of fluoride to drinking water in order to reduce dental caries. Drinking water with a fluoride ion content of one part per million is effective in reducing caries throughout life when given during the years of tooth development. See also fluorosis.

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fluoridation The addition of fluoride to drinking water.

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