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 (1874–1959), 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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