The history of water fluoridation can be divided into three periods. The first (c. 1901–33) was research into the cause of a form of mottled tooth enamel called the Colorado Brown Stain, which later became known as fluorosis. The second (c. 1933–45) focused on the relationship among fluoride concentrations, fluorosis, and tooth decay. The third period, from 1945 on, focused on water fluoridation, which added fluoride to community water supplies.[1]
In the first half of the 19th century, investigators established that fluoride occurs with varying concentrations in teeth, bone, and drinking water. In the second half they speculated that fluoride would protect against tooth decay, proposed supplementing the diet with fluoride, and observed mottled enamel (now called severe dental fluorosis) without knowing the cause.[2] In 1874, the German public health officer Carl Erhardt recommended potassium fluoride supplements to preserve teeth.[3] In 1892 the British physician James Crichton-Browne noted in an address that fluoride's absence from diets had resulted in teeth that were "peculiarly liable to decay", and who proposed "the reintroduction into our diet ... of fluorine in some suitable natural form ... to fortify the teeth of the next generation".[4]
Community water fluoridation in the United States is partly due to the research of Dr. Frederick McKay, who pressed the dental community for an investigation into what was then known as "Colorado Brown Stain."[5] The condition, now known as dental fluorosis, when in its severe form is characterized by cracking and pitting of the teeth.[6][7][8] Of 2,945 children examined in 1909 by Dr. McKay, 87.5% had some degree of stain or mottling. All the affected children were from the Pikes Peak region. Despite the negative impact on the physical appearance of their teeth, the children with stained, mottled and pitted teeth also had fewer cavities than other children. McKay brought this to the attention of Dr. G.V. Black, and Black's interest was followed by greater interest within the dental profession.
Fluoridation became an official policy of the U.S. Public Health Service by 1951, and by 1960 water fluoridation had become widely used in the U.S., reaching about 50 million people.[9] By 2006, 69.2% of the U.S. population on public water systems were receiving fluoridated water, amounting to 61.5% of the total U.S. population; 3.0% of the population on public water systems were receiving naturally occurring fluoride.[10] In some other countries the pattern was similar. Fluoridation was introduced into Brazil in 1953, was regulated by federal law starting in 1974, and by 2004 was used by 71% of the population.[11] In other locations, fluoridation was used and then discontinued; for example, in Kuopio, Finland, fluoridation was used for decades but was discontinued because the school dental service provided significant fluoride programs and the cavity risk was low.[12]
McKay's work had established that fluorosis occurred before tooth eruption. Dean and his colleagues assumed that fluoride's protection against cavities was also pre-eruptive, and this incorrect assumption was accepted for years. By 2000, however, the topical effects of fluoride (in both water and toothpaste) were well understood, and it had become known that a constant low level of fluoride in the mouth works best to prevent cavities.[13]