Early efforts to incorporate fluoride into dental preparations as well as research towards understanding the fluoride content of teeth gave conflicting results. A phenomenon called "Brown Stain", associated with too much fluoride ingestion, was thought to be "typical caries" in a paper presented in 1904 before the German Society for Surgery.3 Mckay and Black investigated what had been termed Colorado Brown Stain as early as 1916. They found that this stain was present in other communities and associated it with the communal water supply, although they were not certain of the cause.4 These and other findings led the United States Public Health Service to do extensive epidemiological surveys to study both dental caries and dental fluorosis in the late 1930s.5 When it was confirmed that fluoride intake from water was associated with the prevalence of dental fluorosis as well as a reduction in dental caries, many delivery systems and strategies were investigated to optimize the benefit of fluorides at the community level as well as the individual level. In 1937, a dental preparation claiming to prevent decay was not favorably looked upon by the American Dental Association's (ADA) Council on Dental Therapeutics. The possibility of toxicity, conditions of usage and absorption questions led to the ADA's conclusion that "The use of fluoride in dentifrices is unscientific and irrational, and therefore should not be permitted."6 At that time, dental problems were considered to be a personal matter. The finding that the single greatest reason for rejecting people from the military in World War II was a result of poor oral health changed this sentiment. Very quickly, oral health became a national security issue and was recognized as a public health problem. Studies in which the water supply of cities was artificially fluoridated were done in order to determine potential effectiveness of such a measure. Fluoridation of the community water supply has been said to be an ideal public health measure. Initial studies were placed in Grand Rapids, MI in 1945, with Muskegon, MI acting as the control city. Other sister city studies were also begun around that same time. The overall results demonstrated a significant reduction in dental caries without cosmetically displeasing dental fluorosis, when the fluoride concentration in the local water supply was maintained at about 1 ppm.4 The mechanism of action was thought to be mainly the incorporation of fluoride into the enamel structure, thereby reducing the solubility of the enamel. Fluoridation of community water supplies has since been considered to be an ideal public health measure.