On Jan. 25, 1945, at 4:00 p.m., Grand Rapids, Michigan, achieved a historic milestone by becoming the inaugural city to implement water fluoridation. Engineers at the Monroe Avenue Water Filtration Plant begin adding a carefully controlled amount of sodium fluoride to the city’s water supply.

Later that year, a planned 15-year trial of community water fluoridation was launched in four cities. Each fluoridating city was paired with a “control,” a nearby city of similar size and demographic makeup, with a low-fluoride water source similar to that of the trial city. Fluoridating Grand Rapids, Michigan, was paired with neighboring Muskegon; Newburgh, New York, with Kingston; Evanston, with Oak Park; and—in Canada—Brantford, Ontario, with nearby Sarnia. Two other cities with water having a natural fluoride content near 1.0 ppm served as fluoridated controls.

In 1949, the first children to drink fluoridated water since infancy begin reaching school age. Dental examiners in Grand Rapids, Newburgh, and Brantford reported a sharply lower number of cavities among the children starting school in 1949. Cities and small towns across Michigan, Texas, and Wisconsin began fluoridation programs of their own. The number of Americans receiving fluoridated tap water nearly doubled in just 1 year, with the total number climbing to just under 1 million.

In June, 1950, the American Dental Association, Association of State and Territorial Dental Directors, and USPHS all issue statements endorsing community water fluoridation. The U.S. Surgeon General declares that any community wishing to fluoridate its water supply should be “strongly encouraged” to proceed. By year’s end, another half-million Americans are receiving fluoridated tap water, raising the total number to 1.5 million.

In 2018, community water systems that contain enough fluoride to protect teeth served more than 200 million people or 73 percent of the U.S. population. Fluoridation is one of the greatest public health and disease-prevention measures of all time. Its advantages include effectiveness for all, ease of delivery, safety, equity, and low cost.

Previously observed caries reductions of one-half to two-thirds are no longer attainable in the United States because other fluoride methods and products have reduced caries prevalence in all areas, thus diluting the measurement of effectiveness, and because benefits of fluoridation are dispersed in many ways to persons in nonfluoridated areas.

Water fluoridation itself, however, remains as effective as it ever was among groups at high risk for dental caries. Water fluoridation also provides an important source of topical fluoride and facilitates tooth remineralization.