You'd think that the benefits of fluoride would be discovered on people with either a high exposure to fluoride with perfect teeth, or a low exposure with troubled teeth. Turns out that in 1901 in Colorado, a dentist noticed his patients had mottled brown teeth . . . and very few cavities [source: CDC].
After a few more investigations into water sources, it was determined that high fluoride concentration in water could cause fluorosis (the mottling or corrosion of teeth) and that lower levels of fluoride could prevent cavities (sometimes referred to as "caries"). In 1945, a full-scale, long-term study took place in three U.S. and one Canadian city, where fluoride was added at a 1.0-1.2 parts per million (ppm) ratio. Over the course of 13-15 years, cavities were reduced by 50%-70% in children in these communities, and fluorosis was seen at levels comparable to places with a natural 1.0 ppm fluoride source [source: CDC].
Community water fluoridation quickly spread, and the results were pretty stunning: from 1966 to 1994, the percentage of 12 year-olds in the United States with decayed, missing (due to cavities) or filled teeth declined 68% [source: CDC].
Cavities have declined in communities both with and without water fluoridation, which is ascribed to a prevalence of fluoride toothpaste. Also worth considering: many of our foods and beverages are processed in places with fluoridated water [source: CDC]. But with this trend of fluoridation, are we actually over-exposing ourselves to fluoride? Find out more by sinking those pearly whites into the next section.