The history of fluoride in Grand Rapids, Michigan, dates back to January 25, 1945, when it became the first city in the world to introduce fluoride to its municipal water supply as part of a large-scale experiment to test the benefits of fluoridation. The city was selected for the investigation because it had a low level of fluoride naturally occurring in its water, a capable water filtration plant, and a large population of school-age children who suffered from a high rate of dental caries. At six years of age, 80 percent of children had an average of 14 cavities.
Fluoride, when ingested, helps to strengthen teeth when they are developing. It also initiates the remineralization of tooth enamel, allowing teeth to repair themselves when cavities occur. Some scientists believe that it also hinders the ability of plaque to produce the kinds of acid that cause cavities. In both of these ways, fluoride stops tooth decay while it is still in its initial phase, limiting the formation of cavities.
The 15-year study in Grand Rapids revealed a 60-65% reduction in dental caries. Many other cities, including the control city in the experiment, Muskegon, chose to add fluoride to their water supplies. Today, approximately 64% of Americans drink fluoridated water, and very few adults need full dentures at age 55