Tooth decay and cavities are among the most common afflictions in the world, however they used to be far more common. In the mid-20th century, an 15-year experiment was performed directly by the National Institute of Dental Research in Grand Rapids, Michigan to test whether adding fluoride its drinking water would reduce the rate of cavities. Amazingly, children born after fluoride was introduced had a 60% lower rate of cavities. The USA quickly became the first nation to incorporate fluoride into water sources, but even more importantly this study demonstrated to the world fluoride’s effectiveness at treating tooth decay. Fluoridated water is estimated to prevent 27% of cavities.