The United States first started introducing fluoride to public water supplies back in 1945, and by 2012 74.6 percent of the U.S. population had access to fluoridated water. Water fluoridation prevents tooth decay by replacing minerals on tooth surface that are removed by acid from certain bacteria in the mouth. A video uploaded by SciShow explains why we use fluoride to keep teeth healthy when they’re made mostly of calcium.
Fifteen years after Grand Rapids, Michigan became the first city in the U.S. to intentionally fluoridate its water in 1945, health officials found that the number of cavities among the city’s children had dropped by 60 percent. Today, more than 204 million people in the U.S. benefit from water supplies with enough fluoride to protect teeth.