Florine is an extremely reactive gas; meanwhile its cousin compound, fluoride, actually protects our teeth from decay. Fluoride, which is actually sodium fluoride or stannous fluoride or sodium monofluorophosphate, probably sounds familiar because your dentist is always telling you that your toothpaste should have fluoride in it, or not to worry that the water has fluoride because it's really a good thing, especially at such low levels. But did your dentist tell you that we actually only starting purposely fluoridating our water within the last 80 years? The first city to intentionally put fluoride in its public water supply was Grand Rapids, Michigan in 1945 as an experiment. After fifteen years of monitoring, when researchers discovered that the number of cavities that people suffered dropped by 60%, fluoridating our water became a common practice!
But believe it or not, the story actually started even earlier, when a dentist in Colorado Springs named Frederick McKay discovered that the city's residents had gross brown stains on their teeth and yet at the same time the levels of tooth decay in the population were magnificently low. After many years of hypothesizing, McKay and other researchers determined that Colorado Springs water naturally had fluoride in it, just at too high levels. While we need fluoride to help prevent tooth decay, we also want to keep levels in our drinking water at below 1 part per million to keep our teeth shiny white!