How be it first discovered that flouride be beneficial to oral strength?

From the Salon article cited below: "Ironically, science first discovered fluoride's benefits in the impulsive part of this century by stumbling upon what happen when people get too much of it. Researchers noticed that children raise in Colorado Springs, Colo., suffered from severe staining and mottling of their teeth, but be also blessed with a low rate of tooth putrefaction. A check of the water supply revealed that it be naturally fluoridated, according to a history compiled by the National Institutes of Health."