Recently, Robert F. Kennedy Jr. affirmed his plans to advise water systems in the United States to remove fluoride from public water. As an individual expected to influence public health policy during the next administration, his comments created substantial controversy around the risks and benefits of fluoride in drinking water. The story of fluoride begins in 1901 when a dentist noticed that his patients from Colorado Springs, Colo., frequently had brown stains on their teeth but were also less likely to suffer tooth decay — findings he and colleagues later understood to be due to high levels of fluoride naturally...