Water fluoridation
Health and dental organizations worldwide have endorsed its safety and effectiveness. Its use began in 1945, following studies of children in a region where higher levels of fluoride occur naturally in the water. Further research showed that moderate fluoridation prevents tooth decay.
Dental fluorosis
In 1931, 3 different groups of scientists around the world published their discoveries that this condition was caused by fluoride in drinking water during childhood. The condition then started to become termed "dental fluorosis". Through epidemiological studies in the USA, Henry Trendley Dean helped to identify a causal link between high concentrations of fluoride in the drinking water and mottled enamel. He also produced a classification system for dental fluorosis that is still used in modern times, Dean's Index. As research continued, the protective effect of fluoride against dental decay was demonstrated.