Water fluoridation
In the GDR (East Germany) in the late 1980s, about 3.4 million people (20%) were receiving water with added fluoride. Fluoride tablets were also provided. The fluoridated areas of the GDR included the towns of Karl-Marx-Stadt (now Chemnitz), Plauen, Zittau, and Spremberg. Children in those towns were part of large long-running studies of caries prevalence. A fluoride cessation study found that consistent with a previously observed population-wide phenomenon that the rate of cavities continued to drop after the fluoride concentration in water fell from the augmented 1.0 ppm to its natural level below 0.2 ppm. Water fluoridation was discontinued after the German reunification although still exists on some US military bases.