 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.