As long ago as 1925 it was observed in the United States that fluorine ingested from fluoride-rich water sources could lead to a significant decrease in the incidence of tooth decay. Following years of research, fluoridation of drinking water began in Grand Rapids, Michigan, in 1947. The water distribution system in Switzerland did not lend itself to this type of fluoridation, but in the 1950’s, Swiss scientists determined that fluorine in the form of potassium fluoride could be added to edible salt.
Extensive tests showed that results were similar to those achieved by water fluoridation. A World Health Organisation programme recommended fluoridation of edible salt as the best way of preventing dental caries wherever water fluoridation was not possible, and potassium fluoride is now routinely added to edible salt in many parts of Central and South America. Fluoridated salt is also available to a limited extent within the European Union.
Two other compounds, sodium fluoride and sodium monofluorophosphate, are also essential components of toothpaste formulations, and are similarly important in helping to prevent dental caries.