e/History of water fluoridation

Information
has gloss	eng: The history of water fluoridation can be divided into three periods. The first ( 1901–33) was research into the cause of a form of mottled tooth enamel called the Colorado Brown Stain, which later became known as fluorosis. The second (c. 1933–45) focused on the relationship between fluoride concentrations, fluorosis, and tooth decay. The third period, from 1945 on, focused on water fluoridation, which added fluoride to community water supplies.
lexicalization	eng: History of water fluoridation
instance of	(noun) a nonmetallic univalent element belonging to the halogens; usually a yellow irritating toxic flammable gas; a powerful oxidizing agent; recovered from fluorite or cryolite or fluorapatite atomic number 9, F, fluorine