condition in which fluoride is insufficient or is not utilized properly. Fluoride is a mineral stored in teeth and bones that strengthens them by aiding in the retention of calcium. Studies have determined that the enamel of sound teeth contains more fluoride than is found in the teeth of persons prone to dental caries, and the incidence of dental caries is reduced in areas where natural fluoridation of water is moderate. For these reasons, fluoride is added to water supplies in some areas to help reduce tooth decay, although such actions have in some cases provoked controversy. Excess amounts of fluoride may cause tooth mottling, which presents no problem other than appearance.

Massive doses of fluoride can be lethal, and fluorides are used as the toxic ingredient of many insect poisons.