In the body, most fluoride is contained in bones and teeth. Fluoride is necessary for the formation and health of bones and teeth.
FLUORIDE DEFICIENCY
Fluoride deficiency can lead to tooth decay and possibly osteoporosis. Consuming enough fluoride can prevent tooth decay and may strengthen bones. The addition of fluoride (fluoridation) to drinking water that is low in fluoride or the use of fluoride supplements significantly reduces the risk of tooth decay. In areas where drinking water is not fluoridated, children may be given fluoride by mouth.
FLUORIDE EXCESS
People who live in areas where the drinking water has a naturally high fluoride level may consume too much fluoride—causing a condition called fluorosis. Fluoride accumulates in teeth, particularly permanent teeth. Chalky white, irregular patches appear on the surface of the tooth enamel. The patches become stained yellow or brown, causing the enamel to appear mottled. The teeth may also become pitted. These defects appear to affect appearance only and may even make the enamel more resistant to cavities. Fluoride also accumulates in bones. Rarely, consuming too much fluoride for a long time results in dense but weak bones, abnormal bone growths (spurs) on the spine, and crippling due to calcium accumulation (calcification) in ligaments.
The diagnosis is based on symptoms.
Treatment involves reducing fluoride consumption. For example, if people live in areas with high fluoride levels in the water, they should not drink fluoridated water or take fluoride supplements. Children should always be instructed not to swallow fluoridated toothpaste.
Resource: Merck Manual Home Edition