Fluoride occurs naturally in the body as calcium fluoride. Calcium fluoride is mostly found in the bones and teeth.
Small amounts of fluoride help reduce tooth decay. Fluoridation of tap water helps reduce cavities in children by 50 - 60%. Fluorides also help maintain bone structure. Low doses of fluoride salts may be used to treat conditions that cause faster-than-normal bone loss, such as menopause.
Yates AA, Schlicker SA, Suitor CW. Food and Nutrition Board, Institute of Medicine, National Academy of Sciences. Dietary Reference Intakes: the new basis for recommendations for calcium and related nutrients, B vitamins, and choline. J Am Diet Assoc. 1998 Jun;98(6):699-706