While conventional dentistry tends to regard the use of fluoride to prevent cavities as a remarkable triumph of preventive medicine, proponents of alternative medicine have long taken the opposite view. To them, water fluoridation, in particular, is a form of medically sanctioned environmental pollution. These strongly emotional and diametrically opposed views have created a murky world of charges and countercharges. In this article, we will limit ourselves to the current scientific evidence regarding fluoride and cavities and avoid delving into the numerous myths, rumors, exaggerations, and conspiracy theories associated with the topic.
Fluorine is an element in the family of chlorine, bromine and iodine. A “fluoride” is a certain type of chemical compound containing fluorine. The most common forms of fluoride used to prevent cavities are sodium fluoride (analogous to sodium chloride, or common salt), sodium monofluorophosphate, and sodium hexafluorosilicate. Stannous fluoride, a compound containing tin, was once popular, but it is now seldom used.
The use of fluorine for preventing cavities originally derived, at least in part, from the observation that people who grow up drinking water that is high in fluorides, but not too high, have a much reduced incidence of cavities. This observation led dental researchers to conclude that if fluoride is present during the initial stages of tooth formation, those teeth will emerge with stronger enamel. Direct application of fluoride to teeth was also thought to provide benefit, but only to a much lesser extent. Therefore, it became common practice to recommend that infants and young children receive fluoride supplementation, either through the water supply, or via fluoride supplements.
However, subsequent evidence has shown that these early researchers had it backwards. It now appears that fluoride acts only on teeth that have already erupted.1 When fluoride comes in direct contact with tooth enamel, it replaces some of the calcium in the enamel, forming a surface that is more resistant to cavities. The only dental value of fluoridated water, therefore, occurs during the process of drinking it, when the fluoride in the water bathes the surface of the teeth.
However, there are more direct ways of bringing fluoride into contact with tooth enamel. The most common of these is the use of fluoride toothpastes. Very strong evidence shows that such toothpastes help prevent cavities.2 These toothpastes are so widely used, in fact, that water fluoridation is probably of little to no value except in poorer, less developed countries, where use of fluoride toothpastes is not so universal.1
Fluoride mouth rinses, available over the counter, may offer additional benefit to fluoride toothpastes.3 However, there is little to no scientific support for the use of the much more expensive professionally applied fluoride varnishes.4
Just as fluoride replaces some of the calcium in dental enamel, fluoride can also replace calcium in bone. This has led to the hypothesis that fluoridated water may prevent osteoporosis. On the other hand, when too much calcium is replaced by fluoride, bone strength decreases. For this reason, it has been suggested that water fluoridation may increase risk of osteoporosis. However, a judicious examination of the evidence suggests that neither of these outcomes occurs in real life: water fluoridation appears to have little or no effect on osteoporosis rates, one way or the other.5
The bottom line: While water fluoridation in US cities is a continuing source of impassioned controversy by both opponents and proponents, this emotional energy would probably be better spent elsewhere, as the practice is most likely both safe and unnecessary.
1. Pizzo G, Piscopo MR, Pizzo I, et al. Community water fluoridation and caries prevention: a critical review. Clin Oral Investig. 2007;11:189-193. Epub 2007 Feb 27.
2. Marinho VC, Higgins JP, Sheiham A, et al. Fluoride toothpastes for preventing dental caries in children and adolescents. Cochrane Database Syst Rev. 2003;CD002278.
3. Marinho VC, Higgins JP, Logan S, et al. Fluoride mouthrinses for preventing dental caries in children and adolescents. Cochrane Database Syst Rev. 2003;CD002284.
4. Marinho VC, Higgins JP, Logan S, et al. Fluoride varnishes for preventing dental caries in children and adolescents. Cochrane Database Syst Rev. 2002;CD002279.
5. Demos LL, Kazda H, Cicuttini FM, et al. Water fluoridation, osteoporosis, fractures—recent developments. Aust Dent J. 2001;46:80-87.
Last reviewed December 2015 by EBSCO CAM Review Board Last Updated: 12/15/2015