Background


Researchers became interested in fluoride’s role in dental health when they noticed that certain areas of the United States had fewer cases of severe tooth decay than others. Groundwater in regions that were rich in fluoride had high amounts of the ion, whereas groundwater in areas with low concentrations had negligible amounts of fluoride.

This discovery led to public-health policies that added fluoride to drinking water, a practice that has been estimated to reduce dental caries in both children and adults by up to 40%.4 During the latter half of the 20th century, researchers also discovered the role fluoride plays in the development of strong bones. 


Science


The basic mechanism of action by which fluoride prevents cavities in teeth and promotes strong bones is by enhancement of the remineralization that occurs naturally and constantly in these tissues.5 When the pH in the mouth falls below 5.5, tiny craters can begin to form on the tooth surface.

If left untreated, these areas eventually become a true cavity. Fluoride ions in saliva bond with the ambient hydroxyapatite from the dissolved enamel, speed remineralization, and prevent further erosion of the enamel.5 Dental caries are not affected by the ingestion of fluoride until after tooth eruption.


A similar mechanism strengthens bone matrix. Bone mass is a constant balance between the activity of osteoblasts, which build new bone, and osteoclasts, which tear away old bone. Supporting the use of fluoride for osteoporosis, early studies documented increased bone mineral density of the lumbar spine, one of the areas most susceptible to fracture, following fluoride treatment at certain doses.6

However, later data increasingly showed that too much fluoride led to bone that was more brittle and increased nonvertebral fractures.7

Since the utility of fluoride for dental health was established, commercial products began to appear and dominate the oral-health marketplace. Multiple studies now verify the safety and efficacy of the routine use of fluoridated toothpastes and mouthwashes.

A recent meta-analysis found that topical fluoride was as effective as fluoridated water in the prevention of dental caries.8 Since the late 1970s, a trend toward fewer caries has been documented, even in areas that do not fluoridate public water supplies.9

Safety, interactions, side effects


In developed countries around the world, at least a small amount of fluoride occurs naturally in groundwater and food.10 The National Institutes of Health and the Academy of Nutrition and Dietetics have issued recommendations for the minimum daily intake of fluoride from all sources.10,11

Fluoride levels of community water in the United States are set at 0.7 mg/L, which results in the need to defluorinate in some areas that are rich in ground fluoride.1,12 The maximum amount of elemental fluoride that is safe for daily ingestion is 10 mg.13

Excessive, chronic ingestion of fluoride can increase bone fragility, discolor tooth enamel, and cause severe gastric distress.10 The only specific contraindication against additions of fluoride to the diet is for postmenopausal women with known osteoporosis.


Cost, how supplied, dose


Fluoride is supplied mainly through community water supplies and topical fluoride products, which are usually in the form of toothpaste or mouthwash and costs from $3 to $7 per unit. 


Summary


The efficacy of fluoride in the prevention of dental caries is well-established. Cultural development has potentially eliminated the need for fluoridation of public water supplies. However, the efficacy of topical products is only as good as compliance with their use.

Sherril Sego, FNP-C, DNP, is a staff clinician at the VA Hospital in Kansas City, Mo., where she practices adult medicine and women’s health. She also teaches at the nursing schools of the University of Missouri and the University of Kansas. 

References


  1. Mullen J; European Association for Paediatric Dentistry. History of water fluoridation. Br Dent J. 2005;199
(7 Suppl):1-4. Available at nature.com/bdj/journal/v199/n7s/full/4812863a.html

  2. Centers for Disease Control and Prevention. Community water fluoridation: 2010 water fluoridation statistics. Available at cdc.gov/fluoridation/statistics/2010stats.htm

  3. Centers for Disease Control and Prevention. Achievements in public health, 1900-1999: Fluoridation of drinking water to prevent dental caries. MMWR. 1999;48(41):933-940. Available at cdc.gov/mmwr/preview/mmwrhtml/mm4841a1.htm

  4. Griffin SO, Regnier E, Griffin PM, Huntley V. Effectiveness of fluoride in preventing caries in adults. 
J Dent Res. 2007;86(5):410-415.

  5. Cury JA, Tenuta LM. How to maintain a cariostatic fluoride concentration in the oral environment. Adv Dent Res. 2008;20(1):13-16.

  6. Vestergaard P, Jorgensen NR, Schwarz P, Mosekilde L. Effects of treatment with fluoride on bone mineral 
density and fracture risk—a meta-analysis. Osteoporos Int. 2008;19(3):257-268.

  7. Gutteridge DH, Stewart GO, Prince RL, et al. A randomized trial of sodium fluoride (60 mg) +/- estrogen in postmenopausal osteoporotic vertebral fractures: increased vertebral fractures and peripheral bone loss with sodium fluoride; concurrent estrogen prevents peripheral loss, but not vertebral fractures. Osteoporos Int. 2002;13(2):158-170. 

  8. Pizzo G, Piscopo MR, Pizzo I, Giuliana G. Community water fluoridation and caries prevention: a critical review. Clin Oral Investig. 2007;11(3):189-193. 

  9. Hellwig E, Lennon AM. Systemic versus topical fluoride. Caries Res. 2004;38(3):258-262. Available at karger.com/Article/FullText/77764

  10. Hamrick I, Counts SH. Vitamin and mineral supplements. Prim Care. 2008;35(4):729-747. 

  11. Palmer C, Wolfe SH; American Dietetic Association. Position of the American Dietetic Association: the impact of fluoride on health. J Am Diet Assoc. 2005;105(10):1620-1628. Available at andjrnl.org/article/S0002-8223(05)01391-X/fulltext

  12. U.S. Department of Health and Human Services. Proposed HHS recommendation for fluoride concentration in drinking water for prevention of dental caries. Available at federalregister.gov/a/2011-637. 

  13. U.S. Institute of Medicine Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, D.C.: National Academies Press; 1997. Available at nap.edu/openbook.php?record_id=5776


All electronic documents accessed on December 2, 2014.