What About Fluoride?

V. Kim Kutsch, DMD

Fluoride has been extensively studied and has many effects in the role of an anticaries agent.1 It reduces acid production in the biofilm, helps attract calcium and phosphate ion to the tooth surface and form fluorapatite which has a lower critical pH making the enamel more acid resistant, thus increasing the enamel’s resistant to subsequent demineralization. In the effects with enamel, fluoride acts as a remineralization “catalyst”. Fluoride accelerates remineralization by attracting the calcium phosphate to the demineralized surface. Fluoride enhances remineralization by increasing the degree of crystallinity of the enamel. Fluoride reduces acid production in the biofilm and finally it promotes the development of fluorapatite which is more resistant to acid demineralization. Fluoride plays a role in remineralization but requires a source of calcium phosphate for remineralization to occur.2 Enamel and hydroxyapatite, in theory, react in a similar way with fluoride in solution. “Fluoride can substitute for hydroxyl ions in the crystal lattice by solid state reaction. Thus a (partially) fluoridated hydroxyapatite will form Ca1O(PO4)6(OHxFy), with x + y = 2. A faster way of incorporating fluoride in the crystal is by precipitation of a fluoridated hydroxyapatite from the oral fluid onto existing crystallites.”3

Fluoride could better thought of as an anti-demineralizing agent than strictly a remineralizing agent. “Remineralization of superficial enamel lesions is well documented in hundreds of studies completed at numerous laboratories in the last century. Studies on the basic mechanism of remineralization and on methods to stimulate this process have led to the conclusion that the caries preventive effect of fluoride is beyond any doubt. This is partly attributed to the enhancing effect of fluoride on calcium phosphate precipitation, hence remineralization.”4,5

Moreover, the capability of fluoride just endeavors to reduce the disintegration of apatite instead of encouraging remineralization of the inorganic loss from the crystalline HA.6,7,8

The benefits of fluoride and community water fluoridation (CWF) are well established in the scientific literature. There are however concerns about the potential risks of systemic fluoride in community water systems. Attention is being focused on this particular topic and there is a considerable amount of scientific data available, although with some conflicting conclusions. It is well established that fluoride does interfere with certain thyroid hormones.9 A cross-sectional study from England indicated that fluorides does raise some legitimate concerns on thyroid functioning,10 while a more current population study from Canada indicated that current levels of CWF exposure (0.7 ppm) do not increase susceptibility to impaired thyroid functioning at the population-level.11 A more potentially damaging concern is the risk of fluoride exposure and neurodevelopment and cognitive function in children. The premise is that fluoride exposure in childhood leads to lower IQ scores and ADHD.12 Several studies have reported this observation, while others have shown no relationship at current CWF levels.13,14 One study indicated that there was a dose-response to fluoride and cognitive development at high levels of fluoride, but no relationship below 1.5 ppm which is more than double the current levels of CWF in the U.S.15 At best the data at this point is mixed. As new evidence continues to be reported, concerns about fluoride exposure and systemic effects needs to be continually evaluated and responsibly considered.

 

References
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  2. Ten Cate JM, Featherstone JD. Mechanistic aspects of the interactions between fluoride and dental enamel. Crit Rev Oral Biol Med. 1991;2(3):283-96. doi: 10.1177/10454411910020030101. PMID: 1892991.
  3. Featherstone JD. Dental caries: a dynamic disease process. Aust Dent J. 2008 Sep;53(3):286-91. doi: 10.1111/j.1834-7819.2008.00064.x. PMID: 18782377.
  4. Marinho VC, Higgins JP, Logan S, Sheiham A. Topical fluoride (toothpastes, mouthrinses, gels or varnishes) for preventing dental caries in children and adolescents. Cochrane Database Syst Rev. 2003; 4:CD002782.
  5. de Leeuw N. H. Resisting the onset of hydroxyapatite dissolution through the incorporation of fluoride. The Journal of Physical Chemistry B . 2004;108(6):1809–1811. doi: 10.1021/jp036784v.
  6. Jefferies S. R. Advances in remineralization for early carious lesions: a comprehensive review. Compendium of continuing education in dentistry (Jamesburg, N.J.: 1995) . 2014;35(4):237–244.
  7. Zero D. T. Dentifrices, mouthwashes, and remineralization/caries arrestment strategies. BMC Oral Health . 2006;6(1):S9. doi: 10.1186/1472-6831-6-s1-s9.
  8. Roveri N, Battistella E, Bianchi CL, et al. Surface enamel remineralization: biomimetic apatite nanocrystals and fluoride ions different effects. Journal of Nanomaterials 2009, article ID 746383, 9 pages.
  9. Jiang Y, Guo X, Sun Q, Shan Z, Teng W (2015) Effects of excess fluoride and iodide on thyroid function and morphology. Biol Trace Elem Res 170:382–389. 10.1007/s12011-015-0479-0
  10. Peckham S, Lowery D, Spencer S. Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water. J Epidemiol Community Health 2015;69:619–24.
  11. Barberio AM, Hosein FS, Quiñonez C, McLaren L. Fluoride exposure and indicators of thyroid functioning in the Canadian population: implications for community water fluoridation. J Epidemiol Community Health. 2017 Oct;71(10):1019-1025. doi: 10.1136/jech-2017-209129. Epub 2017 Aug 24. PMID: 28839078; PMCID: PMC5754860.
  12. Fiore G, Veneri F, Di Lorenzo R, Generali L, Vinceti M, Filippini T. Fluoride Exposure and ADHD: A Systematic Review of Epidemiological Studies. Medicina (Kaunas). 2023 Apr 19;59(4):797. doi: 10.3390/medicina59040797. PMID: 37109754; PMCID: PMC10143272.
  13. Veneri F, Vinceti M, Generali L, Giannone ME, Mazzoleni E, Birnbaum LS, Consolo U, Filippini T. Fluoride exposure and cognitive neurodevelopment: Systematic review and dose-response meta-analysis. Environ Res. 2023 Mar 15;221:115239. doi: 10.1016/j.envres.2023.115239. Epub 2023 Jan 10. PMID: 36639015.
  14. Do LG, Sawyer A, John Spencer A, Leary S, Kuring JK, Jones AL, Le T, Reece CE, Ha DH. Early Childhood Exposures to Fluorides and Cognitive Neurodevelopment: A Population-Based Longitudinal Study. J Dent Res. 2024 Dec 18:220345241299352. doi: 10.1177/00220345241299352. Epub ahead of print. PMID: 39692252.
  15. Taylor KW, Eftim SE, Sibrizzi CA, Blain RB, Magnuson K, Hartman PA, Rooney AA, Bucher JR. Fluoride Exposure and Children’s IQ Scores: A Systematic Review and Meta-Analysis. JAMA Pediatr. 2025 Jan 6. doi: 10.1001/jamapediatrics.2024.5542. Epub ahead of print. PMID: 39761023.