Since the 1950s, the benefits and risks of fluoridated water use have been debated worldwide. In the past, it was considered that the systemically ingested fluoride would exert its primary preventive effect after being incorporated into the enamel as fluorapatite, making the enamel more resistant to the caries process; however, it is now recognized that the main effect of water fluoridation is local and post eruptive. On the other hand, irrespective of the caries decline reported worldwide, the anticaries benefit of water fluoridation continues to be observed even in developed countries. Regarding the risks, water fluoridation is considered an acceptable community-based method for fluoride delivery, because the risk of developing dental fluorosis lesions due to the ingestion of fluoride during the enamel formation period has been deemed acceptable when contrasted to the anticaries benefits of fluoride. However, the use of fluoride in water to control caries has created a controversy due to data associating water fluoridation as the cause of some systemic diseases. Therefore, the aim of this descriptive review was to discuss the systemic effects (risks) of water fluoridation use.
Table 5 Chronology of campaigns against water fluoridation and allegations used (modified from Newbrun, 1996).
|1960||Toxic waste, polluting|
|1980||Industrial interests, cancer in humans,|
|Aging, Alzheimer’s disease|
|1990||AIDS, bone fracture, birth rate|
|2000-present||Decreased IQ, hypothyroidism|
1 Tenuta, LM; Cury, JA. Fluoride: its role in dentistry. Braz Oral Res 2010;24:9-17.
2 Fejerskov, O; Cury, JA; Tenuta, LMA; Marinho, V: Fluorides in caries control; in Fejerskov, O; Nyvad, B; Kidd, E(eds): Dental Caries: The Disease and Its Clinical Management; ed 3. Oxford; Wiley-Blackwell; 2015, pp 245-276.
3 Rebelo, MAB; Fernandez-Alves, CS; Bulcão, LN; Cury, JA. Benefits and risks of fluoride supplements of Brazilian Market (In Portuguese). Vig Sanit Debate 2014;2:80-85.
4 Cury, JA; Tenuta, LM. How to maintain a cariostatic fluoride concentration in the oral environment. Adv Dent Res2008;20:13-16.
5 Lima, CV; Tenuta, LMA; Cury, JA. Fluoride increase in saliva and dental biofilm due to a meal prepared with fluoridated water or salt: a crossover clinical study. Caries Res 2019;53:41-48.
6 Nobrega, FF; Tenuta, LMA; Cury, JA. Metabolism and toxicity of fluoride. In: Oral Biochemistry (In Portuguese). Cury, JA; Tenuta, LMA; Tabchoury, CPM (Editors) 1st ed. São Paulo: Artes Médicas 2017. p.124-144.
7 Cury, JA; Tenuta, LMA. Acute intoxication by fluoride ingestion. In: Medical emergencies in Dentistry(In Portuguese). Andrade, EA; Ranali, J(Editors) 3rd ed. São Paulo: Artes Médicas 2011. p.145-152.
8 Ekstrand, J. Fluoride metabolism. In: Fluoride in dentistry. Fejerskov, O; Ekstrand, J; Burt, B(Editors) 2nd ed. Copenhagen: Munksgaard 1996 p.55-68.
9 Whitford, GM. Acute and chronic fluoride toxicity. J Dent Res 1992;71:1249-1254.
10 Frazão, P; Peres, MA; Cury, JA. Drinking water quality and fluoride concentration. Rev Saude Publica 2011;45:964-973.
11 Bärdsen, A. “Risk periods” associated with the development of dental fluorosis in maxillary permanent central incisors: a meta-analysis. Acta Odontol Scand 1999;57:247-256.
12 Bergamo, ET; Barbana, M; Terada, RS; Cury, JA; Fujimaki, M. Fluoride concentrations in the water of Maringá, Brazil, considering the benefit/risk balance of caries and fluorosis. Braz Oral Res 2015;29:1-6.
13 Chankanka, O; Levy, SM; Warren, JJ; Chalmers, JM. A literature review of aesthetic perceptions of dental fluorosis and relationships with psychosocial aspects/oral health-related quality of life. Community Dent Oral Epidemiol 2010;38:97-109.
14 Onoriobe, U; Rozier, RG; Cantrell, J; King, RS. Effects of enamel fluorosis and dental caries on quality of life. J Dent Res. 2014;93:972-979.
15 Do, LG; Ha, DH; Spencer, AJ. Natural history and long-term impact of dental fluorosis: a prospective cohort study. Med J Aust. 2016;18;204:225.
16 Brazil. Ministry of Health. SB Brazil 2010: National Oral Health Survey: main results. Ministry of Health. Health Care Secretariat. Health Surveillance Secretariat. Brasília: Ministry of Health, 2012. (In Portuguese).
17 Oliveira, MJ; Martins, CC; Paiva, SM; Tenuta, LM; Cury, JA. Estimated fluoride doses from toothpastes should be based on total soluble fluoride. Int J Environ Res Public Health 2013;10:5726-5736.
18 Martins, CC; Paiva, SM; Lima-Arsati, YB; Ramos-Jorge, ML; Cury, JA. Prospective study of the association between fluoride intake and dental fluorosis in permanent teeth. Caries Res 2008;42:125-133.
19 Warren, JJ; Levy, SM; Broffitt, B; Cavanaugh, JE; Kanellis, MJ; Weber-Gasparoni, K. Considerations on optimal fluoride intake using dental fluorosis and dental caries outcomes–a longitudinal study. J Public Health Dent 2009;69:111-115.
20 Paiva, SM; Lima, YB; Cury, JA. Fluoride intake by Brazilian children from two communities with fluoridated water. Community Dent Oral Epidemiol 2003;31:184-191.
21 Falcão, A; Tenuta, LM; Cury, JA. Fluoride gastrintestinal absorption from Na2FPO3/CaCO3– and NaF/SiO2-based toothpastes. Caries Res 2013;47:226-233.
22 Fejerskov, O; Baelum, V; Richards, A. Dose-response and dental fluorosis. In: Fluoride in dentistry. Fejerskov, O; Ekstrand, J; Bur,t B (Editors) 2nd ed. Copenhagen: Munksgaard, 1996; p.153-166.
23 Catani, DB; Hugo, FN; Cypriano, S; Sousa Mda, L; Cury, JA. Relationship between fluoride levels in the public water supply and dental fluorosis. Rev Saude Publica 2007;41:732-739.
24 Brazil. Ordinance 635 of December 26, 1975. Approves norms and standards on the fluoridation of water from public supply systems. Available in [2006 jan 18]: Available in [2006 jan 18]: http://www.saude.gov/programas/bucal/principal.htm (In Portuguese).
25 [CECOL / USP]. Collaborating Center of the Ministry of Health in Oral Health Surveillance. Technical consensus on public water supply classification according to fluoride content. São Paulo: School of Public Health, University of São Paulo; 2011. (In Portuguese).
26 Levy, SM; Warren, JJ; Phipps, K; Letuchy, E; Broffitt, B; Eichenberger-Gilmore, J; et al. Effects of life-long fluoride intake on bone measures of adolescents: a prospective cohort study. J Dent Res 2014;93:353-359.
27 Näsman, P; Ekstrand, J; Granath, F; Ekbom, A; Fored, CM. Estimated drinking water fluoride exposure and risk of hip fracture: a cohort study. J Dent Res 2013;92:1029-1034.
28 Newton, JN; Young, N; Verne, J; Morris, J. Water fluoridation and hypothyroidism: results of this study need much more cautious interpretation. J Epidemiol Community Health 2015;69:617-618.
29 Grimes, DR. Commentary on “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;69:616.
30 Warren, JJ; Saraiva, MC. No Evidence Supports the Claim That Water Fluoridation Causes Hypothyroidism. J Evid Based Dent Pract 2015;15:137-139.
31 Newton, JN; Verne, J; Dancox, M; Young, N. Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? Comments on the authors’ response to earlier criticism. J Epidemiol Community Health2017;71:315-316.