Are there long-term effects of water fluoridation on the human skeleton?

This summary is based on the article published in the Journal of Dental Research: The Long-term Effects of  Water Fluoridation on the Human Skeleton (November 2010)

Context

Municipal water fluoridation has notably reduced the incidence of dental caries and is widely considered a public health success. However, ingested fluoride is sequestered into bone, as well as teeth, and data on the long-term effect of exposure to these very low doses of fluoride remain inconclusive. Epidemiological studies suggest that effects of fluoride on bone are minimal.

Purpose of the Study

The authors hypothesized that the direct measurement of bone tissue from individuals residing in municipalities with and without fluoridated water would reveal a relationship between fluoride content and structural or mechanical properties of bone.

Conclusion

• Consonant with the epidemiological data, only a weak relationship among fluoride exposure, accumulated fluoride, and the physical characteristics of bone was observed.
• Analysis of our data suggests that the variability in heterogenous urban populations may be too high for the effects, if any, of low-level fluoride administration on skeletal tissue to be discerned.

Further Findings

• Epidemiological studies have failed to observe an effect of municipally fluoridated drinking water on bone (1), but the safety of long-term water fluoridation remains uncertain in public discussions.
• The study showed the lack of a strong relationship between fluoride exposure and bone fluoride content.
• About 40% of the population in areas with water supplies naturally fluoridated at very high levels are unaffected by skeletal fluorosis (2), and about a third of patients who receive fluoride as a therapy for osteoporosis are described as ‘nonresponders’ (3), indicating that intrinsic susceptibility to fluoride varies with the individual. 
• Many decades of epidemiological studies have shown minimal evidence of any effects of fluoride administration on bone, and it is therefore very unlikely that municipally fluoridated water affects adults with healthy bone. In this study, no effects of fluoride on mineralization (by BSE) and no substantive negative effects of fluoride administration on bone mechanical properties were observed.
• The analysis of samples at the tissue level, rather than the population level, reveals high levels of variability in response to water fluoridation, which may account for the lack of differences observed in epidemiological studies (1).
• While we cannot definitively rule out an effect of low-level fluoride accumulation over long periods of time, especially if specific individuals have a genetic or disease background that renders them unusually susceptible to fluoride, it nevertheless appears that the contributors to bone health are too many and varied, and any possible effect of municipal fluoride ingestion is too small, for municipal water fluoridation to be a significant determinant of bone health within the general public.

References

1. McDonagh MS, Whiting PF, Wilson PM, Sutton AJ, Chestnutt I, Cooper J, et al. (2000). Systematic review of water fluoridation. BMJ 321:855-859.
2. Choubisa SL (2001). Endemic fluorosis in southern Rajasthan, India. Fluoride 34:61-70.
3. Dequeker J, Declerck K (1993). Fluor in the treatment of osteoporosis. An overview of thirty years clinical research. Schweiz Med Wochenschr 123:2228-2234.