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(05/01/16) A summary of 'Cochrane Collaboration systematic review of water fluoridation 2015' has been posted in Reports.
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(16/04/14) A critique of 'One in a Million: The Facts' has been posted in Reports.
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(16/04/14) 'Fluoridation: Popularity' has been posted in the Archive.
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(18/04/10) New fluoridation scheme for Southampton

(18/04/10) The Reports and Archive sections have been updated with further documents and links

(11/07/09) A critique of Prof. Newton's report to South Central SHA has been posted in Reports.
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(28/09/08) A critique of the South Central Strategic Health Authority Consultation Paper on Water Fluoridation in Southampton, has been posted in Reports.
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(07/09/08) A response to the Chief Dental Officer's 'Dear Colleague' letter of guidance for new schemes, endorsed by scientists from the York review, has been posted in Reports.
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(23/06/08) Isle of Man has announced on 12th June that it will not be fluoridating its water supply
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An Economic Evaluation of Community Water Fluoridation
Griffin SO, Jones K, Tomar PH [J Public Health Dent 2001; 61(2): 78-86] :
A Critique

1. South Central Strategic Health Authority relies on Griffin et al for its cost-effectiveness figures for a possible fluoridation scheme in the Southampton area. This paper was cited in the report by Abacus International to the SHA on the economic implications of fluoridation, for a reduction in mean incremental caries lesions of 25%.

2. It is important to recognise the uncertainties surrounding such a clear-cut figure. This brief comment concentrates on the effectiveness question, leaving on one side the technicalities of costing. Without a firm base of effectiveness it is not possible to be clear about cost-effectiveness.

3. The referenced sources for Griffin's 25% figure date back to the early 1990s and before. The quality of this evidence base can be gauged from the fact that none of the papers cited by Griffin was of a standard to meet the inclusion criteria of the York systematic review into water fluoridation (2000) when it considered caries reduction. Even those better studies which were admitted to the York review were not of good quality.

4. It is surprising that Griffin makes no reference to York, yet claims to base her findings on "the most current data available on the effectiveness" of fluoridation. This is a major weakness, since York systematically searched the world literature, applying internationally recognised criteria to its assessment of the evidence it found, and provides the scientific benchmark for the benefits and harms of fluoridation. This means that it is hard to place reliance on Griffin's sources and conclusions if they will not even attain York's evidential 'level C' ("high risk of bias").

5. Clarification is needed of what Griffin's 25% means. Page 80 of her analysis lists sources for a 26% "mean caries reduction" in US children; close to 25% "effectiveness parameters" in adult populations; "31% less dental decay" in adults; "20% fewer carious surfaces" among adults; variations in "caries prevalence in children"; and a "national estimate of effectiveness" of 25%. (No source was more recent than 1993; none was systematically reviewed; most relate to the USA.) Abacus, citing Griffin, speaks of a "reduction in mean incremental caries lesions" of 25%, while the SHA's consultant in dental public health writes in a letter of an "estimated reduction in the incidence of decayed missing and filled teeth . . of 25% (From . . Griffin, 2001)".

6. It should surely be clearer for both public and decision-makers in Hampshire to understand exactly what measure is being claimed for their possible new scheme, and with what confidence. If they want the best evidence available for effectiveness they must go to York. York reported the mean difference of the change in the proportion of caries-free children (all ages) between fluoridated and unfluoridated areas, which yielded a median figure of 14.6%. At the same time the York reviewers cautioned against claiming any certainty in figures where the evidence allowed none.

7. Griffin's analysis of cost savings was "limited . . to the permanent dentition", i.e. 6 years and older. The SHA makes its case on 5-year-olds. This may bring further uncertainty.

8. "Because costs are difficult to identify and measure empirically, the potential exists for bias in our cost figures" (p. 83). While this and other caveats by Griffin (pp. 83-4) are what one would expect in the discussion section of a scientific paper, lay readers must realise that they diminish further any reliance on a precise figure for cost-effectiveness. York was asked to look at this question in 1999-2000, but could not find any adequate evidence in the literature and so declined to speculate.

9. Among the prior assumptions made explicit by Griffin (p. 79) is that "The adverse effects resulting from water fluoridation exposure are negligible", these including dental fluorosis. For this claim, and for the assumption that fluoridation is the least costly among modes of fluoride delivery, a 1991 review by the US Department of Health and Human Services is cited. In 2008 this view is untenable. While it is important to stress the absence of any proof of harm, the mixed findings and recommendations about adverse effects by the York review and the warnings of the 2006 report from the US National Research Council of the National Academy of Sciences give no grounds for assuming negligible harm. There is much research on possible harms, recommended by a variety of bodies, still waiting to be done.

10. To anyone who is sensitive to the nuances of bias on both sides of the high-octane fluoride debate, it will seem unfortunate that Griffin chose to open her paper with the statement that "The Centers for Disease Control and Prevention recently identified water fluoridation as one of the 10 great public health achievements in the 20th century". This will be seen as setting the tone for a paper which itself comes from the CDC, the base for two of the three authors. What may fairly be termed a fluoridation culture (there is also an anti-fluoridation culture) is at its strongest within the US dental and public health community, from where the most vocal promotion of fluoridation has traditionally come. Scientists are usually wary of 'in-house' research, i.e. papers produced by people or within institutions that are known to promote a particular viewpoint, because of the subtle biases that can intrude.

Edward Baldwin.
22nd October 2008.

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