Anti-fluoridationist’s flawed attacks on Calgary study


Image credit: Why I will no longer approve anti-fluoride dishonesty – New Anthropocene

The anti-fluoride propagandists are at it again – attacking a recently published scientific paper because the reported data does not fit with their own agenda.

The are attacking this paper:

McLaren L, Patterson S, Thawer S, Faris P, McNeil D, Potestio M, Shwart L. (2016) Measuring the short-term impact of fluoridation cessation on dental caries in Grade 2 children using tooth surface indices. Community Dent Oral Epidemiol 2016.

The Fluoride Action Network (FAN) claims the study is “fatally flawed” and that “key data [was] omitted.” The local FAN organisation – Fluoride Free New Zealand (FFNZ) has gone further claiming the study is “basically a fraud.”

Serious (even slanderous) accusations – let’s see if those charges hold up.

What did the study find?

The paper reports changes in dental caries levels of grade 2 children in Alberta, Canada between 2005/2005 and 2013/2014. Two cities were chosen – Calgary (which stopped fluoridation in May 2011 – after having been fluoridated since 1991) and Edmonton where fluoridation started in 1967 and is still in place. This enabled an assessment of the effect of fluoridation cessation on the dental health of children in Calgary.

Dental caries actually increased in both cities but the data shows a larger increase in dental caries where fluoridation had been stopped (Calgary) than where it continued (Edmonton).


defs = decayed, extracted (due to caries) filled primary tooth surfaces.

The change in Calgary (3.8) is greater than for Edmonton (2.1) and the difference is statistically significant.

The above graphic is for all tooth surfaces – similar results were obtained with smooth surfaces only – Calgary change = 2.9 and Edmonton change = 1.6.

Important features of study

There are several important features of the paper and the data reported:

1: Whereas previous cessation studies had used tooth-level data this study used tooth surface-level data. The authors had previously reported tooth level data which showed similar results.

The WHO prefers and recommends tooth surface-level data to evaluate an intervention such as starting or stopping fluoridation because of its greater sensitivity. The study authors used  tooth surface-level data and focused on smooth tooth surfaces which are most likely influenced by fluoride in this age group.

Most earlier fluoridation cessation studies had used less sensitive tooth-level data so this study was a definite improvement

2: A comparison (or “control”) city was used – Edmonton. Many previous cessation studies suffered from not using a comparison community. Interpretation is more difficult without some sort of “control” as changes due to other factors may be important. Factors like different assessment personnel, changes in diet (eg sugar consumption or bottled water), changes in dental health care, etc. It is difficult to take account of all factors but the inclusion of a similar comparison community helps reduce their effects on the results.

Again, this study was a definite improvement over previous cessation studies which had not used a comparison community.

3: Pre-cessation data were collected several years before cessation. The authors list this as a limitation, saying:

“it would have been preferable to have data collected closer to the year of cessation.”

However, this being the real world, the study used the only tooth surface-level data available for Calgary and Edmonton. There was absolutely no question of data being omitted (or “fraud”) that the anti-fluoride campaigners allege.

So how has FAN supported their charges?

Well, basically by retreating from (or ignoring) the advantages of this study – use of tooth surface-level data and use of a comparison community.

1: They use the limitation that the pre-cessation tooth surface-level data was collected several years before cessation to resort to more recent 2009/2010 data. But, importantly, that data is not tooth surface-level and it is for only one city – Calgary! 

So, they claim, the researchers “omitted key data” – the 2009/2010 data – pretending the researchers had  “hidden” it. But that data was not surface-level data. And, far from “hiding,” it the same research group specifically used this tooth-level data in an accompanying  paper:

McLaren L, McNeil D, Potestio M, Patterson S, Thawer S, Faris P, Congshi S,  Shwart L. (2016). Equity in children’ s dental caries before and after cessation of community water fluoridation: differential impact by dental insurance status and geographic material deprivation. International Journal for Equity in Health 15: 24

2: They ignore completely the importance of using a comparison community. Sure, they might claim that no survey was taken in Edmonton in 2009/2010. But they have thrown the baby out with the bath water in their attempt to discredit the research. They have fallen back on the limitation of so many fluoridation cessation studies which rely on cross-sectional measurements at different times without using a control. Worse still, they do this despite the tooth surface-level data for Edmonton showing an increase in dental caries even though there had been no cessation of fluoridation! They are willingly falling into the trap of ignoring all the other factors which could influence the results.

3: The FAN press release attempts to discredit the researchers saying:

“The lead author of the study, Lindsay McLaren, is not an independent scientist on the fluoridation controversy.”

This “damning by association” of researchers with their institutions, the fact that they receive a wage from their employers and that they write articles about their scientific results (which do not support the claims of the anti-fluoridation lobby) is really disingenuous. It’s a way of discrediting any scientist who produces results an anti-science group does not like. (Anti-science groups often use this argument – for example, anti-fluoride activists haver told me I am not “independent” because I once worked as a scientific researcher and,  therefore, cannot be trusted!).

Ironically, they are hanging themselves with their own rope on this one. Their press release makes mileage by quoting an assessment from an “independent” scientist Dr Trevor Sheldon. I checked with Sheldon and he confirmed that he:

“was invited to comment on this by Fluoride Action Network.  I did not have much time to do this but agreed to do so and received no incentive or reward.”

Now, doesn’t that admission  compromise Sheldon as an “independent” commentator? He immediately responds to a request from an activist political organisation, a group funded by the “natural”/alternative health industry – without any qualms! That confirms in my mind the links and political sympathies Sheldon has with FAN that I have long suspected.

It is perfectly normal (and healthy) for credible scientists to disagree with published papers and there are publication mechanisms to do this effectively. For example “letters to the editor” or comments in the specific journal – or even alternative journals. The fact Sheldon chose an almost immediate critique in the newsletter of a political activist group confirms to me that he is not “independent” on this subject and that he, in effect, belongs to the stable of “tame” anti-fluoride scientists FAN makes regular use of in their press releases. People like Bill Hirzy, Kathleen Theissen, Bill Osmunson, Hardy Limeback, etc.

Some other critical details

FAN relied on Sheldon’s evaluation for their main criticism but there are other details in that evaluation which I can comment on.

1: Sheldon would have preferred “a randomised controlled trial where areas are randomly allocated to start/cease water fluoridation.”

Yes, that would have been nice wouldn’t it.But the fact this has never been done – and Sheldon himself has never initiated such a trial – rather indicates how impossible such a trial is. The Cochrane review of community water fluoridation, which anti-fluoride campaigners love to misrepresent, commented on the silliness of such complaints:

But the fact this has never been done – and Sheldon himself (and similar anti-fluoride critics) has never initiated such a trial – rather indicates how impossible such a trial is. The Cochrane review of community water fluoridation, which anti-fluoride campaigners love to misrepresent, commented on the silliness of such complaints:

“particularly for research questions where evidence from randomised controlled trials is never going to be available due to the unfeasibility of conducting such trials. Community water fluoridation is one such area.”

2: He attempts to  extrapolate from tooth-level data to “fill in the gaps” in the tooth surface-level data. This highly speculative analysis allows him to conclude that most of the increase in dental caries shown by children in Calgary occurred before the cessation of fluoridation.

He accuses the researchers of making a “heroic assumption” but it seems to me the assumptions involved in his extrapolation are worse than “heroic.” Yet  the analysis enables him to make conclusions which seem to be derived more from confirmation bias than from intelligent analysis of the data. Especially as he ignored any data from Edmonton.

3:  He comments on problems resulting from population movements, confounding factors, assessment methods and staff differences, sample size differences, etc. But these are common problems when attempting to make sense of existing data. Importantly, these problems and worse, plague the cessation studies that anti-fluoride campaigners continually quote to support their claims that community water fluoridation is ineffective.


The Calgary/Edmonton study does not have the limitations of most fluoridation cessation studies – in particular, a comparison community was used and the more sensitive and appropriate tooth surface-level data was used rather than tooth-level data. The period between the first assessment and cessation is an admitted limitation but certainly does not indicate the omission of data or hiding data as anti-fluoridationists are claiming. There was just no intermediate data available.

The resort to speculative extrapolation of tooth-level data for only Calgary is disingenuous as it ignores the low sensitivity of that data and the influence of other factors compensated for by the use of Edmonton as a comparison community.

Anti-fluoridation campaigners often make ready use of older cessation studies which showed no effect – despite the obvious limitation. In particular, they often use studies where no comparison community was included and ignore completely the other factors involved such as changes in dental health provisions or social health policies such as replacing fluoridation with mouth rinse campaigns.

It is, therefore, ironic for them to come out fighting in an attempt to discredit a study which has fewer limitations than the ones they rely on. Worse, to accuse researchers of purposely omitting data – or even of scientific fraud.

The real reason for these attacks on honest researchers is that the data just does not fit the anti-fluoridation agenda and therefore, in their eyes, must be discredited.

Oh, and beware of such activists using the word “independent’ to describe a researcher. It inevitably indicates someone with allegiances to their campaign. Someone who can be relied on to give the appropriate quote to be used in their press releases.

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4 responses to “Anti-fluoridationist’s flawed attacks on Calgary study

  1. I guess I wouldn’t be labelled “independent” by the anti-fluoridationists, either.

    After all, I’ve never been a dentist, never worked in public health, never done research related to fluoride… If I see someone with dental problems (not an infrequent occurrence) I refer them to a dentist of their own choice.

    Unfortunately, I went to a medical school and am now being employed by a DHB. I suspect that both of those would disqualify my independence in the view of anti-fluoridationists.

    In reality, I was a “shruggy” over fluoride a couple of years ago. Some inane (my spellchecker wants to say insane!) comments from anti-fluoridationists, that seemed to pay no attention to chemistry, physics or biology, got me re-reading the texts on fluoride, and then more recent literature.

    You could say that the anti-fluoridationists have made me the pro-fluoridationist that I am. And all because they made so many inane/insane comments.


  2. Thanks, Ken. The FAN minions have predictably begun spewing Sheldon’s opinions on Calgary all over the internet. It’s truly a shame to see someone such as Sheldon so damage his credibility by aligning himself with the dubious antifluoridationist faction FAN.

    Steven D. Slott, DDS


  3. Of course the Kens and Stevens of this world fail to see that what Ken writes can be turned on its head and apply to themselves as well.
    The real reason for these attacks on anti fluoridation researchers is that the data just does not fit the pro-fluoridation agenda and therefore, in their eyes, must be discredited.
    Oh, and beware of pro F activists using the word “independent’ to describe a researcher. It inevitably indicates someone with allegiances to their campaign. Someone who can be relied on to give the appropriate quote to be used in their vitriolic comments.


  4. Trev – the attacks, misrepresentation of the research and accusation of neglecting or hiding data – together with claims of scientific fraud by your organisation FFNZ, are coming from the anti-fluoride propagandists. Not the science side.

    And it is the anti-science side who wheel pout people they call “independent” even they are often on the FAB board!

    Proscience people do not usually use that term because it is misleading. They rest their arguments and case on the evidence.


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