As the article notes, this is all based on the Cochrane Collaborative methodology of searching for prior published scientific literature, and is not a conclusion based on a fresh study. The article also points out, "Another 2009 review[link] by the Cochrane group clearly shows that fluoride toothpaste prevents cavities, serving as a useful counterpoint to fluoridation’s uncertain benefits."
"Tooth decay (dental caries) is painful, expensive to treat and can sometimes lead to serious damage to teeth. Fluoride is a mineral that prevents tooth decay. The review of trials found that children aged 5 to 16 years who used a fluoridated toothpaste had fewer decayed, missing and filled permanent teeth after three years (regardless of whether their drinking water was fluoridated). Twice a day use increases the benefit."
On the whole, the Cochrane Collaboration is a force for good, but its methodology of reviewing previous published studies lets it miss important issues of prior plausibility (that is, lack of plausibility) when reviewing "alternative" treatments.
I don't think this has anything to do with Cochrane's methodology. This is about choice of presentation.
They are very clear in the paper that they are reviewing a certain body of studies, and that there are other plausible reasons (not backed up by RCTs) to believe water fluoridation could have beneficial effects. The numbers they quote summarize the evidential content of the RCTs. I don't need or want them to bundle this all into one Bayesian percentage. This would be dominated by their own priors which I do not necessary share nor are necessary shared by anyone I discuss the study with. (Yet we can all agree on the frequentist summary of the RCTs.)
Was that conclusion the result of a meta-analysis of meta-analysis methodologies? And there I thought this was just an amusing cartoon... https://xkcd.com/1447/
> The article also points out, "Another 2009 review[link] by the Cochrane group clearly shows that fluoride toothpaste prevents cavities, serving as a useful counterpoint to fluoridation’s uncertain benefits."
I think you understood this, but I wanted to clarify for others: the Cochrane review that this article is about showed that fluoridated water may not prevent tooth decay. The 2009 review you mention does not contradict this, since it is about fluoridated toothpaste, not water.
"The separate meta-analyses of fluoride gel or mouthrinse combined with toothpaste versus toothpaste alone favour the combined regimens, but differences were not statistically significant; the significant difference in favour of the combined use of fluoride varnish and toothpaste accrues from a very small trial and appears likely to be a spurious result. [Except for two studies finding gel + mouthrinse to be more effective than gel alone,] no other combinations of topical fluoride therapy were consistently superior to a single therapy."
Since fluoride can harm brains, kidneys, and more at certain doses, I'm glad people are interested in which therapies are most effective and are seeking the optimal exposure level.
[link] http://www.cochrane.org/CD002278/ORAL_fluoride-toothpastes-f...
"Tooth decay (dental caries) is painful, expensive to treat and can sometimes lead to serious damage to teeth. Fluoride is a mineral that prevents tooth decay. The review of trials found that children aged 5 to 16 years who used a fluoridated toothpaste had fewer decayed, missing and filled permanent teeth after three years (regardless of whether their drinking water was fluoridated). Twice a day use increases the benefit."