http://www.ncbi.nlm.nih.gov/pmc/articles/PMC27492/
Just like with creationism, vaccinations, the environment, and fluoride; if you polish the bullshit enough, people will follow.
Just like with creationism, vaccinations, the environment, and fluoride; if you polish the bullshit enough, people will follow.
(Can you imagine proposing fluoridation of everyone's drinking water these days based on evidence like that? If fluoride were being proposed to the FDA as a drug, it wouldn't even make it to Phase III trials...)
To expand on this: the heterogeneity is so high that they don't (as meta-analysis guidelines say you should) report the figures. This is why in the figures, you see tight confidence intervals around zero, but also equally-tight confidence intervals many effect-size units away. That's an alarm bell for trying to draw any sort of meaningful conclusion: it means there are so many variables at play that you have no idea whether the net should be zero or big. (Also a concern given the observation that many countries have seen dental problems fall considerably as they developed, which is a big confound.)