I agree with everything you are saying. Let me rephrase what I was saying so you can see we more or less agree. The article is complaining that there are no ra

I agree with everything you are saying. Let me rephrase what I was saying so you can see we more or less agree. The article is complaining that there are no randomized control studies and using this to conclude that there is little evidence to support flossing. They are simply disregarding other types of studies like the observational study you are pointing out have value. These observational studies show such clear benefits to flossing that directing a person to stop would be considered unethical. I am pointing to a more facile example where you would never imagine performing a randomized control study because it is obvious that the no treatment control is dangerously unethical. Doctors end up being susceptible to public misconceptions just as much as the general public. Not everybody reads original research or health guidelines. So someone hears that the official guide recommends 2.5 liters of water, with no mention of the accompanying note that most of this comes through ordinary food intake, and they misinterpret it as needing 8 glasses of water a day. That is the case for the 8 glass a day myth: no scientific study ever recommended it, but half readings of some literature seemed to imply it. If you like myths like those, read through https://www.snopes.com/fact-check/water-works-2/ https://www.snopes.com/fact-check/water-works-2/ especially when it gets to the diuretic effects of caffeinated beverages. I mostly learned about this when I started talking to foreigners about it and realized it just wasn't common knowledge outside of North America that caffeine causes dehydration.