What's really strange to me, is that for all the expertise around dentistry, AFAIK there has never been an actual evidence-based study for how long and how often you should brush and floss.
Its literally the most important piece of dental advice they could study, and no research has been done. How much plaque builds up on average when only brushing once per week, once per month? It makes me question the whole discipline and wonder if they don't just say "brush 10 times a day" in order to sell more dental products.
Maybe they'd discover that actually you only need to brush twice a week, and floss twice a week. Maybe it ends up being flossing every day, and brushing once a month... who knows.