I heard (via Steve Novella of the Skeptic's Guide) that there was similarly light evidence to support flossing, but mostly because nobody's bothered doing the studies.

The reason for that? It's obvious that flossing is going to help. Obviously brushing away cruft is better than not. So why waste the money on a boring study?

I can see the same for the electric toothbrush argument. Of course it's going to be at least as good if not incrementally better than me see-sawing my way around my mouth.

> the single biggest thing that makes a difference is brushing for the full 2 minutes, and electric toothbrushes can help with that by having a built-in timer

As someone who had toothbrushes for the longest time with a single 2 minute timer, and now has one with 4× 30s timers, I can say that the difference is radical.

I don't understand how I got bored in 2 minutes but I don't get bored in 4×30s, but I do not. Every quadrant gets the full time, and twice a day I do it for the full 2 minutes, no exceptions. That wasn't the case before.