How good is the evidence that flossing is effective, and what have randomized controlled trials shown is the optimal toothbrushing and flossing sequence? “Over the years, it has been generally accepted that [the use of] dental floss has a positive effect,”  removing up to 80% of plaque. How do we know? You can use what’s called a “splitmouth design,” where each person can act as their own control — for example, only flossing one quarter of their mouth. They asked study subjects to stop brushing their lower jaw so that plaque would build up, then they were randomized to floss half, and leave the other half as the non-flossed control. After three weeks, not only did the flossing cut plaque about 60%, more importantly, it cut signs of gingivitis in half — bleeding on probing, and another index of gum inflammation. Note, though, this is comparing flossing to nothing. They weren’t allowed to brush the jaw. So yeah, flossing is better than nothing, but is flossing plus brushing better than just brushing alone?…