When should you floss--morning or evening?

When you should remove that plaque depends on why you're removing it in the first place. If you are removing it for prevention of tooth decay or periodontal disease—such as gingivitis, which destroys the root and makes the teeth fall out—then I believe it's best at night. This gives you an eight-hour, food-free rest so your mouth can fight against the ravages it faces all day.

If you floss in the morning, because you have to say hello to people and want nice teeth, that is useful—but less so from a biological point of view. Although it should be noted that this has never been researched—call it the Kinane Hypothesis.

WSJ link