MOST PARENTS ARE pretty good about getting their kids to brush. Two minutes, twice a day, with a pea-sized dollop of toothpaste. But flossing? That's where even the most diligent families tend to fall short. The truth is, flossing isn't optional, even for little teeth. And the habits your child builds now will follow them for life. Here's how to make flossing a natural, painless part of your family's routine.