...don't floss their teeth.
In the dental supply section I found toothbrushes, toothpaste, toothpicks, those "brush ups" things...but no dental floss. Confusing.
(don't worry, i was shopping for floss as a preventative measure. we still have some left, it's just one of those things that it's hard to tell when you're going to run out so i was trying to be sneaky and buy it before it was too late)