Floss is useful for things other than cleaning teeth; it's fairly strong, lightweight, and you can get a lot for little money. You can use it to tie up things, as a wick for a candle or oil lamp, sewing (in a pinch), etc. Basically, get a small roll for your bug-out bag, make sure it is unflavored and waxed.

It's usefulness depends a lot on how straight your teeth are and what kind of food you eat.

okay, you obviously never had a piece of meat stuck between teeth ... it's going to start itching and will drive you literally crazy