1 Young Jamie: All right, let's get out of here.
1 Young Adam: How?
2 Young Jamie: I have some dental floss. We can use it to wear away the bars and cut through them.
3 Young Adam: That's a myth!
4 Young Jamie: Like Nazi space colonies, Martians, and time travel?
4 Young Adam: Those are believable!

The real life MythBusters tested this myth in a 2009 season episode. Grant Imahara built a flossing robot that rubbed dental floss around an iron bar for a week. This wore away enough of the iron to allow the team to calculate that, by working on the bar with floss for 8 hours a day, you could cut through the bar in a bit under a year.

I guess the only problem is explaining to the warder why you go through six packs of floss a day.

It also makes me wonder, if you floss your teeth for 3 minutes a day, how long it would take to wear your teeth away? The dentists never tell you about that!