On a side-note, rip out their teeth?
Probably not, as braces are made from non-magnetic materials. The wire used in braces is usually non-magnetic stainless steel or perhaps titanium. Constant magnetic field will not affect them. A varying or alternating field however, can induce a magnetic and an electric field in any material which conducts electricity so it can have an effect. That's why MRI machines and very, very large power generators could potentially cause nasty effects.
I had braces, and had some very powerful hard-drive magnets sitting around. however, when i put it up to my teeth, it had no effect. the metal used in braces is obviously non-ferrous. Also note that having braces does not affect a metal-detector, such as at an airport
Tricky. It all depends on how strong the connection of the braces to the teeth are. If a car-sized magnet were used, the braces may be pulled out. The teeth, I highly doubt, will ever get pulled due to the perfect design of the seating of the tooth to the bone. With this in mind, you may want to ask this question to Brainiac or Mythbusters and let them do the testing with their teeth, not ours.
