Steve you could run with a scarf or one of those things Gore make. That way your breath will be warmer by the time it reaches your tooth less pain job done run on!
Either that or load up on pain killers before you go, those will have the added advantage of you not being able to feel any pain in your legs so you will be able to run for even longer!
Gore Face Warmer II Only £14.99
Ok you'll look a bit like Doctor Lector, but your tooth might not hurt as much.