Or use the tooth as an arrowhead, for that matter.

Even regular vampires can catch arrows in midflight. At least they can if they are protagonists or anything from Giant Mook up. The Twilight kind should have no problem; even if they are facing the other direction they should hear it coming in time. I'm not sure how much better it would work in a gun - that's where the physics gets a bit arbitrary for the sake of narrative appeal.