I've come off horses and fought in medieval battles using axes, hammers and swords as well as fists. Getting your teeth knocked out is an occupational hazard.
I do still sit back and wonder when I'm in LA if this is all really true or is it all kid-on. But it's great. I always bear in mind that the right place and time have a huge deal to do with it, and there are hugely talented actors who haven't had that break.
I got a couple of front teeth knocked out during a football match when I was hit by a flying elbow.