Funny you should ask...
many years ago, my wife had braces to correct a jaw alignment problem. We never let the braces interfere with some good oral loving, so one night I'm enjoying one incredible bj when I suddenly feel something pierce my foreskin. One of the wires had come undone and went clean through. It wasn't too bad, really, except that she couldn't get my cock out of her mouth... (like that's a problem )
We did finally get extricated, fixed the wire, and she resumed the bj.
I'd still do it again, the big thing is, if something happens, don't panic.
I should have kept the piercing open and put a ring in it or something...