My reply: Right -- if you're a sadist but also want to use your powers for good, dentistry seems the right way to go. I wouldn't be surprised if the nicest doctors -- those who offer an abundance of pain-killers -- are the most serious sadists, because they can do terrible things without the patient even noticing.
...and then I got to thinking about Alan M. Clark's "The Pain Doctors":
Thought I'd share. Clark is a sweet guy, but then there's his art...