Apparently 4, at least when it comes to my son Sasha: myself and 2 nurses (or dental equivalents) to hold his legs, hands and head, and 1 dentist to work on the actual tooth.
After 1.5 hours of struggle (with screams like: "I lied, I lied, my tooth wasn't hurting...It stopped hurting at 11:15." resounding through the dental office) to complete one procedure that should have taken 30 minutes, the dentist kindly asked us not to come back. And this was already the second dentist who threw us out. So the next time he will have dental work done under general anesthesia in a hospital. You'd better start brushing your teeth more carefully, buddy!
I can't really blame him, though. He has his parents' genes when it comes to his dental material. And the water running into your throat during drilling does feel yucky and scary.
He will grow out of it. Right?