I had three teeth taken out today, all of them deep in the bottom-left part of mouth. One of them was apparently a wisdom tooth that had lodged itself in a peculiar angle. That one required surgery (and was not covered by my health card).
When you're there, even when your mouth is numb, even if you're not really scared or anything, once you start to feel that pressure on your jaw, you can't help but be at least a little bit anxious. It's not so much whatever pain gets through the anesthesia that's annoying. It's the fact that you're mentally anticipating that pain. When you start to feel the dentist pushing and pulling at your tooth, you can't help but worry that somewhere, some resilient little nerve of yours has avoided the anesthesia and is just waiting to send you into a world of pain.
Luckily, not only is my dentist very good, but I'm quite comfortable with her, despite the often corniness of her jokes :p