I don't have dentist fear (I've been very lucky with my dentists) but I think the fear is a combination of extreme powerlessness and guilt. You're prone, on your back while people loom over you, and those chairs aren't as easy to roll off of as a hospital bed, and you just have to lie there and take it.

The guilt is because you always kind of know that any filling you get you could have stopped, but all those times you didn't floss, or you ran out of toothpaste or didn't brush as well as you should? And the dentists knows, the dentist sees every cavity and knows that it's because you didn't take care of your teeth properly.

And there is the patient, impotent and ashamed, while the dentist leans over and says, "Now we're just going to see if the numbness has set in."