Dental fear is an interesting phenomenon.  The part that I gravitate to is the lack of control issue. Because there is lack of control people suffer from more fear. Their initial fears can come from past experiences, either with the dentist or possibly similar situations with other health professionals. (Great dental fear research link at the end.)

I do not have fear of the dentist, but I am not free of "irrational" fear.  I do not like riding down hills on my bike or mountains in a car - especially if I am in control of the vehicles. This is especially awkward since I am "in control" in these situations. But in a way I am not in control. My brakes are in control. And what if they fail??!!