Guest, I have the same problem as you. I have been banned from the dentists in my town because I am so badly behaved when I go (not very often) I make appointments and am too scared to go in, or I refuse to open my mouth. Not a very rational way to behave at all. When I do brave the chair and manage to open my mouth - I can tell you that I am terrified. The last time I went(dental hospital in Leeds) was in april this year I had to get something done about a wisdom tooth. I was going abroad and the only thing that made me go was that if it turned into an emergency while I was away - that I would have a foriegn dentist in my mouth. I ended up having to have the tooth and its neighbour removed as the roots were tangled. I did not have gas but had a shot in my gum. The dentist said I had the hardest teeth to pull that he had ever come across. I was in a state of total collapsse by the time the procedure was done - about 2 and a half hours.
Why am I telling you this - don't end up like me - get it sorted now!