I've had phobias around dental work for a long time.
When I was 8 yrs old I had to have 4 teeth pulled. My dad dropped me off at the dentist and left, telling me that when the appoinment was over I needed to walk to school. He was too cheap to pay the extra $20 so that I could have laughing gas.
4 teeth-4 shots of novacaine. Hurt like hell and I cried the whole time. When it was over I started walking to school with a mouthful of bloody guaze, but it made me sick to my stomach and I puked. I skipped school and walked home. When my dad found out I ditched school he beat my ass.
What probably made this all worse was that my dad (too cheap to hire a babysitter) had just taken me to the theater with him to see the premeir of "Marathon Man" with Dustin Hoffman and Sir Laurence Olivier as the sadistic Nazi concentration camp dentist. Not a good movie for an 8 yr old kid to see.
It was a bad day and it soured me on dentists for a long time. The one I have now is a real pro, he uses extra novacaine and laughing gas as needed. This particular procedure took 3 hrs and its hard to breathe the gas that long so he gave me some sedatives. I slept thru half the procedure, and now I sitting at home with a hell of a buzz and glad to have the whole thing over with.