Just to chip in here, the majority of experiences I've had at the dentist have been completely fine, but I guess it depends a little on the actual dentist you are seeing. During my lifetime so far, I suppose I've seen about 8 different dentists, 7 were fantastic, 1 not so much (but even that wasn't that bad). It really is nothing to worry about, and if you go ahead and explain your fears and concerns to them beforehand they are always really helpful and caring.
As an example, my Mother really really hates the dentist but unfortunately seems to always have something wrong with her teeth (oh the irony), and recently had to have some major work on a tooth and its root... Needless to say, she was dreading it and therefore told the dentist and nurse about her concerns. After hearing her fears, they really couldn't have been more supportive and lovely... The nurse held Mum's hand and spoke to her throughout, which kept her calm and comfortable. Afterwards, she couldn't have been more upbeat about her experiences (which was strange - if you didn't know where she had just been you'd never have guessed it was the dentist!!), and it has made her way more confident about going back for the next treatment.
Just be open with them about what you're worried about and i'm sure everything will work out Good luck!