I was proscribed valium for my recent trip to the dentist, perhaps this could be offered to you too?
Like you, i'm petrified of dentists and could (and very nearly do) cry each visit i make. The valium sort of calms your nerves, you're still obviously very much aware of what's going on, but don't mind as much. Infact it made me so brave that I asked if anything could be done about a join mark I had on a front, previously broken tooth whilst I was there.
Believe me, without that valium I wouldn't have dreamt of asking such a thing and i'd have been off that chair as soon as the necessary was done before you could blink.
Can't help with the Coq10 question i'm afraid.