I used to have a good dentist, he offered laughing gas, the dental hygienists were also in my opinion the nicest people in the entire healthcare system. He retired, and I got stuck with some blonde bimbo airhead who ignores and infantilizes me. They stopped using laughing gas one day and just failed to inform me of the change, needless to say I did not appreciate having tons of needles jabbed in me when I have a phobia of that, and certainly wasn't even able to prepare for the situation (ie taking benzos). I still have a really friendly and caring dental hygienist though. The hygienist seems to be more interested and cares about my overall health and well being more than any doctor I have does lol.
With regards to your question "have you ever been strapped down", I don't even see how that would be legal here in Canada. If you are really anxious around dentists, they often will offer a benzo for the appointment like Valium or Ativan, just be sure to ask before hand, since they can take like up to an hour to kick in and you would have to pick up the script from a pharmacy.