Ask what techniques the dentist uses and if they like the dentist. I totally agree with Peggy Oba's advice about first visits and trying to start out making the visits fun before they have cavities and pain. If the first visit you make is for relief of pain or infection and the child is scared, it is much more difficult for the dental team to avoid frightening your child even more. Most severely disabled people need some type of special help to cooperate. In the US now this is very safe and the anesthesia is usually kept at low levels for general dentistry.
Oral surgeons can safely do general anesthesia in their offices.
Anesthesiologists are better than nurse anesthetists. All anesthesia personnel are aware that special needs people present more risks than non-disabled people and they take this into consideration when they recommend anesthesia. If you are skeptical about this, discuss risks with them far in advance of the procedure. Call the hospital and make a special trip just to have your child prescreened by the anesthesiologist, if you are worried. Intravenous sedation in the hospital or a private office.