We got lucky when our son was little - when he needed to visit the school dental van for the first time he'd begun to allow people to get close to him so we weren't deafened by the top-pitch screams that had blessed his specialist visits in the past.
He also had no inkling about dentist phobias and coupled with his high pain threshold we certainly didn't enlighten him.
A quick check had found a cavity in a baby molar, so I was told in a whispered consult outside the dental van.
They had often found the anesthetic needle caused more anxiety and pain than the actual filling of the cavity itself with kids on the Spectrum.
So, with my permission he had a filling without any anesthetic.
His only complaint was the need to keep his mouth open for a long time.
About 12 months later, when several of his teeth refused to shift out to make room for his adult teeth, the dentist again went in without anesthetic.
Again no complaints.
After that, however, he began forcing his baby teeth out the moment he detected even the tiniest wobble; he'd smilingly trot out of the bathroom covered in enough blood to make the producer of Friday the 13th giddy with glee and present the tiny white item for our inspection (and reassurance that the Tooth Fairy would not forget to reimburse him for his efforts).
Things were going swimmingly with his teeth until a check up and the recommendation for braces; off we trotted to the orthodontist and heard the prognosis.
Surgery and/or braces.
We chose just the braces and again he sat back like Lord Muck, mouth wide open being pulled and prodded this way and that, the orthodontist continually asking if he was in any pain or discomfit.
"Nah" was the repeated reply.
The only complaint regarding the braces, to date, has been the need to avoid hard chocolate.