Anxious DC13 scared of dentist ‐how to prepare both dentist and DC?

[EveSix]

DC13 has diagnosed generalised anxiety which seems to float between different objects and situations. This last year, they have become really anxious about going to the dentist. They've always hated it due to sensory issues around invasive touch as well as the different lights, sounds and smells etc (yes, awaiting ASC assessment), but ended up refusing the most recent appointment due to a panic attack.
I'm scared DC will be struck off the patient list if non-compliant and wondering what steps I could take, primarily with our rare-as-hen's-teeth NHS dentist, but also with DC, to smooth the way for our next appointment.
In the spring, DC was unable to participate with an orthodontistry appointment due to anxiety, and despite me emailing ahead to explain the anxiety and request a gentle approach, the orthodontist got quite cross with DC and blamed them for wasting their time (really awful appointment, but that another story), which has made it 100% worse.
Any ideas?

I had a phobia of the dentist as a child, unfortunately this wasn't tackled at the time and carried on until my mid twenties which led to me not going for around 15 years, until I had no choice and lost three teeth to decay. I was so terrified that I couldn't even go into the waiting room. I have ASC, diagnosed as an adult, and it is partly sensory I think.
Anyway, I found a very understanding dentist who used to examine my teeth while I sat in a chair at a desk, rather than in the treatment chair. He did a gradual exposure approach until I could manage sitting in the chair. I still don't like going but I can now have a check up. I have needed dental treatment and I manage this by wearing headphones with a guided meditation playing, I also ask the dentist to let me wear the dark glasses they put on you for some procedures because I find the light too bright. I don't have an issue with the smells but I know some people use scented balms rubbed under their nose.
Unfortunately, I think finding an understanding dentist is the key thing. Some community paediatric trusts have specialist dentists for children with additional needs but they're rare and often have very specific criteria

Thank you, I really appreciate you taking the time to respond.
The idea of the desk sounds like it might be a way in; DC feels so exposed reclining; "like a beetle on its back", they said.
I'll contact the dentist to see if this might be possible.
Our dentist is quite chatty, and, I think, believes that a blow-by-blow account of what she is doing in people's mouths will put clients at ease, but in DC's case, it's probably more stressful as DC feels like they have to respond, which is hard with a mouth full of dentist.
Really useful ideas, thanks again.