There are three elements that contribute to each other for your stress of dental treatment. Its anxiety, fear and pain. Any increase of one will increase the other. It could be you are overly anxious or have great fear that it increases your sensitivity to pain.
Sometimes you can have what we term a "hot" tooth. It is a tooth that can't get numb but that's usually due to severe infection. Usually a course of anti-inflammatories and antibiotics will calm it down and the procedure can be performed at a later date.
Since your original dentist can't get you numb, have you considered possibly going to another dentist?
That's a tough question to answer. I would say that the dentist should have quite a few techniques and different types of anesthetics that they could attempt to use to "numb" the area. But I can't specifically say what he/she has since I'm not there to observe.
That's unfortunate you're not able to switch dentists. There's no process to find another dentist at all within the NHS system? I'm assuming the NHS system is based in Great Britain? Sorry, I'm a US based dentist and not as familiar with the health care systems elsewhere.
Thank you for taking the time to answer my question. I cannot change dentist under NHS but can go privately but cannot afford this at present.
I did take a course of ameobic anitbiotics the strong ones before treatment in case it was infection under this tooth but it didn't make any difference. Before I was never afraid at a dentist but I have had trouble with this tooth in my lower jaw since I had a deep filling before the crown. I have read on these forums that some people have the lower nerve sitting near the bone and it can be difficult to numb it unless the dentist can use an advanced technique to inject anasthetic where the jaw meets. But would my dentist not be aware of this ??