I had not been to the dentist for fifteen years through the sheer terror of being 'butchered' as mentioned above. Recently I had to take Mini Onions to the dentist to have an infected tooth removed. She was utterly unperturbed, but what a difference - music playing, continual explanation of what the dentist was doing and what my daughter could expect to feel, kindness and consideration. The whole experience persuaded me to go and I'm really glad I did.
I had to pretend I was going somewhere else to get over the nerves, but it was, honestly, o.k.
I've had a root canal / crown job done, a deep clean under the gums and two fillings replaced. IT DIDN'T HURT AT ALL, despite her slightly sinister S.A. accent! ( memories of 'Running Man'}
Maybe you could find a child companion to take your friend to the dentist, perhaps 'lookng after' somebody younger would give him the courage to go ahead himself.
I really hope he makes it, a healthy mouth feels so good and ingesting infected stuff can't be good for your general health.
Feel the fear and do it anyway.....as long as it doesn't involve jumping out of aeroplanes eh?