Dentistry seems to have evolved very fast over the last decade, is the reason mechanical (faster drills etc.) or chemical (deeper, quicker pain suppression) or a combination of both?

As a young man I remember the dentist’s chair with fear and trepidation, now it’s so much easier. What caused my fear? When I was in the navy I recall production line dentistry – lots of sailors, not too many dentists, and not too much time. In fact they were on loan army dentists being trained by the army to be dentists, a way to defer the costs of dental school.
They were in training, we were their ‘patients’ and neither will ever forget the experience. I remember one great big matelot from Nova Scotia that took it personally, he jumped out of the chair and chased the dentist for a half a block, till he was subdued by two even bigger leading seamen. That was then (just after the Korean war) and what a difference a few decades make.