Squiggle, I think dentists generally avoid giving general anaesthesia to patients. It would tend to be used when it's a very long operation lasting for hours, where the patient has some form of disability making it difficult for the dentist to operate with the patient awake, or where the patient has an extreme phobia of dentists. It's possible that Scotland has a different policy to England though.
By a coincidence jackassfan who generally only posts on the film section of the forum watched The Great Moment in the last few days. It's a 1944 fillm about Dr W T Morgan who was a pioneer in dental general anaethesia.