From a reader:

Hello Jonah,
I am probably way late with this response, and if you have already had enough of this topic please feel free to stop reading right now.
As a practicing dentist, though, I feel I must respond to your post. What your hygienist told you is a bunch of BS. All dentists must first attend and then graduate from an accredited dental school. Where they are taught all the finer things, such as fillings, extractions, securing patient financing, etc. Once they graduate, they can then go on to further study to be a specialist such as an Oral Surgeon, Endodontist, etc. However, they are still qualified to do all the other stuff they were taught.
Now many specialists devote their lives to their specialty and so an endontist will just do root canals and that’s all. And after a period of time they may not feel comfortable attempting the work they learned in dental school, but haven’t performed in years.
Most private dentists do extractions, and root canals, and some even braces. And most dentists use Nitrous. The specialists are there for when the case would be more difficult and involved.
I hope this helps. I’m available if you need a ‘Dental Guy’.