Ugh this reminds me of the 1996 movie called The Dentist with Corbin Bernsen.
The dentist starts performing cruel dental torture on his patients after learning his wife cheated on him.
Here is the trailer:
https://www.youtube.com/watch?v=MMm2fh8b6Ig
Back in the 80s there was a homosexual dentist in Florida who after discovering he had the HIV virus deliberately infected several of patients with the virus. They subsequently died. There was no effective treatment at that time.