IS it permissible for one to make a doctor/dentist appointment for Shabbos or Yom Tov? Assuming you don’t need to do any paperwork on the day of your appointment, can one, say, go to the dentist to get a cavity filled on Simchas Torah or Shabbos?
Refuah is assur (different situations it would be permitted and in some cases a must)
I doubt it – there is an issur of doing anything on Shabos and Yom Tov which is Refuah.
The doctor or dentist will do work. And it will be for you hanaah (benefit). Which makes it assur.
Filling a cavity is probably worse than refuah.
IF it were life threatening, it would be allowed. For example, if a life threatening condition developed on Erev Shabbos you could arrange to see a doctor on Shabbos (though in practice, most people would go to an Emergency Room, though some life threatening conditions might be better treated in your neighborhood doctor’s office, and he can call the ambulance if needed).
It would be hard to have a life threatening cavity.