Is this sentence correct?
Maria is having an appointment to the dentist tommorrow.
***** NOT A TEACHER *****
Good morning, Chang.
(1) I think it would be helpful if you said:
Maria has an appointment at the dentist's office tomorrow.
(a) Many native speakers shorten that to:
at the dentist's / at the dentist
(2) I think that many native speakers are also comfortable with
an appointment WITH the dentist.
(3) I would not use "to."
Have a nice day!