I would talk to the prof in person, explain your situation, and ask if you can take the exam early. I had exam conflicts 5-6 times and only had one prof who wouldn't allow me to take an exam early. None of them, however, would allow me to take an exam late.
Most profs will be really good about this. Tell him your situation and that you are going to a dental school interview. Not only is this something that is good for you but it also reflects well on the school and he should be very agreeable.👍