Do you have any opportunities to do some work experience in either sector? Talking directly with people who have gone into each profession can shape how you feel. Dentistry will always be in need and could help you if you ever wanted to move to other countries (ie shortlist visa programs). I think that you would learn a lot of transferable skills as a dentist. Chemistry in general may lead you into pharmaceuticals, engineering, research, teaching, mining, and crime scene investigation. I think that the list is very long, it all depends on what the Uni course focuses on and what experiences you seek out. If you have some uni's that you are considering ask if they have student reps from the course that would be willing to talk to you.
Basically, I think the more information that you have from other people's lived experiences and your own the more you will be able to make a decision.