I personally think your main goal should be getting your undergrad marks as high as humanly possible, you need a higher undergrad GPA. After finishing your undergrad, I think you may want to change your focus to applying to dental school after getting a Masters. An upward trend in your undergrad with a high GPA from a Masters degree will look good - and some private schools look favorably on research. There isn't anything stopping you from applying at any time, I think most people on here are coming from a place where they wouldn't suggest spending all that money unless they thought you had a good shot. Applying after a Masters degree would be the safest in my opinion.
Good luck!
Good luck!