To become a Dentist, would a major in biochemistry be the best fit?

Things may well have changed since my school days. I graduated college as a chemistry major. A biochem major as such was not available as an undergraduate, though of course if you've completed the departmental requirements for your major you may well be able to work out a concentration in biochemistry.
However, most dental schools will not have a particular bias toward your major, so long as you are in a rigorous program and have completed all the prerequisites for admissions. Many of the dental schools will post the course requirements for admission on their websites.
If you DO have a particular interest in biochemistry, that may actually help in and after dental school--especially if you're inclined more toward the research rather than clinical end of dental practice. But you've got time to discover and develop your interests, so try not to shoehorn yourself into too narrow a path until you've had the chance to sample the variety of disciplines dentistry has to offer.
Good luck!