Is the limiting factor more like to be: (1) getting in to dental school, or (2) getting through dental school?
I would say the limiting factor is most likely (1). I've met many people who have applied, or wanted to apply to dental school, and through undergrad never made it to dental school. Probably because they were not set up with a good application. There were very few people who didn't make it through dental school for academic reasons.
A separate point: I would also argue that learning skills in undergrad, and life, are more important in preparing your for the demands of dental school than learning the core science material (biochemistry, for example). The core science is very easily forgetten - and you will re-learn it in dental school. No matter how good your undergrad is, most of it is going to be forgotten within a month after taking the exam. But building skills like work ethic, focus, introspection, motivation, life balance, etc all will stay with you and help you through the trials and tribulations of dental school.
So I think you are coming at this from the absolute wrong approach.