I think if you like more theory stuff, go for bio. More of a math person, look at chem. And if you enjoy o-chem, biochem is pretty similar to that.
However, I would recommend possibly going for an alternate major that can still apply for health. It really can set up apart from the thousandth biology major. For instance, a nutrition major. Many schools even offer a nutritional science degree which is designed for, and fills the pre-reqs for medicine and dentistry. Honestly - what you learn in those classes is more applicable than a lot of biology and chemistry classes. It's learning about disease, and the importance of vitamins and minerals in regards to enzymatic processes in your body. You can also always go into clinical dietetics after college if dentistry doesn't work out.