Dental schools have been recently looking for qualities that prove ones commitment to dentistry. This has sprung up and become fairly popular in the past few years. Those who apply to medical and dental school are at a disadvantage if the dental schools become aware.
That said, it is not mission impossible. People who apply to both will still get in; infact, one of my closest friends just did this and ended up at NYU College of Dentistry!
Before doing this, I urge that you make sure dentistry is something you can see yourself doing for the next 20+ years. In my opinion, dentistry is less flexible than medicine in general. It is important that our future of dentists are dentists because they are passionate about the career and not because they couldn’t get into medical school.