Some people seem like gunners, but they're simply working their butt off to land a solid B, or possibly an A. That doesn't make them a gunner, just hard working and realistic.
To get by in dental school, not much effort is required. However, C territory isn't really a comfort zone. Fail one exam, and you end up in D territory. It's a matter of what your time and sanity is worth. Even if you don't plan on specializing, you'll find yourself working for that B, which can be a bit of work for some classes or a breeze with many others.
Generally speaking, you will definitely have a lot of time for yourself if passing and graduating is all you strive for.
BTW, my class seems like a big group of noncompetitive overachievers, myself included. We help each other out freely, and I haven't noticed anyone being cutthroat. Ask anyone a question or for some help, and they'll gladly help out. I do think that my class as a whole is a little more scared than some others. I know I am.