More importantly, what are some of the reasons YOU have for withdrawing your application? I think answering that for yourself (not necessarily here) will help you figure out where you stand. If you just feel like you need a year to get some experience, raise your numbers, get out in the world and be POSITIVE that dentistry is right for you, then I'm sure you'll gain so much in that year that it will be a good thing.
Though if you just had this nagging doubt that eventually took over, maybe it's a clue that you either aren't thrilled about dentistry or that there is something holding you back before you proceed.
I think that if you are going to reapply and are worried about looking good, you can offer a good, clear explanation for your reasons. Simply withdrawing doesn't really mean anything it itself, so the ball's in your court for how you make it appear.
