I sure hope not....I took 10 years off and had a whole other career before deciding to apply. I think it can only help you prove how much you want to be a dentist if you show that you've explored the world and yourself a little before jumping into a major career.
I took off two years. Well a year before applying so that makes two years before actual matriculation. They didn't seem to notice much all but you better have a good explaination of why you took time off / what have you been doing since then. It will probably come up during the interviews.