I'd have to say that if I were on an admissions committee, I'd look more favorably on the applicant who knew his/her limits and didn't go overboard on the courseload. I think it's at least partly a question of whether a person wants to take a few classes and really try to understand them or just wants to get a lot of classes on the ol' transcript. Also, the more courses, the less time for all that non-academic stuff they like to see on your CV.
So many people I know are taking an extra year in college in order to take all the things they'd like to; I think it can be more admirable to stick it out for a longer time in college and try to absorb more from every course you're offered. Also, I think staying longer is becoming a much more common thing to do, if you can manage it financially (but hey, that's what are loans are for, right? 😀 ).
On the one hand, they'll want you to be able to handle the large course load in dent school, but on the other hand, if you take too much at once, they might wonder whether you've been able to get enough from the courses to really be able to excel in dent school. I dunno. Just a thought.