I go to the UW (hopefully you're familiar with the school, since your name implies you're from Seattle) and aside from the general prereqs most schools require, I'm taking microbiology and biochemistry. Not only does the UW dental school require these classes, but I actually feel that they're solidifying my knowledge gained from taking the general biology series, which I find very helpful because biology is not my strong point. Could be very helpful on the biology portion of the DAT.
(And as for your organic chem question, the UW offers two different O-chem series, one that is 2 quarters and one that is 3 quarters long. Maybe your school might have the same offerings? Sorry, I'm not much help here).