In my opinion, DON'T take the bio and chem (especially if it is O chem) in the same summer semester. You will feel frustrated! All your goal is to get a good score and accepted to dental schools. Just try whatever you can to keep high GPA and don't take the risk. You can challenge yourself AFTER you have been accepted to dental schools not before that with the risk that you get low score and put yourself in hard situation to apply.
Yes, a bio, a chem (o-chem), and a physics are definitely doable, but in REGULAR semester not in short summer section. I took the above three classes and one advanced English writing in the regular semester.
If you are going to take G chem I, then go ahead; it is doable and probably you want to add one more GE course. If you are going to take G chem II with lab, then I suggest you only take this course and get A. If you want to take O-chem I without lab, then it is still doable without other courses. If you want to take O-chem II, then DON'T take it in summer. It requires a lot of memorization, practice, and understanding. Good Luck.
