Dental school counts repeated courses in your gpa. That means if you get a C in one class and then retake it and get an A, they will still count the C as well as the A in your gpa calculation. It would still raise your gpa by retaking the C, but the schools don't see it as a positive really, because you are expected to do well the second time around. I say just move on to your next classes.
I don't know how many units you've taken and still have to take, but you should calculate what your overall and science gpa could be if you get all A's in the rest of your classes (basically what you have to get at this point with a 3.0 gpa to bring it up enough), or how many units of A's you need to get to get a certain gpa (3.5 cgpa for instance). The W's will be fine, especially if they are all from the same semester. You just need to explain them if they ask, and it can't be for a reason like "they were too hard" or you "didn't like the professor."
If your "projected" gpa (the one you calculated you could get if you get all A's from here on out) is still too low then you need to consider options such as take more classes (perhaps a minor or a double major), do a masters/post bacc, etc.
Good luck and work hard!
