I actually think you shouldn't take it over. If you are a science major, then you should just go on and take 2nd semester ochem and also biochem. Do well in those classes and prove to the admission officers that your first C is a fluke. Getting an A will not improve your GPA that much, since both grades will be calculated. Also, dental schools will expect a higher grade, so you have to work extra hard to ensure an A. Just do well in upper division classes and you will be fine.
If your're a non-science major, you should definiately take biochem and do well. Also take one or two more science classes beyond the pre-reqs to raise your science GPA.