Wait, what? You were already a dental student and you reapplied to dental school? Or are you saying you were accepted to both USC and Colorado, you chose USC, and now you have buyer’s remorse? If that’s the case you own your decision. It’s not like Colorado didn’t fill the spot they offered you.
Transferring can be done. You may have to start completely over and it’s entirely dependent on if a school has an opening. It also usually happens under some pretty exceptional circumstances.
Big Hoss