Will the Air Force cover half the cost of my bachelor's degree?

I know you have the option of a 4 year contract and a 6 year contract, but I want to know if I can work on majoring in Biology(while I’m enlisted and I know 4 years won’t cover it all), and since 4 years will cover about half of this, can I just leave the AF go to a regular college, major in Biology, and go to Dental school without worrying about serving again? I just need some financial help with college so I figured I could go to the AF and get them to cover half of my first four years of college and take care of the rest myself.