I would advise you to speak to an army/air force recruiter, because they can provide you (biased but relevant) information. Air Force HPSP has always been more difficult than Army and Navy HPSP. Make sure you find out what your options are after acceptance, because for Navy HPSP you are usually stationed by the coast or in a ship which limit your destination options.
In addition, there is another scholarship that DOES NOT cover your dental school expenses fully. I believe it is ~250k, but hey it's something.