This is not a popular MMM point of view, but I'm gonna say it anyway and take the facepunches as they come.
If you don't think that you can grow your income by a very large margin in the next few years, you need to look into IBR/REPAYE and find a way to qualify for Public Interest Loan Forgiveness.
Actually, first you need to have a very serious think about this whole dental school thing. From your post, I'm guessing that you were not a sparkling medical/dental school candidate when you left undergrad and that these MS courses are meant to prepare you for Dental School. Consider what the total cost of your debt is going to be for dental school + residency + opening your own practice, and then consider how much work you're going to have to do to get out from under that, and decide if that's something you are committed to.
Otherwise, you need to investigate your other options.
REPAYE will help; it will reduce the payments on your federal loans to 10% of the amount you earn over the FPL for your family size. This is probably a good idea so you can pay down those Private loans. However -- and it's a big however! -- any interest that isn't covered by your monthly payment is recapitalized into the loan. This is a BIG DEAL for people who are using these programs for loan forgiveness and are not eligible for Public Interest Loan Forgiveness (PILF), because it means the amount you owe will probably grow, probably a lot. And if the program changes or goes poof in the future, you'd be on the hook for that increased amount. Right now, we have an administration that looks favorably on loan for programs. But for standard forgiveness, you're looking at a 25 year time-frame, and betting that no one in Congress or the Oval Office is going to modify the program substantially before your loans are forgiven. I personally find this unlikely, and am sweating out my 5.5 remaining years (of the original 10) until PILF kicks in, hoping that no major changes will be made before I hit forgiveness. But intelligent minds can differ on this issue.
(You also may have additional options other than REPAYE; For IBR, another income-based program, you get a 3 year grace period... for plain old PAYE, you may qualify for no recapitalization, so check into that.)
At any rate, don't make ANY major changes until you've decided if you're completely done with school, because adding additional loans can screw up your forgiveness timeline, if you're counting on that. Once you're sure you're done -- or that you're going to pay cash for future education -- consolidate the federal loans and chose a NON PROFIT servicer in the consolidation. (I'm with Granite State Management, and while I don't love them, the pain in the butt has been limited so far?)
Then, I'd seriously consider trying to get a job with a federal government, State or Tribal Government or an Non-governmental organization, because while they pay lower salaries they qualify for PILF, which can make a huge difference. You have to be employed full time according to the organization's classification, so something like adjuncting or another side-gig type work could work for you in this regard. You've got to make full, on-time payments, but in ten years you should be out from under the federal loans and have paid off the Private ones, as well as having a decent nest egg.
