Honestly, I wouldn't take out private loans...it's a slippery slope that could backfire in the long run. The good thing is that there are two kinds of federal student loans you can take out for dental school:
1. Federal Direct Unsubsidized Loan: Non-need based, low interest. Usually has a cap of around $40,000 you can get per year
2. Grad PLUS loans: higher interest rate but not unreasonably so, not capped. You can take out the rest of what you need using this
I would try to find ways to limit the amount you take out in loans as much as possible (scholarships, finding a cheap place to rent, live frugally, etc.)