There are several ways to get it covered. It's very smart that you are looking into it now. I've heard from practicing dentists that paying for it with loans is a bad idea. You'll be a debt slave for 30 years, have trouble getting a mortgage / starting a practice, etc. You'll definitely be able to survive comfortably, but you'll have that debt hanging over your head.
1. Some people do the military scholarship which pays all tuition and cost of living, but it requires a 4 year active duty commitment (this is what I am trying to do).
2. There is another scholarship with the National Health Service Corps that pays for 100% tuition and part of cost of living. They also require a 4 year commitment working for the fed in an underserved area like a clinic or prison. The problem that I found with them is that they open up applications so close to the beginning of dental school that you don't have time to figure something else out (i.e. military) if you don't get the NHSC scholarship.
3. UPenn offers a 1/2 tuition scholarship to the top applicants.
Those are the only big ones that I know of, dental schools don't offer too many big scholarships, even to the best applicants. But the way I look at it is 4 years of working a less than ideal job vs owing 1/2 a million in student debt. Also, I don't think it will be as easy to pay that loan debt back as many pre-dents think. After taxes and cost of living, how much can a beginning dentist making a 120k salary pay in student loans every year. Maybe 30-40k if you are still living like a student? That would translate into quite a long time living like a student considering the amount of interest loans that big accumulate.