1- Unless you're in Dental school, don't think that far ahead. While it's good to know what you want to to, going through dental schools can and might change your mind.
2- You don't have to specialize right away after dental school if you're worried about the cost. You're looking at about an excess of $300K in debt - maybe even significantly higher than that - just on dental school alone. Specializing into oral surgery MD is about 3-4 years more of schooling, with about the same amount of debt accumulating if not more. You may not want to take that risk, so you could just become a general dentist for a few years as you pay of your debt and make some money yourself.
3- America is the land of debt. People live off of debt. That's the way of life here. Think of dental school as an investment, not an expense. You're investing X amount of dollars to get about Yr(X) amount back through your career as a dentist. If it's what you want to do, go for it and make that paper to pay of your debt doing something you love.
We're not taking this gamble of applying to dental school for nothing. Nearly all of us love dentistry, the lifestyle, the flexibility.. Etc etc. If this is the lifestyle you want to live, go after it and love everything that comes in store.