OP please do not take this advice. I'm going to assume the advice was well intentioned, but it is way off base.
When it comes to dental education, you should almost always go to the least expensive program. You're going to be a dentist regardless of where you come out of: you're going to have the same skills, know the same procedures, and have similar post-grad opportunities. Even if you want to specialize, people specialized from everywhere, and you can keep those doors open with the right grades and test scores.
Dentistry is a profession with very high debt. Once you're out of school (assuming you don't specialize), you're either going to do corporate, become an associate, or become an owner. Becoming an owner is most people's long-term goal because your earning potential is higher. When it comes to ownership, your patients aren't going to ask you where you went to dental school. They're just going to want someone has good diagnostic & hand-skills and friendly disposition. Same with corp gigs and associateships when it comes to hiring.
Coming out of school with less debt will help get you to ownership faster. Moreover, it will give you more geographic flexibility. The post above mentions that California dentists are top earners in the field. I'm not sure where they got that information, but California, especially SoCal, is a very saturated dental market. Opening a practice there is very hard, and the competition is going to drive down your earnings unless you're a really top dentist. So even if you went to USC, the chances that you could stay in SoCal after school -- as a new-grad dentist with ~$500k debt accruing 7% interest each year -- is low.
When you factor in the interest your debt will be accruing while you're in school, there is nearly a $200k difference. Put that money towards your future practice. Save it. Heck, do anything else with it. But please, do not spend $200k additional so that you can graduate with the exact same degree, doing the same procedures, with the same future opportunities.