They base it on the entire application. That said, they do take into account the interview with the faculty AND the student. There is an algorithm they use, I used to remember it but I forget now. If you have a certain amount of "points," you have a good chance of getting in. This existed at least when I was interviewed 5 years ago. And to answer your OOS question -- they were more OOS friendly in the past, but recently the Nevada legislation (in hopes of keeping more dentists in the state after graduation) increased the amount of In state students they want at UNLV. I believe it's 60% in state, 40% OOS now, but again I'm not entirely sure.
Source: I interviewed at UNLV, got accepted, attended, graduated, and am now a dentist.