Dental schools get like 2000-3000 applications a year... there's no way they can interview every one.
In one example, Temple Dent... ~3000 applicants, ~600 interviews, 118 spots i think... so even after the interview... they will choose among the pool of interviewed applicants and give them spots.
Most schools select people for interviews based on their GPA, undergrad major (to measure the relative level of difficulty), DAT scores. Some people take the required pre-req's and then do an easy major, so their GPA's will be a lot higher than others who take harder majors.
When deciding whether to give you a spot, volunteer/clinical experience, reference letters from profs, interview score and also your other personal qualities (like love for music, art, etc.) come into play.