Once they receive your application and screen out for factors like gpa and dat, you are potentially eligble for interview. Once your application passes the initial screening, the adcoms make contact with the professors, dentists, dean, and any personnel involved with your recommendation letters, shadowing hours, extracurricular activities, etc for legitamacy. They don't want to waste time and embarras themselves by inviting liars to their campus and breaking bread. So they wait for their response which takes a sweet amount of time depending on how fast your writer gets back to the adcoms.