I don't have all the exact answers but I can give you what I know. USC is notorious for filling their class late in the cycle. From the school's website: "Generally, the class is assembled on the following cycle: December 1 one quarter; March - one quarter, mid-April - one quarter, end of May - one quarter." (
http://uscsd03.usc.edu/dental/admissions/applicant.htm?button=Click+Here+for+More+Information)
I do know from following theses boards for many cycles that there are abundance of students who interview well after Dec, Jan, Feb who are ultimately accepted.
Word on the street however is this year they are holding more pre-Dec 1st interviews which may skew things a bit this cycle and fill the class up a tad earlier than in the past.