Listen OP... if you are uncomfortable with all 100 of your future classmates, it is time for some serious self reflection.
First off, you are educated enough by now to know that absolutes have almost no statistical validity. The odds of you not liking, or not having people like you, in your class are slim to none. That is part of the interview process to hand select people from many different backgrounds, cultures, and interest groups to make a diverse class. Odds are that the larger your class size is, the greater chances of finding people who have similar interests as you.
Second, cliques will form at any school that is cohort in nature. You will have the partiers, the sports people, the married folk, the going out to dinner people, the outdoor types, the various race groups, etc. However, you are over looking the fact that you will automatically have several things in common with everyone... you all have interests in dentistry and higher education. Use that as a ground work to relate to people.
Lastly, you need to really branch out and hang out with all types of people. Sure you will have your "clique" that you associate most with, but it is in your best interest to associate with everyone. Maybe you don't like to party, but should that stop you from going to a party your classmate is throwing... no, go and socialize, make new friends. Currently i am young and married, so most of my friends are young married people. But we also will go to the occasional "party" that my or her coworkers throw, we go country and swing dancing with certain people, we often host BBQ's for football games with other friends, then we hike and snowboard with others, i have my poker buddies, and sometimes we combine these groups for a big game night. It is good to have a diverse group of friends... not only will this make you happier, but i guarantee you will have lots of fun. It is also healthy for you to do this, because it will make your more relate-able to your future patients.