Y would you hold more than one spot...u will just be holding up others who are waiting to get accepted...i know its a tough decision but dental schools need to start cracking down on people who hold many spots like Med schools do....
just choose a school and stop wasting your money. There are plenty of people on the waiting lists of different school hoping that after 5/1, more people will drop out and they will get go to the school they want to go to.