A deposit is simply a payment that reserves your seat at that dental school. You are not contractually obligated to attend that school. That is the purpose of a deposit. The school retains your deposit as a consolation fee in the event that you choose not to attend their school.
However, if you do get into your top choice, it is common etiquette that you withdraw your applications in a timely manner to allow the dental school to make their decisions. Also once you send in a deposit to a school, other schools do have access to this information now, and they may decide to withdraw your application from further consideration if they want in order to keep you from holding multiple acceptances for a long period of time.