Yes there are different exams for different regions. Each school will administer either WREB or NERB, and if you want to practice in Georgia you have to take CRDTS and if you want to practice in Florida, there is the ADEX. There is also something called GPR or AEGD residency after dental school. The residency is minimum of 1 year. (New York requires residency to practice there). If you do a residency and want to practice in Washington, Minnesota, California or Connecticut you DONT have to take an exam.
If you take WREB, you can practice in the following states:
http://www.wreb.org/Information/MemberStates.aspx
If you take NERB, you can practice in the following states:
http://www.nerb.org/b/member_states_b.html
Each exam has states that will overlap... its ******ed, they should just make one exam, but it is what it is..
Good Luck.