I have had my DENTPIN since 2010 and that was for my hygiene boards, totally unrelated to the DAT. I used the same one to schedule my DAT. It doesn't change, ever and you shouldn't need a new one. Did you try to reschedule it yet? According to prior SDN threads, all you should have to do is use your old DENTPIN and go through that permission process again, and pay the fee, that's it.
What does the FAQ say exactly? On the ADA website it doesn't say you need a new one, but yes it indicates there are DENTPINs stored for those who took the exam prior to 2009. However, I think that is so people do not try to make a new one because that was 3 years ago, about the max for DAT scores. Try to schedule it, it should be fine.
http://www.ada.org/dentpin.aspx