Find some schools that take more Canadians than usual - I know NYU is one. Hopefully you applied to the Canadian schools, too, although I hear they're even harder to get into. I think you should try to get those DAT scores up, but if you do try, try to kill it and show some improvement.
I always say this, but I don't *actually* know if it helps: shadow some specialists. I don't know why anyone would shadow just one dental professional, or why a school would give any credence to someone who has (not sure if you did that, but I know some who have).
You might consider starting one of those post-baccs or Masters programs that everyone always recommends, but, I'll be honest, I would think those numbers would at least land you an interview. It may be your residency situation, unfortunately.