This is a REALLY good question.
I have spent serious time pondering this one. Here are a few I the questions I would ask. (These may not apply to you.)
A. Will there be an opportunity for me to continue my research? Does the CD offer a joint degree program like PhD/DMD or MD/DMD?
B. As a general rule how many of this schools graduates go on to specialize and what type of preference is shown towards your own graduates in the respective programs?
C. Can you talk to me about what it is like to be a dental educator? Considering my TA experience and research interests, I am interested in teaching. What is your day like?
These are very specific to me so they may not apply to you, but a more broad approach would be....
A. Talk to me about the CD's teaching philosophy and what role does the CD play in the community?
B. How does the CD approach the ever-present technological advancements in dentistry?
C. What is the school's philosophy about preserving tooth structure?
(Don't ask this unless you know EXACTLY what you are talking about)
D. Do the students here consider the program challenging? Tell me about what a students day is like?
Hope this Helps,
-C