Having sizable research experience is one of those things that can really set you apart from the crowd, so I'm in agreement with victoria here, how can too much be bad? hehe. Unless say.... you've done research for like 6 years and have nothing to really show for it.
Don't worry about what it looks like. If you are an honest person, then they should want you at their school. Don't try to impress them constantly. Just be yourself. What's wrong with PHD/DMD? Don't worry about it.
I interviewed at Pitt with one of their top research dentists, and he totally loved talking about my research, and how research in the dental field is an actual option to go for - granted most practice for a few years to pay off debt, hehe. My research PI is also a DDS/MS/PhD.