I just finished a 7-year dental program. When I was looking at summer programs for summer 2000, UCSF and UCONN has summer research programs with dental research components to them. The one at UCSF was called SRTP I think. Check if they still have them.
I did 2 summer research programs while I was in undergrad. Even if you aren't into research, they are still a good experience - a good social experience, some have very nice stipends with room and board, spending some time in a new place, make some new friends, etc. I got into several that I applied to, and most of them said they were for underrepresented students and minorities. Many of them said they were looking for people interested in PhD or MD careers. Small bit of advice - lie a little. Don't lie about the minority part, b/c that would be very bad if you get in and it is obvious that you are not a minority when you said you were. I'm talking about the PhD or MD career part. I never stated in my essay (except to the essay for UCSF and UCONN) that I was in a combined dental program or that I wanted to go to dental school. I just stuck to a "I want more research experience" focus in my essay. A lot of the applications didn't even have "DDS" as an option for future career choice. In that case, I just marked PhD b/c DDS/PhD is an option out there that I did consider (I didn't drop the idea fully till I started dental school). How are you going to know if it's right for you unless you get some research experience?
Of course, grades and prior research experience count for a lot of the application as well. Even though my second program said "No prior experience necessary," all of us who were accepted had prior research experience. Hmmmmmm.
If you have zero experience and are considering a summer research program, get some experience in a lab at your current undergrad in the upcoming school year.