In March the ADEA releases a book with dental school acceptance info for every school. Buy that right once it's released and read admissions criteria for schools in respect to DAT, GPA, In-State versus Out-of-State Acceptances, etc. Every year people waste hundreds to thousands of dollars applying to schools that won't accept out-of-state students regardless of gpa. So apply places that will be friendly to you and your application and won't just throw it in the trash immediately.
As far as applying to reach schools, I say go for it. I applied to my reach school even though my gpa sucked and my DAT score was 2 full points lower than their averages. They turned out to be the only school to interview me and even accepted me. While 10 other schools who I met the criteria for rejected me without an interview.
As far as Harvard goes (I don't know much about Columbia), they are a research oriented school. If you haven't done scientific research before then it'll probably make it harder to be accepted. Harvard is known for their excellent dental research. So if you don't want to do research, then you might apply elsewhere.