I took almost all of my prereqs at our local community college. I actually found my classes at the CC harder than some of the university classes I took. Dental schools know that colleges/professors offer varying levels of difficulty, which is why the DAT is the more standard metric. If you have a 3.1 GPA but a 27 in the DAT, that's gonna look a lot better than the university student with a 4.0 and a 17 DAT score.
TLDR: Where you got your credits matters to a very select few schools (maybe around 3?). I wouldn't worry about it and just do research ahead of time on where not to apply to save money.