I've lived in Philly for the past 2.5 years with an apartment lease and right now I'm trying to cover all my bases with residency but it is really hard. Go to Temple's registar's webpage and it has guidelines for what it takes to become a resident. You basically have to establish a home - that is there for the purposes other than education. You have to show that you have no intent of leaving after school (although this probably isn't a disqualifier if you don't), you have to get all your bills, taxes, bank accounts, license, all that stuff changed to reflect a Pennsylvania address. You can't have any ties to other states (like being claimed a dependent on your parents tax returns, being on their health insurance, or getting financial aid money). Oh and you have to show that you are self-supporting.
If you are just moving here from some other state for dental school, you're not gonna get in-state tuition right off the bat obviously. But whats cool is that you can apply at any and all times for residency, and its all on a case-by-case basis.