Depends on how sure you are about specializing, how confident you are in your academic abilities, how competitive the specialty you want is, and how much you're willing to pay. Most of the schools that make specializing easier are also pretty expensive (e.g. Harvard, Columbia) and the ones that aren't tend to be pretty hard to get into (e.g. UConn). You can specialize from any dental school if you do well enough, but I don't know how confident you are about ranking in the top X% of your class, or even if you'll need to - not all specialties are equally competitive.