Absolutely not. For starters, you wouldn't know exactly what's going to be covered and in what detail at your particular school. Your free time before dental school is probably the last, great opportunity you're going to have before you retire. Travel, relax, work on a hobby, etc. and you'll be glad you did, trust me.
And as a note on "pre-studying": it's entirely useless. Unless you manage to pre-study the entirety of your school's curriculum, whatever head start you give yourself is going to disappear eventually. At some point, you're going to have to be able to learn the material at the pace at which it is taught. Admissions committees pride themselves (and do a very good job) on selecting candidates who will be able to do just that. If you got in, you'll be able to handle it. Like I said, your precious free time before school starts is a terrible thing to waste.