How did you fail so many courses..? Yeah, policies very drastically by school. At Tufts, if you fail one course, you get to retake an exam in that course (and if that pushes you up to passing, then you pass). If you fail two courses, you might have an opportunity to remediate during the summer (losing your 2-month summer break), but only if the promotions committee has mercy on you. If you fail 3 courses, you must redo the D1 year, paying an extra year of tuition and fees ($87K!); we had 5 kids redo the D1 year and joined our D13 class. Most likely, you will have to redo the D1 year (let's hope your school has that policy), but hey, that's much better than getting kicked out.
If the dental school give you another chance, make sure you make the most of it. Don't fail another course. Keep C's across the board at least. Get a tutor if you have to, and limit whatever social activity is keeping you from getting passing grades.