Does not sound like a good idea. Chances are you will not retain all of the info you learned in D1 with a year off, which will make D2 twice as hard. If this is a mental health issue, seek some counseling. If on the other hand, this is a physical/medical problem, talk to your dean. You will need some type of verification for a year of medical leave. In either case, good luck. Dental school is extremely challenging. Practicing dentistry the first ten years is even harder. Make sure you are ready to proceed.