I don't think there asking to transfer to a new program, but starting a PhD. I have heard of people transferring dental schools before (it happens), and a PhD could likely be starterd at any year of dental school, and you just continue until you've completed it. I'd say you could look into this.
For a place like Michigan, we could make it work out. However, you'd probably have to finish dental school at our institution. You may even need to retake all those years, so it wouldn't make logical sense (unless you're very early in your training). It'd be better for you to finish dental school, then come and do your PhD. Contact me further, I'm a dual student at U of M School of Dentistry.