Transfer/Adv. Standing Questions

Does anyone have info regarding transfer/advanced standing students? Specifically, I am looking for info about 1) whether there are any transfer students at the schools they are attending now, 2) Do dental schools normally have any attrition and 3) which year would you most likely see a student or two dropping out of their program?

I know the ability to transfer is on a space-available basis, and that transferring during a dental curriculum is not as easy as in undergrad. Any information would be greatly appreciated-

J.T.