Some time ago, there was talk that dental schools would gravitate toward the 3yr program ( I forget where I read this), but the dental schools seemed to not have taken to that idea since UOP is the only school that does this to date.
Instead of decreasing the actual dental school curriculum from 4yrs to 3yrs, dental schools incorporated 3+4 programs to help reduce the total time from undergrad to dental school.
In all, it seems that academics were uncomfortable with idea of decreasing the amount of time allotted for students to complete the robust dental school education. Furthermore, with the advent of some 5 yr programs one could argue that some schools are going in the opposite direction.
I think there is evidence to support both sides of this issue of shortening the amount of time in dental school, but it seems that the dental schools by in large are hesistant to decrease the traditional 4 yr curriculum. In my opinion, most dental schools seem to drag their feet towards change anyway. Take care and GOD bless.