From my understanding, the CED (Council of European Dentists) met in 2011 to amend the legislation from 2005. Because of the way it is currently worded, it is possible that a student could be qualified after 5 years of part-time study. This is clearly not the case at Peninsula and within the UK but has paved the way for the accelerated 4 year course which saves money and has been proven to qualify the same quality of dentist.
Unfortunately, the wording of the new amendments would mean that a dental course has to run for 5 years and must be a minimum of 5000 hours in length which would affect the 4 year courses. So based on the current legislation, the 4 year course is completely valid so the universities aren't at fault, it just so happens that if the changes go ahead, it will be compulsory for a course to be run as a 5 year course.
Hope this clears things up.