You can, but they count your top 9 grades now - 4 points for an A*, 3 points for an A, and nothing for a B or less, then you have to sit an entrance exam on top.
They add the two scores together and determine places based on that for both Medicine and Dentistry.
If you have 9 A*s, then it doesnt matter what else you have as only those 9 count, but if you have 6 A*, 1 A, and 2 B's, thats only 7 grades counted out of the 9 max, leaving you 6-9 points short from someone with 9 A*s - As.