Dentistry SQA Glasgow

Hi, i have just got my results for my highers in S5 and have achieved 5A's including Higher Bio and chem. I was wondering if it was necessary for me to take 3 Advanced highers in S6 or could I take two advanced highers and one Higher. Currently I have taken advanced higher chemistry, advanced higher biology and advanced higher maths. Is it possible I could drop advanced higher maths and take a Higher or does that lower my chances of being accepted at Glasgow and Dundee University for dentistry. Could someone please let me know. Thank you.