Im not what you would call an expert but here are my 2 cents since noone else is replying at the moment.
First of all check these links to get the differences between the gpas http://www.adea.org/dental_education...20Subjects.pdf
For school specific information predents.com is a great website, its easy to use and straight to the point. Way it makes sense to me is obviously schools would rather your sgpa be higher since its the gpa of your science classes, and dental schools are all about science.
Hope that helps in the meantime while you wait for someone with more expertise.