In metropolitan sydney, only USYD offer Dentistry however its a post-grad course. I'd recommend doing B Sc/Ad Sc/Med Sc and then do post-grad dent. Requirements are pretty rough for dentistry, you must do GAMSAT which I heard is 100 times harder than UMAT (its a REALLY long exam) as well as having a 5.5 GPA (which is basically a distinction? I'm not sure) and passing an interview. In NSW, Charles Sturt also offers dentistry which has a cut-off of 90 but they have a preference to rural students and you have to demonstrate you're commitment to practice in rural NSW to get accepted there. You could always try inter-state? I know University of Adelaide and JCU offers it and I think University of Queensland does too.
I'm not too sure about medicine but you'll be wanting to do UMAT over GAMSAT and its very competitive so a HIGH ATAR as well as a HIGH score in UMAT.