listen. im gonna get this cleared up but it may be contested. as long as you have biology, chemistry and another facilitating subject( e.g, english, humanities, languages,etc) then you should be good. as long as u feel geography is a good choice as it interests u. cos if Ur not interested, how do u expect to do well enough in the exams to actually go into dentistry. now, there are loads of people who can claim that they hated a subject and got an A* on it for A-levels, but a majority of students who hate something wont do well in it regardless. they're just anomalies in a large range of statistics of grades, as harsh as it may seem.