It's actually much lower than half. I don't have exact figures, but I've heard AADSAS say that this year there were approximately 13,000 applicants. And for roughly 3,500 spots, the math comes to be around 1/3. Given this is a very general, and rounded-off estimation, but keep in mind that the field is becoming more and more attractive; you'll have pre-med kids making the switch to dentistry, and of course the re-applicant pool will increase each year, making the overall applicant pool larger.