You do not know how well you've done as of yet, I was sure I had done awfully in my AS's and couldn't apply to dentistry that year but I got AAB which was good enough to apply with. You can try to apply this year, even if the worst came to the worst with poor grades (depends, reckon you could get away with ABB but I doubt you'd get an offer with any less) provided you had a top notch PS and UKCAT. However, if you don't get in this following academic year, you can make sure you get your AAA and take a gap year?