Since I’m not a dentist and don’t know any dentists I don’t have an immediate answer to this. But the way I’d try to find out would be to do a google search of entry requirements for denistry and see what came up. I’d probably then pick a few universities that I fancied and check out their courses and requirements. The other people to speak to would be your career’s teachers at school (there are usually a few people who specialise in helping with career questions). Good luck!
I’m not entirely sure, but I have a friend who is a dentists and I think I remember her telling me that she needed chemistry and biology A-levels, as well as another A-level, in order to do her degree in dentistry. I’m not sure what grades you need, because that would depend of the university, but I imagnine that they would need to be pretty good.