Getting all 9s at GCSE isn't an easy feat, and your UCAT score is above the average. Your application is excellent. If you got this a few years ago, you would have been able to choose any dental school. Dentistry is a very competitive course where not everyone gets into dental school first time. A low proportion are successful. Everyone, like you, is ambitious and highly skilled. I don't blame you for being disappointed.
There are more medical schools than dental schools, so more choice when selecting strategically. Even though your application didn't go as planned and it seems your friends did, it's still good you did it strategically. Like
@AntonSlayer was saying, you still have a chance to get into dentistry through Plymouth. The interview is the last hurdle. By this point, they practically believe you're a good candidate, but they just need to narrow it down for the sake of number of places available. High number of interview invites does mean a lower chance but if you give them the answers they want to hear, everything will go smoothly. They'll only reject you if you give them a reason to.
I'd offer my input on how your application may have been unsuccessful (I will if you want it and I'm sure others on this thread would like to help), but please focus on getting your grades and passing the interview. There's still time and there's little meaning to reflect on your dentistry application, if you still have a chance of gaining a place. That being said, none of this is your fault. Good luck with everything ahead.