I used to get cavities filled without numbing, until I was 22 and needed a root canal. They make you get numbed and I haven’t gone back when getting work done. I don’t think the tooth pain is bad, and if you feel tooth pain, let them know. It should be completely shut down. The most uncomfortable part is really having your mouth kept open if they do it right. The light in your eyes too, but you can close your eyes. Also the vibrations sometimes make my nose hairs tickle. All that should be worse than the pain.
When I was around 8 or so, I was more afraid of the needle than the drill. It does hurt, but all pain is something you can get through. If you’re numbing though, it shouldn’t hurt. Also you may fell numb for over 6 hours afterwards. If they do it right you shouldn’t feel pain after it goes away either.