OP here. They did stop pretty quick, after it started hurting, before it got too bad. Anesthetic tolerance runs in the family (and no, I don't use any drugs). They edited the fact that since it had been having issues getting numb, they'd already given me the maximum safe dose of anesthetic for the day, so I had to reschedule for the next available appointment 3 weeks out, and get a temporary filling and prescription for Vicodin (which would make me sick and keep me from safely working) to tide me over. Long story short, my tooth is not only better, it's worse, and I am still waiting, (If you've ever needed a root canal you know the pain.) so the pain at the endodontist's was all for nothing.