I have had two very different experiences, but both were successful root canals.
The first, a healthy tooth had been banged several times and died. There was no cavity. I finally went to the endodontist (NOT a dentist, but a proper endodontist who specializes in root canals and other similar dental surgeries) because I was in so much pain I couldn't function, sleep, anything. I was at the point where I was ready to bash the tooth out with a rock (seriously). The root canal went well, but the horrible pain returned as soon as the numbing wore off. It took several days for the pain to go away. I was still in absolute agony 24 hours later. I was also pregnant and unable to take anything but a little Tylenol (ha ha ha). owwwwwwww.
The second, a molar had a deep cavity with a lot of decay and it had reached the root. I had no pain. In fact, I didn't really have any feeling in the tooth. I was so. scared. it was going to hurt like the other one. However, other than being a bit sore afterwards for a day or so, I never had any major pain with that one. I was also pregnant when that one was done.
What hurt way more than the root canal the second time was my gums. Oh boy did that hurt. They throbbed and throbbed, for at least 24-48 hours. When decay is in there like that and that major work is done in the area, it can reeeeallly hurt. It was hard to believe gums could hurt that much. It also got better though, in a couple of days or so.
HTH and I hope you're feeling better soon. I hate dental work.
