During the procedure you should feel no pain: the tooth is fully numbed first.
NHS guidance says you are given a local anaesthetic for root canal treatment, so you are awake but will not feel any pain. The reputation comes from the wrong end of the timeline: the infected tooth beforehand is what hurts, often badly, and treatment relieves it. Afterward, expect several hours of numbness and some soreness or swelling around the tooth that improves over a couple of weeks, controlled with acetaminophen or ibuprofen. Anything beyond that pattern deserves a call to the practice.
What to do
Common questions
Do root canals hurt?
The procedure itself, no; the toothache that sent you there, yes. The NHS is direct: before root canal treatment you get a local anaesthetic, so you are awake but will not feel any pain. Most patients say it feels like getting a long filling, not the ordeal of its reputation. In fact, the severe pain people associate with root canals is usually the infected tooth before treatment, and the root canal is what ends it. Afterward, your jaw and face can stay numb for several hours, and the area around the tooth may feel swollen and sore for a couple of weeks, managed with acetaminophen or ibuprofen while it settles. If pain during the procedure breaks through, tell the dentist immediately; more anaesthetic fixes that. If pain after treatment is severe, worsening after several days, or comes with swelling or fever, call the practice, since that pattern can mean the infection needs more attention. The NHS advises seeing a dentist for any toothache lasting more than 2 days rather than white-knuckling it at home.