But of course they do! Or why would people go through them and pay so much for the procedure!
A root canal that is well done, and that is finished with a proper post, filling or crown, has a very high success rate. 85 % of root canal treatments last for a lifetime.
If a tooth becomes infected again years after root canal has be done, that tooth can often be retreated, which means that the root canal can be done again. However in rare cases where the root of the tooth is fractured or decayed, or if there is severe gum disease, the tooth would need to be extracted.