Series on Reviews puts post root canal chronic pains >6 months anywhere from 5% to over 7%. Cases have been treated with Botulinum.
J Endod. 2010 Feb;36(2):224-30.
Frequency of persistent tooth pain after root canal therapy: a systematic review
and meta-analysis.
Nixdorf DR, Moana-Filho EJ, Law AS, McGuire LA, Hodges JS, John MT. free article here
Conclusions— “Frequency of all-cause persistent tooth pain following endodontic procedures was estimated to be 5.3%, with higher report quality studies suggesting >7%.”
Causes listed include:
- an untreated or incompletely obturated canal,
- failed coronal seal,
- tooth fracture,
- pain associated with an adjacent tooth,
- referred pain from a nonodontogenic structure,
- deafferentation pain.
Comments – do patients know they are going to end up potentially with chronic pain? – this is another case similar to the post hernia surgery cases that don’t realize the could end up in pain after surgery.
At the Montreal Pain Congress I came across the suggestion that botox injected into the base of the tooth could help the pain – a study needs to be done on that..