During the days following a completed root canal, the tooth might feel sensitive because of inflammation, states WebMD. This discomfort can typically be solved with an over-the-counter pain medication such as Advil, Motrin or Aleve.
Post root canal infections can also arise due to a number of complications, reports WebMD. Causes for infections after a complete root canal include an undetected crack in the root of a tooth, a faulty or inadequate tooth restoration that allowed bacteria into the inner recesses of the tooth, or a deterioration of the sealing material over time, which also allows bacteria into the inner tooth area.
A tooth that has undergone a root canal is partially hollowed out, which makes the tooth prone to fracture, says MedicineNet. Getting a crown on the tooth usually prevents this, but sometimes there are undetected cracks at the site during the root canal and the tooth may require later extraction even if the root canal was well done.
Another cause for post root canal infections is that sometimes there are more than the usual amount of root canals in the tooth and the dentist might miss one. The skipped canal could still contain infected tissue and needs to be cleaned out and filled, states MedicineNet.