In the early stages of infection you may not notice any pain. In some cases, your tooth could darken in colour, which may mean that the nerve of the tooth has died (or is dying) and this would require root canal treatment.
The aim of the treatment is to remove all infection from the root canal. The root is then cleaned and filled to prevent any further infection. A temporary filling is put in and the tooth is left to settle. The tooth is checked at a later visit and when all the infection has cleared, the tooth is permanently filled. If the pulp becomes infected, the infection may spread through the root canal system of the tooth. This may eventually lead to an abscess - an inflamed area in which pus collects and can cause swelling of the tissues around the tooth. The symptoms of an abscess can range from a dull ache to severe pain and the tooth may be tender when you bite. If root canal treatment is not carried out, the infection will spread and the tooth may need to be taken out.