Nobody wants one…but saving your teeth is likely the best option.
A root canal is needed after infection has been identified in the pulp of the tooth. Infection can be caused by repeated dental procedures, trauma to the tooth, cracks, chips or things such as deep decay. You may be able to tell you have an infection if there is sensitivity to the tooth with hot or cold temperatures, swelling or pain in the tooth or gums. When a root canal is performed, any infection or decay is removed and the canal system thoroughly cleaned and sealed.
Hopefully forever…but sometimes further or additional treatment is necessary. Occasionally root canal retreatment is necessary because of recurrent infection or an accessory canal that needs shaping and cleaning. Root canaled teeth become brittle following treatment and can fracture over time resulting in tooth loss. Proper steps should be taken to prevent any and all complications.
Unless you have some type of sedation, you will just have local anesthetic, like when a filling is done, and do not need someone to drive you home after your root canal procedure.
Most of the time the color of the tooth is not affected by having the root canal. Often when a tooth turns dark it is the result of trauma that requires a root canal. Once the root canal is completed, internal bleaching is a conservative option to correct the discoloration.
A root canal is needed because the pulp in the tooth has become damaged or infected. Like any untreated infection, it can cause the infection to spread to other surrounding areas leading to swelling, pain and serious complications. The other option is to have the tooth extracted and ideally have that tooth replaced with either a bridge or dental implant.