If your tooth has been keeping you awake at night, is tender to tap, is sensitive or painful to heat, and requires regular medication to keep comfortable, it may have an irreversible pulpitis and need root canal treatment, also known as endodontic treatment.
Inside your teeth are nerves and blood vessels called the 'pulp'. The pulp is remnants of the cells that formed the tooth when you were very young. When the pulp becomes infected with bacteria the infection causes swelling. Obviously the inside of a tooth is not able to allow any swelling so it is very painful, and if left untreated the swelling may appear in the gum around the tooth. Antibiotics are ineffective at eliminating the infection inside the tooth and will only temporarily relieve symptoms.
Root canal treatment (RCT) allows the tooth to be kept in place by removing the infected or dead tissue from inside the tooth, (while numbed effectively with local anaesthetic), cleaning, disinfecting and shaping the canals then filling the space to seal it from further infection.
Most teeth that are having RCT have been significantly damaged by decay or are broken. Once RCT is complete it is imperative that the tooth is rebuilt and molars and premolars are given protection from chewing forces that will break them further. The best practice is to reduce the height of molars and premolars by about 2mm at the start of RCT and once completed rebuild this in a restorative material. Ideally crowns would be placed on molars to provide the most robust protection.
The alternative to RCT is to have the tooth extracted.