Root canal therapy or endodontic treatment, is a dental procedure in which the diseased or damaged pulp (blood vessels and nerve in the centre of the tooth) of a tooth is removed and the inside areas (the pulp chamber and root canals) are filled and sealed.
The aim of the root canal treatment is to avoid tooth extraction wherever possible. Without treatment it can cause terrible toothaches due to infected pulp To cure the infection and save the tooth, it is necessary for the dentist to drill into the pulp chamber, and remove the infected pulp by scraping it out of the root canals. Once that is done, the dentist fills the cavity with an inert material and seals up the opening. This procedure is known as root canal therapy.

Procedure for this treatment:
Root canal treatment is performed under local anesthesia. A thin sheet of rubber, called a rubber dam, is placed in the mouth to isolate the tooth. The dentist removes any tooth decay and makes an opening through the natural crown of the tooth into the pulp chamber. Creating this access also relieves the pressure inside the tooth and can dramatically ease pain
The length of the root canals is determined with a series of x rays. The entire canal space of diseased pulp tissue and bacteria are cleaned with small wire like files. The canals are also slightly enlarged and shaped to receive an inert (non-reactive) filling material called gutta percha. However, the tooth is not filled and permanently sealed until it is completely free of active infection. The dentist may place a temporary seal, or leave the tooth open to drain, and prescribe an antibiotic to counter any spread of infection from the tooth. This is why root canal treatment may require several visits to the dentist.
Once the canals are completely clean, they are filled with gutta percha and a sealer cement to prevent bacteria from entering the tooth in the future. A metal post may be placed in the pulp chamber for added structural support and better retention of the crown restoration. A temporary filling or crown protects the tooth until a permanent restoration may be made.

Preparation
No extensive preparation is required for the root canal treatment. Once the tooth is opened to drain, an antibiotic treatment may be prescribes for patients. They are advised to take the full prescribed course. With the infection under control, local anesthetic is more effective, so that the root canal procedure may be performed without discomfort.

The tooth may be sore for several days after filling. Pain relievers, such as ibuprofen (Advil, Motrin) may be taken to ease the soreness. The tissues around the tooth may also be irritated. Rinsing the mouth with hot salt water several times a day will help. Chewing on that side of the mouth should be avoided for the first few days following treatment. A follow-up appointment should be scheduled with the dentist for six months after treatment to make sure the tooth and surrounding structures are healthy.
Risks
There is a possibility that the root canal treatment will not be successful the first time. If infection and inflammation recur and an x ray indicates retreatment is feasible, the old filling material is removed and the canals are thoroughly cleaned out. The dentist will try to identify and correct problems with the first root canal treatment before filling and sealing the tooth a second time.
In cases where an x ray indicates that retreatment cannot correct the problem, endodontic surgery may be performed. In a procedure called an apicoectomy, or root resectioning, the root end of the tooth is accessed in the bone, and a small amount is shaved away. The area is cleaned of diseased tissue and a filling is placed to reseal the canal.
In some cases, despite root canal treatment , the tooth dies anyway and must be extracted.