Root canal treatment is the preferred way to treat an infection in the nerve center of the tooth, known as the pulp. The pulp is the soft, inner core of the tooth that consists of blood vessels, nerves, and connective tissue. When the pulp is diseased or injured and cant repair itself, it dies. The most common cause of pulp death is a cracked tooth or a deep cavity. Both of these problems can let bacteria enter the pulp. Bacteria can cause an infection inside the tooth. Left without treatment, pus builds up at the root tip, in the jawbone, forming a "pus-pocket" called an abscess. Usually pain and swelling will result. Without treatment, your tooth may have to be removed. 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. Root canal treatment is a skilled and time-consuming procedure. Most courses of treatment will involve two or more visits to your dentist. At the first appointment, the infected pulp is removed. The root canal is then cleaned and shaped ready for the filling using thin files (as seen in the first x-ray). 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. About 90 percent of root canals are successful and the pain does not return. However, sometimes a root canal needs to be redone or the tooth extracted.