Root canal treatment is needed when an injury or a large cavity damages the tooth's root. The root becomes infected or inflamed. The dentist numbs the tooth. An opening is made through the crown of the tooth to the pulp chamber. Special files are used to clean the infection and unhealthy pulp out of the canals. Then they shape the canals for the filling material. Irrigation is used to help clean the canals and remove debris. The canals are filled with a permanent material. Typically, this is done with a material known as gutta-percha. This helps to keep the canals free of infection or contamination. A temporary filling material is placed on top of the gutta-percha to seal the opening. The filling remains until the tooth receives a permanent filling or a crown. A crown, sometimes called a cap, looks like a natural tooth. It is placed over the top of the tooth.