When a cavity spreads to the nerves inside a tooth, called the pulp, it becomes infected. Root canal treatment can save an infected tooth and avoid the loss or emergency extraction of a tooth. When the pulp becomes infected, the infection becomes dangerous because it can eat away at bone or weaken the immune system. Root canal treatment cleans out infected tooth pulp in the canals of the tooth. Once the infected area is disinfected, the canal is filled to avoid additional infection. After a root canal treatment, a crown is suggested to protect and restore the tooth.