A root canal is necessary when the cavity has spread into the pulp-(nerve of the tooth) or when the nerve dies as a result of trauma. As the bacteria from the cavity reaches the pulp, it contaminates the entire tooth, often times traveling down the canal in the root into the bone. This infection can lead to an abscess causing swelling around the tooth and gums. This swelling places pressure on the bone to expand with can lead to a severe tooth ache. Root Canal Therapy removes the bacteria and any contaminated tissue and the canals are thoroughly rinsed with a disinfectant. After drying the canals, a filling material is placed into the canals to seal the tooth followed by a restoration to repair the cavity. It is usually recommended to place a crown on the treated tooth to support and protect the brittle tooth.