Root canal treatment treatment treats the inside of the tooth. It is necessary when the pulp becomes inflamed or infected. The inflammation or infection can have a variety of causes: deep decay, repeated dental procedures on the tooth, faulty crowns, or a crack or chip in the tooth. In addition, trauma to a tooth may cause pulp damage even if the tooth has no visible chips or cracks. If pulp inflammation or infection is left untreated, it can cause pain or lead to an abscess.