Many conditions can cause the pulp (nerve and blood vessels) of the tooth to become inflamed, infected, or non-viable. For example, the pulp can be exposed to bacteria either through decay or tooth fracture, or teeth can suffer trauma or dislocation during sports or auto accidents. Even without direct exposure to bacteria, deep decay results in a deep filling, and the pulp is affected. Sometimes the pulp can recover, sometimes it cannot. When it cannot, the pulp is treated with endodontic therapy (root canal) to save the tooth. This therapy cleans, shapes, and then seals the pulp system from further bacterial exposure. If the pulp has been altered and cannot recover, the only alternative to endodontic therapy is extraction and replacement.