Tooth decay leaves the tooth vulnerable to external factors. When decay reaches the pulp, meaning the root canals, it causes infections and the tip of the tooth root opens into the mouth. Root canal treatment is a procedure that must be performed to save the tooth and is not optional. Root canal treatment should be done before filling an infected tooth. Root canal treatment is not a painful procedure. If the tooth is not necrotic, meaning it is still vital, root canal treatment is performed under local anesthesia.