Root canal treatment may be required to save a tooth when there is an infection or inflammation of the nerve of the tooth and the nerve begins to die. This can be caused by many factors, including a deep cavity or breakdown of a filling or crown, a cracked or chipped tooth, or an accident or trauma. There are a few symptoms that may indicate the need for treatment, which include swelling and/or pain in the gums around the tooth, tooth sensitivity to hot or cold, and tooth discolouration.