Teeth that require root canal treatment include irreducible pulpitis, pulp necrosis, intradental resorption, and apical periodontitis. 1. Irreducible pulpitis: the tooth has paroxysmal, spontaneous severe pain and the pain worsens at night, which requires root canal treatment. 2. Pulp necrosis: acute pulpitis untreated or pulp necrosis caused by dental trauma, pulp vitality can not be restored by other means, the tooth can only be root canal treatment. 3. Intra-pulpalatal resorption: Intra-pulpalatal resorption caused by endodontic disease cannot be restored by other means and can only be treated with root canal therapy. 4. Periapical periodontitis: Periapical periodontitis means that the inflammation of the tooth has reached the root apex, and root canal treatment is needed to completely clean out the necrotic tooth tissues in the root canal, and then choose the appropriate filling material to seal in the root canal to provide continuous anti-inflammatory effect. Need to do root canal treatment may have other conditions, tooth discomfort timely to the hospital, clear cause of the active treatment, so as not to delay the condition.