Toothache can be prevented or remedied with a root canal treatment. Unfortunately a root canal treatment can also be the cause of pain. During a root canal treatment pain can be suppressed by local anesthesia, the use of the airotor, the attitude of the dentist and his communication with the patient. Afterpain has three causes: damage and iatrogenic apical periodontitis, pulpitis and continuing apical periodontitis. In this article the possible treatment of pain by a root canal treatment are extensively discussed.