Interappointment pain: mechanisms, diagnosis, and treatment

Knowledge on the causes of and the mechanisms behind interappointment pain in endodontics is of utmost importance for the clinician to properly prevent or manage this undesirable condition. The causative factors of interappointment pain encompass mechanical, chemical, and/or microbial injury to the pulp or periradicular tissues, which are induced or exacerbated during root canal treatment. Microorganisms can participate in causation of interappointment pain in the following situations: apical extrusion of debris; incomplete instrumentation leading to changes in the endodontic microbiota or in environmental conditions; and secondary intraradicular infections. Interappointment pain is almost exclusively due to the development of acute inflammation at the periradicular tissues in response to an increase in the intensity of injury coming from the root canal system. When an interappointment emergency occurs, proper diagnosis and active treatment are required for the clinician to succeed in solving the problem. This review focuses on the mechanisms of interappointment pain, with special emphasis placed on the causative agents and the host response to injury that can precipitate pain. In addition, diagnostic measures and treatment approaches to manage interappointment pain are also discussed.