Abstract: The invention relates to a flexible diaphragm which is surrounded at its periphery by an annular ring. This diaphragm is implanted into the pulp chamber after endodontic treatment and provides a covering for the root canal system to prevent infiltration of bacteria and other sources of infection. The device finds particular utility in the context of post-operative inflammation and/or infection in the supporting tissues which may result in build up of intraosseous pressure. The flexibility of the diaphragm material permits it to expand under pressure, thereby minimizing any discomfort which may be otherwise experienced by the patient.