ORN is abbreviation for Osteoradionecrosis. Dental extractions increase the risk of developing this serious side effect. It is scary, but should be understood before undergoing an extraction. Everything possible should be done to avoid dental extractions post chemo-radiation in order to avoid this risk. Sometimes a root canal can be attempted.

Information: http://oralcancerfoundation.org/complications/osteoradionecrosis/