Osteoradionecrosis is a very rare but the most serious complication of radiation to the head and neck, occurring in 2% of patients. It is manifested by an area of exposed bone which persists for more than three months. ORN may or may not be accompanied by symptoms such as pain, bad breath and paresthesia which can significantly reduce the quality of life. Risk factors for ORN are trauma (including dental extraction), tumor location, total dose of radiation, surface area of the irradiated bone, periodontal health and oral hygiene, consumption of alcohol and tobacco products, and uncontrolled diabetes. ORN is classified into three stages according to the extent of bone involvement and the appearance of signs such as pathological fracture of the jaw, necrosis of the skin and the appearance of fistulae. The treatment of ORN is long and unpredictable. Stage I is treated conservatively with oral antiseptics. Stage II is treated with systemic antibiotics, and, where appropriate, sequestrectomy with primary wound closure. Stage III is treated with a resection of the affected bone segment and reconstruction with a bone-muscle flap. Because of the unpredictable and long-term therapy, all patients need to take measures for the prevention of ORN. These include dental treatment with extractions of teeth that need to be extracted prior to radiation. After radiation, the patient should have regular checkups, conduct daily fluoridation of the teeth and a thorough oral hygiene to minimalize the need for extractions after radiation. These measures can reduce the incidence of ORN by up to 3 times.