Osteoradionecrosis is one of the most serious and dreaded complications of irradiation therapy for head and neck tumors. The reported frequency ranges from 1% to 35% (87). Osteoradionecrosis was traditionally thought to represent a form of osteomyelitis; however, the concept has been redefined and is no longer a primary infection of bone but rather a radiation-induced vascular defect. There is a sequence that is described within this defect that entails a hypocellular hypoxic tissue and finally a non-healing wound that may or may not become secondarily infected.
Pathologically, osteoradionecrosis consists of six basic processes, which include hyperemia, inflammation, thrombosis, cell loss, hypovascularity, and fibrosis (87). This loss of blood vessels leads to devitalized tissue, which usually appears six months after the irradiation (88).
Within the oral cavity, the mandible is far more susceptible to osteoradionecrosis than the maxilla. Consequently, this difference is believed to be due to the small blood supply to the mandible and the predominance of compact bone in the composition of the mandible (89). The onset of osteoradionecrosis is related to the dose of irradiation, the dental status of the patient, and the anatomic site of the tumor. The risk for osteor-adionecrosis increases with the dosage is more likely to occur in dentulous rather than edentulous patients and is usually found in patients with a poor oral hygiene (89).
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