Osteoradionecrosis

Osteoradionecrosis (ORN) is a serious complication associated with the use of radiotherapy in the management of mouth cancer which can result in infection and possibly pathological jaw fractures. It is defined as exposed radiated bone that fails to heal without any evidence of persisting tumour. Reported prevalence varies from 0.4% to 56%. Modern radiotherapy has changed significantly and more modest occurrences have been reported recently, 4.3% over 10 years and 8% over 30 years. A significant change in radiotherapy has been the development of Intensity-modulated radiation therapy (IMRT). The development of proton beam radiation therapy may also help.No Sinus/ fistulas (Asymptomatic)No Sinus/ fistulas (Symptomatic)Sinus/ fistulas (Asymptomatic)Lower border of mandible is not involved No Sinus/ fistulas (Symptomatic)Lower border of mandible is not involved Sinus/ fistulas Lower border of mandible is involved Osteoradionecrosis (ORN) is a serious complication associated with the use of radiotherapy in the management of mouth cancer which can result in infection and possibly pathological jaw fractures. It is defined as exposed radiated bone that fails to heal without any evidence of persisting tumour. Reported prevalence varies from 0.4% to 56%. Modern radiotherapy has changed significantly and more modest occurrences have been reported recently, 4.3% over 10 years and 8% over 30 years. A significant change in radiotherapy has been the development of Intensity-modulated radiation therapy (IMRT). The development of proton beam radiation therapy may also help. Bone is relatively radio-resistant compared to other tissues due its blood supply and limited reparative ability and poses a problem when irradiated. ORN is more common in the posterior mandible due to a reduced blood supply. Additional risk factors include: poor dental health, tobacco and alcohol use, operative surgery involving mucosa and bone in the site of the radiotherapy and high dose radiation. ORN can occur spontaneously, due to periodontal and apical disease and possibly after trauma induced by dentures, or after surgery or tooth extraction. A balance of tumour eradication and normal tissue preservation must be reached to achieve cure without further debilitating the patient. There are not many specific clinical signs of ORN. It may be first seen as an area of exposed bone which is not healing, or the non-specific signs may become evident prior to this. Symptoms vary depending on the degree of ORN that has occurred. An early indicator may be paraesthesia or numbness of the lip or other area of the mouth such as; If symptoms are evident, these should be reported to the patient's doctor or healthcare team as soon as possible. In 1926, Erwing described the changes in bone that associated with radiotherapy as radiation osteitis. The precise pathogenic mechanisms are not fully understood but in 1983, a theory was proposed by Marx, suggesting that osteoradionecrosis is cumulative tissue damage induced by ionising radiation from radiotherapy rather than trauma or bacterial infection of soft tissue or bone. Marx described ORN as disturbance in complex metabolism and tissue homeostasis that result in local tissue hypoxia, hypocellular and hypovascular tissue. This would eventually lead to breakdown of infected tissue and chronic non-healing wounds due to avascular necrosis. There are also various of studies and clinical cases to support the Marx’s theory. The mandible is more commonly affected than maxilla due to the lesser vascularity. Irradiation to the overlying soft tissue, periosteum and bone would possibly undergo hyperaemia and endarteritis. Osteoradionecrosis of the mandible is mainly due to radiation-induced obstruction of the inferior alveolar artery and ultimately lead to ischaemic of tissue. The damaged periosteum and hypovascularity decrease the chance of revascularisation of tissue by the branches of facial artery. The buccal cortex of the premolar, molar, and retromolar of the mandible are the most commonly affected areas. Cells such as fibroblasts, osteoblasts, and undifferentiated osteocompetent cells in irradiated area are most likely damaged as a result of free radicals and inflammation. A series of growth factors chronically activate the fibroblast. Some studies showed proliferation and function of fibroblast are affected but high dose of radiation. The affected fibroblast has lower production and secretion of collagen to the surrounding tissue and there is a significant drop of cell number in response to radiation exposure. This is also known as fibroatrophic. High and/ or fractioned radiation doses would cause radiation induced fibrosis (RIF). There are different factors that may increase the severity and presentation of RIF such as age, obesity, high blood pressure, diabetes, surgery in irradiated area, chemotherapy, and concomitant radiotherapy. The staging system can be useful as a baseline reference for management after a definitive diagnosis of ORN has been established. ORN is one of the most serious complications arising from head and neck radiation therapy