Osteoradionecrosis or death of jaw tissue, can occur in the lower jaw (mandible) following radiation therapy for cancer, administered with machines using Cobalt 60 ionizing radiation (irradiation), high energy x-rays (photons), or electron beams. Osteoblasts and osteoclasts within the bone cells may be irreparably damaged by beams or rays emitted from radiotherapy devices because they destroy and devitalize bone, eroding the jaw. Inflammation of a membrane lining of the jaw artery (endarteritis), occurs because the radiation therapy creates an environment of low oxygen for the lower jaw, decreases bone marrow cell population and abnormally lowers blood vessel growth (Please see definitions for hypoxia, hypocellularity and hypovascularity). The incidence of Osteoradionecrosis following cancer radiotherapy has been reduced by using Intensity modulated radiation therapy – IMRT which provides a more uniform dose of radiation to cancerous tissue and spares unaffected areas of the mandible (see picture below). Conventional fractionation, which involves dividing radiation into small, titrated doses with even spacing between radiation treatments and careful attention to dental hygiene also have been proven to prevent necrosis of bone following irradiation.
The leading cause of Osteoradionecrosis damage is due to harm to the inferior (lower situated) artery located in small saclike (alveolar) structures in the jaw. The first event that triggers Osteoradionecrosis is damage to osteoclast bone cells, that renders them less able or unable to multiply and reproduce new bone, reducing bone turnover - the rate at which bone is broken down and replenished.
Posted by: Joanna Smith