Osteonecrosis of the jaw (ONj) is a severe bone disease that affects the jaws, including the maxilla and the mandible. Jaw bone (osteo-) damage and death (-necrosis) occurs as a result of reduced local blood supply (ischaemia). The condition is thus included in the general category of ischaemic or avascular osteonecrosis (literally "dead bone from poor blood flow.").
Various forms of ONj have been described over the last 160 years, and a number of causes have been suggested in the literature. In recent years, an increased incidence of ONj has been associated with the use of high dosages of bisphosphonates, required by some cancer treatment regimens, especially when the patient undergoes subsequent dental procedures. The possible risk from lower oral doses of bisphosphonates, taken by patients to prevent or treat osteoporosis, remains uncertain. (More...)