Radionecrosis, or radiation necrosis, is a term used in the medical industry to describe the aftereffects of radiation therapy. It refers to the breakdown of body tissue at the original tumor site and occurs some time after radiation has been completed. It takes the form of a focal structural lesion that may potentially be a long-term complication of radiosurgery or radiotherapy that affects the central nervous system (CNS). If radiation necrosis occurs, the body may not be able to replace the damaged tissue. While radionecrosis can occur in any type of body tissue treated with radiation, the most common form of this condition found in dentistry is osteoradionecrosis, or the necrosis (death) of bone tissue. Osteoradionecrosis is quite rare, but when it does develop, it typically does so in the lower mandible or jawbone because this area has a lower blood supply than other bony structures of the mouth and jaw.