Necrosis means cell death. A number of different conditions can lead to this and the tissues involved are broadly divided into hard tissue and soft tissue necrosis.

There are a variety of causes for this which can give an appearance of tissues literally rotting away. These causes, in the oral and maxillofacial setting are usually radiation / radiotherapy (osteoradionecrosis) and chemical effects (medication related osteonecrosis of the jaws).