The classification is similar to the classification of OM generally, according to the length of time the inflammation has been present and whether there is suppuration (the formation of pus). Acute osteomyelitis is loosely defined as OM which has been present for less than one month and chronic osteomyelitis is the term used for when the condition lasts for more than one month. Suppurative osteomyelitis of the jaws is uncommon in developed regions, and more common in developing countries. In Europe and the United States, most cases follow dental infections, oral surgery or mandibular fractures. There have been many reported cases occurring in Africa which are coexistent with acute necrotizing ulcerative gingivitis or cancrum oris.
