Differences between florid osseous dysplasia and chronic diffuse sclerosing osteomyelitis. Florid osseous dysplasia (FOD) is confused in the literature with chronic diffuse sclerosing osteomyelitis. Two cases of each condition are presented to demonstrate the differences between them. In FOD, there are multiple lobulated sclerotic masses in several quadrants of the jaws, usually in black females. In some cases, the sclerotic masses are exposed to the oral cavity, resulting in a secondary osteomyelitis. Periapical cemental dysplasia is often found in association with FOD. Chronic diffuse sclerosing osteomyelitis is a primary inflammatory condition of the mandible. Patients have cyclic episodes of unilateral pain and swelling. The affected region of the mandible exhibits a diffuse opacity with poorly defined borders. Although women are affected more often than men, black persons are not particularly susceptible. 