In sickle cell disease, the characteristic jaw/skull radiographic changes (such as a 'stepladder' trabecular pattern or 'hair-on-end' skull appearance) are primarily caused by:

Sickled red blood cells cause vascular occlusion and bone marrow infarcts; the bone marrow then compensates with hyperplasia, producing the characteristic radiographic patterns. While sickle cell patients are also at increased risk for osteomyelitis (often Salmonella), the baseline radiographic trabecular changes themselves come from chronic infarction/marrow hyperplasia, not infection.