Mandible

a bone of the skull that forms the lower jaw. The condyle of the mandible and the mandibular fossa constitute part of the temporomandibular joint. Also, see mandible.

2. Pathology

In Caffeys disease the mandible may show new bone formation in soft tissue swellings directly contiguous to the cortex, sometimes reaching twice the usual width of the bone. The hyperostosis may clear after 6 months to a year.

Patients with scleroderma may exhibit thickening of the periodontal membrane, which appears as a prominent radiolucent area between the tooth and mandible. Bone erosion may also be seen in scleroderma.

Juvenile chronic arthritis may be associated with micrognathia and limitation of bite. On radiographs the mandibular condyles appear flattened, and the body and vertical rami of the mandible are shortened. In addition, the mandibular notches may be widened and antegonial notching (a concavity on the undersurface of the mandible just anterior to the gonion) may be present.

After radiotherapy, osteonecrosis of the mandible is common owing to the presence of compact bone and poor blood supply. On radiographs it appears as a poorly defined destructive lesion without evidence of sequestration or a soft tissue mass, at times difficult to distinguish from tumour recurrence.

Injury to the mandible is a common cause of temporomandibular joint pain and dysfunction. Fractures of the mandible frequently occur at more than one site in the bone; often a condylar fracture is associated with a fracture of the body or ramus. Complications such as loss of teeth, malunion or nonunion, infection and displacement with deformity occur in some patients. Secondary complications include malocclusion and internal derangement of the temporomandibular joint.

DR