Osteomyeltis

The mandible (lower jaw), due to decreased vascularity (blood supply & flow), is involved 6 times more often than the maxilla (upper jaw).

The mandible has a relatively limited blood supply and dense bone with thick bony (cortical) plates. Infection causes acute inflammation in the medullary (bone marrow) soft tissues and inflammatory exudate (a fluid with a high content of protein and cellular debris which has escaped from blood vessels and has been deposited in tissues or on tissue surfaces, usually as a result of inflammation. It may be septic or non-septic) spreads infection through the marrow spaces. It also compresses blood vessels confined in the rigid boundaries of the vascular canals.

Thrombosis (the formation or presence of a thrombus [a clot of coagulated blood attached at the site of its formation] in a blood vessel) and obstruction then lead to further bone necrosis.

Dead bone is recognisable microscopically by lacunae (a cavity, space, or depression, especially in a bone, containing cartilage or bone cells) empty of osteocytes (a cell characteristic of mature bone tissue. It is derived from osteoblasts and embedded in the calcified matrix of bone. Osteocytes are found in small, round cavities called lacunae and have thin, cytoplasmic branches) but filled with neutrophils (white blood cells) and colonies of bacteria which proliferate in the dead tissue.

Pus, formed by liquefaction of necrotic soft tissue and inflammatory cells, is forced along the medulla and eventually reaches the sub-periosteal region by resorption (an organic process in which the substance of some differentiated structure that has been produced by the body undergoes lysis and assimilation) of bone. Distension of the periosteum by pus stimulates sub-periosteal bone formation but perforation of the periosteum by pus and formation of sinuses on the skin or oral mucosa are rarely seen now.

At the boundaries between infected and healthy tissue, osteoclasts (a specialised bone cell that absorbs bone) resorb the periphery of the dead bone, which eventually becomes separated as a sequestrum (a fragment of dead bone separated from healthy bone as a result of injury or disease). Once infection starts to localise, new bone forms around it, particularly sub-periosteally.

Where bone has died and been removed, healing is by granulation with formation of coarse fibrous bone in the proliferating connective tissue. After resolution, fibrous bone is gradually replaced by compact bone and remodelled to restore normal bone tissue and structure (and function).

Piercing, deep and constant pain predominates in the clinical presentation in adults, while low or moderate fever, cellulitis, lymphadenitis, or even trismus may also be noted.

In the mandible, changes in sensation affecting the lower lip (paræsthesia or dysæsthesia of the lower lip) may accompany the disease. When the disease spreads to the peri-osteum (definition) and the surrounding soft tissues, a firm painful œdema (definition) of the region is observed, while the tooth becomes loose and there is discharge of pus from the periodontium. Radiographic examination reveals osteolytic (definition) or radiolucent (definition) regions

Therapy entails combined surgical (incision, drainage, extraction of the tooth and removal of sequestrum) and chemo-therapeutic treatment (with antibiotics).