Epidemiology and pathogenesis of osteonecrosis of the jaw

Osteonecrosis of the jaw (ONJ) is defined as exposed bone in the oral cavity that persists despite appropriate therapy. Over the past decade, ONJ has been reported in about 5% of patients with cancer receiving high-dose intravenous bisphosphonates, and more recently in similar patients treated with denosumab, another potent inhibitor of osteoclastic bone resorption. The condition has also been described in patients treated with bisphosphonates for benign diseases, such as osteoporosis, but whether bisphosphonates or denosumab increase the incidence above that seen in untreated patients of comparable age and frailty is yet to be established. The pathogenesis of ONJ is uncertain: the toxic effects of bisphosphonates in a wide variety of cells could increase susceptibility to infections in the oral cavity or impair mucosal healing, and denosumab might interfere with monocyte and macrophage function. Local osteolysis is an important defense against infection on bone surfaces that is blocked by both bisphosphonates and denosumab. Preventive dentistry prior to high-dose antiresorptive therapy is a critical measure in cancer patients, but is not usually justified in patients with osteoporosis. The management of established ONJ lesions is problematic: the greatest success seems to come from vigorous antimicrobial therapy with judicious use of surgical debridement.