 The degree of risk for osteonecrosis in patients taking oral bisphosphonates, such as alendronate (Fosamax), for osteoporosis is uncertain and warrants careful monitoring.Patients taking dexamethasone and other glucocorticoids are at increased risk.Matrix metalloproteinase 2 may be a candidate gene for bisphosphonate-associated osteonecrosis of the jaw, since it is the only gene known to be associated with bone abnormalities and atrial fibrillation, both of which are side effects of bisphosphonates.