Bisphosphonates and osteonecrosis of the jaw: cause and effect or a post hoc fallacy?

Background: An increasing amount of reports are being published suggesting a relationship between the use of bisphosphonates (BPs) and the development of osteonecrosis of the jaw (ONJ). We reviewed the currently available evidence and explore the potential mechanisms of action based on the known effects of the concerned BP.
Design: The MEDLine, Current Contents and Science Citation Index Expanded databases were queried and the results augmented by analyzing cited references and recent congress proceedings.
Results: 22 papers were included detailing 225 patients, all based on retrospective chart review without control groups. The prevalence of ONJ was estimated at 1.5%. The involved BPs were pamidronate, zoledronic acid, alendronate and risedronate, all potent nitrogen-containing agents. The most common symptom was pain (81.7%), although 12.2% of cases were asymptomatic. In 69.3% of patients ONJ was preceded by a dental extraction. At the time of diagnosis, 74.5% of patients were receiving chemotherapy and in 38.2% of cases corticosteroids were administered. Although various conservative and surgical treatment modalities were reported, residual sites of ONJ persisted in 72.5% of cases.
Conclusion: Although not enough evidence is available to prove a causal link, it seems that under specific circumstances local defenses can become overwhelmed resulting in ONJ.