Jaw Osteonecrosis and Medication-Related Complications

Osteonecrosis of the jaw is the death of bone in the maxilla or mandible that becomes exposed through the overlying mucosa and fails to heal. Its most widely studied form is medication-related osteonecrosis of the jaw (MRONJ), which occurs in patients exposed to antiresorptive drugs such as bisphosphonates and denosumab, or to certain antiangiogenic agents. First recognized in the early 2000s, MRONJ has become a defining example of how systemic drug therapy can produce a localized, treatment-resistant complication in the jaws.

Definition

Medication-related osteonecrosis of the jaw is, by the standard working definition, exposed bone (or bone that can be probed through a fistula) in the maxillofacial region that has persisted for more than eight weeks, in a patient who has received antiresorptive or antiangiogenic therapy and who has no history of radiation to the jaws or obvious metastatic disease at the site.

Scope

This entry covers osteonecrosis of the jaw with a focus on the medication-related form: the drug classes implicated, the working case definition used to identify it, and the leading hypotheses for why the jaws are uniquely susceptible. It is a reference and educational overview; it deliberately avoids drug dosing, prevention protocols, and individualized treatment guidance.

Core questions

• How is medication-related osteonecrosis of the jaw defined and distinguished from other causes of exposed jaw bone?
• Which drug classes are implicated, and how might they predispose jaw bone to necrosis?
• Why are the jaws, rather than other bones, the site where this complication occurs?

Key concepts

• Exposed, non-healing jaw bone
• Antiresorptive drugs (bisphosphonates, denosumab)
• Antiangiogenic agents
• Suppressed bone remodelling and turnover
• Working case definition (8-week persistence)
• Distinction from osteoradionecrosis

Mechanisms

Medication-related osteonecrosis of the jaw is associated with drugs that suppress bone remodelling or angiogenesis. Antiresorptive agents — nitrogen-containing bisphosphonates and the RANKL inhibitor denosumab — markedly reduce osteoclast-mediated resorption and overall bone turnover, while antiangiogenic agents impair new blood-vessel formation; both are thought to leave jaw bone unable to repair the microdamage and respond to the infectious challenge that follow events such as tooth extraction (Ruggiero, 2022). The jaws are considered uniquely vulnerable because they have high baseline remodelling, are covered by thin mucosa, carry teeth that provide a route for oral bacteria to reach bone, and are frequently subjected to surgical trauma. The condition was first described as an emerging entity in patients on intravenous bisphosphonates in the early 2000s (Marx, 2003), and successive position papers have refined the working case definition and broadened the implicated drug list from bisphosphonates alone to the wider antiresorptive and antiangiogenic categories (Ruggiero, 2014; Ruggiero, 2022).

Clinical relevance

Because the drugs that can precipitate jaw osteonecrosis are widely used for osteoporosis and for skeletal complications of cancer, the condition is relevant across dentistry, oral and maxillofacial surgery, oncology, and endocrinology. This entry describes the condition as a body of knowledge — what it is and why it arises — and is not a source of preventive, dosing, or treatment instructions for any individual; those decisions rest with the responsible clinicians.

Epidemiology

Medication-related osteonecrosis of the jaw is uncommon overall, and its frequency depends strongly on the drug, dose, route, and indication. Reported risk is substantially higher among patients receiving high-dose intravenous antiresorptive therapy for cancer than among those taking lower-dose oral therapy for osteoporosis. Invasive dental procedures, particularly tooth extraction, are recognized as common precipitating events.

Debates

Should the entity be defined by drug class or by mechanism?

As cases linked to denosumab and antiangiogenic agents accumulated, the older bisphosphonate-specific label was broadened to medication-related osteonecrosis of the jaw, reflecting a shift from a drug-specific to a mechanism- and class-based concept of the condition.

Key figures

• Robert Marx
• Salvatore Ruggiero

Seminal works

• marx-2003
• ruggiero-2014
• ruggiero-2022

Frequently asked questions

Is osteonecrosis of the jaw caused only by bisphosphonates?

No. Although it was first recognized with bisphosphonates, the broader entity termed medication-related osteonecrosis of the jaw is also associated with the antiresorptive drug denosumab and with certain antiangiogenic agents.

Why are the jaws affected rather than other bones?

The jaws have high baseline bone turnover, thin overlying mucosa, teeth that provide a route for oral bacteria, and frequent exposure to surgical trauma such as extractions, which together make them the characteristic site for this complication.