Osteonecrosis of the Jaw (ONJ) is a severe condition involving the destruction and death of bone tissue in the maxilla or mandible. This necrotic bone subsequently becomes exposed through the overlying gum tissue. When bone is exposed and does not heal over several weeks, it signals a serious underlying issue with the bone’s health and ability to repair itself. ONJ is often linked to certain medical treatments, making awareness and early detection important for patients and healthcare providers.
Defining Osteonecrosis of the Jaw
Osteonecrosis literally means “bone death,” describing the localized demise of bone cells. In the jaw, this leads to the progressive destruction of the bone structure, compounded by the hostile, bacteria-rich environment of the mouth. The defining characteristic of ONJ is the presence of exposed, necrotic jaw bone that persists without healing for more than eight weeks.
The underlying pathology involves a failure of the bone’s natural remodeling cycle, where old bone is typically replaced by new tissue. When this mechanism is impaired, the bone becomes weakened and susceptible to breakdown, often triggered by a minor injury or dental procedure. Because the dead bone lacks a proper blood supply, the body cannot effectively repair the damage or fight off infection, resulting in a persistent, non-healing lesion.
Clinical Appearance and Visual Signs
The most striking visual sign of ONJ is the appearance of bone visible within the mouth through a break in the gum line. This exposed bone often looks whitish, yellowish, or brownish, and has a rough or irregular texture. It is the underlying jawbone that has died and is now exposed to the oral cavity, though it can be mistaken for a retained tooth root or a sharp bone fragment.
The exposed bone is most frequently located in the lower jaw (mandible), often where a tooth was recently removed or where a denture rubs. While early stages may be painless, the exposed tissue quickly becomes infected, leading to secondary symptoms. These associated signs include swelling, redness, and tenderness of the surrounding gum tissue.
Infection often results in a pus-like discharge (suppuration), draining from the exposed bone or from a small opening in the gums called a sinus tract. Patients may also report a feeling of heaviness or numbness in the jaw, signaling potential nerve damage. Other localized symptoms include mobile teeth adjacent to the necrotic area, bad breath due to infection, and non-healing gum sores.
Primary Causes and Risk Factors
The vast majority of ONJ cases are classified as Medication-Related Osteonecrosis of the Jaw (MRONJ), linked to specific drug classes. Antiresorptive medications, such as bisphosphonates and denosumab, are the primary culprits because they slow down the natural bone turnover process. These drugs treat osteoporosis or manage bone complications in cancer patients, though intravenous administration for cancer carries a substantially higher risk than oral use for osteoporosis.
Anti-angiogenic agents are another implicated drug class, as they inhibit the formation of new blood vessels. This mechanism impairs the jawbone’s ability to heal and repair itself. MRONJ development is often triggered by local trauma, such as a tooth extraction or invasive oral surgery, but the bone can also become exposed spontaneously without a preceding dental procedure.
Beyond medication, prior radiation therapy to the head and neck region is a major risk factor, known as osteoradionecrosis (ORN). This radiation damage decreases blood supply to the bone, leading to tissue death distinct from MRONJ. Systemic risk factors include co-morbidities like diabetes, which impairs wound healing, and poor oral hygiene, which increases the risk of infection.
Staging and Diagnostic Imaging
The severity and extent of ONJ are classified using a staging system, such as the one proposed by the AAOMS. Stage 0 indicates non-specific symptoms like pain or numbness without visible exposed bone. Stage 1 involves exposed bone but without infection or symptoms, while Stage 2 includes exposed bone accompanied by pain and signs of infection, such as redness and swelling.
Stage 3, the most advanced form, involves exposed bone with infection and severe complications, such as a jawbone fracture or extension into the sinus cavity. Although clinical examination confirms the diagnosis of exposed bone, diagnostic imaging is essential for determining the full extent of the disease. Conventional X-rays, like panoramic radiographs, can reveal bone destruction, sequestration (fragments of dead bone), and sclerosis.
More advanced imaging techniques, such as Computed Tomography (CT) or Cone-Beam Computed Tomography (CBCT), provide a detailed three-dimensional view of the jaw structure. These scans accurately measure the size of the necrotic area and assess the involvement of surrounding structures like the maxillary sinus. Imaging helps the clinician classify the stage and plan the appropriate management strategy.
Management and Prevention
The management of ONJ focuses on controlling symptoms, eliminating infection, and preventing bone destruction. Treatment for early stages is often conservative, involving systemic antibiotics and antiseptic mouth rinses, such as chlorhexidine, to keep the area clean. Pain management is also a primary goal, addressed with analgesic medications.
Surgical intervention is reserved for more advanced or unresponsive cases. This involves minimally invasive debridement to remove the exposed, infected dead bone (sequestra) until healthy, bleeding bone tissue is reached. In severe Stage 3 cases, a more aggressive surgical resection of the affected jaw portion may be required to resolve the infection and prevent fracture. The goal of surgery is to cover the remaining healthy bone with soft tissue to promote healing.
Prevention is the most effective approach, especially for patients starting high-risk medications. A thorough dental examination, including necessary X-rays, should be completed before starting treatment with antiresorptive or anti-angiogenic drugs. Teeth with a poor prognosis or active infections should be extracted at least three weeks prior to starting the medication. Maintaining meticulous daily oral hygiene and scheduling regular dental check-ups are ongoing strategies for minimizing risk.