Osteonecrosis of the jaw is a rare but serious condition where bone tissue in the jaw dies and may become exposed through the gums, causing pain and complications for patients taking certain medications or undergoing specific cancer treatments.

Understanding Osteonecrosis of the Jaw

Osteonecrosis of the jaw, often abbreviated as ONJ, is a medical condition where the bone cells in the jawbone die and the bone itself may poke through an opening in the gums. The term “osteonecrosis” comes from two words: “osteo,” which means bone, and “necrosis,” which means death. When this happens, blood cannot reach the exposed area, causing more bone tissue to die over time.^[1]

This condition is also sometimes called avascular necrosis, which refers to the lack of blood flow through the blood vessels in your body’s circulatory system. When blood flow slows down or stops completely to the jawbone tissue, the cells begin to die. The exposed bone appears in the mouth and persists for more than eight weeks, often causing significant discomfort and complications.^[2]

Most cases of ONJ occur after a dental procedure, such as having a tooth pulled or other oral surgery. However, in some instances, the condition can develop spontaneously without any obvious triggering event. The bone that becomes exposed doesn’t receive the blood supply it needs, and as a result, it continues to deteriorate.^[1]

How Common Is This Condition?

Osteonecrosis of the jaw is uncommon overall. Among people with cancer who receive intravenous medications to help with bone loss and ease bone pain caused by cancer that has spread to the bones, approximately 2 out of every 100 patients develop this condition. For people who don’t have cancer or who take lower doses of bone-strengthening medications in pill form for conditions like osteoporosis, the condition is even rarer.^[1]

The risk varies depending on several factors. For patients taking antiresorptive medication specifically for cancer treatment, the risk ranges between 1% and 5%. People with osteoporosis who take lower doses of these medications have a much smaller risk, less than 0.1%. Some studies have shown slightly different rates, but all agree that ONJ remains a relatively rare complication.^[22]

One recent study found that about 8% of women diagnosed with breast cancer who received certain bone-strengthening treatments developed osteonecrosis of the jaw. This rate was higher than previously reported, suggesting that the condition may be more common in certain patient groups than initially thought. Women who received a combination of different medications had the highest rates of developing this condition.^[17]

What Causes Osteonecrosis of the Jaw

ONJ tends to occur after oral surgery procedures like tooth removal, dental implant placement, or dental bone grafts that may leave some of the jawbone exposed. During these procedures, if the gum tissue doesn’t heal properly after the dental work, the jawbone remains exposed. Since the exposed bone cannot receive adequate blood flow, the bone cells begin to die.^[1]

The condition can also be caused by several rare side effects of taking specific medications. It may occur when antiresorptive medications, which are drugs designed to reduce the risk of bone fractures, are given to treat cancer that has spread to the bones. These medications work by slowing bone loss and increasing bone strength, but they can interfere with the jaw’s ability to heal properly.^[2]

Another related condition called osteoradionecrosis can develop in people who receive radiation therapy for head and neck cancers. This occurs in 3% to 10% of these patients. Radiation therapy to the head or neck can destroy the blood vessels that carry blood to the bones, leading to bone death. A tooth extraction or other invasive dental procedure after radiation therapy significantly increases the chances of developing this complication.^[1]

ONJ may also develop following an injury to the jaw, particularly in patients with gum disease, areas of the mouth with no teeth, or trauma from poorly fitting dentures. In rare cases, the condition may occur spontaneously over bony growths in the roof or inner parts of the mouth.^[2]

Risk Factors for Developing ONJ

Anyone can potentially develop osteonecrosis of the jaw, but certain factors significantly increase the risk. The most important risk factor is receiving antiresorptive medications called bisphosphonates. These medications are given through an intravenous (IV) line and work by slowing bone loss and increasing bone density to help prevent fractures. They also ease pain from cancer that has spread to the bones and lower the risk of fractures after receiving certain cancer treatments.^[1]

Bisphosphonate medications include drugs such as alendronate, risedronate, ibandronate, and zoledronic acid. Another medication called denosumab, which is a different type of drug that also affects bone metabolism, can also increase the risk of ONJ. Patients who receive intravenous bisphosphonates as part of their cancer treatment face a higher risk than those who take much lower doses in pill form for osteoporosis treatment. Studies haven’t shown a clear link between lower-dose oral antiresorptive medicines for osteoporosis and ONJ.^[3]

Age plays a role in the development of this condition. People who are 65 years old or older have an increased risk compared to younger individuals. This may be related to changes in bone healing capacity and blood vessel health that occur with aging.^[1]

Several medical conditions and treatments can raise the risk of developing ONJ. Patients receiving chemotherapy treatments face higher risks. People with diabetes have an increased likelihood of developing the condition, possibly because diabetes can affect blood flow and healing. Those with a history of gum disease or periodontal disease, including periodontitis (a serious gum infection that damages soft tissue and can destroy the bone supporting teeth), are more vulnerable.^[1]

Long-term use of corticosteroids, which are medications used to reduce inflammation, also increases risk. People who have had facial fractures or trauma to the jaw area are more susceptible. Smoking significantly raises the risk of ONJ, as it impairs blood flow and healing. Even past infections like shingles have been associated with an increased risk of developing this condition.^[1]

The risk may be slightly higher in people who require invasive dental procedures, such as dental extractions or dental implant placement, especially if they are also taking bisphosphonates. People with multiple myeloma, a type of blood cancer, seem to have a slightly higher risk of developing osteonecrosis of the jaw compared to patients with other types of cancer.^[4]

Recognizing the Symptoms

The symptoms of osteonecrosis of the jaw can vary from person to person. Some people experience no symptoms at all in the early stages, while others develop noticeable signs shortly after a dental procedure. If you’ve recently had dental work and develop ONJ, you may notice pain on the side of your mouth where the procedure took place.^[1]

The most definitive symptom of ONJ is the presence of exposed bone in the jaw that can be seen through lesions in the gums, and this exposed bone does not heal. Pain, inflammation of the surrounding soft tissue, secondary infection, or drainage may or may not be present initially. The exposed bone may appear in your mouth and persist for weeks or months without healing.^[9]

Common signs and symptoms include jaw pain, which can range from mild discomfort to severe pain. You may notice loose teeth that weren’t loose before, as the dying bone can no longer properly support them. Mouth sores may develop around the affected area. A pus-like discharge may appear in your gums and mouth, indicating infection. Swollen gums around the exposed bone are common, and the affected area may appear red and inflamed.^[1]

Other symptoms can include soft tissue swelling around the jaw area, drainage from the affected site, a feeling of numbness or a “heavy jaw” sensation, or a general unpleasant abnormal feeling in the jaw. Some patients report bad breath that doesn’t improve with normal oral hygiene. Signs of infection in the gums may be present, though it’s important to note that the bone beginning to weaken and die does not always cause pain in the early stages.^[2]

The development of these symptoms is most frequent after invasive dental procedures, such as tooth extractions, but can also occur spontaneously without any obvious trigger. Lesions are more commonly found on the lower jaw (mandible) than on the upper jaw (maxilla).^[9]

How to Prevent Osteonecrosis of the Jaw

Prevention is the most effective approach to managing the risk of osteonecrosis of the jaw. Good oral hygiene and regular dental care are the best ways to lower your risk of developing this condition. Maintaining healthy teeth and gums reduces the need for invasive dental procedures that could trigger ONJ.^[3]

If you’re planning to start treatment with bisphosphonates or other bone-modifying medications, schedule a comprehensive dental examination before beginning treatment. Make sure to receive any necessary dental work, including tooth extractions, dental implants, or other procedures that involve bone surgery, before you start taking these medications. This allows your mouth time to heal properly before the medications begin affecting your bone turnover.^[2]

Once you begin treatment with antiresorptive medications, inform all your healthcare providers, especially your dentist, about the medications you’re taking. This information is critical for them to provide appropriate care and make informed decisions about any dental procedures you might need. Your dentist may consider using more conservative approaches to dental procedures, such as performing a root canal instead of extracting a tooth if the tooth can be saved.^[3]

Maintain excellent oral hygiene habits by brushing and flossing your teeth after every meal to reduce the risk of infection and gum disease. Use an antibacterial mouth rinse twice daily to help keep your mouth clean. Attend regular dental check-ups so that any problems can be identified and treated early, before they require more invasive procedures.^[17]

If you wear dentures, have your dentist check and adjust them as needed to ensure they fit properly and don’t cause trauma to your gums. Full-mouth dental extractions or periodontal surgery should be avoided if possible while on antiresorptive therapy. Patients with periodontal disease should consider non-surgical treatments before choosing surgery.^[3]

Tell your dentist and oncologist immediately if you notice bleeding gums, pain, signs of infection in your mouth, or any unusual feelings in your teeth or gums. Early detection of problems allows for prompt treatment and may prevent the development of ONJ. If you detect any mouth pain or problems while taking these medications, seek dental care right away.^[17]

What Happens in Your Body

Understanding what happens in your body when ONJ develops helps explain why this condition is so challenging to treat. The jawbones and teeth are affected differently by antiresorptive medications compared to other bones in the body. The jaws regenerate and repair themselves more often than other bones because of the constant stress from chewing and the close connection to teeth.^[22]

Antiresorptive drugs work by targeting and inhibiting cells called osteoclasts, which are responsible for breaking down bone tissue. This breakdown normally occurs as part of the body’s healing process and in response to bone-weakening diseases like osteoporosis. By blocking osteoclast activity, these medications help prevent bone loss and maintain bone strength. However, this same action can interfere with the jaw’s natural ability to repair itself.^[22]

Because the jawbones undergo more frequent repair and remodeling than other bones, more of the medication concentrates in jaw tissues. The teeth are separated from the jawbone only by a small ligament, which means that less bone healing and building occurs in the areas around teeth. This creates a situation where the jaw becomes more vulnerable to damage.^[22]

When ONJ develops, the bone tissue loses its blood supply through processes that are not yet fully understood. Researchers believe multiple factors may contribute, including the loss of the bone’s ability to repair itself, a decrease in the formation of new blood vessels, and increased susceptibility to infection. The combination of medications, microbial contamination from the mouth, and local trauma from dental procedures or normal wear and tear can trigger this condition.^[3]

Once the bone tissue dies and becomes exposed in the mouth, it cannot receive the nutrients and oxygen it needs from the blood. The exposed bone may become infected with bacteria normally present in the mouth, leading to further complications. The cycle of infection and attempted healing becomes disrupted, and the area fails to heal properly. The dead bone tissue remains exposed, and surrounding healthy tissue may also begin to deteriorate.^[1]

The mandible (lower jaw) is more commonly affected than the maxilla (upper jaw). This may be because the lower jaw has a denser bone structure and receives blood supply from fewer major arteries compared to the upper jaw, making it more vulnerable when blood flow is compromised.^[14]