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  • Writer's pictureSurviving Breast Cancer

Osteonecrosis of the Jaw: A Little Known Side Effect of Breast Cancer Treatment

Updated: Nov 21, 2022

What is Osteonecrosis of the Jaw?

Osteonecrosis of the jaw (ONJ) is a possible side effect of some breast cancer treatments. It is a condition that results in the death of bone tissue in the jaw. ONJ can lead to pain, infection, and exposure of the teeth. Around 2% of breast cancer patients may experience this side effect.

The exact cause of Osteonecrosis of the Jaw is not known, but it may be related to a decrease in blood supply to the jawbone. It is most commonly seen in patients who take drugs that belong to a group called bisphosphonates, which are used to reduce bone loss and prevent fractures. Other risk factors include radiation therapy or chemotherapy.

The symptoms of Osteonecrosis of the Jaw usually appear four to eight weeks after starting breast cancer treatment. These can include pain or swelling in the mouth, loosened teeth, exposed bone or tissue in the gums, difficulty opening your mouth wide enough for eating or brushing your teeth, unusual bleeding from the gums, and bad breath.

What are the symptoms of ONJ?

Symptoms of ONJ include jaw pain, tooth loss, and exposed bone in the mouth. The condition can also make it difficult to eat and speak. The most common symptom of ONJ is a pain in the jaw, which can range from mild to severe. Other symptoms include:

  • Swelling or infections around the gums

  • Numbness or tingling in the jaw

  • Jawbone exposure (seen as a hole in the gums)

  • Redness

  • Drainage from wounds

  • Exposed bone

  • Loose teeth

  • Problems chewing or swallowing

If you are undergoing cancer treatment and experiencing any of these symptoms, be sure to tell your oncologist or dentist right away. Osteonecrosis of the jaw can be difficult to diagnose, but if you experience any of the above symptoms, it is important to seek medical advice. Your doctor or dentist will likely perform a physical exam and may order x-rays or other imaging tests.

What Causes ONJ?

ONJ is most commonly seen in patients who have received intravenous bisphosphonate therapy, either as part of their cancer treatment or to prevent osteoporosis. Bisphosphonates are drugs that help to strengthen bones and reduce the risk of fractures. However, in some cases, they can cause the jawbone to deteriorate.

ONJ is caused by a reduction in blood flow to the jawbone. This can be the result of cancer treatments that reduce the levels of minerals in the blood, such as bisphosphonates or denosumab. Chemotherapy and radiation therapy can also lead to ONJ.

What are Bisphosphonates?

Bisphosphonates are a type of drug commonly used to treat bone loss in people with breast cancer. They work by reducing the activity of cells that break down bone, ultimately leading to increased bone density and reduced risk of fractures. Bisphosphonates are typically administered as an injection or intravenous infusion. While there are many benefits to taking these drugs, Osteonecrosis of the Jaw is a rare but possible side effect.

Breast cancer patients often take bisphosphonates to lessen the skeletal-related issues that come with metastatic disease, and to stop the bone loss caused by adjuvant therapy. Outside of cancer treatment, bisphosphonates have been studied for their potential in directly inhibit breast tumor cell growth and spread.

One example of a bisphosphonate is Zometa. Zoledronic acid is a drug that's given to reduce the risk of breast cancer spreading to the bones and other parts of the body. Zometa works by reducing the activity of cells that break down bone, ultimately leading to increased bone density and reduced risk of fractures. Zometa can be administered as an injection or intravenous infusion.

What are the Side Effects of Bisphosphonates?

Common side effects of bisphosphonates include nausea, vomiting, constipation, diarrhea, and abdominal pain. Bisphosphonates can also cause Osteonecrosis of the Jaw (ONJ). ONJ is a rare but serious condition that causes damage to the jawbone. It is typically caused by a decrease in blood.

What is the Risk of Developing ONJ?

The risk of developing Osteonecrosis of the Jaw is low, with estimates ranging from 0.3-3%. The risk increases with the duration of therapy and total cumulative dose received.

A large phase III randomized study found that receiving 3 to 5 years of bisphosphonate treatment after surgery and chemotherapy for early-stage breast cancer doesn’t improve survival any more than receiving 2 years of bisphosphonate treatment. The study also found that receiving more than 2 years of bisphosphonate therapy increases the risk of Osteonecrosis of the Jaw.

It is important to weigh the benefits and risks of taking any drug, including bisphosphonates. If you have breast cancer and are considering taking a bisphosphonate, it is important to discuss this with your oncologist. That being said, the risk of Osteonecrosis of the Jaw is still low and should not be a cause for undue concern.

Diagnosing Osteonecrosis of the Jaw

ONJ is diagnosed through a combination of medical history, physical examination, and imaging tests. Your doctor will ask about your medical history and any bisphosphonate therapy you've received. They will also perform a physical examination of your mouth and jaw. Imaging tests such as X-rays, CT scans, and MRIs may also be ordered to get a closer look at the Jawbone.

How is Osteonecrosis of the Jaw Treated?

There is no one-size-fits-all approach to treating ONJ. Your doctor will work with you to develop a treatment plan that meets your individual needs. ONJ is typically treated with a combination of medication and surgery. In some cases, a dental prosthesis (false teeth) may be required. Because ONJ is caused by a lack of blood flow to the jawbone, treatments focus on increasing blood circulation to the area. Oral surgery is typically only recommended if other treatments or medications have not been effective. There are many factors to consider. Antibiotics may also be prescribed to help prevent or treat an infection in the jaw, gums, or tooth. While there is no guaranteed way to prevent ONJ, maintaining good oral hygiene during cancer treatment may help reduce your risk.

Questions to Ask Your Oncologist About ONJ

- What is Osteonecrosis of the Jaw?

- What are the risks of taking a bisphosphonate?

- How can I reduce my risk of Osteonecrosis of the Jaw?

- How will Osteonecrosis of the Jaw be diagnosed and treated if it occurs?

- What other treatments or medications can I take to reduce my risk of Osteonecrosis of the Jaw?

- Are there any alternative treatments available if Osteonecrosis of the Jaw occurs?

- How will Osteonecrosis of the Jaw affect my quality of life and treatment plan?


Osteonecrosis of the jaw is a rare but serious side effect that can be caused by bisphosphonate therapy for treating breast cancer. It occurs when there is a reduction in blood flow to the jawbone and can lead to pain, infection, and exposure of the teeth. If you are currently undergoing treatment for breast cancer, be sure to watch for symptoms of ONJ and notify your oncologist or dentist right away if you experience any jaw pain, tooth loss, or exposed bone in the mouth. By catching ONJ early and getting proper treatment, you can help manage this condition and improve your quality of life during and after cancer treatment. If you experience any symptoms of ONJ, it's important to see your doctor right away for an evaluation.

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Cynthia S
Nov 21, 2022

So sorry Dawn. I'm getting ready for my second Zometa infusion and I continue to be very nervous about this. My oncologist had me get the go-ahead from my dentist first and he seems to be on top of it. I will always see him prior to the infusion. I'm really sorry you went through that.


Nov 20, 2022

So sorry that you had to go through all of that. I’m grateful for this group that brought it to my attention it’s one side effect I didn’t get so glad you’re doing better. 


Nov 20, 2022

ONJ hurts like he--. My dentist didn't know what to do. So he did nothing. I ask his assistant what can I take fir pain? She told me to go get tested oral gel. So I did that until I could get an appointment with a different dentist. Well he didn't know what do to either. He did a washout, and it did nothing but cost me money. He had to send me somewhere else. I finally git a dentist that knew what I needed. He put me on penicillin fir 6 months and it cleared up. The bone died and fell out and the pain was finally gone after 9 months. Don't delay get help right away. No fu…


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