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What is ONJ or Osteonecrosis of the Jaw?

Osteonecrosis of the jaw (ONJ) is a rare condition where the bone of the lower or upper jaw becomes exposed (usually because of tooth extractions) and does not heal properly. Scientists originally thought that the bone tissue in the jaw was more active than other bones in the body and that the cause of ONJ could be related to the long term use of bisphosphonates because they suppress the activity of the osteoclasts and limit the healing ability of bone cells. However, a 2014 study found no difference in the amount of bone activity in the hip bones and the jaw bones of 90 female patients.

In 2009, a research team at Kaiser Permanente published a study that surveyed over 13,000 patients in Northern California about the possible presence of ONJ. Among the 8,000 who returned the survey, ONJ was detected in 0.10% of patients, occurring mostly in patients who had been on a bisphosphonate for more than four years. Despite the overall rarity of ONJ, it does appear to be more common among patients who use bisphosphonates, especially the more potent ones — like zolendronic acid — that are used with cancer patients.

Should I worry about ONJ?

While rare, ONJ seems to be occur most in patients who are taking very potent intravenous bisphosphonates (most often pamidronate and zoledronic acid) to prevent fractures and bone loss associated with the cancer or cancer treatments. In these cases, the drugs are given frequently and in relatively high doses.

If you are thinking about starting treatment with a bisphosphonate, get a routine dental examination, take good care of your teeth and be alert for the symptoms of ONJ. If possible, avoid invasive dental procedures such as extractions, implants, and jaw or gum surgery during bisphosphonate treatment and if you wear dentures, be sure they are well-fitted.

If you need an invasive dental procedure, do it prior to starting treatment with a bisphosphonate. If you need dental surgery during bisphosphonate treatment, it may be wise to withhold treatment for a period of time prior to and after the dental procedure. If you have symptoms or signs of ONJ get an evaluation by an oral surgeon and consider stopping the treatment.

If you are taking an oral bisphosphonate, take good care of your teeth and visit your dentist regularly.

Who Is at Risk?

According to the American Dental Association, “while it is not possible to identify who will develop MRONJ and who will not, research suggests the following as risk factors:

  • age older than 65 years;
  • periodontitis;
  • poor oral hygiene;
  • dentoalveolar surgery, including tooth extraction;
  • high dose and/or prolonged use of antiresorptive agents (more than 2 years);
  • smoking;
  • malignant disease (multiple myeloma, and breast, prostate, and lung cancer);
  • chemotherapy, corticosteroid therapy, or treatment with antiangiogenic agents;
  • denture wearing;
  • diabetes.”


Symptoms of ONJ include jaw discomfort, mouth sores, loose teeth, and poor healing after tooth extraction or dental surgery.

Revised: 09/19/2019

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