Finnish study finds poor oral health increases jawbone necrosis risks in breast cancer patients

Antiresorptive drugs, which reduce bone breakdown, are an important part of treatment for breast cancer that has spread to the bones. However, their use can be associated with osteonecrosis of the jaw (MRONJ), a condition in which bone tissue in the jaw dies. In a Finnish registry study, osteonecrosis of the jaw was diagnosed in 12.6% of patients treated with denosumab during long-term follow-up.

A nationwide registry study conducted by researchers at the University of Oulu has, for the first time in Finland, investigated how common medication-related osteonecrosis of the jaw is among patients with breast cancer that has spread to the bones, and which factors are associated with the condition. All patients included in the study were receiving antiresorptive treatment.

During follow-up, osteonecrosis of the jaw was diagnosed in 12.6% of patients treated with denosumab alone. Among patients who had initially received bisphosphonates before switching to denosumab, the corresponding figure was 15.3%. The condition was diagnosed in a small proportion of patients treated with bisphosphonates alone.

Antiresorptive drugs are used, among other purposes, to prevent skeletal complications caused by breast cancer that has spread to the bones. Osteonecrosis of the jaw is a recognised adverse effect of these medications, but its incidence among Finnish breast cancer patients had not previously been investigated.

Monitoring oral health is important

The study also found associations between dental procedures related to oral infections and osteonecrosis of the jaw. Tooth extraction and root canal treatment, in particular, were associated with a higher risk of the condition. However, the number of patients who underwent root canal treatment was small, and the finding does not establish that the procedure itself causes osteonecrosis of the jaw.

The findings alone do not warrant changing or discontinuing anti-resorptive treatment. Instead, the benefits and potential risks of treatment must be assessed on an individual basis. Nor should necessary dental treatment be withheld because of the associations observed. Our results highlight the importance of identifying and adequately treating potential sources of oral infection before starting antiresorptive therapy, as well as monitoring oral health throughout treatment. This requires close collaboration between oncology and oral healthcare professionals.”

Miika Kujanpää, doctoral researcher, University of Oulu

First Finnish population-based study on the topic

The study was conducted as a retrospective nationwide registry study, combining data from the Finnish Institute for Health and Welfare (THL) and the Social Insurance Institution of Finland (Kela).

The study included 652 breast cancer patients with bone metastases who received anti-resorptive treatment between 2013 and 2015. The patients were followed until the end of 2020.

The nationwide, population-based dataset made it possible to assess the incidence of medication-related osteonecrosis of the jaw and the factors associated with it specifically among Finnish patients with breast cancer that had spread to the bones.

Further research needed on the impact of preventive dental care

According to the researchers, further studies should investigate in greater detail how drug dosage, treatment duration and cumulative exposure are associated with osteonecrosis of the jaw. More precise information is also needed on the timing of oral infections, dental procedures and the onset of osteonecrosis of the jaw, to help distinguish the effects of different factors.

The researchers also emphasise the importance of sufficiently long follow-up. A long follow-up period of multiple years may be necessary, as osteonecrosis of the jaw can develop over an extended period and shorter follow-up may underestimate its incidence.

A particularly important research question is how much planned, preventive oral healthcare can reduce the risk of osteonecrosis of the jaw.

The study was supported by research grants from the Finnish Dental Society Apollonia.

The study was published in the journal Clinical Oral Investigations on 29 September 2026.