Medication-Related Osteonecrosis of the Jaw According to Antiresorptive Treatment Indication: Disease Severity and Associated Factors

Background/Objectives: Medication-related osteonecrosis of the jaw (MRONJ) may differ in clinical presentation and severity according to the indication for antiresorptive therapy. This study compared patients with MRONJ treated for an oncologic indication or osteoporosis and evaluated factors associated with advanced disease, defined as American Association of Oral and Maxillofacial Surgeons (AAOMS) stages II and III. Methods: This retrospective observational study included 119 patients with MRONJ, comprising 73 patients with an oncologic indication and 46 treated for osteoporosis. Demographic, clinical, treatment-related, and selected biochemical data were collected from medical records. MRONJ severity was classified according to the AAOMS staging system. Between-group differences were assessed using non-parametric and categorical tests, and multivariable logistic regression was used to examine associations with advanced MRONJ after adjustment for selected covariates. Results: Patients with an oncologic indication were younger and had a shorter duration of antiresorptive therapy than those treated for osteoporosis. The distribution of AAOMS stages differed between groups (p = 0.001). Stage III disease was more frequent in the oncologic group than in the osteoporosis group (32.9% vs. 8.7%), whereas stage II frequencies were similar (43.8% vs. 41.3%). Advanced MRONJ was also more frequent in the oncologic group (76.7% vs. 50.0%; p = 0.003). In the multivariable model, older age (OR, 1.16; 95% CI, 1.06–1.27; p = 0.001) and diabetes mellitus (OR, 8.88; 95% CI, 2.29–34.50; p = 0.002) were associated with higher odds of advanced MRONJ. Compared with oncologic patients, those treated for osteoporosis had lower adjusted odds of advanced disease (OR, 0.14; 95% CI, 0.05–0.44; p < 0.001). No statistically significant association between recorded treatment duration and advanced MRONJ was detected in the sensitivity analysis. Conclusions: MRONJ severity differed between patients treated for an oncologic indication and those treated for osteoporosis, with the difference particularly pronounced for stage III disease. These findings should be interpreted in the context of differences in antiresorptive treatment regimens and do not establish an independent causal effect of treatment indication.