Abstract Introduction Surgery has increasingly been reported as an effective treatment for medication-related osteonecrosis of the jaw (MRONJ), but concrete intervention criteria are lacking. On computed tomography (CT) images, the boundary between the healthy site and necrotic lesion, which we defined as “MRONJ demarcation line”, is sometimes visible. This study aimed to identify the factors associated with this boundary to improve surgical planning. Materials and methods 95 patients with MRONJ who underwent their first CT at our institution between May 2010 and June 2022 were included. The Mann–Whitney U test, Fisher’s exact test, and multivariate logistic regression analysis were performed. The cumulative incidence rates were calculated using the Kaplan–Meier method. Statistical significance was set at p < 0.05. Results MRONJ demarcation line was observed in 63 patients and absent in 32. Significant associations were identified between MRONJ demarcation line formation and denosumab ( p = 0.013), antiresorptive agent (ARA) discontinuation ( p = 0.024), and periosteal reaction ( p = 0.034). The cumulative incidence rates of MRONJ demarcation line formation at 12, 24, and 36 months after discontinuation of high-dose ARA were 58.0%, 89.2%, and 96.4% for denosumab, and 29.9%, 68.8%, and 88.3% for bisphosphonates, respectively. In the low-dose group, the rates at 12, 24, and 36 months after discontinuation of denosumab were 41.7%, 51.4%, and 63.5%, respectively, while those for bisphosphonates were 22.2%, 35.8%, and 51.1%. Conclusion Denosumab administration, ARA discontinuation, and periosteal reaction are significantly associated with the MRONJ demarcation line, which may help in establishing criteria for surgical intervention.
Tadokoro et al. (2026) studied this question.