Medication-related osteonecrosis of the jaw (MRONJ) is a known complication of antiresorptive therapies such as bisphosphonates and denosumab. It can lead to bone damage in the jaw, with variable clinical outcomes depending on disease stage and management.

Cone Beam Computed Tomography (CBCT) is currently recommended for diagnosis and follow-up of MRONJ. However, most studies rely on qualitative or descriptive imaging findings, and little is known about how bone quality evolves over time using quantitative imaging parameters.

This retrospective multicenter study aims to describe the evolution of bone quality in patients with MRONJ using CBCT imaging. Bone parameters such as bone mineral density and trabecular structure will be measured at diagnosis and during follow-up.

The study will help improve understanding of bone changes over time in MRONJ and may contribute to better assessment and management of the disease.

Medication-related osteonecrosis of the jaw (MRONJ) is a serious adverse effect associated with antiresorptive therapies, including bisphosphonates and anti-RANKL monoclonal antibodies. It is characterized by necrotic bone lesions of the jaw, often triggered by dental procedures, and is associated with significant morbidity.

Current imaging evaluation relies primarily on Cone Beam Computed Tomography (CBCT), which is recommended for both diagnosis and follow-up. However, most published studies provide only qualitative or descriptive assessments of bone lesions. Quantitative and longitudinal analyses of bone microarchitecture remain limited.

This retrospective, multicenter, observational study aims to describe the evolution of bone quality in patients with MRONJ managed according to current clinical guidelines.

The primary objective is to evaluate changes in bone mineral density (BMD) measured on CBCT scans at diagnosis and during follow-up.

Secondary objectives include longitudinal assessment of bone morphometric parameters using CBCT imaging and dedicated software (3D Slicer), including:

Bone volume to total volume ratio (BV/TV) Trabecular number (Tb.N) Trabecular separation (Tb.Sp) Hounsfield units (HU), when applicable

Data will be collected retrospectively from clinical records and imaging databases across multiple centers. All data will be pseudonymized prior to analysis.

Statistical analyses will be descriptive. Quantitative variables will be expressed as mean ± standard deviation or median with interquartile range, depending on distribution. Qualitative variables will be presented as frequencies and percentages. Comparisons between subgroups may be performed using appropriate statistical tests (Chi-square or Fisher's exact test for categorical variables, Student's t-test or Mann-Whitney test for continuous variables), with a significance level set at p < 0.05.

The study is conducted in accordance with applicable data protection regulations (MR-004 framework), with minimal risk to participants, as it involves retrospective analysis of existing clinical and imaging data.

Inclusion Criteria:

• Adult patient aged 18 years or older
• Diagnosis of medication-related osteonecrosis of the jaw (MRONJ), stage 0, 1, or 2
• Available diagnostic CBCT and at least 2 follow-up cone beam computed tomography (CBCT) examinations
• Able to understand the study information and not opposed to participation

Exclusion Criteria:

• Other jaw bone disease
• History of cervicofacial irradiation
• Stage 3 medication-related osteonecrosis of the jaw
• Fewer than 2 follow-up cone beam computed tomography (CBCT) examinations

Adult patients with medication-related osteonecrosis of the jaw identified retrospectively from clinical and imaging records at participating French hospital centers, including CHU de Nantes, Centre Léon Bérard, CHU de Nancy/Centre Oscar Lambret, and AP-HP Pitié-Salpêtrière.