BACKGROUND
Dense bone island (DBI), also known as idiopathic osteosclerosis, is a localized intraosseous radiopacity of unknown etiology that is typically asymptomatic and incidentally detected. It most commonly occurs in the posterior mandible as a well-defined, homogeneous radiopaque lesion without cortical disruption or effects on adjacent structures. Its behavior in patients receiving antiresorptive therapy remains largely unexplored. Medication-related osteonecrosis of the jaw (MRONJ) is a recognized complication associated with antiresorptive agents, including denosumab and bisphosphonates. This case report describes a 70-year-old woman receiving long-term denosumab therapy for osteoporosis who developed MRONJ at the site of a pre-existing mandibular lesion provisionally diagnosed as a DBI and was evaluated using cone-beam computed tomography (CBCT).
CASE REPORT
A 70-year-old woman receiving long-term denosumab therapy for osteoporosis developed Stage 2 MRONJ at the site of a presumed pre-existing mandibular DBI. CBCT initially demonstrated a hyperdense lesion in the left posterior mandible. Four years later (at age 74), the patient presented with an intraoral fistula. Follow-up CBCT revealed a mixed osteolytic-osteosclerotic process at the same site, with mandibular canal involvement, and sequestrum formation. Surgical excision and histopathologic examination confirmed MRONJ.
CONCLUSIONS
This case highlights the value of longitudinal CBCT in documenting the radiographic evolution of MRONJ at the site of a previously identified lesion provisionally diagnosed as a DBI. However, the observed temporal and spatial association does not establish a causal relationship between the baseline lesion and subsequent development of MRONJ.

Keywords: Cone-Beam Computed Tomography; Denosumab; Osteonecrosis; Osteoporosis; Osteosclerosis