Diagnostic Spectrum and Temporal Trends of Necrotic and Inflammatory Jawbone Lesions: A 22-Year Retrospective Study

Background/Objectives: Medication-related osteonecrosis of the jaw (MRONJ), osteoradionecrosis (ORN), and osteomyelitis exhibit overlapping histopathological features, making clinical context essential for etiological differentiation. This study aimed to evaluate the clinicopathological characteristics and temporal distribution of four diagnostic categories of necrotic and inflammatory jawbone lesions over a 22-year period. Methods: This retrospective, single-center study reviewed 25,133 oral and maxillofacial pathology reports from 2004 to 2025. A total of 650 patients were included and categorized using clinicopathological diagnoses and available medication history. Demographic, clinical, anatomical, and temporal characteristics were analyzed, and multivariable logistic regression was performed to identify factors associated with MRONJ. Results: MRONJ was the most frequent diagnosis (51.5%), followed by osteomyelitis (39.2%), ORN (4.9%), and sclerosing osteomyelitis (4.3%). The proportion of MRONJ increased from 24.7% in 2004–2010 to 61.7% in 2018–2025, whereas osteomyelitis declined from 58.1% to 30.0% (p < 0.001). Calendar year was associated with MRONJ classification in the linear regression model (adjusted odds ratio = 1.114; 95% CI: 1.079–1.149; p < 0.001), although sensitivity analyses indicated a nonlinear temporal association. Among MRONJ patients with documented underlying disease, 37.5% had osteoporosis. The number of recorded osteoporosis-associated MRONJ cases increased from 3 in 2004–2010 to 75 in 2018–2025. Conclusions: The distribution of recorded clinicopathological diagnoses of jawbone lesions has shifted substantially, with MRONJ becoming increasingly prominent, including among patients treated for osteoporosis. These findings highlight the importance of integrating biopsy findings with clinical history and medication exposure for etiological differentiation. Changes in diagnostic recognition, terminology, referral patterns, and biopsy practices may have influenced these trends, which do not establish changes in disease incidence.