Radiographic changes of mandibular cortical bone in bisphosphonate drug holiday

Objectives: There have been few studies to date on the residual effect of bisphosphonate. This study investigated the radiographic changes of man-dibular cortical thickness upon bisphosphonate drug holiday.Materials and Methods: This retrospective study includes 36 patients diagnosed with MRONJ (medication-related osteonecrosis of the jaw) at Ajou University Dental Hospital in 2010-2021. All patients stopped taking bisphosphonate under consultation with the prescribing physicians. Panoramic ra-diographs were taken at the start of discontinuation (T0), 12 months after (T1), and 18 months after (T2) discontinuation of bisphosphonate, respectively. Mental index and panoramic mandibular index were calculated using Ledgerton's method. Paired t-tests were used to analyze differences over time.Results: The difference in indices (mental index and panoramic mandibular index) between T0 and T1 was not statistically significant (paired t-test, P>0.05). However, the difference in these indices between T1 and T2 was statistically significant (paired t-test, P<0.05).Conclusion: The cortical thickness of the mandible decreased in the late stage (after 18 months) as observed by panoramic radiograph.