Antiresorptive drug-related changes of the mandibular bone densitiy in medication-related osteonecrosis of the jaw patients

Objectives: Medication-related osteonecrosis of the jaw (MRONJ) is a well known side-effect of anti-resorptive drugs. Changes in bone density might potentially constitute the development of ONJ. This study aimed to investigate, to which degree bisphosphonates (bp) and denosumab (db) induce changes in bone density that can be determined from routine diagnostic CT. Methods: CT scans of 101 patients were investigated. MRONJ was present in 61 patients (n = 26: db-treated; n = 35 bp-treated). 40 patients were included as a reference group. Bone density was measured at two distinct locations in the mandible (M1: anterior of the mental foramen; M2: retromolar), each on the contralateral side to the necrosis. Results: The bone density values measured at both locations were found to be significantly higher in the bp-group compared to the db-group (p = 0.027) and to the reference-group (p = 0.016). Almost no difference (p = 0.84) in bone density value was found between the db-and reference-groups. Investigating the effect of duration of treatment, none of the measured values showed significant differences in both locations of db- and bp-group. Conclusion: The findings from this study suggest that that bisphosphonates change the microarchitecture of the alveolar bone by being embedded in the mandible, which may subsequently lead to a bp-specific corticalization, and a decrease in vascularization of the lower jaw. This process may be distinctive for bp-treatment and seems to induce the congestion of cancellous bone rather rapidly after the first administrations. This effect could not be determined in denosumab-treated patients.