Heterogeneity of Bone Mineral Density in Osteonecrosis of the Jaw

Objectives: Radiopaque and radiolucent regions in severe medication-related osteonecrosis of the jaw (MRONJ) likely visualize abnormal bone mineral density (BMD). The objective of this study was to examine whether detailed BMD distribution in the disease regions is different from normal regions of bone in the human jaw.
Methods: After IRB approval, 4 oral bone regions were resected from 3 patients (1 male, 68 yrs, and 2 females, 57 and 70 yrs) during surgery to treat MRONJ. These bone specimens were scanned by micro-computed tomography (µCT) with 20 micron resolution. 6 radiopaque and 10 radiolucent local bone sites were identified and a 4 mm³ cube was digitally isolated from each site. As a normal group, mandibular basal cortical bones obtained from 10 human cadavers (7 males and 3 females, 60 to 94 yrs) were scanned using the µCT. Gray value distribution, which is proportional to BMD distribution, was analyzed to obtain mean and standard deviation (SD). Multivariate analysis of variance was performed to compare the gray value parameters between the bone site groups (significant, p<0.05).
Results: The diseased radiolucent bone site had a significantly lower mean gray value than the diseased radiopaque and normal bone sites (p<0.001), while the radiopaque bone site did not have significantly different mean gray value from the normal bone site (p=0.234). The SD of the normal bone site was significantly lower than both disease bone sites (p<0.001) and the radiopaque bone sites had significantly higher mean value of SD values than the radiolucent bone sites (p=0.001).
Conclusions: The current findings indicated that abnormal bone mineralization in the disease bone sites increase heterogeneity (SD) of BMD. These results suggest that the disease bone sites can be distinguished from normal bone sites by the SD of BMD.