Effect of Zoledronic Acid on Bone Structure of the Mandible in Ovariectomized Mice

: The objective of this study was to determine the effect of zoledronic acid on mandibular bone quality in osteo porotic model mice. Zoledronic acid was administered to ovariectomized mice, and mandibular bone was harvested. Pol ished specimens were prepared, and the biological apatite (BAp) crystal alignment and changes in collagen fiber bundles in the alveolar and basal regions of the mandible were analyzed. It was found that ovariectomy increased BAp crystal align -ment. The administration of zoledronic acid post-ovariectomy normalized BAp crystal alignment in the basal region of the mandible. However, BAp crystal alignment in the alveolar region decreased significantly. Ovariectomy decreased the diam eters of collagen fiber bundles in both the alveolar and basal regions and significantly increased their lengths. The adminis tration of zoledronic acid post-ovariectomy decreased both the diameters and lengths of collagen fiber bundles. These re sults showed that the microarchitecture of the mandibular bone changes to compensate for osteoporosis-induced loss of bone mass and adapts to the load environment resulting from mastication. Interestingly, they suggested that zoledronic acid severely reduces the bone quality of osteoporotic alveolar bone in a site-specific manner.