Multiscale characterization of jawbone treated with osteoporosis therapeutic agents

The objective of the current study was to determine whether treatments of bisphosphonate (alendronate (ALN)), parathyroid hormone (PTH), and their combination have an effect on the jawbone in estrogen deficient rats. Six female rats (4-month-old) were used for each sham surgery (SHAM). Twenty-four rats (4-month-old) were ovariectomized and randomly assigned to four equal groups: saline injection (VEH), PTH following saline injection (VEH/PTH), bisphosphonate (ALN), or a combination (ALN/PTH). A hemimandible was randomly dissected from each rat for multiscale (10^-2 to 10^-7 m) characterization including static and dynamic mechanical stability of teeth in the alveolar socket, tissue mineral density distribution (TMD), and nanoindentation properties of the jawbone matrix. Most jawbone characteristics in OVX and its treatment groups were not significantly different from those of the SHAM group. The surface of alveolar bone (AB) surrounding teeth showed a trend of more erosion and addition of new bone tissues in the OVX rat groups compared to the SHAM group. All TMD parameters rapidly increased up to 60 μm from the periodontal ligament surrounding teeth regardless of the treatment groups. Treatments using each therapeutic agent and its combination did not substantially change those characteristics of jawbones in OVX rats. These findings are different from those of lumbar vertebrae in the same rats that showed a significant bone alteration by OVX and treatments. Thus, the current multiscale characterization of jawbone provides comprehensive information that can help better understand jawbone-specific responses to bone-related complications, including postmenopausal osteoporosis and bisphosphonate-related osteonecrosis of the jaw.