Objective: To determine the synergistic effect of parathyroid hormone (PTH) [1–34] in combination with hyperbaric oxygen (HBO) on bone graft in a rat calvarial bone defect model under impaired osteogenic conditions. Materials and Methods: Twenty-four rats were divided into three groups. Localized radiation with a single 12 Gy dose was administered to the calvaria. Four weeks after radiation, calvarial circular defects were created in the parietal bones. All defects were filled with biphasic calcium phosphate. After the bone graft, PTH [1–34] was injected subcutaneously, and HBO was administered. At 6 weeks after the bone graft, the rats were sacrificed, and specimens were harvested. Results: Histomorphometric evaluation showed that the percentage of new bone area was higher in the PTH and PTH/HBO groups than in the control group. The percent residual material area was decreased in the PTH/HBO group compared with the control group. The percentage blood vessel number was highest in the PTH group. Micro-CT evaluation showed that the new bone volume was highest in the PTH/HBO group. The residual material volume was lowest in the PTH/HBO group. Conclusion: Within the limitations of this study, our data indicate that PTH combined with HBO may reverse radiation-induced impairment of bone healing.
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