Morphological changes and vascular regeneration in tooth extraction sockets after carbonate apatite granule grafting, as assessed using a microvascular resin casting technique

To evaluate the effects of carbonate apatite (CO₃Ap) grafts in premolar extraction sockets of beagle dogs by analyzing the time-dependent morphological patterns of bone regeneration in relation to vascularization. We prepared microvascular resin cast specimens of extraction sockets and performed scanning electron microscopy to assess morphological changes in bone height and bone regeneration. Specimens were obtained on postoperative days 14, 30, and 90, and CO₃Ap-grafted sites were compared with non-grafted controls at each time point. On postoperative day 14, the sockets of the control group were filled with blood clots, whereas those of the CO₃Ap group were filled with granules, which served as a support for angiogenesis and bone regeneration, leading to an elevation of the alveolar ridge. On day 30, new bone accompanied by vascular regeneration formed in both groups, but in the control group, the height of the alveolar ridge continued to decrease. On day 90, the control group still did not show recovery of bone height, whereas the CO₃Ap group exhibited compact lamellar bone including bone marrow cavities and organized microcirculation, demonstrating superior structural and vascular regenerative capacity compared with the control group. This study demonstrates that CO₃Ap as a bone graft material maintains alveolar crest height after tooth extraction and facilitates well-organized vascularization-driven bone formation. These findings suggest CO₃Ap as a useful graft that can help compensate for the limitations of other bone substitutes in alveolar reconstruction.