Abstract
<title>Abstract</title> <p>Background Alveolar ridge preservation (RP) is performed to reduce post-extraction alveolar bone resorption and support bone regeneration. Octacalcium phosphate collagen complex (OCP/Col) has osteoconductive potential; however, its effects on early vascular and osteogenic responses during extraction socket healing remain incompletely understood. This study investigated early bone formation, CD31/endomucin double-positive vessel distribution, and Osterix expression following RP with OCP/Col in mouse extraction sockets. Methods RP was performed after extraction of the lower first molars in C57BL/6J mice using OCP/Col, β-tricalcium phosphate (β-TCP), or Bio-Oss. Extraction-only sockets served as controls. Samples were collected on Days 1, 4, 7, and 14. Micro-computed tomography, bone morphometric analysis, histological assessment, and fluorescence immunohistochemistry were used to evaluate bone formation, CD31/endomucin double-positive vascular signals, and Osterix-positive cells. Results RP reduced alveolar bone resorption compared with extraction alone. On Day 14, bone volume/tissue volume and trabecular thickness were significantly greater in the OCP/Col group than in the other groups. Residual granules persisted in the Bio-Oss and β-TCP groups, whereas OCP/Col was associated with extensive new bone formation. CD31/endomucin double-positive vascular signals were observed throughout the healing period and were significantly more abundant in the OCP/Col group. Osterix-positive cells were frequently observed adjacent to these vascular structures and newly formed bone. Conclusions RP with OCP/Col was associated with reduced alveolar bone resorption, enhanced early bone formation, increased CD31/endomucin double-positive vascular signals, and Osterix-positive cells in mouse extraction sockets. These findings suggest that OCP/Col may provide a favorable microenvironment for early bone regeneration during extraction socket healing.</p>