Ridge Preservation with an Octacalcium Phosphate Collagen Complex (OCP/Col) Promotes New Bone Formation and Type H Vessel Distribution with Osterix Expression in Extraction Sockets in Mice

Purpose Alveolar bone resorption after tooth extraction leads to gingival recession and invagination, which may result in the stalling of tooth movement and difficulties in orthodontic tooth movement. Bone substitutes used for alveolar ridge preservation should exhibit bioaffinity, appropriate initial calcification, ease of handling, replacement by bone, long-term stability, and formation of an abundant vascular network. Therefore, this study focused on ridge preservation (RP) using an octacalcium phosphate collagen composite (OCP/Col). Type H vessels are known to appear at sites of active bone formation, and osteoblast markers are observed in their vicinity, creating a microenvironment conducive to osteogenesis. The objective of this study was to investigate the distribution of newly formed bone and Type H vessels in extraction sockets following ridge preservation with OCP/Col, as well as the expression of Osterix. Methods RP of the lower first molars in mice was performed using OCP/Col. Bone mass, bone quality, and angiogenesis were analyzed by micro-computed tomography, bone morphometry, and histological and fluorescence immunohistochemical staining. Results In RP with OCP/Col, the granularity of the bone substitute tended not to be preserved, and immature woven bone formation was observed, which prevented alveolar bone resorption. A microcapillary vascular network including Type H vessels was formed, and osteoblast markers were induced in the surrounding area, promoting new bone formation. Conclusions These findings suggest that RP with OCP/Col promotes early new bone formation associated with Type H vessels and may be beneficial for orthodontic treatment.