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Scaffolds having appropriate mechanical strength and providing a proper microenvironment for osteogenesis are expected to be effective alternatives to autografts for bone regeneration. In this study, ant-nest type porous (ANP) scaffolds consisting of CO 3 Ap were fabricated using calcium carbonate powder or slurry and two types of polyurethane foam through a dissolution-precipitation reaction. ANP-type, three-dimensional, interconnected porous CO 3 Ap scaffolds were fabricated by burning out the struts of polyurethane foams embedded in CaCO 3 , followed by compositional transformation from CaCO 3 to CO 3 Ap. The types of polyurethane foam and impregnation methods of CaCO 3 into polyurethane form affected the geometry of the resulting ANP structures. Mechanical and in vivo biological performances of these scaffolds relied on the geometry of the ANP structures. The ANP structures displayed had a clear structural advantage in bone regeneration, owing to the promotion of cell and tissue migration throughout the scaffolds. In particular, ANP-structured scaffolds, which had highest porosity, interconnectivity, and smallest strut thickness, had a mechanical strength comparable to cancellous bone, formed more new bone, were highly resorbed, resulting in cancellous bone-like bone tissue regeneration at 12 weeks of healing. The results suggest that bone regeneration after the migration of cell and tissue into the entire scaffolds is affected by strut thickness preferentially over porosity and interconnectivity. ANP-structured CO 3 Ap scaffolds are attractive for bone regeneration., (© 2023 Wiley Periodicals LLC.)

The composition of carbonate apatite (CO 3 Ap) aids bone regeneration. Other features, such as porosity and pore interconnectivity of artificial bone, also govern bone regeneration. In general, a trade-off exists between the porosity and mechanical strength of artificial bone. Therefore, this suggests that the interconnected pores in the ant-nest-type porous (ANP) structure of artificial bone accelerate bone regeneration by minimizing the sacrifice of mechanical strength. The unique structure of polyurethane foam has the potential to endow CO 3 Ap with an ANP structure without forming excess pores. This study investigated the efficacy of polyurethane foam as a porogen in providing ANP structure to CO 3 Ap artificial bone. The polyurethane foam was completely decomposed by sintering and the resulting CO 3 Ap displayed ANP structure with a compressive strength of approximately 15 MPa. Furthermore, in vivo experiments revealed that the migration of cells and tissues into the interior of CO 3 Ap through the interconnected pores accelerated bone regeneration in the ANP-structured CO 3 Ap. Thus, this indicates that using polyurethane foam as a porogen endows the CO 3 Ap artificial bone with an ANP structure that accelerates bone regeneration., (© 2022 Wiley Periodicals LLC.)