Fabrication and histological evaluation of ant-nest type porous carbonate apatite artificial bone using polyurethane foam as a porogen

The composition of carbonate apatite (CO₃Ap) 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 CO₃Ap with an ANP structure without forming excess pores. This study investigated the efficacy of polyurethane foam as a porogen in providing ANP structure to CO₃Ap artificial bone. The polyurethane foam was completely decomposed by sintering and the resulting CO₃Ap 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 CO₃Ap through the interconnected pores accelerated bone regeneration in the ANP-structured CO₃Ap. Thus, this indicates that using polyurethane foam as a porogen endows the CO₃Ap artificial bone with an ANP structure that accelerates bone regeneration.