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

The composition of carbonate apatite (CO 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 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 Ap artificial bone. The polyurethane foam was completely decomposed by sintering and the resulting CO 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 Ap through the interconnected pores accelerated bone regeneration in the ANP-structured CO Ap. Thus, this indicates that using polyurethane foam as a porogen endows the CO Ap artificial bone with an ANP structure that accelerates bone regeneration.