Biomaterial properties of octacalcium phosphate (OCP) and its collagen composite bone substitute

Octacalcium phosphate (OCP), a precursor to hydroxyapatite (HA), has recently garnered significant interest from biomaterial researchers both domestically and internationally because OCP has been confirmed to possess the capacity to activate bone-related cells, such as osteoblasts and osteoclasts, and to exhibit high osteogenic potential and bioresorbability if implanted in bone defects. Since OCP contains a large amount of water molecules in its structure, it cannot be sintered as a single crystal phase. Therefore, efforts have been paid to develop molding OCP through combining polymer materials, such as collagen (Col). OCP/Col has been approved in Japan for clinical application as a bone substitute material for combination uses with dental implants in the oral and maxillofacial surgery fields. The aim of this review is to summarize the process leading to the OCP/Col fabrication, as well as the clinical application of OCP/Col, focusing on these materials from chemical, physical, and biological perspectives as biomaterials.