Natural Resource-Derived Calcium Silicate Bioceramics for Bone Tissue Engineering

Bone is a complex tissue that provides the foundation for physical movement in humans, load-bearing capacity to the skeleton, biological elements necessary for hematopoiesis and protection from injuries to internal organs. It stores about 85% of the body's phosphorus and 99% of calcium and plays a vital role in maintaining homeostasis in the circulating body fluids [1]. Bone is divided into two types at the macro level: cortical and cancellous bones, which are characterized by different micro-level entities, and consequently have different functions and mechanical properties (Table 1.1). All the bones inside the body contain both cortical and cancellous bone types, but the distribution ratio varies based on the anatomical site [2]. Cortical bone is dense and solid with average density of 1.8 g/cm3 and possesses low porosity of around 2-13%, and is located in the very outer part of the tissue. The structural unit of the cortical bone is designated the osteon or haversian system in which the lamellae are organized into concentric circles of about 3 ?m thickness, surrounding a vertical haversian canal containing blood vessels and nerves (Fig.1.1 (a)). On the other hand, cancellous bone contains a sponge-like structure with interconnecting porosity of 50-90% and low density of around 0.2 g/cm3, and is located at the internal section of the bone. The cancellous bone is composed of honeycomb-like network of trabecular plates with large spaces, and the spaces between trabeculae are filled with bone marrow because of which there is light and porous bone that is strong against multidirectional forces and is crucial for initiating body movement