*5.2.1 Ceramic-based bone grafts*

 Ceramic-based grafts are ionically bonded inorganic preparations, which can be described as a family of materials with a wide variety of composition, porosity, manufacturing, and structure. Calcium sulfate, hydroxyapatite, tricalcium phosphate, bioactive glasses (silicon dioxide, calcium oxide, phosphorous pentoxide, and sodium oxide), and synthetic hydroxyapatite come under this category. Not only this group of materials varies in terms of material properties, but also differs in biodegradability, mechanistic strength, and binding. Glass ionomers have been used to seal defects in the skull, sinus augmentations, and otorhinolaryngologic surgeons for auditory ossicular reconstructions [56]. They are also used for the application of orbital implants, ossicular replacements, and prosthetic joint linings [57]. Calcium phosphate does not show any osteogenic properties; however, this material is used with the combination of hydroxyapatite and tricalcium phosphate and calcium carbonate and monocalcium phosphate monohydrate. This mixture is used as an injectable into the bone defect site, to harden. This product undergoes long-term remodeling, and the graft is eventually replaced with the in-growth of new bone [58, 59]. Hydroxyapatite-based materials are used for coat implants because of their great osteo-integrative capabilities [60, 61].

Over all, ceramic-based bone grafts are specifically found useful in iliac crest bone grafting and as a bone graft extender in lumbar spine fusion procedures [62]. The special feature of ceramic-based graft is their porosity, which is helpful in adhesion of mesenchymal cells, and later gets differentiated into osteoblasts. Further, this group of grafts is superior as the benefits of its different constituents can be availed simultaneously leading to better bone regeneration [63]. Some of the commercially available synthetic bone graft substitutes are mentioned in **Table 3**.
