Bone grafting is the major challenge the modern world is facing, the allografts have limitations including the immunogenic response of the host to foreign tissues and potential disease transmission. To avoid these limitations, natural coral graft substitutes are evaluated. Corals belong to phylum Cnidaria a marine invertebrate, classified into soft corals and hard corals. Coral reefs are primarily composed of the shells of aragonite and crystalline forms of CaCO3. The shells are secreted by the corals that maintain symbiotic association with tiny algae known as Zooxanthellae. These algae live on the coral’s surface and provide them with their vibrant color.
The structure of the coral skeleton and human bones are similar. However, researches revealed that coral skeletons are made of Calcium Carbonite which break down before new bone grows on it. The biodegradable property of coral helps in the growth of bone and structural support. Scientists are working to explore more about the chemistry of coral skeletons so they might find the solution of using coral in human bone grafts. Coral bone is the natural substitute to the current synthetic bone grafts that can provide a better biological safety profile. The coral skeleton is heated to convert CaCO3 into hydroxyapatite which is the main element in bone. The transformation to hydroxyapatite lessens the resorption of grafts and makes it a permanent implant. They are similar to cancellous bone due to their highly porous structure. Raw coralline grafts are resorbed by the host because they are brittle and lack mechanical strength. The rate of biodegradable coral is variable depending on the porosity of the exoskeleton.
Coral grafts work like an adequate carrier for the growth of broken bones as they allow cells attachment when applied appropriately. It depends on the alignment of the rate of resorption of the coral exoskeleton with the bone formation rate of the implantation site, thus, the natural exoskeleton is the best bone graft substitute.
