Biological Mechanisms of Bone Grafting - Bone grafting replaces missing bone to repair fractures - Small or acute fractures can heal without bone grafting - Large fractures like compound fractures require bone grafting - Bone grafts can be autologous, allograft, or synthetic - Most bone grafts are resorbed and replaced as natural bone heals - Osteoconduction supports tissue ingrowth for bone formation - Bone graft material serves as a scaffold for new bone growth - Osteoblasts from the margin of the defect utilize the graft material - Bioactive chemicals in implants promote osteoconductivity - Bone graft material should be osteoconductive - Osteoinduction stimulates osteoprogenitor cells to form new bone - Bone morphogenetic proteins (BMPs) are osteoinductive cell mediators - Osteoconductive and osteoinductive graft material promotes faster integration - Osteoinduction can be enhanced with enamel matrix derivative - Osteoinduction does not stimulate new bone growth alone - Osteopromotion enhances osteoinduction without being osteoinductive - Enamel matrix derivative enhances osteoinductive effect of bone grafts - Osteopromotion does not stimulate new bone growth alone - Osteopromotion can be used in combination with other graft materials - Osteopromotion improves the effectiveness of bone grafting - Osteogenesis occurs when osteoblasts from graft material contribute to new bone growth - Autograft tissue and allograft cellular bone matrices support osteogenesis - Osteogenesis is one of the mechanisms involved in successful bone grafts - Osteogenesis contributes to bone remodeling - Osteogenesis does not occur with synthetic graft materials

Types of Bone Allografts - Fresh or fresh-frozen bone - Freeze-dried bone allograft (FDBA) - Demineralised freeze-dried bone allograft (DFDBA) - Hydroxyapatite-based synthetic grafts - Calcifying marine algae-based synthetic grafts

Alloplastic Grafts - Hydroxyapatite-based synthetic grafts - Bioactive glass-based synthetic grafts - Polymers like PMMA and PHEMA used as alloplastic grafts - Alloplastic grafts coated with calcium hydroxide for adhesion - Fluoro-hydroxy-apatitic (FHA) biomaterial alloplastic bone grafts

Synthetic Variants - Flexible hydrogel-HA composite with mineral-to-organic matrix ratio similar to human bone - Ceramics like hydroxyapatite, tricalcium phosphate, and Bioglass used as synthetic grafts - Doped synthetic grafts with growth factors and ions like strontium - Synthetic grafts mixed with bone marrow aspirate to increase biological activity - Similar mechanical properties to bone with lower risk of infection and rejection

Xenografts - Bone xenografts involve transplanting animal species cells into humans - Derived from bovine sources like cows or pigs - Sterilised and processed for safe implantation into human tissue - Can be freeze-dried or demineralised and deproteinised - Coral-based xenografts made from calcium carbonate or transformed into hydroxyapatite