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