Alveolar bone defects were classified according to their morphology and pattern of bone loss into Class I where buccolingual loss occurs while maintaining the vertical height( Horizontal defect), Class II where vertical bone loss occurs with no buccolingual width loss (Vertical defect) and Class III where combination of vertical and horizontal bone loss occurs . These defects require augmentation before implant placement, several techniques were approached including autogenous and non autogenous bone grafting , Guided bone regeneration (GBR), ridge splitting and distraction osteogenesis. Bone grafts used with these techniques are categorized into : autografts, allografts , xenografts and alloplasts.~Autogenous bone is considered to be the gold standard in grafting because it is osteogenic in nature, osteoinductive , osteoconductive and immunologically safe The autogenous bone can be harvested intraorally from the chin area, mandibular ramus, retromolar area, maxillary tuberosity, Coronoid process, zygomatic bone or palatal and mandibular tori if present . Intraoral harvesting has the advantage of good access and no need for hospitalization but the main disadvantage is the donor site morbidity and the small amount of harvested bone. Extraoral harvesting sites include the ilium, calvarium, ribs, tibia and fibula. Extraoral harvesting solved the problem of the limited amount of harvested bone graft but the main disadvantages are the need of hospitalization, performing the harvesting procedure under general anesthesia and high morbidity due to the second surgical site Recently, tissue engineering has been used for bone regeneration so called bone tissue engineering (BTE) which aims to combine the progenitor cells to differentiate into osteoblasts, growth factors needed for regenerative process and osteoconductive scaffolds for therapeutic applications. BTE involves harvesting osteogenic cells from an autologous harvesting site ( bone marrow or adipose tissue) and/or ex vivo amplification and seeding the scaffold with cells for in vivo implantation aiming to replicate the properties of autogenous bone and decrease the need for invasive harvesting Bone marrow contains a heterogenous population of progenitor cells such as Mesenchymal stem cells (MSC),hematopoietic stem cells (HSC) and endothelial progenitor cells in addition to several growth factors, including platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF-b), and bone morphogenetic protein (BMP)-2 and BMP-7, which are known to have anabolic and anti-inflammatory effects. Concentration of the mononuclear cell fraction (MNC) of bone marrow aspirate ( which includes MSCs) by density gradient centrifugation process to remove erythrocytes, granulocytes, platelets and immature myeloid precursors to form Bone Marrow Aspirate Concentrate (BMAC) is considered important step in BTE. .~Many clinical studies proved the use of Bone Marrow Aspirate Concentrate for treatment of osseous defects and cartilage defects due to the ability of MSCs to differentiate into osteoblasts, chondroblasts or adipocytes.~The mesenchymal stem cells (MSCs) are highly biologically competent as they possess the ability to adhere on plastic (scaffolds) in vitro, form colony forming fibroblasts (CFU) and differentiate into mesenchyme lineages ( adipocytes, osteocytes, chondrocytes, tenocytes, myocytes) in addition to their potential of self renewal and promotion of hematopoiesis. Also, they suppress alloresponse after transplantation .~Scaffolds are support structures used in tissue engineering to allow 3D growth of cells in an organized way and can be classified into natural (such as collagen plug) , synthetic aliphatic polyesters such as polycaprolactone (PCL), polyglycolic acid (PGA) and polylactic acid (PLA) and their copolymers and derivatives and composite scaffold which are made by combining bioceramics with polymers or xenogenic biomaterials together with bioceramics or polymers .
BMAC is used on 3D printed PCL scaffold for horizontal ridge augmentation in aesthetic zone , BMAC contains MSCs which can differentiate in osteogenic medium into osteoblasts which can lay down bone