**3. Allografts**

Bone transfers are genetic characteristics made between different individuals. The first literature report was made by MacKewen [39]. Allografts; porous structures contain many chemical domains that are retained by progenitor cells and endothelial cells. They also contain growth factors in the bone matrix that are released when resorbed by osteoclasts. The allograft bone also contains a small amount of bone morphogenic protein with osteoinductive properties.

Demineralization increases the bioavailability of growth factors in the allograft bone matrix. In addition, demineralization prevents HIV infection [40].

In the early allograft use, the graft cells were completely destroyed and the skeleton of the bone roof served as a scaffold. Fresh bone allografts result in both humoral and cellular immunological responses, which allow the graft to be recognized by the recipient. Antibody production results in cell lysis and vascular destruction resulting in graft rejection. The frequency of allograft rejection depends on the degree of antigen mismatch between the graft and the recipient. Vascularized bone allograft rejection is seen on postoperative third day. The first affected members have been shown to be osteocytes and vascular endothelium [41]. Rejection can be suppressed by the use of cyclosporine. Every allograft causes an immunological reaction in the recipient.

The alignment of allografts is different than that of autografts. Both vascular invasion and perivascular new bone formation are slower. This adaptation also affects the size of the graft, the level of immunological response to the graft and the conditions under which allograft is stored [12].

The immunological response to allografts results in the sensitization of the recipient to histocompatibility antigens in osteogenic and hematopoietic cells, leukocytes, blood vessels, nerves and connective tissue matrices within the graft. Therefore, this is a secondary immunological response. This is a cellular immune response [42]. Herndon et al. allografts have found widespread use, demonstrating that the immune response with frozen allografts decreases. Attention has shifted to allograft preservation techniques [43].

If allografts are separated from their cells, they are prevented by immunological reactions. The bones obtained from cadavers are used as osteoconductive skeleton by decellularization [19]. Thus, the disease is prevented from passing between people. Among the processes used are irradiation, debridements, ultrasonic washing, liquid nitrogen, ethylene oxide and deep freezing. Allografts are prepared and maintained in tissue banks.

Frozen-dried bones are poorly immunogenic to both the humoral and cellular immune system. However, passing the bone through these processes destroys osteoinductivity when changing mechanical properties [44]. Bone banks were needed for the use and development of these methods and bone banks were established in many parts of the world.

## **3.1. Bone banks**

*2.4.4. Nonvascularized autografts of radius, trochanter major and olecranon*

34 Bone Grafting - Recent Advances with Special References to Cranio-Maxillofacial Surgery

ferred in situations where the iliac crest is unavailable.

In addition, demineralization prevents HIV infection [40].

Attention has shifted to allograft preservation techniques [43].

*2.4.5. Bone marrow*

**3. Allografts**

used immediately after aspiration.

logical reaction in the recipient.

stored [12].

Cortical and cancellous bone needs are not among the preferred donor sites. They are pre-

Bone marrow can be used alone as an osteogenic graft. Bone marrow obtained after aspiration; cytokines, osteoblastic progenitors such as other bone marrow-derived cells, and a rapidly revascularized absorbable biological fibrin matrix. An average of 1400 connective tissue progenitors was found in the iliac crest aspirated bone marrow [38]. Bone marrow should be

Bone transfers are genetic characteristics made between different individuals. The first literature report was made by MacKewen [39]. Allografts; porous structures contain many chemical domains that are retained by progenitor cells and endothelial cells. They also contain growth factors in the bone matrix that are released when resorbed by osteoclasts. The allograft bone also contains a small amount of bone morphogenic protein with osteoinductive properties.

Demineralization increases the bioavailability of growth factors in the allograft bone matrix.

In the early allograft use, the graft cells were completely destroyed and the skeleton of the bone roof served as a scaffold. Fresh bone allografts result in both humoral and cellular immunological responses, which allow the graft to be recognized by the recipient. Antibody production results in cell lysis and vascular destruction resulting in graft rejection. The frequency of allograft rejection depends on the degree of antigen mismatch between the graft and the recipient. Vascularized bone allograft rejection is seen on postoperative third day. The first affected members have been shown to be osteocytes and vascular endothelium [41]. Rejection can be suppressed by the use of cyclosporine. Every allograft causes an immuno-

The alignment of allografts is different than that of autografts. Both vascular invasion and perivascular new bone formation are slower. This adaptation also affects the size of the graft, the level of immunological response to the graft and the conditions under which allograft is

The immunological response to allografts results in the sensitization of the recipient to histocompatibility antigens in osteogenic and hematopoietic cells, leukocytes, blood vessels, nerves and connective tissue matrices within the graft. Therefore, this is a secondary immunological response. This is a cellular immune response [42]. Herndon et al. allografts have found widespread use, demonstrating that the immune response with frozen allografts decreases. The preferred age range for choosing donors for bone banks is from 16 to 65 [45]. Donors; acute or fatal chronic infection, malignancy, exposure to radiation in the area to be caught, venereal disease, hepatitis, slow virus diseases, AIDS or HIV infection, drug use, steroid use for more than 1 week, diffuse osteoporosis, immune complex disease, connective tissue disorders and long-term insulin-dependent diabetes should not have an anamnesis such as grafting with live virus vaccine in the near future [46, 47]. Donors can live in cadaver. Live donors require adequate physical examination and a good anamnesis, and a detailed autopsy is required for cadavers.

#### **3.2. Demineralize bone matrix**

Demineralized bone matrix (DBM) is used to fill bone defects and voids as an osteoconductive and osteoinductive material. DBM is rapidly re-vascularized and is also a good carrier for autologous bone marrow. There are differences between tissue banks and firms according to DBM acquisition phases [22]. Studies have shown that DBM results in long bone pseudoarthroses and bone loss similar to autologous bone grafts [48]. DBM can be used by mixing with cancellous graft to increase and intensify autologous bone graft when bone loss is large. It can also be considered as an alternative in patients who cannot use autologous bone graft [22].

#### **3.3. Morselized and cancellous allografts**

They are osteoconductive. They provide mechanical support against compression. They are prepared by freeze-drying (lyophilization) and vacuum packaging. It can be used to fill cavities formed after curettage in bone cysts and to remove bone surfaces in periarticular metaphyseal fractures.

#### **3.4. Osteochondral and cortical allografts**

They are obtained from the pelvis, costume, femur, tibia and fibula and used in major bone and joint loss. They also provide both structural and mechanical support for the treatment of periprosthetic fractures. They carry osteoconductive properties.
