## 4 Bone Grafts and Substitutes for Bone Repair
### Natural Bone Grafts and Substitute Materials
#### 4.1.1 Autografts  
Autografts are considered the \"gold standard\" among the different materials for bone augmentation [14; 15]. This status is due to their osteogenic character, which keeps bone cell structures from the harvesting site alive [16], but also to their osteoinductive properties which favor the differentiation of mesenchymal stem cells in osteoblasts due to their growth factors content [17; 18]. Having an identical origin with the affected tissue means that the \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Product (Commercial)** & **Company** & **Composition** & **Delivery Form** & **Properties** \\ \hline Xenograft & Bio-oss & Chemically and thermally treated cancellous bovine bone & small or large granules & Good mechanical support; osteoconduction facilitates the development of new blood vessels \\  & & & Amorphous calcium phosphate & Undergoes cell-mediated remodeling \\ Accufill & Zimmer & (ACP) and diaclcium phosphate & Syringe filled with flowable material & into natural bone; physical properties comparable to cancellous \\  & & & dihydrate (DCPD) & Springe filled with flowable material & Osteoconductive and osteointegrative properties \\ HydroSet & Stryker & Tetra-calcium phosphate (TeCP) & & \\  & & & & \\  & & & & \\ Vitoss & Stryker & Highly porous (up to 90\%) beta & Foam strips & scaffold for bone remodeling that \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\ \multicolumn{4}{l}{Citifuse} & ApaTech Ltd. & Silicate-substituted calcium & Granules & Osteoconductive/osteostimulative \\  & & & phosphate (Si-CaP) & Syringe filled with flowable material & silicate \\ Ceraform & \multicolumn{4}{l}{Teknimed} & Hydroxyapatite HA and beta & Granules & Osteoconductive \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\ \end{tabular}
\end{table} 
Table 1: Current major commercial products for bone repair. possibility of an unwanted immune rejection reaction is eliminated, achieving a success rate of over 95% [19; 20]. The most frequent harvesting site for autografts is the iliac crest; from this region, both cortical and spongious graft can be harvested, depending on the necessities. On the other hand, the obtained bone can be arranged to adapt as best as possible to the receiving site. The other sites are distal femur (especially for a spongious graft), the peroneal shaft for structural graft, ribs and distal radius. In dentistry, autologous augmentation materials are usually obtained from the same individual, such as the mandibular symphysis, mandibular branch and external oblique ridge, but also from other donor places such as the iliac crest or distal area of the ulna due to good cortical and spongious bone resources [21]. Autograft bone harvested from the mandibular branch presents low risks compared to other areas of the oral cavity. It must be taken into account that this harvest may endanger the inferior alveolar nerve. Tissue harvesting from the mandibular branch is suitable to use when the area of the receptor is less than 4 mm thick and extends to at most four teeth [22]. Even though there are also other augmentation materials commonly used to manage bone defects, block autologous grafts are still commonly used in more complex oral augmentation procedures, as very few other augmentation materials can produce a volume of new bone tissue similar to those obtained after the use of autografts. This is due to the fact that these autogenous bone blocks improve the repaired bone structure both in terms of volume and quality, favoring the use of implants with a larger diameter that facilitate the proper distribution of forces [23; 24; 25]. Moreover, in orthopedic treatments, autografts are considered the \"gold standard\". Cancellous autografts are the most frequently used as they bring to the receiving site mesenchymal stem cells which provide the capacity to stimulate the formation of new tissue in the affected area [26].