**2. History of bone graft**

 First bone graft was allograft from dog to human in 1682. While xeno-or allograft of bone was a major in the Western countries during the Middle Ages, human bone autograft was noted first in 1820, Italy. The use of bovine-demineralized bone matrix (DBM) was reported first in 1889. The xenogenic DBM was grafted into human skeletal defects caused by osteomyelitis. Many DBM papers were published in the twentieth century [18]. Generally, fresh autogenous bone remains the gold standard of treatment for nonunion and large bone defects [19].

**Figure 1.**  *Types of dentin materials.* 

However, cortical bone block inhibits the invasion of cells and blood vessels, because the calcified structure is highly dense like a castle wall [20].
