been the gold standard of bone replacement for long time [36, 37]. Also, this is the
safest transplant because of the compatibility of the grafts and, therefore, the chance
of rejection is negligible. However, there are a few limitations in various clinical
situations, i.e., (a) insufficient amount of grafts when dealing with large bone
defects, (b) donor site morbidity, (c) complexity in making the required shape,
(d) complications in wound healing, and (e) extra surgery.
2.5.2 Allografts
This is another method for bone grafting, whereby tissue is transplanted between
genetically non-identical members of the same species. In 1908, the first clinical
use of an allograft was carried out by Lexer [38]. Generally, cancellous, cortical, or
both in combination can be used as allograft materials. Cadaver’s bones, which are
generally frozen or freeze-dried, can be stocked in the bone banks. However, their
strength is less after sterilization and they are not resorbed completely after
implantation. As a result, they often remain as dead tissue that gradually becomes
fragile and can cause medical complications with neighboring tissues. Allografting
eliminates harvesting a surgical site, post-operative pain, and the expense of
additional surgery. However, allografts are always associated with disease transmission such as hepatitis B, hepatitis C, immune deficiency syndrome (AIDS), and
lower effectiveness because of the cleansing and disinfecting process during which
the bone growth cells and proteins are removed [39, 40]. These restrict its
applications. However, in the case of a large bone defect or when the defect is
not repairable by autografting because of insufficiency of the graft materials, this
method has particular importance.
2.5.3 Xenografts
Xenografting is a method of transplanting tissue between members of different
species; bone from animal to human, for example. Xenografting comes from the
Greek word xenos, which means strange. In the early 1960s, bone
transplantations were mainly performed by xenografts. The bone banks usually
stock a plentiful quantity of graft materials because of their simple harvesting
compared to bone from humans. Currently, multiple xenografts are being
processed, such as frozen calf bone, freeze-dried calf bone, decalcified ox
bone, and deproteinized bovine bone [41]. A commercially available xenografts
is kiel bone, which comprises deproteinized bone from freshly sacrificed calves
[42]. Unlike autografting or allografting, xenografting is not very successful,
mainly because of the risk of antigenicity. However, organ scarcity has
encouraged continued research in this field.
Hydroxyapatite-Packed Chitosan-PMMA Nanocomposite: A Promising Material for. . .
145
safest transplant because of the compatibility of the grafts and, therefore, the chance
of rejection is negligible. However, there are a few limitations in various clinical
situations, i.e., (a) insufficient amount of grafts when dealing with large bone
defects, (b) donor site morbidity, (c) complexity in making the required shape,
(d) complications in wound healing, and (e) extra surgery.
2.5.2 Allografts
This is another method for bone grafting, whereby tissue is transplanted between
genetically non-identical members of the same species. In 1908, the first clinical
use of an allograft was carried out by Lexer [38]. Generally, cancellous, cortical, or
both in combination can be used as allograft materials. Cadaver’s bones, which are
generally frozen or freeze-dried, can be stocked in the bone banks. However, their
strength is less after sterilization and they are not resorbed completely after
implantation. As a result, they often remain as dead tissue that gradually becomes
fragile and can cause medical complications with neighboring tissues. Allografting
eliminates harvesting a surgical site, post-operative pain, and the expense of
additional surgery. However, allografts are always associated with disease transmission such as hepatitis B, hepatitis C, immune deficiency syndrome (AIDS), and
lower effectiveness because of the cleansing and disinfecting process during which
the bone growth cells and proteins are removed [39, 40]. These restrict its
applications. However, in the case of a large bone defect or when the defect is
not repairable by autografting because of insufficiency of the graft materials, this
method has particular importance.
2.5.3 Xenografts
Xenografting is a method of transplanting tissue between members of different
species; bone from animal to human, for example. Xenografting comes from the
Greek word xenos, which means strange. In the early 1960s, bone
transplantations were mainly performed by xenografts. The bone banks usually
stock a plentiful quantity of graft materials because of their simple harvesting
compared to bone from humans. Currently, multiple xenografts are being
processed, such as frozen calf bone, freeze-dried calf bone, decalcified ox
bone, and deproteinized bovine bone [41]. A commercially available xenografts
is kiel bone, which comprises deproteinized bone from freshly sacrificed calves
[42]. Unlike autografting or allografting, xenografting is not very successful,
mainly because of the risk of antigenicity. However, organ scarcity has
encouraged continued research in this field.
Hydroxyapatite-Packed Chitosan-PMMA Nanocomposite: A Promising Material for. . .
145