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Bone healing and bio-engineered
bone grafts:
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One of the highest concentrations
of TGF in the body is found within blood platelets. The
TGF is a so-called "super family" of growth
factors containing specific Bone Morph genetic Proteins
(BMP). When TGF is released by platelet degranulation,
they represent a growth factor mechanism that not only
initiate bone regeneration, but also can sustain long-term
healing. |
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With plasma sequestration
the patients' platelets become concentrated, and therefore
increase the concentration of these growth factors (TGF)
in the graft manifold, thereby improving the likelihood
of more successful and faster healing of the grafts and
tissue. |
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Currently, when bone
is needed to restore or reconstruct an area where there
is a bony deficit or bone growth is desired (spinal fusions),
grafting procedures are utilized with several different
materials. The "gold standard" is still considered
to be bone taken from the patient being treated (an autogenous
bone graft). However, associated with the harvesting of
autogenous bone might be the disadvantage of a second
surgical site, with its attendant morbidities (pain, interference
with function, risk of infection, etc.), and a limited
amount of tissue available. In an attempt to decrease
the morbidity associated with harvesting bone from the
patient, substitute materials could be considered, either
as the sole material, or in combination with autogenous
bone, to decrease the amount of bone that must be harvested. |
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Bone regeneration may occur
in several ways as a result of bone grafting: |
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The
first is by osteogenesis, which occurs when autogenous
bone is used. During osteogenesis, bone-forming cells
and growth factors, derived from living cells that survive
the transfer of the bone graft itself, occurs directly
from bone. |
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The
second is by osteo-induction. Osteo-induction occurs
when a bone graft material is used which induces cells
from the surrounding host tissues to invade the graft
to form bone. The graft material recruits from the surrounding
bed of messenchymal-type cells, which then differentiate
into bone-forming cells. Osteo-induction is mediated by
graft-derived factors; chemicals (growth factors) in the
graft material which induce or influence the differentiation
of these messenchymal cells into bone-forming cells. It
is believed that demineralized bone (allografts) are osteo-inductive
as a result of growth factors in the graft becoming exposed
by the demineralization process. These growth factors
then interact with, and stimulate messenchymal-type, cells
to form bone. |
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The
third way is by a process osteo-conduction. With
osteo-conduction, the graft material just acts as a trellis,
or scaffold, on which new bone, derived from the host
tissue, can be formed. The graft material allows for the
in growth of new host bone from the recipient bed into
the structure of the graft, but nothing more. Most mineralized
bone allografts are osteo-conductive; however, if growth
factors are added to these osteo-conductive grafts, they
may become osteo-indictive as well. |
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The successful healing
of a bone graft is dependent upon: |
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The biological
activity of the living cells in the graft itself
(if any), and in the surrounding host tissue (osteoblasts;
fibroblasts; messenchymal-type cells). |
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The presence
of signaling molecules (growth factors) in the graft,
which activate surrounding host tissues to induce
an appropriate bone-forming response. |
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The ability of
the graft to act as a scaffold and support the ingrowth
of host tissue. |
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When mixed with
the graft material, whether autogenous bone, allograft
material, or even xenografts, or a combination of
these, the PRP will provide high concentrations
of these growth factors, which will enhance the
healing and quality of the grafted bone. |
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