BONE GRAFT MATERIAL AND PROCEDURE
Bone grafting procedures may be necessary to create enough bone
volume and height to facilitate implant placement. The
grafting might need to be performed months in advance
of the actual implant placement surgery to allow
adequate transformation and maturation of the graft
material in to the host site. Sometimes the graft is
performed at the same time as the implant placement.
Regardless of the point in time when the graft procedure
is performed in relation to the implant placement, the graft site needs to be covered with a
barrier membrane to prevent epithelial
in growth in to the graft material.
The graft material source can be divided in to five groups.
1. Autogenous
Harvested from
the recipient of the graft. Possible harvest sites
include but are not limited to the chin, ilium, ramus, fibula
or tibia. Autogenous grafts work through osteogenesis, regeneration through
living cells. If the graft is not a block graft the harvested bone is ground in
to smaller particles in a bone mill and compacted in a syringe to ensure the
largest possible number of cells in relation to its volume. The harvested bone
needs to be used immediately or stored in sterile saline or lactated Ringer's
solution.
2. Allograft
Derived from bone of
the same species as the future recipient of the graft
material. Commonly referred to as deminieralized
freeze-dried bone allograft (DFDBA) and freeze-dried
bone allograft (FDBA).
Allograft can be made of all cortical or cancellous and a mixture of both bone
types. Allografts work through osteoinduction, stimulation of osteoprogenitor
cells. The demineralization of frieze-dried bone allograft (DFDBA) makes bone
morphogenic proteins (BMP) more readily available for bone formation. Cortical
bone has a higher concentration of BMPs than cancellous bone.
3. Isograft
Taken from
a genetically identical donor as the recipient of the
graft. This is a rare occurrence since donor and recipient
have to be monozygotic twins.
4. Xenograft
Derived from a different species (usually bovine or porcine)
than the recipient.
Xenograft can be made of all cortical or cancellous and a mixture of both bone
types. Xenografts work through oteoconduction, providing a scaffold for bone
growth.
5. Alloplast
Synthetic
in-organic bone substitutes. Alloplasts work through oteoconduction, providing a
scaffold for bone growth. Alloplasts can be divided in to bioinert and
bioactive. Bioinert materials (aluminum or titanium oxides) do not bond directly
to the underlying natural bone and need to be mechanically fixated in place.
Bioactive materials (calcium carbonate, calcium phosphates, calcium sulfate)
readily bond to the underlying bone. Both, bioinactive and bioactive materials
are available in a resorbable and a non resorbable variant.
Grafting procedures can be classified in to three groups,
block graft, particulate graft and osseo-distraction,
although the later is not a true bone graft.
1. Block
Grafts are
performed with autogenous, allograft and isogafts. Blocks
of donor site bone are adapted to the host site morphology and fixated with
titanium screws or a titanium mesh and titanium screws.
2. Particulate
Grafts are usually achieved with allograft,
xenograft and alloplast. As the name already suggests,
particulate graft material are small grains much like
salt or pepper granules of varying size. In some instances
the particulate is premixed with a binder to effect a
putty like consistency for ease of handling and host site
adaptation. In its pure granulated form the particulate
is often mixed with platelet rich plasma (PRP)
to enhance bone growth, handling properties and limit particulate
migration.
3. Sinus lift (osteotome type)
Summers
4. Sinus graft (lateral window)
Tatum 1974
5. Ridge splitting
6. Osseo-Distraction
Is not a true bone
graft but rather augmentation through segmental osteotomy.
The bony defect is sectioned and reattached to the bone with
a device that holds the segmented bone in its original
place without direct contact to the bone it was sectioned
from. After closing the tissue flap over the augmentation
site one or two distraction device screws extend through the
tissue and are turned on a daily basis to vertically advance
the sectioned block of bone until adequate bone height is
achieved.
Bone graft material suppliers:
BioHorizons®
-Allograft: Grafton® DBM, MinerOss®
Biomet 3i
-Allograft: RegenerOss®, Alloplast: Biogran®, Calcigen
Dentsply
-Alloplast: PepGen P-15, Xenograft: OsteoGraf
Keystone
-Allograft: Accell, DynaBlast, DynaGraft-D
Straumann®
-Alloplast: BoneCeramic
Zimmer®
-Allograft: Puros® cortical, Puros® cancellous, Puros® block