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