Bone graft

defined as : a bone fragment transplanted, whole or in pieces, from one site to another

Bone is : the second most commonly implanted material in the human body, after blood transfusion

Bone graft

Principles of grafting

1.Host bone regeneration capacity 2. Surgical asepsis 3. Host site preparation 4. Optimization of growth factor 5. Graft immobilization 6. Soft tissue coverage

Bone graft

Note ridge resorption

After ridge augmentaion

Types of bone grafts

•Autograft•Allograft•Xenograft•alloplast

Biological mechanism

Osteoconduction

graft material serves as a scaffold for new bone growth

Osteoinduction

Chemical process wich stimulation of osteoprogenitor cells to differentiate into osteoblasts that then begin new bone formation . Themost widely studied type of osteoinductive cell mediators are (BMP)

Osteogenesisbone formation, from cells that survive in

the graft and are capable of produce new bone

Structure of grafts

Cortical bone

cancellous bone

used primarily for structural support

cancellous bone grafts for osteogenesis

Mechanism of bone formation

Mechanism Mechanism of bone formation in a cancellous cellular bone

emanate from survival of the osteoprogenitor cells (osteoblst & marrow cells)

Transplanted osteoprogenitor cells survive within the recipient tissue for first 3-4 days by a nutritional diffusion from the surrounding vascular tissue envelop

From 3rd day – capillary buds start proliferation from surrounding tissue. This establish oxygen gradient

Between 3rd and 14th day – complete revascularization occur

Healing principles

Mechanism revascularization of a cancellous graft may be completed within 2 weeks.

In contrast, revascularization of cortical grafts is much slower , due to lack of anastomoses

Grafted cortical bone particles may not entirely be replaced with host bone at the recipient bed

but grafted cancellous bone will be completely replaced by new host bone within the first year after transplantation

Sources of grafts

Inraoral extraoralMax. tuberosityRamusSymphysis

ribtibiaIliac crestCalvarial bone

Autogenous grafts

Autogenous

DisadvantagesLow availability of bone volumeRequire a second operative siteSignificant patient morbidity

Considered the “ gold standard ” by which other materials are judged

Osteoinductive, osteoconductive, and osteogenic properties

No risk of infection

Sources of grafts

1.FRESH FROZEN - Highly antigenic2.Mineralized freeze dried allograft - Osteoconductive -Low bioavailabilty and activity of (BMP)3.Demineralized freeze dried bone -Osteoinductive -The process exposes BMP

BMP cause differentiation of mesenchymal cells into osteoblasts

Human cadavers source Method to supress antigenicity

Disadvantages Risk of disease transmission and

unpredictability Possible infections, and antigenicity

risks

MinerOss®

allograft

Demineralized freeze dried bone

Mechanism BMP are associated with the organic matrix of bone and embedded

within mineral content, so demineralised process increases its bioavailability

BMP attract mesenchymal stem cells and induce them to differentiate into chondrocytes leading into endochondral bone formation.

Endochondral bone formation is attributed to a osteoinductivity response,

while intra-membranous bone formation is indicative of an osteoconductive response

Xenograft Naturally derived hydroxylapatite

from bovine, coral Osteoconductive Similar structure, chemistry, and

porosity of human bone

Disadvantages Risk of disease transmission Remains in the defect for years Continuous macrophage activity

MinerOss®

Sources of grafts

• Hydroxyapetite• Polymers • bioactive glass• Tricalcium

phosphate• Calcium

sulphate

alloplast

Cancellous Bone

Coralline hydroxyapatite

Sources of grafts

Techniques for using autogenous bone graft

Osseous coagulum : blood misture with bone dust

Bone blend : placing bone fragment placed in capsule & tituration

Techniques for using autogenous bone graft

Intraoralcancellous bone marrow transplant : from -max. tuberosity -healing socket -edentulous areaBone swaging :

pushing the bone (of edentulous area adjacent to the defect ) into contact with the root surface without fractureing its base

Technically diffcultNo longer use

Extraction socket allowed to heal for 2-3 months before reintering

Grafting application

Alveolar socket preservation

Onlay grafting Procedure

Disadvantage : increase vertical load ridge resorption

interpositional Procedure Le Fort I

osteotomy

Alveolar bone split osteotomy

Used to increase ridge thickness

Sinus lift procedure

Maxillary sinus lift

lateral window

Distraction osteogenesis

By llizarov Biologic process of new bone

formation between surfaces of separated bone segment by traction forces

Gradual lenthening of the bone by application of a specific device (distractor)

Complication of grafting

1. Perforation of the Schneiderian membrane 2. Soft tissue dehiscence 3. Infection 4. Exposure of GBR membrane 5. Mobilisation of the graft 6. Graft resorption 7. Cyst formation 8. Transmission of diseases

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