application of bone graft in dentistry
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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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