BONE GRAFTS

What are bone grafts?

Bone grafts are the materials used for replacement or augmentation of the bone.

·         Enhances regenerative capacity of bone

·         Achieve new attachment apparatus

Biologic concept of using bone graft:

1.      Osteoconduction

2.      Osteoinduction

3.      Osteogenesis

OSTEOCONDUCTION (Trelli’s effect): “Physical effect” by which the matrix of the graft forms a scaffold that favors outside cells to penetrate the graft and form new bone.

E.g: Alloplast, FDBA

OSTEOINDUCTION: Chemical process by which molecules contained in the graft (e.g., bone morphogenetic proteins) convert the neighboring cells into osteoblasts, which in turn form bone.

E.g: DFDBA

OSTEOGENESIS: Osteoblasts in the transplanted bone    having adequate blood supply & cellular viability forms new     centers of ossification within the graft.

E.g: Autogenous graft

 

INDICATIONS FOR GRAFTS

1.      Deep Intraosseous Defects

2.      Tooth Retention

3.       Support for Critical Teeth

4.       Bone Defects Associated With Aggressive Periodontitis  Esthetics (Shallow Intraosseous Defects)

5.       Furcation Defects

OBJECTIVES OF BONE GRAFTING

1.      Probing depth reduction

2.      Clinical attachment gain

3.      Bone fill of the osseous defect

4.      Regeneration of new bone,  cementum, and  periodontal ligament

 

CLASSIFICATION OF BONE GRAFTS

I.Depending on the rate of their bioresorption:

·         Fast     Resorbing: Wherein graft gets resorbed within 8-10 weeks after  placement.

·         Slow    Resorbing: Grafted material stays for many months. E.g: β-  TCP

·         Nonresorbing: Those which do not resorb for years.

E.g: Natural coral materials, hydroxyapatite

II. Based  on the origin:

·         Autografts: A tissue transferred from one position   to another within the same individual.

·         Allografts / Homografts: Obtained from genetically dissimilar individual of same species.

·         Xenografts / Heterografts: Tissue transferred from one species to another species.

·         Alloplasts: A synthetic graft or inert foreign body implanted into tissue.

IDEAL CHARACTERISTIC OF BONE GRAFT

1.      Nontoxic

2.      Nonantigenic

3.       Resistant to infection

4.      No root resorption or ankylosis

5.       Strong and resilient

6.      Easily adaptable

7.      Readily and sufficiently available

8.      Minimal surgical procedure

9.       Stimulates new attachment

AUTOGRAFT: It is from two sites

1.      AUTOGRAFT FROM EXTRAORAL SITES ( Illiac crest, ribs, cranium, tibial metaphysis)

2.      AUTOGRAFT FROM INTRAORAL SITES (Maxillary tuberosity, exostoses, healing wounds, extraction  sites ( Soehren et al, 1979), edentulous ridges, mandibular symphysis,  ramus ,osteoplasty /osteotomy  sites ,areas distal to last tooth)

ADVANTAGES:

·         Excellent results in 2 and 3 wall intraosseous  defects

DISADVANTAGES:

•      Creating a second surgical site

•      Procurement problem

•      Donor site morbidity

•      Increase intra-operative time

INTRUMENTS USED:

1.      Bone trap collecting osseous coagulum

2.      Maxillon bone retrieval device collection of  bone shavings

Gold standard because: (Marx 1994; Kim et al. 2005).

(1)   Osteogenic potential

(2)   A tissue reaction is induced without inducing immunological reactions

(3)   Minimal inflammatory reaction

(4)   Rapid revascularization around the graft particles

(5)   Potential release of growth & differentiation factors sequestered within grafts

 

ALLOGRAFT: Commercially available from tissue banks

1.      Fresh frozen bone

2.      Freeze dried bone allograft (fdba): osteoconductive

3.      Demineralised freeze dried bone allograft (dfdba) : osteoconductive + osteoinductive

FRESH FROZ EN BONE:

 1. Possibility of disease transfer

2. Antigenicity for cases of HIV have been reported

3. Need for extensive cross-matching

4. Disallowed the use of fresh frozen bone in modern  periodontics.

 

WHICH BONE TO USE?

  Cortical bone is recommended rather than cancellous bone -------- American Academy of Periodontology

ADVANTAGES:

1. Material is available in large quantities

2. No donor site within the patient

3. Reduces antigenicity

4. Facilitates long-term storage

Vacuum sealing in glass containers protects against contamination and degradation of the graft material while permitting storage at room temperature for an indefinite period of time

DISADVANTAGES:

•      Risk of disease transmission

•      Induces immunologic reactions

•      Expensive

FREEZE DRIED BONE ALLOGRAFT:

1.      Introduced to periodontal therapy in 1976

2.       Osteoconductive.

3.      Although FDBA contains inductive proteins, the polypeptides are sequestered by calcium.

4.       This material is resorbed and replaced by host bone very slowly.

5.       Only graft material that has undergone extensive field testing for the treatment of adult periodontitis.

DEMINERALISED FREEZE DRIED BONE ALLOGRAFT:

·         Osteoinductive graft.

·         Synonymous - allogeneic, autolyzed, antigen-extracted (AAA) bone, demineralized bone powder, demineralized bone matrix.

·         DFDBA in periodontal defects results in significant probing depth reduction, attachment level gain, and osseous regeneration.

·         Delaying the procurement of donor bone after death, improper storage conditions, or other processing factors may play a significant role in the bioactivity of the final DFDBA preparation.

·         Age, gender, and medical status of deceased donors may also affect osteogenic activity in the grafts taken from them.

XENOGRAFT:

1.      BOVINE DERIVED: BOVINE BONE chemically treated            with ethylenediamine to remove its organic components. Trabecular & porous architecture is retained (Similar to human) 

Function: Clot stabilization & revascularization to allow cell migration of osteoblasts. Have Osteoconductive property.

Brand name:- Bio Oss

 

2.      CORAL DERIVED: Derived from natural coral which has calcium carbonate. Have Osteoconductive property

DISADVANTAGES:

•      Carry the theoretical risk of transmission of bovine spongiform encephalopathy (BSE) Precheur, 2007

•      Provoke immune response

ALLOPLASTS:  Synthetic inorganic inert material.

            Characteristics:

1. Biocompatible &/or Bioactive

2. Osteoconductive

3. Resorbable in long run.

ADVANTAGES:

1. Absence of antigenicity

2. NO potential for disease transmission

 3. Unlimited supply

ALLOPLASTS ARE OF TWO TYPES:

1.      CERAMICS: includes calcium sulfate, calcium phosphates, bioactive glass.

2.      POLYMERS : includes PMMA: Polymethylmethacrylate

                                          PHEMA: Polyhydroxyethlymethacrylate

CERAMIC BASED BONE GRAFTS

1.      Widely used

2.      Function primarily through osteoconduction

3.      Have also been considered osteointegrative, because of the tenacious, intimate bond formed between the new mineralized tissue & graft material

POLYMERS

·         Polymers are more widely used as barrier materials in GTR procedures for treatment of periodontal defects.

·          At present, several polymer systems are being used for bone & periodontal regeneration (Polylactic acid (PLA)-based polymers) copolymers.

·         These polymers have proved to be effective in periodontal applications as barrier materials.

·         Biocompatible microporous polymer containing PMMA, PHEMA, & calciumhydroxide is available.

·         Hydrophilic and osteophilic

Histologic evaluations revealed that the polymer was associated with minimal inflammation & infrequent foreign body giant cells, with evidence of both bone apposition & soft tissue encapsulation, at 1 to 30 months following implantation.

                                                                                   

                                                                                                            Dr. Anjusha Sharda