جراحه

• Oral and Maxillofacial Surgery


  A field of surgery focused on the treatment of diseases, injuries, and defects in the head, neck, face, jaws and the hard and soft tissues of the oral and maxillofacial region
• Defects of the jaw bones have a variety of causes, such as: Eradication of pathologic conditions, Trauma, Infections, Congenital deformities
• Defects in the oral and maxillofacial region

  • The size varies considerably, from small alveolar clefts to mandibulectomy or maxillectomy defects
  • The goals of successful reconstruction are to recreate normal oral function, provide a satisfactory cosmetic result, and permit prompt and careful follow-up

  
• Oral cavity defects can extend to involve critical sites and cause significant functional disabilities in terms of airway, speech, swallowing, and/or mastication
• Bone graft


  A tissue that is transplanted and expected to become a part of the host to which it is transplanted
• Bone healing and bone graft healing

  1. New bone formation that arises from tissue regeneration rather than from simple tissue repair with scar formation

  2. Requires cellular proliferation and collagen synthesis
• Mechanisms of bone generation

  • Osteogenesis
  • Osteoinduction
  • Osteoconduction
• Osteogenesis


  The formation of new bone from living cells transplanted within the graft
• Osteoinduction


  New bone formation through the recruitment and stimulation of recipient site osteoprogenitor cells using bone growth factors transplanted within the grafted material
• Osteoconduction


  The physical process in which the graft acts as a 3D scaffold on which the cells are able to form new bone
• Two-phase theory of osteogenesis

  1. Phase I: Transplanted cells in the graft proliferate and form new osteoid

  2. Phase II: Angiogenesis and fibroblastic proliferation from the graft bed, osteogenesis from host connective tissues
• Types of bone grafts

  • Autogenous grafts
  • Allogeneic grafts
  • Xenogeneic grafts
  • Alloplasts
• Autogenous grafts


  Tissues from the same individual, the only type that can supply living, immunocompatible bone cells essential to phase I osteogenesis
• Forms of autogenous bone grafts

  • Block grafts
  • Particulate marrow and cancellous bone grafts
  • Composite grafts
• Block grafts


  Solid pieces of cortical bone with or without underlying cancellous bone
• Particulate marrow and cancellous bone grafts

  Obtained by harvesting the medullary bone and the associated endosteum and hematopoietic marrow, produce the greatest concentration of osteogenic cells
• Composite grafts


  Autogenous bone grafts while maintaining their blood supply, the number of surviving osteogenic cells is potentially more
• Methods of composite grafts

  • Pedicled flaps
  • Vascularized free tissue transfer
• Advantages of autogenous grafts

  • Provide osteogenic cells for phase I bone formation
  • No immunologic response occurs
• Disadvantages of autogenous grafts

  • Necessitate another site of operation for procurement of the graft (donor site morbidity)
  • Expansion and irregularity of bone
• Allogeneic grafts


  Grafts taken from another individual of the same species, recognized as a foreign substance by the host which will mount an intense response
• Advantages of allogeneic grafts


  • Do not require another site of operation in the host
  • A bone of similar shape to that being replaced can be obtained
• Disadvantages of allogeneic grafts


  • Do not provide viable cells for phase I osteogenesis
  • Rigorous screening of donors is required to reduce the risk of disease transmission
• Xenogeneic grafts


  Grafts taken from one species and grafted to another, the antigenic dissimilarity is greater than with allogeneic bone
• Advantages of xenogeneic grafts

  • Do not require another site of operation in the host
  • Large quantity of bone can be obtained
• Disadvantages of xenogeneic grafts

  • Do not provide viable cells for phase I osteogenesis
  • Must be rigorously treated to reduce antigenicity
• Alloplasts


  Alloplastic synthetic biomaterials with varying physicochemical properties, can be both degradable and nondegradable
• Advantages of alloplasts


  • Do not require another site of operation in the host
  • Large quantity of bone can be obtained
• Disadvantages of alloplasts


  • Do not provide viable cells for phase I osteogenesis
  • They are osteoconductive without any osteoinductive or osteogenic potential on their own
• Adjuvants


  Biologics used to enhance bone repair, including blood components, gene therapy, and recombinant proteins
• Bone morphogenetic proteins (BMPs)


  Osteoinductive proteins that belong to the transforming growth factor-beta (TGF-β) family, capable of stimulating mesenchymal cells to become osteoblastic and form bone
• Advantages of BMPs


  • Do not require another site of operation in the host
• Disadvantages of BMPs


  • Do not provide viable cells for phase I osteogenesis
  • Require a carrier to maintain the BMP at the site of implantation
• Platelet concentrates


  Autologous platelet concentrates that provide a high concentration of growth factors to enhance wound healing and have a potential bone regenerative effect
• Types of platelet concentrates

  • Platelet-rich plasma (PRP)
  • Platelet-rich fibrin (PRF)
  • Concentrated growth factor (CGF)
• Platelet-rich plasma (PRP)


  The first generation of platelet concentrate, prepared by two-step centrifugation of collected blood with anticoagulant, promotes the release of growth factors for a short period (24 hours)
• Platelet-rich fibrin (PRF)


  The second generation of platelet concentrates, prepared by a constant speed single-step centrifugation of collected blood without anticoagulant, possesses an anti-inflammatory effect and contributes to sustained and prolonged release of growth factors for more than seven days
• Concentrated growth factor (CGF)


  The third generation of platelet concentrates, prepared by a single step of centrifugation with alternate speed, induces a constant and sustained release of growth factors longer than PRP and PRF, which may last up to 14 days
• Combination of bone grafts

  • Allogenic grafts as a scaffold that can provide the desired bulk and shape supplemented with autogenous particulate marrow and cancellous bone to provide the osteogenic cells necessary for phase I bone formation
• Advantages of combination grafts

  • Same as those of autogenous and allogeneic grafts