Mandibular reconstruction / oral surgery courses


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Mandibular reconstruction / oral surgery courses

  2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education
  3. 3. INTRODUCTION  Mandibular defects in OMFS are common.  Mandibular reconstruction in OMFS is a major challenge.  Gold standard for reconstruction  Newer techniques.
  4. 4. DEFINITION OF RECONSTRUCTION :  Reconstruction refers to the rebuilding or the restoration of original form and function that have been lost owing to disease or treatment of disease. CLASSIFICATION OF BONY DEFECTS  Cantor and curtis  HCL classification
  5. 5. MANDIBULAR RECONSTRUCTION a. Immediate  Inability to detect recurrence  Increased risk of graft rejection b. Delayed  Late covering of primary site  Increase in complication  Increased hospital stay  Cost
  6. 6. GOALS OF RECONSTRUCTION :  Restore maxillofacial form  Maintain quality of tissues  Maintain oral competence  Maintain oral cavity function  Achieve coverage of soft tissue defect
  7. 7. RECONSTRUCTION TECHNIQUES : Free bone grafts Poor tolerance to infection ‘K’ Wires Failure rate of 70% Stainless steel intra meduallary pins Scarring & Contracture AO plates Excellent cosmetic result Titanium, Vitallium Good outcome Stainless steel wire mesh Good outcome Allo plast + Free bone grafts Greater potential neovascularization for
  8. 8. Osteomyocutaneous flaps :  Pec. major flap with 5th and 6th rib  Trapezius flap with scapular spine  Sternocleido mastoid flap with clavicle  Latissmus dorsi flap with iliac crest Distraction osteogenesis
  9. 9. LIMITATION OF CONTEMPORARY TECHNIQUES :  Limited application  Short supply of graft material  Risk of disease transmission  Potential morbidity at donor site
  10. 10. TISSUE ENGINEERING Definition : Construction of a device in the laboratory containing viable cells and biological mediators in a synthetic or biologic matrix that could be implanted in patients to facilitate regeneration of particular tissues.  Bone morphogenic protein - BMP  Platlet rich plasma – PRP
  11. 11. BONE MORPHOGENIC PROTEIN History :  Neuhof in 1917 and Huggisn in 1930 demosntrate “Heterotropic osteogenesis”.  In 1965 Urist unveils the concept of auto induction – Ectopic bone formation.  In 1971 the term osteoinduction was coined.  In 1988 Wozney and Colleagues clones morphogeneic protein using recombinant technology. bone
  14. 14. BMP - Present in high concentration in bone matrix, osteosarcoma tissue, dentin matrix. TGFb – Found in high concentration in platlets about 50ng / ml of whole blood, sequestred within platlets. PERIOSTEUM – Source of Osteoprogenitor cells in bone
  15. 15. TYPES OF BMP BMP1 - Regulatory molecule; activates BMP BMP2 - Ectopic bone formation; OI ; present in bone spleen, liver, brain, kidney, heart, placenta. BMP3 - OI ; Present in lung, kidney, brain, interstine. BMP4&5 - OI ; Embryogenesis BMP6 - Not Osteoinductive BMP7 - OI ; Bone differentiation BMP8&9 - OI ; Bone formation BMP 12&13- Inhibition of terminal differentiation of myoblast.
  16. 16. STEPS IN OSTEOINDUCTION :  Chemotaxis of osteoprogenitor cells.  Synthesis of Type III collagen.  Differentiation of chondroblasts.  Conversion of connective tissue into cartilage.  Invasion by capillaries.  Calcification  Synthesis of Type IV collagen  Synthesis of Type I collagen  Ossification
  17. 17. FUNCTIONS : Growth factors - Cell to cell interaction in skeletal tissue. BMP Type 2 - a. Acts on immature osteoprogenitor cells. b. Differentiate them into osteoblasts and chondroblasts for bone formation. TGFb2 - Stimulates proliferation of osteoprogenitor cells and also chemotactically attracts osteoprogenitor cells to sites of bony defects.
  18. 18. BMP in mandibular reconstruction  Pleiotropy  Bone graft - Cortical, cancellous or both  Scaffolds ; -They are the supporting or carrier materials. -They are rigid, solid, gel, paste or injectible fluid. -They can be absorbable, resorbable, osteoconductive or osteoinductive.  Matrix metallo proteinases - Biodegrades matrices and hydrogels. biodegradable,
  19. 19. FORMS OF BMP :  Bovine BMP – bBMP  Recombinant human BMP – rhBMP -‘K. Bessho’ advocates rhBMP due to consistency of safety and quality for clinical application. -rhBMP is not fully characterized -Activity of rhBMP is 1/10th of bBMP. -Synthesis of bBMP is very minimal 10 – 20mg / kg dry bone
  20. 20. APPLICATION OF BMP : - In clinical surgery BMP is applied as a paste. - It contains 1mg of purified BMP per cm3. - BMP action is decreased on sterilization by irradation - BMP is sterilized by defatting via chloroform / ehtanoland freezing to -70º.
  21. 21. LIMITATION OF BMP : - Bone inducing capacity is unpredictable - Pathologic expression of BMP (Yashika & Colleagues in CANCER in 1994) revealed 40% of osteosarcoma or osteoinductive - Osteoblast and fibrohistio cytic types account for highest level of BMP - No evidence to support BMP causes oncogenesis. - Researchers in 10 years of animal studies in rhBMP has reported no evidence of oncogenesis. - In 2004, FDA cancels sanction for use of rhBMP for clinical use in OMFS
  22. 22. CLINICAL RESEARCH : 1. Reconstruction of primate mandible with rhBMP2 and bone marrow. (Ichiro, Izumi, Shoji) JOMS, 2001 University of Japan. - Implantation of bone marrow alone, rhBMP + bone marrow and rhBMP alone in mandible of Japanese Monkey after creating segmental mandibular defects. Carrier – PGLA. - Results : rhBMP + BM > BM > rhBMP.
  23. 23. 2. Reconstruction of mandibular defects with autologous tissue engineered bone. (Bradford, B. Kaban, Maria) JOMS, 2004 University of Boston. - MSC isolated from ilium of porcine were expanded in culture and seaded to PGLA & Scaffolds. Four defects of 2x 2 cm was created and filled with autogeneous graft, only scaffold, empty as control. - Results : Mandibular defects can be successfully regenerated by MSC on polymer scaffold with penetration of bone and vessels.
  24. 24. 3. Mandibular defects repair by TGFb and IGF1 released from osteoconductive gel. (Rachmiel ; Blumenfeld, Liune) JCFS, 2005 University of Japan. - Mandibular defects in rat mandible was filled with TGFb, IGF1, both hydrogel and control and tested after 3rd and 6th weeks - Results : Defects filled with TGFb and TGFb + IGF1 showed greater bone formation with hydrogel scaffold.
  25. 25. PLATLET RICH PLASMA Definition : PRP is an autologous concentration of human platlets in a small volume of plasma. History : 1997– PRP was first introduced in OMFS by Whitman. 1998 – PRP’s role in bone formation with autogeneous bone by Marx et al.
  26. 26. COMPONENTS OF PRP :  IGF1  PGDF  TGF – b  VEGF  EGF  Cell adheshion molecules
  27. 27. FUNCTIONS :  PGDF – Mitosis of healing cells, angiogenesis, macrophage activation.  IGF – Secreted by osteoblast, mytogenic to osteoblast line of cells.  PRP – Increases the number of growth factors in the graft
  28. 28. PROCUREMENT OF PRP :  Withdraws 400 – 450ml of whole blood, 50ml per minute with a speed of 5000 rpm.  Citrate phosphate dextrose 1 : 5 for anticoagulation Layers of PRP  PPP – 200 ml  PRP – 70 ml  RBC – 180 ml  1 to 3 ml of RBC layer is also added to PRP.
  29. 29. APPLICATION OF PRP :  Initiation of clotting process  PRP is mixed with PCBM  10 ml of CaCl2 and 10,000 units of topical bovine thrombin  In 10 ml syringe 6ml of PRP + 1ml of CaCl2 + 1ml of air is added to form a gelatin mass.  A PRP count of 1 million per micro litre is the benchmark for “therapeutic dose of PRP”.
  30. 30. ROLE OF GROWTH FACTRORS IN PRP :  Stimulation of cellular activity  Release of PGDF, TGFb and IGF from platlets in the graft  PDGF stimulates mitogenesis of marrow stem cells.  Angiogenesis of capillary endothelial mitosis. budding by inducing  TGFb activates fibroblast and preosteoblast to initiate mitosis and lay down bone matrix and collagen matrix to support capillary in growth.  By day 3, capilliaries penetrate the graft  By day 14, complete permeation of capillaries takes place
  31. 31.  Life span of platlets in a site is 5 days.  Aftermath, bone regeneration is by macrophages.  Phase I Bone : a. Formed in the first four weeks b. Bone formed is disorganized woven bone c. Little structural integrity present.  Phase II Bone : a. Mature lamellar bone b. Presence of Haversion system c. Presence of structural integrity d. Formation of periosteum and endosteum
  32. 32. USES OF PRP :  Accelerated rate of bone formation was demonstrated on plain radiograph using PRP.  Rate of bone generation is not only faster but also greater, verified by histiodensitometric study.
  33. 33. CLINICAL RESEARCH : 1. PRP : Evidence to support its use (Richard E. Marx) JOMS, 2004 University of Miami Clinical Contraversy - Failures are due to inappropriate sequestration of platlets, less therapeutic platelet level, inappropriate preparation of PRP. - Benefits are continuity defects, sinus lift augmentation grafting, ridge preservation grafting, periodontal / perioimplant defects - Autologous PRP is the safest - PRP does not promote infection, pH is 6.5
  34. 34. 2. Differential growth factor retention by platlet rich plasma. (Rick ; Jenifer, Sidney) JOMS, 2005 - To evaluate an optimal substrate for extended growth factor retention. - PRP + TRAP ; PRP + Bovine thrombin ; PRP + bone substitues. - PRP + bovine thrombin results in large immediate release of growth factors which is lost via interstitium. - PRP + TRAP – release of growth factor at a slow and sustained rate for longer period
  35. 35. 3. Effect of PRP with autogeneous bone graft for maxillary sinus augmentation in a rabbit model (Kevin ; Jeffry ; Gloria) JOMS, 2005 - This study fails to find a direct stimulatory effect of PRP on healing of autogeneous bone graft using static and dynamic histomorphometric analysis.
  36. 36. SUMMARY :  Tissue engineering methods in bone regeneration is promising based on the scientific studies carried out in animals.  The hurdles of large bone reconstruction by tissue engineering has yet to be explored especially in in humans.  With strides of advancement in technology and global research there is little down that reconstruction of bony defect will be a reality.
  37. 37. REFERENCE :  Tissue engineering – Richard E Marx ; Lynch  Bone morphogenic protein – Lindholm  JOMS ; 2001, 2004, 2005  JCFS ; 2005  IJOMS ; 2004
  38. 38. Thank you Leader in continuing dental education