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Bone density ppt

this gives a detailed description for the bone density consideration during implant placement.

The presentation is available upon request. Mail me at apurvathampi@gmail.com

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Bone density ppt

  1. 1. PRESENTED BY: APURVA THAMPI BONE DENSITY
  2. 2. Contents •Introduction •Bone morphology •Bone physiology •Influence of bone density on implant success rates •Aetiology of various bone density •Bone classification schemes •Bone density classification - Misch •Bone density location •Radiographic assessment of bone density •Tactile sense - bone density •Scientific rationale •Effect of bone density on surgical approach and healing •Case studies •Conclusion •References
  3. 3. Basic bone biology in implantology
  4. 4. Bone 33% organic67% inorganic hydroxyapetite 28% collagen 5% non collagenous protiens 2/25/2017 TEXTBOOKOF HUMAN HISTOLOGY , INDERBIR SINGH ; 5TH ED 4
  5. 5. There are 4 types of cells in bone tissue….Osteoprogenitorcells • Unspecialised cells • Develop into osteoblasts • Found in periosteum, endosteum and in canals of vital teeth Osteoblasts • Formation of bone • Role in calcification • Synthesis of protien Osteoclasts • Responsible for bone resorption Osteocytes • Maintenance of bone • Exchange of calcium between bone and ECF TEXTBOOKOF HUMAN HISTOLOGY , INDERBIR SINGH ; 5TH ED
  6. 6. Can be broadly classified into : Compact bone Trabecular bone TEXTBOOKOF HUMAN HISTOLOGY , INDERBIR SINGH ; 5TH ED
  7. 7. What is lamellar bone? Structure of adult bone Made up of layers – lamellae – thin plate of bone consisting of collagen fibres and mineral salts Lacunae – between each lamellae Each lacuna consists of one osteocyte Canaliculi spread out from each lacuna A B C Unit of bone - lamellus Bone acquires thickness by stacking of lamellus Between adjoining lamellae – spaces called lacunae - Occupied by osteocytes TEXTBOOKOF HUMAN HISTOLOGY , INDERBIR SINGH ; 5TH ED
  8. 8. What is woven bone? Osteocyte in lacuna canaliculi Collagen fibres present in bundles – at random Interlaced – woven bone All newly formed bone Abnormal persistence of woven bone – Paget’s disease
  9. 9. Compact bone VS Trabecular bone
  10. 10. Osteon of compact bone Trabeculae of spongy bone Haversian canals Volkmann’s canal periosteum osteon canaliculi lamellae Lacunae containing ostecytes
  11. 11. Compact bone Lamellae arranged in concentric circles – surround - Haversian canals Occupied by blood vessels and nerves Haversian canal + lamellae = osteon or haversian system Between adjoining osteons – interstitial lamellae At the surface – lamellae are parallel – circumferential lamellae TEXTBOOKOF HUMAN HISTOLOGY , INDERBIR SINGH ; 5TH ED
  12. 12. Trabecular bone Bony plates or rods – meshwork – trabeculae Made of number of lamellae Enclose wide spaces filled with bone marrow – receive nutrition
  13. 13. Bone physiology
  14. 14. Calcium metabolism
  15. 15. Rapid influx of calcium from bone fluid Short term response of osteoclasts and osteoblasts Long term control of bone turnover Normal serum calcium levels – 10mg/dL Low calcium level  tetany and death High serum calcium levels – kidney stones, dystrophic calcification of soft tissues CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  16. 16. Dec in calcium levels – transport of ions to osteocytes Calciferol enhances pumping of calcium ions from cells into ECF Net flux of Ca ions PTH + calciferol + calcitonin Transiently suppresses bone resorption Profound effect on skeleton PTH is the primary regulator – mean bone age Important determinant of fragility Instantaneous regulation (within seconds) Short term regulation Long term regulation CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  17. 17. Calcium conservation Kidney excretes phophates by minimising loss of calcium Renal dysfunction – high risk for osseous manipulative procedures – renal osteodystrophy Body spends 300mg calcium per day – recovered by absorption from gut – depends of Vit D Kidney is the primary calcium conservation organ of the body CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  18. 18. Cortical bone growth and maturation Osseous landmarks for superimpos ition Anterior curvature of the sella turcica Cribriform plate Internal curvature of frontal bone Most reliable means of determining post adolescence growth  essential for treatment planning MELSEN, BIRTE. THE CRANIAL BASE: THE POSTNATAL DEVELOPMENT OF THE CRANIAL BASE STUDIED HISTOLOGICALLY ON HUMAN AUTOPSY MATERIAL. VOL. 32. ACTA ODONTOLOGICA SCANDINAVICA, 1974.
  19. 19. Influence of bone density on implant success rates
  20. 20. Anterior mandible Anterior maxilla Posterior mandible Posterior maxilla Position / Arch location Quality of bone dependent on the position CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  21. 21. •10% greater success rates in anterior mandible as compared to anterior maxilla (Adell et al) •Lower success rates in posterior mandible as compared with the anterior mandible (Schnitman et al) •Highest clinical failure rates – posterior maxilla – force is greater and poor bone density CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  22. 22. Quality of bone CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  23. 23. Aetiology of various bone density
  24. 24. Hormones Vitamins Mechanical influences Duration of edentulousn ess Changes in bone - adaptability CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  25. 25. “Every change in the form and function of bone or of its function alone is followed by certain definite changes in the internal architecture, and equally definite alteration in its external conformation in accordance with mathematical laws” Wolff - 1892
  26. 26.  Adaptive phenomena  Alteration of mechanical forces and strain development within the bone  density evolves as a result of mechanical deformation from microstrain MODELLING Independent sites of formation and resorption Results in change in shape and size of bone REMODELLING Resorption and formation at the same site Replaces previously existing bone CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  27. 27. The maxilla is a force distribution unit and mandible is a force absorption unit CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  28. 28. The trabecular bone in dentate mandible is more coarse compared to the maxilla CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  29. 29. Anterior mandible Posterior maxilla Density change after tooth loss. • Initial density • Flexure and torsion • Parafunction before extraction NEUFELD JO: CHANGES IN THE TRABECULAR PATTERN OF THE MANDIBLE FOLLOWING THE LOSS OF TEETH, J PROSTHET DENT 685-697, 1958
  30. 30. ORBAN B: ORAL HISTOLOGY AND EMBRYOLOGY, ED 3, ST LOUIS, 1953, MOSBY
  31. 31. Based on Frosts’s mechanostat theory 50 1500 3000 10000+ Acute Disuse window Adapted window Mild Overload window Pathologic Overload window Spontaneous fracture Stress F/A Strain O Strain Acute disuse window : lowest microstrain amount Adapted window : ideal physiologic loading zone Mild overload zone : cause microfracture; triggers an increase in bone remodelling – more woven bone Pathologic overload : increased fatigue fractures, remodelling and bone resorption FROST, H. M. "MECHANICAL ADAPTATION. FROST’S MECHANOSTAT THEORY." STRUCTURE, FUNCTION, AND ADAPTATION OF COMPACT BONE (1989): 179-81.
  32. 32. Acute disuse window •Loses mineral density •Disuse atrophy – modelling for new bone inhibited •Net loss of bone •Microstrain – 0 – 50 •Cortical bone density decrease – 40% and trabecular bone density decrease – 12% CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  33. 33. Adapted window phase •50 – 1500 microstrain •Equilibrium of modelling and remodelling •“homeostatic window of health” •18% trabecular bone and 2-5% cortical bone •Ideally desired around an endosteal implant
  34. 34. Mild overload zone •1500 – 3000 microstrain •Greater rate of fatigue microfracture •Bone strength and density decreases •State of bone when endosteal implant is overloaded •Repair – woven bone is weaker than lamellar – “safety range” for bone strength is reduced CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  35. 35. Pathologic overload zone •Microstrains <3000 units •Physical fracture of cortical bone •Formation of fibrous tissue •Marginal bone loss in implant overloading – implant failure
  36. 36. Bone classification schemes in implant dentistry
  37. 37. Linkow in 1970 : Class I • Ideal • Evenly spaced trabeculae with small cancellated spaces Class II • Less uniformity • Larger cancellated spaces • Large marrow filled spaces exist CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  38. 38. Lekholm and Zarb in 1985: Quality 1 •Homogenous compact bone Quality 2 •Thick layer of compact bone around a core of dense trabecular bone Quality 3 •Thin layer of cortical bone around dense trabecular bone •Favorable strength Quality 4 •Thin layer of cortical bone around a coreof low density trabecular bone CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  39. 39. Misch in 1988 Bone density Description Tactile analogue Typical anatomic location D1 Dense cortical Oak / maple wood Anterior mandible D2 Porous cortical and coarse trabecular White pine or spruce wood Anterior mandible Posterior mandible Anterior maxilla D3 Porous cortical (thin) and fine Balsa wood Anterior maxilla Posterior maxilla Posterior mandible D4 Fine trabecular Styrofoam Posterior maxilla
  40. 40. D5 type of bone exists – most immature bone – found in a developing sinus graft. CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  41. 41. To be continued…
  42. 42. Bone density location
  43. 43. Location of bone density types (% occurance) Bone Anterior maxilla Posterior maxilla Anterior mandible Posterior mandible D1 0 0 6 3 D2 25 10 66 50 D3 65 50 25 46 D4 10 40 3 1 CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  44. 44. CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  45. 45. D1 Bone •Incresed torsion / flexure •Div A Kennedy’s class IV •Antr/postr mandible – lingual cortex D2 Bone •Partially edentulous antr/postr mandible (premolar) •Single tooth or 2 teeth missing D3 Bone •Most common in maxilla •Also present in posterior mandible D4 Bone •Softest bone •Posterior maxilla – after sinus augmentation or iliac crest bone graft CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  46. 46. • First way to identify bone density in implant site ◦ Anterior maxilla – D3 ◦ Posterior maxilla - D4 ◦ Anterior mandible - D2 ◦ Posterior mandible – D3 D2 D3 D4 CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  47. 47. Radiographic bone density
  48. 48. IOPAR OPGs • Lateral cortical plates obscure the trabecular bone density • More subtle changes cannot be qualified
  49. 49. Correlation between Misch bone density classification and Hounsfield units…. Type of bone Hounsfield units D1 >1250 HU D2 850 – 1250 HU D3 350 - 850 HU D4 150 – 350 HU D5 <150 HU SOGO, MOTOFUMI, ET AL. "ASSESSMENT OF BONE DENSITY IN THE POSTERIOR MAXILLA BASED ON HOUNSFIELD UNITS TO ENHANCE THE INITIAL STABILITY OF IMPLANTS." CLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH 14.S1 (2012): E183-E187.
  50. 50. Correlation between Lekholm and Zarb’s bone density classification and bone density… NORTON, MICHAEL R., AND CAROLE GAMBLE. "BONE CLASSIFICATION: AN OBJECTIVE SCALE OF BONE DENSITY USING THE COMPUTERIZED TOMOGRAPHY SCAN." CLINICAL ORAL IMPLANTS RESEARCH 12.1 (2001): 79-84.
  51. 51. Failure in mandible – higher Hounsfield units • Lack of vascularisation • Overheating ROTHMAN, STEPHEN LG, MELVYN S. SCHWARZ, AND NEIL I. CHAFETZ. "HIGH-RESOLUTION COMPUTERIZED TOMOGRAPHY AND NUCLEAR BONE SCANNING IN THE DIAGNOSIS OF POSTOPERATIVE STRESS FRACTURES OF THE MANDIBLE: A CLINICAL REPORT." INTERNATIONAL JOURNAL OF
  52. 52. Bone density – tactile sense
  53. 53. Bone density Description Tactile analogue Typical anatomic location D1 Dense cortical Oak / maple wood Anterior mandible D2 Porous cortical and coarse trabecular White pine or spruce wood Anterior mandible Posterior mandible Anterior maxilla D3 Porous cortical (thin) and fine Balsa wood Anterior maxilla Posterior maxilla Posterior mandible D4 Fine trabecular Styrofoam Posterior maxilla
  54. 54. Scientific rationale for a bone density - based treatment plan
  55. 55. Bone strength and density Bone elastic modulus and density Bone density and implant bone contact interface Bone density and stress transfer
  56. 56. Bone density and strength Bone density is directly related to the strength of bone before microfracture CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION 1 2 43 5 6 7 8 9 10 D1D2D3D4
  57. 57. MISCH, C. E., AND M. W. BIDEZ. "IMPLANT-PROTECTED OCCLUSION: A BIOMECHANICAL RATIONALE." COMPENDIUM (NEWTOWN, PA.) 15.11 (1994): 1330-1332.
  58. 58. Elastic modulus and density Directly related to the density of bone Relates to the stiffness of the material Amount of strain as a result of a particular amount of stress EM of bone more flexible than Ti Pathologic overload Stresses minimized – adapted window zone Lamellar bone at the interface MISCH, C. E., AND M. W. BIDEZ. "IMPLANT-PROTECTED OCCLUSION: A BIOMECHANICAL RATIONALE." COMPENDIUM (NEWTOWN, PA.) 15.11 (1994): 1330-1332.
  59. 59. Ti - D1 bone interface – very little microstrain Ti – D4 bone interface – pathologic overload MISCH, C. E., AND M. W. BIDEZ. "IMPLANT-PROTECTED OCCLUSION: A BIOMECHANICAL RATIONALE." COMPENDIUM (NEWTOWN, PA.) 15.11 (1994): 1330-1332.
  60. 60. Bone density and bone-implant contact percentage Area  less area = greater stress D1 bone has greatest BIC D2 has 65 – 75% BIC D3 bone has 40 – 50% BIC D5 bone has 30% BIC CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  61. 61. Bone density and stress transfer Different stress contours for different types of bone Bone implant contact Bone density Elastic modulus Crestal bone loss and early implant failure due to increased stress D1 bone Stress is of lesser magnitude Highest strains near the crest D2 bone Sustains greater strain  intensity of stress extends farther apically D4 bone Greatest crestal strain  magnitude of strain is further apical Adapted window Mild overload Implant failure CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  62. 62. A nutshell…. Each bone density has different strengths Bone density affects elastic modulus Density differences result in difference in BIC Different stress-strain distribution at a B-I interface CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION
  63. 63. Effect of bone density on treatment planning
  64. 64. Modifications in treatment plan Prosthetic factors Implant surface condition Implant number Need of progressive loading Implant design Implant size CONTEMPORARY IMPLANT DENTISTRY, CARL E MISCH, 3RD EDITION Aim : decrease strain in the bone thereby decrease microfracture  increase SA
  65. 65. Dense cortical D1 Bone Analogous to oak or maple wood Almost all dense cortical bone Mostly seen in anterior mandible and sometimes in posterior mandible
  66. 66. Advantages/disadvantages of D1 bone Highly mineralized Excellent bone strength Best implant bone contact Less force transmission to apical thirds Implant crown ratio>1 Less blood supply – not regenerative Easily overheated Implant height limited to less than 12mm
  67. 67. Prior to osteotomy… Amount of heat generated by each drill is directly related to the bone removal by each drill First drill – 2mm diameter Rotational speed – 2000rpm Intermittent pressure  “bone dances”
  68. 68. Osteotomy preparation in D1 bone •Ext/Int irrigation •Intermittent pressure •Pause 3-5mins •New drills •Incremental drill sequence Overheating •Primarily from periosteum •Minimal reflection •Precise approximation Blood supply •Greater width •Greater height •Slower speed used Final osteotomy drill
  69. 69. •Short of full osteotomy depth •Allows passive implant fit •Removed drill remnants Bone tap •Unthread ½ turn to relieve internal stresses Final implant placement •Slower healing rate •5 months to achieve mature interface healing •3-4 months •May use immediate loading Stage II recovery
  70. 70. D2 bone Dense-to-thick porpus cortical and carse trabeculae Hounsfield values – 750-1250 units Analogous to spruce or white pine wood Occurs mostly in anterior mandible and posterior mandible Ideal implant dimension – 4mm diameter ; 12 mm height
  71. 71. Advantages/disadvantages Excellent implant surface healing Secure initial rigid interface Intrabony blood supply
  72. 72. Osteotomy preparation in D2 bone Rotation of drill – 2500 rpm Ext/int irrigation used Pause every 5-10 seconds – pumping motion Drill sequence similar to D1 bone Crestal bone drills should be used – reduce mechanical trauma Bone tap – engages lateral or apical cortical bone
  73. 73. Healing Excellent blood supply Initial rigid fixation Lamellar bone interface < 60% - 4 months healing interval Abutment placement may commence
  74. 74. D3 bone Thinner porous cortical bone Hounsfield values – 375 – 750 HU Analogous to balsa wood Found in anterior maxilla and anterior mandible/maxilla Ideal implant dimension – 4X12 Roughened implant body – acid etched or resorbable blast media
  75. 75. Advantages/ disadvantages Time and difficulty for preparation is minimal Blood supply is excellent Highest survival rate
  76. 76. Disadvantages of D3 bone Bone anatomy • Anterior maxilla is narrow Osteotomy • Lateral perforation • Oversize by mistake • Apical perforation BIC • 50% Implant placement • One time • In level with crestal bone Implant design •TPS or Hydroxyapatite coated •Costly •Threaded •Greater SA •Press fit Healing •6 months •Progressive loading more important than D1 or D2
  77. 77. D4 bone Least density – no cortical crestal bone Found in posterior molar region Analogous to stiff Styrofoam Ideal Implant height – 14 mm (min 12 mm)
  78. 78. Disadvantages Difficult to obtain rigid fixation Rotating drills not to be used apart from pilot drill Osteotomes may be used to compress osteotomy site Cortical bone in the opposite landmark to be engaged (if any) Increase number of implants to improve load distribution No cantilever advocated
  79. 79. Summary Densities vary depending of the location of edentulous ridge and the period of edentulousness D1 is the strongest bone - 10 times greater than D4 Minimum of 12mm height of implant required for initial stability Additional bone healing and incremental loading will improve bone density
  80. 80. Conclusion Bone remodels in relationto the forces excerted upon it – density varies
  81. 81. References Textbookof human histology , Inderbir Singh ; 5th ed Contemporary implant dentistry, Carl E Misch, 3rd edition Orban B: Oral histology and embryology, ed 3, St Louis, 1953, Mosby Melsen, Birte. The cranial base: the postnatal development of the cranial base studied histologically on human autopsy material. Vol. 32. Acta Odontologica Scandinavica, 1974. Neufeld JO: changes in the trabecular pattern of the mandible following the loss of teeth, J Prosthet Dent 685-697, 1958 Frost, H. M. "Mechanical adaptation. Frost’s mechanostat theory." Structure, function, and adaptation of compact bone (1989): 179-81
  82. 82. Sogo, Motofumi, et al. "Assessment of bone density in the posterior maxilla based on Hounsfield units to enhance the initial stability of implants." Clinical implant dentistry and related research 14.s1 (2012): e183-e187. Norton, Michael R., and Carole Gamble. "Bone classification: an objective scale of bone density using the computerized tomography scan." Clinical oral implants research 12.1 (2001): 79-84. Misch, C. E., and M. W. Bidez. "Implant-protected occlusion: a biomechanical rationale." Compendium (Newtown, Pa.) 15.11 (1994): 1330-1332.
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this gives a detailed description for the bone density consideration during implant placement. The presentation is available upon request. Mail me at apurvathampi@gmail.com

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