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Growth and development of the mandible /certified fixed orthodontic courses by Indian dental academy

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Growth and development of the mandible /certified fixed orthodontic courses by Indian dental academy

  1. 1. GROWTH AND DEVELOPMENT OF THE MANDIBLE www.indiandentalacademy.com
  2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  3. 3. GROWTH AND DEVELOPMENT OF THE MANDIBLE ANATOMY  PRE NATAL GROWTH  POST NATAL GROWTH  ANOMALIES OF DEVELOPMENT  www.indiandentalacademy.com
  4. 4. Prenatal growth of the mandible www.indiandentalacademy.com
  5. 5. Neural crest cells Ist brachial arch Mandibular process Mandibular bone www.indiandentalacademy.com CT tissue
  6. 6. www.indiandentalacademy.com
  7. 7. 36 – 38 DAYS Ectomesenchymal condensation mandible Lateral to Meckels cartilage Osteogenic membrane www.indiandentalacademy.com
  8. 8. 6 th week www.indiandentalacademy.com
  9. 9. 10 – 12 weeks  Secondary accessory cartilages appear www.indiandentalacademy.com
  10. 10. 10 week - condylar cartilage   Appears in the Ramal region Endochondral bone (14 week) www.indiandentalacademy.com
  11. 11. Condylar Cartilage Serves as a growth site  Brings changes in the mandibular position and form  Growth increases during puberty  Peak 12 – 14 years  Ceases by 20 years  www.indiandentalacademy.com
  12. 12. 7 th month IUL    1 or 2 small cartilages appear in the future mental region Mental ossicles Incorporated into the intramembranous bone of symphsis www.indiandentalacademy.com
  13. 13. Features of neonatal mandible  Ascending Ramus low and wide Large Coronoid process  Body – open shell containing tooth buds and partially formed deciduous teeth  Mandibular canal that runs low in the body  www.indiandentalacademy.com
  14. 14. Features of neonatal mandible High Coronoid process Wide Ramus www.indiandentalacademy.com
  15. 15. Differential growth During fetal life    8 weeks - mandible > maxilla 11 weeks - mandible = maxilla 13 – 20 weeks maxilla > mandible At birth   Mandible tends to be retrognathic Early post natal life orthognathic www.indiandentalacademy.com
  16. 16. Post natal growth of the mandible www.indiandentalacademy.com
  17. 17. Main sites of post natal growth in the Mandible  Condylar cartilage  Posterior border of the Rami Width  Height length Alveolar ridges www.indiandentalacademy.com
  18. 18. Symphysis Menti   Limited growth till fusion No widening after fusion www.indiandentalacademy.com
  19. 19. Mental Foramen www.indiandentalacademy.com
  20. 20. Mental Foramen  Vertical relation within the body of the mandible www.indiandentalacademy.com
  21. 21. Mental Protuberance   Formed by mental ossicles from accessory cartilage and ventral end of Meckel’s cartilage Poorly developed in infants www.indiandentalacademy.com
  22. 22. Mental Protruberance Forms by osseous deposition during childhood  Prominence is accentuated by bone resorption above it  www.indiandentalacademy.com
  23. 23. Mental Protuberance    Reversal between 2 growth fields Concave convex Reversal line could be High or low www.indiandentalacademy.com
  24. 24. Alveolar process    Adds to the height and thickness of the mandibular body Teeth absent fails to develop Teeth extracted resorbs www.indiandentalacademy.com
  25. 25. Alveolar process    Acts as buffer zone Maintains vertical height Adaptive remodeling makes orthodontic tooth movement possible www.indiandentalacademy.com
  26. 26. Alveolar process Lingual movement of anteriors www.indiandentalacademy.com
  27. 27. Condylar cartilage   Secondary cartilage Important contribution to the overall length of the mandible www.indiandentalacademy.com
  28. 28. Condylar cartilage  ‘ v ‘ principle of Enlow www.indiandentalacademy.com
  29. 29. Is the Condylar cartilage the principle force that produces the displacement of the mandible ?  For many years considered primary growth center  FMH - Condyle absent yet mandible positioned normally  Considered secondary cartilage -no intrinsic growth potential www.indiandentalacademy.com
  30. 30.  PETROVIC ET AL – role of hormones  Experiments involving transplantation of the condyle  JOHNSTON ETAL detached condyle from the body of mandible in guinea pigs  Injection of papain –inhibition of chondrogenesis  RANCHOW MOSS - Condylectomy – immediate resumption of growth www.indiandentalacademy.com
  31. 31.    Condylar cartilage and functioning muscles translate the mandible and in the absence of one the other does best to compensate Integrity of periosteum is important When environment is changed compensatory contributions are enhanced www.indiandentalacademy.com
  32. 32. CURRENT CONCEPT   Condylar cartilage does have a measure of intrinsic genetic programming But extra condylar factors are needed to sustain this activity Physiologic inductors Intrinsic and extrinsic biomechanical forces ENLOW :   Increase pressure – growth inhibition Decrease pressure – stimulates growth www.indiandentalacademy.com based mainly on animal experiments
  33. 33. Lingual Tuberosity   Grows posterior and medial by deposition Resorptive field belowLingual fossa www.indiandentalacademy.com
  34. 34. Coronoid Process  POSTERIOR Lingual surface SUPERIOR MEDIALLY  Follows ‘v’ principle www.indiandentalacademy.com
  35. 35. Coronoid Process  ‘’V’ PRINCIPLE OF ENLOW www.indiandentalacademy.com
  36. 36. Coronoid Process  Deposition on lingual side MEDIAL  Resorption INCREASES VERTICAL LENGTH POSTERIOR GROWTH - buccal surface www.indiandentalacademy.com
  37. 37. RAMUS   Posterior border deposition Anterior border resorption www.indiandentalacademy.com
  38. 38. Ramus   Superior part of ramus below sigmoid notch Lower part of ramus below the Coronoid process LINGUAL -DEPOSITION BUCCAL RESORPTION BUCCAL DEPOSITION LINGUAL RESORPTION www.indiandentalacademy.com
  39. 39. Ramus www.indiandentalacademy.com
  40. 40. Posterior border of Ramus   Depository and keeps pace with condylar growth Angle of growth vertical  horizontal Posterior margin below condyle --resorptive field www.indiandentalacademy.com
  41. 41. Ramus Uprighting Posterior border – deposition Inferior > superior  Anterior border – resorption Inferior >superior  Condylar growth more vertical www.indiandentalacademy.com
  42. 42. Age related differences in mandibular growth MARK HANS , DONALD ENLOW AJO DEC 1995     30 well preserved human mandibles from dental ages 1 – 13 years Ground and polished microscopic sections were obtained from the Ramus Distribution of various types of resorptive vs depository surfaces were recorded 2 additional patterns of Ramal remodeling were noted www.indiandentalacademy.com
  43. 43. Type A – Classical Pattern www.indiandentalacademy.com
  44. 44. Type B – Vertical Variation  www.indiandentalacademy.com
  45. 45. Type C - Rotation Variation www.indiandentalacademy.com
  46. 46. Conclusions    All 3 patterns cause downward & forward displacement but to varying degree ENLOW’S original description of general body growth & remodeling type A most common but one pattern of remodeling is incomplete The difference in pattern were large enough to influence orthodontic treatment www.indiandentalacademy.com
  47. 47. Ramus corpus junction   Inferior Border of junction resorption Forms Antegonial notch www.indiandentalacademy.com
  48. 48. Gonial region  Anatomically variable B - Resorption  Gonial flares inwardly outwardly L - deposition B -deposition L - resorption  Depends upon growth direction of ramus and condyle www.indiandentalacademy.com
  49. 49. Mandibular foramen    Ramus -- posterior and superior direction Mandibular foramen drifts in backward & upward direction Maintains constant position -[A-P] www.indiandentalacademy.com
  50. 50. Condylar neck     Anterior margin deposition Posterior margin Lingual and buccal margin Rotation – posterior border resorption Periosteal resorption Endosteal deposition www.indiandentalacademy.com
  51. 51. Ramal growth     Backward transportation of entire ramus – elongation of mandibular body Displacement of corpus –anterior direction Vertical lengthening of ramus as mandible is displaced Movable articulation during various growth changes www.indiandentalacademy.com
  52. 52. Role of muscles in Mandibular growth MOSS    CORONOID GONIAL ANGLE Medial CONDYLE Temporalis Masseter & pterygoid internal pterygoid www.indiandentalacademy.com
  53. 53. Skeletal units of mandible www.indiandentalacademy.com
  54. 54. Role of muscles in Mandibular growth  Decrease muscle activity Flattening of Gonial angle Reduction of Coronoid process www.indiandentalacademy.com
  55. 55. Growth of mandible during pubescence ARTHUR LEWIS , ALEX ROCHE AJO OCT 1982    Spurts in the mandible were analyzed in 67 subjects from Fels longitudinal study Spurts in Ar-Go , Ar-Gn , Go-Gn A spurt was defined as an annual increment exceeding the immediately preceding annual increment by at least 1 mm www.indiandentalacademy.com
  56. 56. Growth of mandible during pubescence www.indiandentalacademy.com
  57. 57. Growth of mandible during pubescence conclusion      Spurts in mandibular dimensions are common but not universal More common in boys 1.5 yrs earlier in girls 1st pubertal spurt usually occurs before PHV Almost all 1st pubertal spurts occur one year after US ossification and before menarche www.indiandentalacademy.com
  58. 58. Anomalies of development  AGNATHIA – deficiency of neural crest cells in lower part of the face DOWNS  MICROGNATHIA - TREACHER COLLINS PIERRE ROBIN www.indiandentalacademy.com
  59. 59. Anomalies of development  BIFID /DOUBLE CONDYLE  MACROGNATHIA  MICROGENIA  TORUS MANDIBULARIS www.indiandentalacademy.com
  60. 60. References        Craniofacial embryology – SPERBER Facial growth – ENLOW Contemporary orthodontics – PROFFIT Handbook of orthodontics – MOYERS Principles and practice of orthodontics – GRABER Growth of mandible during pubescence – ROCHE,LEWIS AO OCT 1982 Age related differences in Ramus growth – ENLOW,HANS AJO DEC 1995 www.indiandentalacademy.com
  61. 61. Thank you www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com

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