Growth rotations 1 /certified fixed orthodontic courses by Indian dental academy


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Growth rotations 1 /certified fixed orthodontic courses by Indian dental academy

  1. 1. Growth Rotations 1
  2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education 2
  3. 3. “An intensive study of the growth of the human head will inevitably lead to the realization that it involves the most complicated anatomical complex in all creation. The interrelationships are infinite and the causes and effects of these relationships are almost imponderable. The more our knowledge increases the more our ignorance unfolds. The vast stretches of the unanswered and the unfinished still outstrip our collective 3 comprehension. It is little wonder that the allied
  4. 4.  Introduction  Terminologies  Concepts of Mandibular Rotations  Concepts of Maxillary Rotations  Tooth eruption and facial development  Prediction of growth rotations  Clinical implications of Rotations  Conclusion 4
  5. 5. Introduction  First publication on the growth of the face-18th century.  Hunter suggested that mandible lengthens due to resorption of the anterior surface of ramus and deposition posteriorly. 5
  6. 6. Introduction Growth was studied using stains and inserting metal wires 6
  7. 7. Introduction  Cephalometrics introduced in 1930s.  Originally used to reveal the anatomy of head.  Since longitudinal study is possible it was used to test various concepts concerning the mechanisms of postnatal enlargement of head. 7
  8. 8. Introduction  Measurements and tracings showed little changes in the facial form.  The development in the form of the face was considered static. 8
  9. 9.  With the use of metallic implants as markers it was seen that mandibular corpus rotates during growth but the shape is kept stable by surface remodeling. 9
  10. 10. 10
  11. 11. Introduction  Lande in 1952 observed that the lower border becomes less steeply inclined with growth.  The phrase ‘growth rotation’ was introduced by Bjork in 1955.  Metallic implants were precise markers from which sites and amount of growth and resorption could be found.  Superimposing two consecutive tracings showed that the older mandible had rotated. 11
  12. 12. Types of rotation  Forward rotation (Bjork)/ Counterclockwise (Schudy)  Backward rotation (Bjork) / Clockwise (Schudy) 12
  13. 13. Posterior growth is greater than the anterior growth 13
  14. 14. Anterior growth is greater than posterior growth. 14
  15. 15. Terminologies.  1965-Schudy introduced clockwise and counterclockwise rotation.  1969-Bjork discussed different directions of rotation of the mandibular implant line and the relation of these to mandibular form. 15
  16. 16.  1970-Odegard described rotation as the change in the orientation that can occur between implant line and lower border of the mandible.  1977-Lavergne and Gasson described the terms Positional and Morphogenetic rotations.  1983-Bjork and Skieller gave the termsTotal rotation. Matrix rotation. Intramatrix rotation. 16
  17. 17.  1985-Dibbets introduced the term Counterbalancing rotation.  1988-Solow,Houston True rotation. Apparent rotation. Angular remodeling of the lower border.  Proffit- used the terms Internal rotation. Total rotation . External rotation. 17
  18. 18. 18
  19. 19. Core 19
  20. 20. 20
  21. 21. Total / True / Internal  Is the rotation of the mandibular corpus and is measured as a change in inclination of the implant line, in the mandibular corpus relative to the anterior cranial base. 21
  22. 22. When implant line rotates forward relative to the S-N , total rotation is designated negative. Converging S-N lines-forward rotation. 22
  23. 23. 23
  24. 24. MATRIX / APPARENT /TOTAL  Rotation of the soft tissue matrix of the mandible relative to the anterior cranial base.  Soft tissue matrix is defined by a tangential mandibular line . 24
  25. 25. Negative when mandibular line rotates forward relative to S-N line. ‘Pendulum movement’. Centre of rotation at the condyle. 25
  26. 26. 26
  27. 27. Intramatrix / Angular remodeling of lower border / External rotation- Defined by the change in inclination of the implant line relative to the tangential mandibular line. 27
  28. 28. 28
  29. 29.  Rotation of the corpus inside the soft tissue matrix.  Forward rotation of the corpus relative to the tangential line is negative.  Centre of rotation some where in the corpus.  Dependent on the rotation of maxilla and occlusion of teeth. 29
  30. 30. ----- + +++ ++ 30
  31. 31. + ----- +++ ++ - 31
  32. 32. According to Bjork and Skieller  The mandible “wiggles” within the matrix  This wiggling is associated with the corpus but is caused by the growing condyle.  Rotation results from or compensates for, a genetically determined program. 32
  33. 33. ANGULAR REMODELING OF LOWER BORDER  Rotation should be used to describe the angular movement of one rigid body relative to another.  Single body changes in form-surface accretion and removal- Angular changes  Makes a terminological distinction between-the measure of the amount of remodeling that occurs at the mandibular border and the rotational process that causes it. 33
  34. 34. BJORK SOLOW,HOUSTON PROFFIT Rotation of the mandibular core relative to cranial base. Total Rotation True Rotation Internal Rotation Rotation of mandibular plane relative to cranial base. Matrix Rotation Apparent Rotation Total Rotation Rotation of mandibular plane relative to core of the mandible. Intramatrix Rotation Angular External Remodeling of Rotation lower border 34
  36. 36.  Direction of total rotation more forward than the matrix rotation pronounced remodeling takes place at the lower border of the mandible.  Forward intramatrix rotation lifts up the anterior part of the corpus from the soft tissue matrix-APPOSITION.  Posterior part pressed down into the matrix-RESORPTION. 36
  37. 37.  The center of rotation for total rotation depends on the other 2 centers.  The vertical facial development is strongly related to the rotation of both the jaws.  Average individual-rotation 4-adult life Total rotation: -15.4o Matrix : -4.1o (27%) Intramatrix : -11.3o (73%) 37
  38. 38.  Total Rotation- Matrix Rotation =Intramatrix Rotation  Expression of remodeling at the lower border. 38
  39. 39. Positional and Morphogenetic Rotation.  Introduced by Lavergne and Gasson. Positional Rotation Describes the position of mandible within the head. 39
  40. 40. Morphogenetic Rotation Concerns the shape of the mandible.  Superimposition done on line through condylion and pogonion.  The angle formed between the 2 implant linesdegree of morphogenetic rotation.  Similar to Bjork’s intramatrix but not identical. 40
  41. 41.  Bjork considered key factor of intramatrix to be found in a rotation of mandibular corpus inside the matrix.  Lavergne and Gasson – consider the forward and backward growth of the ramus the main mechanism for shortening and elongating the effective length. 41
  42. 42.  Sagittal discrepancies-minimized by opening and closing the mandible. 42
  43. 43.  “It is a compensating mechanism which is capable of enlarging or reducing mandibular length as measured along the condylion-pogonion diagonal” 43
  44. 44. 44
  45. 45. The Third Option-Dibbets  The first option-Bjork and Skieller’s Intramatrix rotation-rotation of the mandibular core relative to the lower border is the result of genetically determined condylar growth.  The second option-Hunterian concept or the Morphogenetic rotation . 45
  47. 47. Superimposed on the implants Change in the inclination of the implant line relative to the mandibular plane. 47
  48. 48.  This suggests1.when the mandibles are superimposed on the their contours they are identical in shape and size. 2.The condyle grows on a circular arc (c-c’) with radius from the chin to condyle.  This concludes1.The external configuration need not change. 2.Any depositional-resorptive activity maintains the original contours. 48
  49. 49. The painting may be rotated within the frame but the external outline, configuration and dimensionality, of the frame is not lost. 49
  50. 50.  ‘Every deflection of condylar growth direction creates the possibility of compensatory remodeling mostly of the lower border resulting in intramatrix rotation’.  Actual effect of growth of the condylar cartilage is neutralized to a given extent. 50
  51. 51.  The second option-The Hunterian concept or principle of Morphogenetic rotation. Superimposition based on traditional Hunterian conception of Posterior ramal deposition and Anterior ramal resorption. Enlarging and reducing the mandibular length measured along the Co-Pog line. 51
  52. 52.  The third option-Based on 2 divergent patterns of mandibular growth. 1.Intramatrix rotation with absence of enlargement. 2.Linear condylar growth-evidencing mandibular enlargement. Suggested mechanism - COUNTERBALANCING ROTATION 52
  53. 53. COUNTERBALANCING ROTATION“It pertains to the circular condylar growth, accompanied by selective co-ordinated remodeling , which does not contribute to the incremental growth of the mandible”. 1.The actual path of the condyle relative to fixed and stable points inside the mandible is accompanied by selective remodeling-neutralizes growth. 2.Resuts in selective enlargement of the mandible, apart and distinct from mechanisms that have been described in literature. 53
  54. 54. Counterbalancing Proportion  It is the quotient between mandibular and condylar incremental growth and is expressed as a percentage.  Condylar growth and mandibular growth are weighted in relation to one another.  The proportion gives a percentage of condylar relocation that has contributed to actual mandibular enlargement. 54
  55. 55.  Mandibular growth= Pg-Ar1-PgAr2  Condylar growth=distance from Ar1 to Ar2. Counterbalancing proportion= Growth from Ar-Pg x 100% Condylar incremental growth 55
  56. 56.  According to the concept of congruous mandibular growth the proportion should be 100%.  But study done by Dibbets shows that it ranges from 50% to 90%.  This percentage strongly correlates type of malocclusion.  Class III-85%  Class I -76%  Class II-59% 56
  57. 57. Concepts of Mandibular rotations What causes mandibular rotation ? 57
  58. 58. Enlow’s concept.  The ramus has a sequence of remodeling changes to provide for 4 basic functions. 1. Elongation of the corpus. 2. Accommodates for horizontal growth of middle cranial fossa and pharynx. 3. Accommodates for vertical growth of nasomaxillary complex. 4. To position the mandibular corpus in proper position to maxillary corpus. 58
  59. 59.  The ramus provides intrinsic capacity for adaptation .  If its adequate then class I occlusion results. MANDIBULAR ROTATIONS Displacement Remodeling 59
  60. 60. Displacement  Changes in the junctional contact with the cranial floor and maxilla.  Cranial base angleOpen-downward and backward rotation of mandible. Closed-forward rotation. 60
  61. 61. 61
  62. 62. Closed angle Open angle 62
  63. 63. Short nasomaxillary complex-forward rotations 63
  64. 64. Long nasomaxillary complex – backwad rotations 64
  65. 65. Remodeling 65
  66. 66.  Mandible has to remodel to1.Produce a more upright ramus. 2.To accommodate for displacement rotations. 66
  67. 67.  Opening and closing of the gonial angle compensates for extreme forward or backward rotation. 67
  68. 68. Ramal remodeling Ramus moves posteriorly-increasing the length of the corpus. Grows horizontally to match the growth of the pharyngeal space. Ceases when growth stops 68
  69. 69.  2nd type of remodeling.  Makes ramus more upright but does not increase the horizontal dimension. 69
  70. 70. Schudy’s concept  Variation in the growth at the condyles and the molar area is responsible for the rotation of the corpus of the mandible.  Clockwise rotation-More posterior vertical growth than condylar growth.  Counterclockwise-More condylar growth than the combined vertical growth. 70
  71. 71. 71
  72. 72.  Vertical ‘elements’ of growth Growth at the condyles = I- AP growth of nasion. II- Vertical growth of corpus of maxilla. III-Vertical growth of maxillary alveolar process. IV-Vertical growth of mandibular alveolar process. 72
  73. 73. Posterior growth analysis  Ratio between the vertical and horizontal growth.  A=I+II+III+IV 73
  74. 74. Bjork’s concept  Implant studies show-growth of the mandible occurs essentially at the condyles.  The anterior aspect of the chin-stable.  Lower border of the mandibleAt the symphysis-apposition. At the angle -resorption.  The appositional and resorptive areas may change-determining the type of growth. 74
  75. 75.  The growth of the condyle occurs in a upward and forward curving manner.  The center of rotation may be located-posteriorly or anteriorly or somewhere in between.  The center may not always lie at the TMJ. 75
  76. 76. 76
  77. 77. FORWARD ROTATION  THREE TYPES: TYPE I -center at the TMJ. -underdeveloped anterior face height. -deep bite. Cause: imbalance or powerful musculature. 77
  78. 78. 78
  79. 79.  Type II -center at the incisal edges of the lower teeth. - marked increase in posterior face height and normal anterior face height. Increase in posterior face height Lowering of the middle cranial fossa. Increased height of ramus 79
  80. 80.  Increase in ramus height maybe due to vertical growth of the condyle.  But this vertical lowering manifestes as forward rotation –muscular and ligamentous attachments.  Eruption of the molars keep pace with the rotation. 80
  81. 81. 81
  82. 82. Type III -center of rotation is at the premolars. -deep bite occurs. cause: Anomalous occlusion-large overjets. 82
  83. 83. 83
  84. 84.  The inclination of teeth influenced by jaw rotations.  Path of eruption of teeth-mesial.  Crowding occurs in the anterior segment‘PACKING’ 84
  85. 85. BACKWARD ROTATION  TWO TYPES:  Type I -center at the TMJ. -underdevelopment of the posterior face height occurs-open bite. causes: 1.middle cranial fossa is raised. 2.orthodontic bite raising appliance. 3.oxycephaly. 85
  86. 86. 86
  87. 87. TYPE II -center at distal most occluding molars. Cause: sagittal (backward ) growth of the condyle. -The mandible is carried forward but due to muscle and ligaments attachments its rotated backwards. 87
  88. 88. - the eruption of lower molars was hindered-the rotation not due to overeruption. -seen in condylar hypoplasia. 88
  89. 89. 89
  90. 90. 90
  91. 91. Thank you Leader in continuing dental education 91