Growth & development of mandible /fixed orthodontic courses


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  • Growth & development of mandible /fixed orthodontic courses

    2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education
    3. 3. INTRODUCTION The human mandible has no one design for life. Rather it adapts & remodels through the seven stages of life, from the slim arbiter of things to come in infant, through a powerful dentate machine & even weapon in the full flesh of maturity, to the pencil thin, porcelain like problem that we struggle to repair in the adversity of old age.” “
    4. 4. prenatal growth of mandible
    6. 6. prenatal growth of mandible °Nerve→osteogenesis(Neurotrophic factors) Ectomesenchyme interacts(36-38days iul) Epi of 1st Arch Osteogenic Memberane
    7. 7. Trough for acc dev Tooth buds 1 centre of ossification(6th week) below around Inferior Alv Nerve Incisive branch
    8. 8. prenatal growth of mandible • spread of IM ossification dorsally and ventrally →body and ramus of the mandible presence of neuromuscular bundle→Mandibular foramen and canal and mental foramen
    9. 9. Fate of Meckel`s cartilage
    10. 10. PRENATAL GROWTH OF MANDIBLE SECONDARY ACC CARTILAGES (10TH -14TH WEEK I U L) -condylar cartilage -coronoid cartilage -Mental ossicle cartilage
    11. 11. PRENATAL GROWTH OF MANDIBLE • Secondary cartilage of coronoid process • Develop within temporalis muscle • Incorporated into IMB of ramus • Disappear before birth
    12. 12. PRENATAL GROWTH OF MANDIBLE • 1/2 Cartilages Ossify (7th month of IUL) Mental ossicles syndesmosi s Intramembranous bone → synostosis
    13. 13. PRENATAL GROWTH OF MANDIBLE • CONDYLAR CARTILAGE(10TH WEEK IUL) • Grow interstitially and oppositionally
    14. 14. CONDYLAR CARTILAGE • 1ST Evidence of endochondral bone (14th week iul) • Much of cartilage replaced with Bone by middle of fetal life • Upper end →Growth cartilage and Articular cartilage • Changes Mand position and form • Growth ↑ at puberty peak b/n 12 ½ -14yrs • Ceases →2o yrs of life
    15. 15. NEONATAL MANDIBLE Ramus→Low & wide coronoid→large & above the condyle Body→open shell containing tooth buds Mand canal→low in the body
    16. 16. DIFFERENTIAL GROWTH During fetal life 8weeks - MANDIBLE> MAXILLA 11weeks -MANDIBLE= MAXILLA 13-20weeksMAXILLA>MANDIBLE AT BIRTH Mandible tends to be retrognathic Early postnatal life -orthognathic
    18. 18. MECHANISMS OF GROWTH Growth Of The Mandible Primarily Involve Bone remodeling Process Of Bone Deposition And Resorption Cortical drift Combination of bone deposition and resorption resulting in growth movement towards deposition surface Displacement Movement of whole bone as a unit I) Primary displacement II) Secondary displacement
    19. 19.
    20. 20.
    21. 21. THEORIES OF GROWTH • GENETIC THEORY Bone ̶ primary determinent Cartilage̶ primary determinent The soft tissue matrix
    22. 22. SUTURAL THEORY • Craniofacial growth→sutures • Suture transplanted • Sutures pulled apart • Sutures compressed • Sutures are sites that react ̶ not primary dereminants
    23. 23. CARTILAGINOUS THEORY • Growth of maxilla ̶ Nasalseptum cartilage • Transplantation Epiphyseal plate Nasalseptal cartilage Condylar cartilage Removal of condyle
    24. 24. FUNCTIONAL MATRIX THEORY OF GROWTH • Skeletal growth occur as a response to functional needs & mediated by the soft tissue in which it is embedded
    25. 25. ENLOW’S EXPANDING ‘V’ PRINCIPLE The growth movement & enlargement of these Bones occur towards the wide ends of the ‘V’ as a result of differential deposition & selective resorption
    26. 26. ENLOW’S COUNTERPART PRINCIPLE • The growth of any given facial /cranial part relates specifically to other structural & geometric ‘counterparts’ in the face & cranium Diff parts & counter parts Maxillary & Mandibular arches Middle cranial fossa breadth of Ramus
    27. 27. Parts of Mandible derived From 1. INTRAMEMBRANOUS OSSIFICATION * Whole body of mandible except the anterior part * Ramus of mandible as far as mandibular foramen 2 . ENDOCHONDRAL OSSIFICATION * Anterior portion of the mandible (symphysis) * Part of ramus above the mandibular foramen * Coronoid process * Condylar process
    28. 28. Timing of growth • Growth in width is completed 1st then growth in length finally growth in height
    29. 29. Growth in width • Intercanine width does not ↑ much after 12yrs • Both molar & bicondylar width show small ↑ until the end of growth in length • Ant width stabilize earlier
    30. 30. Growth in length • Continues through the period of puberty Girls – 14 -15 yrs Boys – 18 yrs
    31. 31.
    32. 32.
    33. 33. POST NATAL GROWTH OF MANDIBLE • Mandible – Developmentally & Functionally divisible into skeletal subunits
    34. 34. • Mandible undergoes largest amt of growth postnatally and exhibits largest variability in morphology • The main sites of postnatal growth ‫٭‬At condylar cartilages ‫ ٭‬Posterior border of rami ‫٭‬Alveolar ridges
    35. 35. THE RAMUS • Key role of ramus in placing the corpus & dental arch into ever changing fit with growing maxilla & the faces limitless strl variations • By Remodeling adjustments in Ramus length & Ant post width.
    36. 36.
    37. 37. THE RAMUS Relocates postly Resorption Deposition posteriorly anteriorly
    38. 38. LINGUAL TUBEROSITY • Direct Anatomic equivalent of Max tuberosity • Inaccessible to cephalometric studies • Major Growth & Remodeling site • Effective boundary b/n Ramus & corps
    39. 39. LINGUAL TUBEROSITY • Deposition • Resorption Postly & Medially Below (Lingual fossa )
    40. 40. Lingual Tuberosity Remodels in post direction with slight lateral shift Lingual shift of Ant part of Ramus ↑ Length of corpus
    41. 41. Ramus to carpus Remodeling • Making room last Molar
    42. 42. Ramus to carpus Remodeling Growth direction fallows‘V’PRINCIPLE ‘X’ arrows Remodeling activity does not occur only on ant & post barder
    43. 43. Coronoid process • Propellar like twist • Lingual side faces posteriorly superiorly medially
    44. 44. Coronoid process Fallows ‘V’ PRINCIPLE ‘V’ oriented vertically
    45. 45. Coronoid process ‘v’ PRINCIPLE ‘V’Oriented horizontally
    46. 46. Coronoid process Coronoid process → medially to become post part of carpus Buccal side → Resorptive
    47. 47. Ramus • Superior part of ramus the area below sigmoid notch
    48. 48. Ramus
    49. 49. Antigonial notch Size of the notch ↑ed – downward rotation Of carpus relative to the Ramus
    50. 50. The size of the notch depends upon Ramus – Carpus junction
    51. 51. Post edge Ramus is a major growth site Condyle grows obliquely upward & backward The angle of growth is variable The gonial region is Anatomically variable
    52. 52. Mand Foramen – midway b/n Ant & post borders of Ramus
    53. 53. The Mandibular condyle • Secondary cartilage • not a primary center of growth, but rather * Secondary in Evolution * Secondary in Embryonic origin * Secondary in adaptive responses
    54. 54. condyle • Cartilage is special nonvascular tissue • firm matrix – unyielding to the pressure • Endochondral growth mechanism
    55. 55. • Provides pressure tolerant articular contact • Multidimensional growth capacity in response to ever changing developmental conditions & variations
    56. 56. • Capsular layer of poorly vascularised connective tissue –highly cellular • Chondroblasts –cellular proliferation • Chondroblasts – hypertrophy • Zone of resorptive & Bone deposition
    57. 57. • Proliferative process produces upward & backward growth movement • Multidirectional proliferative capacitythe arrangement of daughter cells does not reflect direction of growth
    58. 58. • The cortical layer of IMB continues on to the condylar neck Ant margin of condylar neck – depository grows supe’ly post margin - depository grows on to post barder
    59. 59. • Lingual & Buccal sides - Resorptive
    60. 60. • V-shaped cone of condylar neck growing towards its wider end
    61. 61. • The condyle can’t play king pin role of “Master center” in pace-setting the growth Bilaterally condyle-lacking mand occupy normal Anatomic position Condylar remodeling acts with displacement as co-participants but not as driving force
    62. 62. Current concept • Condylar cartilage does have some intrinsic genetic programming • But extracondylar factors are needed to sustain this activity 1)Intrinsic & extrinsic biomechanical forces 2)physiologic inductors ENLOW; ↑amt of pressure – inhibit the growth ↓ amt of pressure – stimulate the growth
    63. 63. • Mandible is less responsive to orthopedic forces than maxilla • Mand orthopedics must modify growth signals targeted at both ramus & condyle to be maximally effective
    64. 64. MENTAL FORAMEN
    65. 65. ALVEOLAR PROCESS Adds ht & thickness to the body of the Mand Teeth absent fails to develop Resorbs after tooth extraction
    66. 66. Alveolar process • Maintain occlusal relationship during differential mandibular & midfacial growth– buffer zones • Maintains vertical height • Adaptive remodeling makes orthodontic tooth movement possible
    67. 67. Lingual movement of anteriors
    68. 68. Mental protuberance Formed by mental ossicles from accessory cartilage and ventral end of Meckel’s cartilage Poorly developed in infants
    69. 69. Mental protuberance Forms by osseous deposition during childhood Prominence is accentuated by bone resorption above it Reversal between 2 growth fields Concave  convex Reversal line could be High or low
    70. 70. Chin • Protrusive chin is unique human trait • More prominent in male • Less prominent in female
    71. 71. Factors Affecting Growth Systemic Factors Genetic Hormonal imbalance Nutrition Systemic illness or chronic illness Localized alteration/ diseases of uterus Systemic illness in mother Drugs
    72. 72. B) Local factors 1. Vascular abnormality 2. Lymphatic disturbance 3. Neurologic disease 4. Local infection 5. Ear infection or mastoiditis 6. Ankylosis 7. Trauma or fracture 8. Birth injury 9. Habits
    73. 73. Anomalies of mandible Some of the syndromes associated with mandibular abnormality 1)Down’s syndrome 2)Marfan’s syndrome 3)Turners syndrome 4)Kleinfelter’s syndrome 5) Pierre-robin syndrome 6) Treacher- collin syndrome
    74. 74. Congenital • Agnathia • Micrognathia • Macrognathia • Facial hemihypertrophy • Facial hemiatropy
    75. 75. Developmental • Infantile cortical hyperostosis • Achondroplasia • Torus mandibularis • Stafne’s cyst • Odontogenic cyst • Odontogenic tumor
    76. 76. Age changes of Mandible At birth Adult Old age 1 Mental foramen Near the lower border Midway b/n upper & lower border Near the upper border 2 Angle of the mandible 3 coronoid & condyloid processes Obtuse (180) Right angle Obtuse (140) Coronoid is larger & above condyle Condyle is above the coronoid 4 Mandibular canal Runs little above the mylohyoid line Present;two halves united fibrous tissue Runs parallel to the mylohyoid line Condyle is above the coronoid but in extreme old age –bent backwards Runs close to the upper border 5 Symphysis menti Reprasented by faint ridge only in the upper part Not recognisable or absent
    77. 77. References * Craniofacial embryology – SPERBER * Facial growth – ENLOW * Contemporary orthodontics – PROFFIT * Handbook of orthodontics – MOYERS * Principles and practice of orthodontics –GRABER
    78. 78.
    79. 79. Thank you Leader in continuing dental education