POST NATAL GROWTH OF MAXILLA AND MANDIBLE.pptx

The knowledge of growth-related changes is essential in planning orthodontic treatment.
Postnatally, the maxilla grows downward and forward through displacement, growth at sutures, and surface remodeling.
The mandible grows at the condylar cartilage, posterior border of the ramus, and alveolar ridges. Growth occurs through remodeling and apposition of bone.

1. POST-NATAL GROWTH OF craniofacial structures DR. TAHIR NADAF 1 ST YEAR PG DEPT. OF ORTHODONTICS 1

2. PART - 1 2

3. POSTNATAL GROWTH OF CRANIUM AND MAXILLA CONTENTS INTRODUCTION POST NATAL GROWTH OF CRANIAL BASE ANATOMY MECHANISM OF GROWTH CLINICAL IMPLICATIONS ANATOMY OF MAXILLA ARTICULATIONS OF MAXILLA AGE CHANGES IN MAXILLA 3

4. POSTNATAL GROWTH OF MAXILLA DIRECTION OF GROWTH THEORIES OF GROWTH CLINICAL SIGNIFICANCE DEVELOPMENTAL ANOMALIES OF CRANIUM REFERRENCES 4

5. INTRODUCTION The organization and complexity of growth and development is clearly evident in the changes that take place in the head and face. Face is the window of man’s mind to the world . 5

6. POST NATAL GROWTH OF CRANIAL BASE The maxilla is attached to the cranial base by means of number of sutures. The mandible too is attached to the cranial base at TMJ Cranial base is formed by endochondral ossification. 6

7. Anatomy Cranial base is divided as: Anterior cranial fossa . Middle cranial fossa . Posterior cranial fossa 7 Human Anatomy – B.D Chaurasia

8. Mechanisms of growth 8

9. Cortical remodelling refers to a net result of the process where bone deposition and resorption occur so as to bring about change in size, shape and oriental relationship of the bone. The cranium is divided into a number of compartments by bony elevations and ridges present in the cranial base. 9

10. The elevated ridges and bony partitions show bone deposition, while the predominant part of the floor shows bone resorption. 10 Essentials of Facial Growth – Enlow and Hans

11. Sutural growth Cranial base has a number of bones that are joined to one another by means of sutures. The floor of the cranium provides for the passageway of cranial nerves and the major blood vessels. The process of remodelling growth in the cranial base provides for the stability of these nerve and vascular passageways. 11

12. Synchondrosis A synchondrosis is a cartilaginous immovable type of joint where hyaline cartilage divides and is subsequently converted into bone. Certain bands of cartilage remain at the junction of various bones. These areas are called as “ synchondroses”. 12

13. In the cranial base, four types of synchondroses are seen:- 1] Intersphenoidal 2] Intraoccipital 3] Sphenoethmoidal 4] Sphenoccipital or basioccipital 13

14. Endochondral ossification starts from all the corners of synchondrosis. Ossification starts from 12-13 years and is completed by 16-17 years. Stage in hyaline cartilage described as asbestos transformation – degeneration of synchondrosis. 14

15. Synchondrosis provides pressure or compression adapted bone growth, in contrast to the tension adapted bone growth seen in sutures. Length of cranial base at birth – 63% of adult size. First year- 83% complete. 15 years – 98% complete 15

16. 16 Essentials of Facial Growth – Enlow and Hans

17. CLINICAL IMPLICATIONS ACHONDROPLASIA Deficient growth at the synchondrosis Maxilla is not translated forward -This results in abnormal depression of the bridge of the nose. THE CRANIAL BASE

18. Anomalous development of the presphenoidal elements Excessive separation of orbits and abnormally broad nasal bridge - HYPERTELORISM 18

19. MAXILLA Maxilla is a membranous bone and development/growth of maxilla is completed early when compared to mandible. Maxilla (especially width) also follows closely neural growth curve more than the general growth curve in scammon's curve. Maxilla cannot be considered as a separate bone, it has to be nasomaxillary complex because of close association or attachment of maxilla to cranial base. 19

20. Anatomy of Maxilla 20 (Human Anatomy – B.D Chaurasia )

21. Body (Corpus Maxillae) : 21 (Human Anatomy – B.D Chaurasia )

22. Posterior/ Infratemporal Surface : 22 (Human Anatomy – B.D Chaurasia )

23. Superior / Orbital surface : 23

24. Nasal / Medial Surface : 24

25. Processes : Zygomatic Frontal Palatine Alveolar process 25

26. Age Changes : At Birth : 26

27. In Adults : 27

28. In Old Age : 28

29. Percentage of craniofacial growth completed at different stage:- STAGES 1-5years 5-10years 10-20years Cranium 85% 11% 4% Maxilla 45% 20% 35% 29

30. Articulations of Maxilla Superiorly, it articulates with three bones, the nasal, frontal and lacrimal . Medially , it articulates with five bones, the ethmoid , inferior nasal concha , vomer , palatine and opposite maxilla. Laterally , it articulates with one bone, the zygomatic bone. 30

31. Postnatal Growth of Maxilla Just as the mandible remodels in a predominantly posteriosuperior manner as it simultaneously becomes displaced in an opposite anteroinferior direction the nasomaxillary complex also grows in a generally comparable way. 31

32. Mechanisms of growth 32

33. GROWTH MOVEMENTS Drift (cortical remodelling ); Combination of simultaneous deposition and resorption resulting in a growth movement towards the depositing surface has been described as cortical drift by Enlow (1963). Displacement (movement of entire bone) Primary Secondary 33

34. Displacement Maxilla is attached to the cranial base by means of a number of sutures. Thus the growth of cranial base has a direct bearing on the nasomaxillary growth. 34 Essentials of Facial Growth – Enlow and Hans

35. Primary type of displacement is also seen in the forward direction by growth of the maxillary tuberosity 35

36. A passive or secondary displacement of the nasomaxillary complex occurs in a downward and forward direction as the cranial base grows. 36

37. Growth at Sutures These includes The maxilla is connected to the cranium and cranial base by a number of sutures. Fronto -nasal suture Fronto -maxillary suture Zygomatico -temporal suture Zygomatico -maxillary suture Pterygo -palatine suture 37

38. Sutural growth mechanism 38

39. 39

40. Weinmann and sicher have pointed out that these sutures are all oblique and more or less parallel to each other. This allows the downward and forward positioning of the maxilla as growth occurs at this sutures . 40

41. SURFACE REMODELLING Massive bone remodelling by deposition and resorption occurs to bring about : Increase in size Change in shape of bone Change in functional relationship 41

42. Maxillary Tuberosity and Arch Lengthening Remodeling at the maxillary tuberosity causes horizontal lengthening. It is a depository field, hence causes lengthening and widening of the arch and provides space for the eruption of molars. Allows the clinician to “expand the arch” by distalization of molars into an area of bone deposition. 42

43. 43 Essentials of Facial Growth – Enlow and Hans

44. Lacrimal Suture The lacrimal bone is a bony island with its entire perimeter bounded by sutural connective tissue contacts separating it from many other surrounding bones . Without this ‘ perilacrimal sutural system’ a developmental gridlock would occur among the multiple developing parts. 44 Essentials of Facial Growth – Enlow and Hans

45. Key Ridge Major change in surface contour occurs along the vertical crest just below the malar protuberance called the key ridge. Anterior to it – Resorption Posterior to it – Deposition. 45

46. Alveolar Ridges It occurs by bone deposition at alveolar margins. It is termed as vertical drift. This increases the maxillary height and depth of palate 46 Essentials of Facial Growth – Enlow and Hans

47. As the teeth start erupting, bone deposition occurs at the alveolar margins. - This increases the maxillary height and the depth of the palate Alveolar bone 47

48. Palatal Remodelling The external labial side of the whole anterior part of the maxillary arch is resorptive with bone being added into the inside of the arch, the arch increases in width and the palate becomes wider . 48 Essentials of Facial Growth – Enlow and Hans

49. Anteriorly - labial side is Resorptive and palatal side is depository causes widening of palate according to “V principle 49 Essentials of Facial Growth – Enlow and Hans

50. Nasal cavity The lining surface of the bony walls and floor of the nasal chambers are predominantly resorptive , which produces a lateral and anterior expansion of the nasal chambers. 50

51. Nasal cavity Lateral surface of bony wall and floor Resorptive Downward relocation of palate Lateral and anterior expansion 51 Essentials of Facial Growth – Enlow and Hans

52. Zygomatic Bone The zygomatic bone moves in a posterior direction. This is achieved by resorption on the anterior surface and deposition on the posterior surface. The face enlarges in width by bone formation on the lateral surface of the zygomatic arch and resorption on its medial surface . 52 Essentials of Facial Growth – Enlow and Hans

53. Maxillary Sinus The lining cortical surface of the sinus are all resorptive except the medial nasal wall which is depository as it remodels laterally to accommodate nasal expansion. 53

54. Downward Maxillary Displacement The primary displacement of the whole ethmomaxillary complex in an inferior direction is accomplished by simultaneous remodelling in all areas, inside and out throughout the entire nasomaxillary region. 54

55. Direction of growth 55

56. Maxillary Width Growth in the median suture is more important for appositional remodeling in the development of maxillary width. Growth increases at the median suture mimic the general growth curve for body height and maximum pubertal growth in the median suture coincides with the time for maximum growth in the facial sutures as seen in the profile radiograph. 56

57. Maxillary Depth Length increases in the maxilla after about the second year, occurs by apposition on the maxillary tuberosity and by sutural growth toward the palatine bone. Bjork and Skieller’s implant studies show that anterior surface to be rather stable sagitally , but the maxillary arch is remodeling as it grows downward, which is why the anterior region is resorptive. 57

58. 1) Growth at maxillary tuberosity . 2) Growth at palato-maxillary suture. 3) Primary and secondary displacement 58

59. Maxillary Height . Classic implant studies of Bjork and Skiellerlo confirm that maxillary height increases because of sutural growth towards the frontal and zygomatic bones and appostional growth in the alveolar process 59

60. Eruption of teeth Palatal remodelling Primary displacement 60

61. Relevant Theories of Growth 1) Remodelling theory by Brash (1930’s) : First general theory of craniofacial growth. Postulated that all the growth occurs exclusively by bone remodelling and that sutures and cartilages have little or no role in growth of craniofacial skeleton Growth of jaw is characterized by deposition of bone at the posterior surface of maxilla and mandible. 61

62. 2 ) Sutural Dominance Theory by Weinmann and Sicher (1940’s) : According to this theory, the nasomaxillary complex is attached to the cranial base by a number of sutures which push the nasomaxillary complex downward and forward. 62

63. 3) Nasal Septal Theory by Scott (1950’s) : Also known as Cartilagenous theory. It considers that the nasal septum is the most active and important for the craniofacial skeleton growth prenatally and early post natal period. During which time, the anterior inferior growth of nasal septal cartilage which is buttressed against the cranial base posteriorly drives the midface downward and forward . 63

64. But the agreement today is that the nasal septum functions essentially to support the roof of the nasal chamber, but does not actively participates in the displacement of palate . 64

65. 4) Functional matrix Hypothesis by Moss (1962) : “The origin, form, position, growth and maintenance of all skeletal tissues and organs is always secondary, compensatory and mechanically obligatory, necessary response to chronologically and morphologically prior events or processes that occur in specifically related non-skeletal tissues, organs or functioning spaces.” 65

66. Hence the growth of maxilla and mandible is the enlargement of the nasal and oral cavities which grow in response to functional needs such as breathing, mastication.etc. 66

67. 5) Enlows ‘V’ Principle : Many facial and cranial bones or their parts have a V-shaped configuration. Bone deposition occurs on the inner side of V and resorption occurs on the outer side, hence bone moves in the direction of the wide end of the V and at the same time, increases in overall dimension. Eg - Palatal and orbital growth. 67

68. 6) Enlows Counter Part Principle : Growth in any one region of the skull necessarily influences growth in other and consequently a functional equilibrium is maintained. Growth of certain skeletal parts of the craniofacial region are related specifically to other structural and geometric counterparts in the face and cranium. Balanced equilibrium occurs if the regional parts and counterparts enlarge to the same extent. 68

69. Growth in dimensions- Palate Pre-natal life (appositional growth in the alveolar margin) [length > width] At birth (appositional growth in the maxillary tuberosity) [length = width] Post natal life [width > length] 69

70. Clinical Significance : Maxilla is formed from the first branchial arch and ectomesenchymal cells. Any etiological factors which interfere with the function of this structure may give rise to under developed maxilla. Maxilla forms the middle 1/3 rd of the face, hence underdevelopment leads to midface deficiency especially in cases of trauma to the nose. 70

71. Mid palatine suture closes around 15-19 years uptill which age the transverse growth continues and can be utilized for expansion of narrow arch by RME or SME. Maxilla is surrounded by an envelope of facial muscles restricted growth of which can retard the growth of maxilla. Eg : Scarring after CLP repair 71

72. Vertical lengthening of maxilla is equal in both anterior and posterior regions and any discrepancies can cause open bite or deep bite. Development of dentition is directly related to development of alveolar bone which in turn is related to vertical height. Maxilla to cranial base = 82° Steiners analysis. Less than 82 – Retrognathic maxilla More than 82 – Prognathic maxilla. 72

73. Developmental anomalies Craniosynostosis Premature ossification of one or several sutures of the skull. This condition may lead to abnormal skull shape or retarded skull growth. 73

74. The shape of the skull depends on which of the sutures closes prematurely. Scaphocephaly: Early closure of the sagittal suture results in frontal and occipital expansion, and the skull becomes long and narrow. Brachycephaly : Premature closure of the coronal sutures results in a short skull 74

75. Triganocephaly –Premature closure of metopic suture causes small skull due to failure of brain to grow Microcephaly causing the inability of the frontal bones to grow laterally 75

76. If the coronal sutures close prematurely on one side only, then the result is an asymmetric flattening of the skull called plagiocephaly 76

77. crouzon’s syndrome Cranio- synsostosis Premature fusion of the posterior and superior sutures of the maxilla along the walls of the orbit with cranial base involvement. symmetric maxillary deficiency that affects the infraorbital area. Exophthalmoses Parrot beaked nose Hypertelorism Brachycephaly Mid-face hypoplasia 77

78. Apert syndrome Skull bones to fuse together prematurely, a process called craniosynostosis. Wide-set, bulging eyes, often with poorly-closing eyelids ,A sunken middle face. Similar to crouzon’s syndrome and have syndactyly as an additional clinical feature It is characterized by midfacial malformations , symmetrical syndactyly of hands and feet and mental retardation, Steep forehead. Ocular proptosis 78

79. Maxillary – Byzantine shaped arch and severe dental crowding Cleft palate 79

80. Anencephaly “Open skull” Major portion of vault of skull is missing. Neural tube defect. Short, narrow chondrocranium 80

81. Achondroplasia caused by the failure of primary growth cartilages of the limbs and cranial base to grow properly growth is diminished at the synchondroses. short arms, legs and characteristic midface deficiency (most accentuated at the bridge of the nose). 81

82. Pfeiffer syndrome Characterized by premature fusion of skull bones (craniosynostosis). Orbital dystopia, midface hypoplasia, broad and medial deviated thumbs and great toes. Syndactyly of the hands and feet. Clover-leaf shaped head. 82

83. REFERENCES Sridhar Premkumar : textbook of craniofacial growth Human Anatomy – B.D Chaurasia Essentials of Facial Growth – Enlow and Hans Craniofacial Embryology- G.H.Sperber 83

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85. PART - 2 85

86. POSTNATAL GROWTH OF CRANIUM AND MAXILLA CONTENTS INTRODUCTION POST NATAL GROWTH OF CRANIAL BASE ANATOMY MECHANISM OF GROWTH CLINICAL IMPLICATIONS ANATOMY OF MAXILLA ARTICULATIONS OF MAXILLA AGE CHANGES IN MAXILLA POSTNATAL GROWTH OF MAXILLA DIRECTION OF GROWTH THEORIES OF GROWTH CLINICAL SIGNIFICANCE DEVELOPMENTAL ANOMALIES OF CRANIUM REFERRENCES 86 PART -1

87. POSTNATAL GROWTH OF MANDIBLE CONTENTS : INTRODUCTION POST NATAL GROWTH GENES IN GROWTH AND DEVELOPMENT WOLFS LAW OF TRANSFORMATION AGE CHANGES IN MANDIBLE DEVELOPMENTAL ANOMALIES GROWTH ROTATIONS SYNDROMES ASSOCIATED WITH MANDIBLE ORTHODONTIC IMPLICATIONS CONCLUSION REFERENCE S 87

88. P0ST NATAL GROWTH MANDIBLE The shape and size of the diminutive fetal mandible undergo considerable transformation during its growth and development . Although the mandible appears as a single bone in the adult , it is developmentally and functionally divisible into several skeletal subunits . 88

89. The functioning of the related tongue and the perioral muscles and the expansion of the oral and the pharyngeal cavities provide stimuli for mandibular growth to reach its full potential . Of all the facial bones, the mandible undergoes the most growth postnatally . 89

90. The main sites of the post natal mandibular growth are at the condylar cartilage , the posterior border of the rami, and the alveolar ridges . By the end of 1 st year life , the mandible appears as a single bone. It configures symmetrically as a U- shaped structure as it accommodates the mandibular dentition and completes with the maxillary dentition, the dental arches . 90

91. According to MOSS while mandible appears in the adult as single bone, it is divisible into several skeleton subunits Condylar process Coronoid process Angular process Ramus Lingual tuberosity Body of mandible Alveolar process Chin. 91

92. MANDIBULAR CONDYLE It is a major site of growth Historically, the condyle has been regarded as a kind of cornucopia from which the whole mandible itself pours forth. The condyle functions as regional field of growth that provides an adaptation for its own localized growth circumstances. 92

93. The condylar cartilage is a secondary type of cartilage Its real contribution is to provide regional adaptive growth Main functional role of condyle is (1) provides a pressure tolerant articular contact (2) it makes possible a multidimensional growth capacity in response to ever-changing, developmental conditions and variations. 93

94. The condylar growth mechanism itself is a clear-cut process. Cartilage is a special non-vascular tissue and is involved because variable levels of compression Endochondral growth occurs only at the articular contact part of the condyle In Figure the endochondral bone tissue (b) formed in association with the condylar cartilage (a) The enclosing bony cortices (c) are produced by periosteal-endosteal osteogenic activity 94

95. CORONOID PROCESS The coronoid process has propeller like twist, so that its lingual side faces three general directions all at once posteriorly , superiorly and medially. 95

96. When bone is added onto the lingual side of the coronoid process , growth thereby precedes superiorly and this part of ramus increased in vertical direction . 96

97. The same deposits of bone on the lingual side also bring about a posterior direction of growth movement . produces backward movement of two coronoid process even though deposits on the inside (lingual) surface. 97

98. These same deposits on the lingual side also bring about medial direction of growth in order to lengthen corpus area occupied by anterior part of ramus in mandible becomes relocated and remodeled into posterior part of corpus in mandible . 98

99. RAMUS At birth the two rami of mandible are quite short, they grow by the process of direct surface apposition and remodeling. THE PRINCIPLE GROWTH VECTORS ARE IN POSTERIOR & SUPERIOR DIRECTION Bone growth occurs at the mandibular condyle and along the posterior part of ramus to the same extent as anterior part has undergone resorption . 99

100. The lower part of ramus below the coronoid process also has a twisted contour. Its buccal side faces posteriorly toward the direction of backward growth and thus characteristically has a depository type of surface. The opposite lingual side, being away from direction of growth, is resorptive . 100

101. MANDIBULAR FORAMEN The mandibular foramen likewise drift backward and upward by deposition on the anterior and resorption on the posterior part of its rim. 101

102. BODY OF MANDIBLE Increase in length- remodelling at the anterior border of the ramus. Increase in height- development of the alveolar process - tooth eruption . When seen from the side , the entire inferior border is depository, while resorption is seen in the antegonial notch area . In CS , remodelling patterns widen the base of the mandible laterally 102

103. THE LINGUAL TUBEROSITY Grows posteriorly by deposits on the posterior facing surface. The prominence of tuberosity is increased by presence of large resorptive fields just below it which produces a sizable depression, the lingual fossa . 103

104. The combination of resorption in the fossa and deposition on the medial facing surface of tuberosity itself greatly accentuates the contours of both region Deposition on the lingual surface of the ramus just behind the tuberosity produces a medial direction of drift that shifts this part of the ramus into alignment with the axis of corpus. 104

105. CHIN Protrusive chin is unique human trait, at birth no prominent chin deposition of bone on the anteroinferior surface and resorption anterosuperiorly at the root apices of the mandibular incisors and due to late mandibular rotation in a forward direction. More prominent in male Less prominent in female 105

106. ALVEOLAR PROCESS: Develops as the teeth erupt in response to functional demands. Partial anodontia – growth of alveolar process is hampered. eg : in children with ectodermal dysplasia, alveolar processes are virtually non existent in areas where teeth fail to erupt 106

107. ROLE OF GENES IN DEVELOPMENT OF MANDIBLE These include genes like MSX-1, MSX-2, DLX-1, BARX-1 and ET-1. 107

108. MSX-1 and MSX-2: It plays a special role in specification of skull and face. Disruption of MSX-1 and MSX-2 in experimental animals has led to loss of palatine shelves, absence of palatine bones, maxillary and mandibular hypoplasia and tooth agenesis. Defective expression of MSX-2 causes defects in skull ossification due to defective osteoprogenitor proliferation during calvarial morphogenesis. 108

109. DLX-1: It is another gene which regulates the formation of neural crest derived elements in maxillary and mandibular arches. It mainly controls the proximal arch structures 109

110. Endothelin-I(ET-1): Endothelin-I (ET-1), a member of that family codes for a vasoactive peptide which play a role in regulation of blood pressure. Disruption of this gene in experimental animals produced cardiovascular abnormalities, reduction in tongue size, micrognathia and cleft palate . 110

111. Sonic Hedgehog: It is another protein which is necessary for the patterning of the neural plate. Defective patterning of the neural plate results in holoprosencephaly, failure of cleavage in the midline forebrain and cyclopia. Sonic hedgehog, also expressed in the mesenchyme of the frontonasal process and maxillary process, is found to be necessary for their normal development 111

112. WOLF’S LAW OF TRANSFORMATION Represents the alignment of bony trabeculae in stress trajectories to better prepare the bone to resist number of frictional forces 112

113. In 1870’s Wolf claimed that the trabecular alignment was primarily due to functional forces. A change in the intensity and direction of these forces would produce a change in the internal architecture & external form of the bone. This was referred as “LAW OF ORTHOGONACITY”. ROUX & others introduced functional factors in the development called “LAW OF TRANSFORMATION” which states that the stresses of tension or pressure on bone stimulate bone formation. 113

114. TRAJECTORIES OF FORCE According to koch in 1817 the lines of orientations of the bony trabaculae corresponds to the pathway of maximal pressure & tension in bone. Trabaculae are thicker in this region where the stress is greater. 114

115. In 1867 an anatomist named Meyer with the help of mathematician Culman propounded the TRAJECTORIAL THEORY OF BONE FORMATION He pointed out that the alignment of bony trabeculae followed a definite engineering principles eg : trajectories seen in a crane. Many of these trajectories are crossed at right angles. 115

116. BENNINGHOFF studied the natural lines of stress in the skull by piercing small holes into fresh skull . When skull were dried he observed that the holes assumed a linear form in the direction of bony trabeculae. THESE LINES OF STRESS ARE CALLED BENNINGHOFF LINES indicates the direction of functional stresses. 116

117. MANDIBULAR GROWTH ROTATION In 1969 Bjork used the metal implants which were inserted in bone, to do the prediction of mandibular growth rotation. Growth - unconstrained bone - may change its inclination in several ways. 117

118. Mandibular growth pattern growth occurs in the condyles anterior aspect of the chin is extremely stable, no growth occurs. Greater variations seen in individuals Growth is seen slightly forward or occasionally even backward. upward- and forward-curving growth at the condyles, there is resorption on the lower aspect of the gonial angle 118

119. 119

120. FORWORD ROTATION – TYPE I There is a forward rotation about centers in the joints gives rise to a deep bite underdevelopment of the anterior face height 120

121. FORWORD ROTATION – TYPE II center located at the incisal edges of the anterior teeth. due to the combination of development of posterior face height and normal increase in anterior height The posterior part of the mandible then rotates away from the maxilla. 121

122. FORWORD ROTATION – TYPE III In anomalous occlusion of the anterior teeth, The dental arches are pressed into each other and basal deep-bite develops Due to underdevelopment of anterior face height 122

123. BACKWORD ROTATION – TYPE I center of rotation - TMJ. Bite raising Other causes, such as incomplete development in height of the middle cranial fossae [oxycephaly] Results in an increased anterior facial height Open bite as consequence 123

124. BACKWORD ROTATION – TYPE II Rotation center - most distal occluding molars. Due to sagittal growth in mandibular condyles. Basal open-bite may develop and there is difficulty in closing the lips without tension The symphysis is swung backward & chin is drawn back. Formation of double chin. 124

125. AGE CHANGES IN MANDIBLE 125

126. 126

127. CLINICAL IMPLICATIONS 127

128. ANOMALIES OF DEVELOPMENT AGNATHIA: Grossly deficient or absent mandible which reflects of neural crest tissue in lower part of face 128

129. 129 MICROGNATHIA: small jaw

130. MACROGNATHIA ; Cross bite (anterior & posterior) 130 CONDYLAR HYPERTROPHY

131. HEMIFACIAL HYPERPLASIA: enlargement of the right side of the face. same patient with associated enlargement of the right half of the tongue. panoramic radiograph of the same patient showing enlargement of the mandible and teeth on the right side. 131

132. BIFID OR DOUBLE CONDYLE: Results from the persistence of septa dividing the foetal condylar cartilage. 132 Radiograph of the mandibular condyle showing a double head

133. HEMIFACIAL HYPERTROPHY: Unilateral enlargement of mandible, the mandibular fossae & the teeth of unknown etiology. 133

134. MANDIBULAR CLEFTS: Occasionally both lip & jaw may be involved TMJ ANKYLOSIS : unilateral / bilateral 134

135. INJURY DUE TO FORCEPS DELIVERY Forceps delivery can cause fractures of the mandible. 135

136. Problems of Mandibular Growth and Their Orthodontic Significance • Hypognathism • Prognathism • Unilateral Condylar Hypertrophy • Bilateral Condylar Hypertrophy • TMJ Ankylosis • Imbalanced Growth • Excessive Transverse Growth • Poor Transverse Growth 136

137. Hypognathism Congenital, Developmental Disorder Restricted growth of mandible Fetal intrauterine moulding Common in Pierre robin sequence Trisomy-18 syndrome Unilateral/bilateral Condylar hypoplasia patients of cleft lip and palate injury or trauma new born low birth weight 137

138. Features Convex Facial Profile Hypo divergent face Skeletal and Dental Class II malocclusion Poor airway Increased Nasolabial Angle Deep bite Lip in competency 138

139. Prognathism Excessive growth of mandible Mainly hereditary Common in males and in conditions like acromegaly  childhood osteogenetic disorders mechanical factors ( malocclusion ) Asymmetric mandibular Prognathism Condylar head temporomandibular joint disorder Crouzon’s syndrome Bilateral Condylar hypertrophy 139

140. Features • Concave facial Profile • Hyper divergent face • Dental and Skeletal Class III malocclusion • Anterior and Posterior Cross bite • Anterior cross bite resulting in restricted growth of maxilla 140

141. Unilateral Condylar Hypertrophy Hemi mandibular hypertrophy Due to some developmental or genetic reasons Unilateral clefts Features Facial Asymmetry Chin divergent on side opposite to hypertrophy Excessive growth at TMJ Lingual cross bite on one side and buccal cross bite on the other side 141

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143. Bilateral Condylar Hypertrophy Genetic or Hormonal causes Common in males Usually expresses in late teen age when growth of mandible continues at condyle • Clinical feature similar to mandibular hypertrophy • More likely to be a high angle 143

144. TMJ Ankylosis Usually because of trauma that results in intracapsular bleeding in TMJ Condylar fracture Systemic diseases like typhoid fever, syphilis Infections like rheumatoid arthritis, osteoarthritis Can be either unilateral or bilateral Can be osseous for fibrous Clinical Features similar to Hypognathism Deviation of chin to affected side Limited mouth opening Airway embarrassment 144

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146. Imbalanced growth Due to hyperplasia / hypertrophy of condyle injury /fracture Improper muscle activity Local Areas of imbalances growth results in minor facial asymmetry • Shift of midline • Local malocclusions • Crowding or spacing of teeth 146

147. Excessive Transverse Growth Due to genetic reasons Common in Prognathic patients Brachycephalic Appearance Bilateral Cross bite Anterior Divergent face Total lingual non occlusion – Crocodile bite 147

148. Poor transverse growth • Clinical features similar to Hypognathic patients • Usually class II cases • Dolichocephalic appearance Posterior Divergent faces • In severe cases there can be complete buccal non occlusion – Broodie’s Bite 148

149. Problems Of Ramal Growth Excessive Vertical Ramal Growth Brachycephalic Patients Low angle cases Anterior deep bite 149

150. Poor Vertical Ramal Growth: Dolichocephalic Patients High Angle Cases Anterior open bite 150

151. Excessive Horizontal Ramal Growth: More broad oropharynx Poor Horizontal Ramal Growth: Narrow oropharynx Chances of airway embarrassment 151

152. Problems in chin growth • Prominent chin common in males • Due to late bone deposition • Due to excessive mental bone resorption 152

153. Problems in angular growth  Excessive transverse growth Common in males Due to excessive bone deposition at angles 153

154. significance  Timely identification interception of developing malocclusions orthodontic and esthetic facial problems • Knowing the timing of development of different facial structures gives you idea about the long term facial appearance of the patient • Timely diagnosis to treat the problem with functional appliances 154

155. SYNDROMES ASSOCIATED WITH MANDIBLE APERTS SYNDROME Maxillary hypoplasia Ankylosis of joints Craniosynostosis High steep forehead Cleft palate 155

156. TREACHER COLLIN SYNDROME Anti mongoloid slope Retrusive chin Convex facial profile Cleft palate Short ramus Accentuation of antegonial notch and steep mandibular angle Ramus is short, condyles are positioned posteriorly and inferiorly Maxillary sinus may be underdeveloped or absent 156

157. CROUZONS SYNDROME Arises because of prenatal fusion of superior and posterior sutures of maxilla along the wall of the orbit Maxillary hypoplasia Mandibular Prognathism Frog like face Unilateral or bilateral cross bite 157

158. GORLIN’S SYNDROME Odontogenic keratocyst in mandible Multiple basal cell neavi Cleft lip and/or cleft palate is seen Bifid ribs are seen 158

159. ANKYLOSIS Could be due to Abnormal development, Birth injury, Congenital syphillis can be fibrous or bony bilateral ankylosis leads to under development of lower face 159

160. TYPES OF ANKYLOSIS 160

161. FETAL ALCOHOLIC SYNDROME When a woman drinks alcohol during pregnancy, she risks giving birth to a child who will be born with fetal alcohol syndrome (FAS) 161

162. CONCLUSION “Growth is said to be raw material for orthodontic treatment”. Problems with facial growth can result in aesthetic & functional complaints. Using a simple method of clinical evaluation the orthodontist can identify facial growth problems in the anteroposterior , vertical & transverse dimensions. These problems can then be referred for evaluation & treatment by a variety of means to obtain optimal results. 162

163. REFERENCES Sridhar Premkumar : textbook of craniofacial growth Prediction of mandibular growth rotation – A. Bjork , AJO 1969 Human Anatomy – B.D Chaurasia Essentials of Facial Growth – Enlow and Hans Handbook of Orthodontic – Robert Moyers 163

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