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- 1. Growth and development of Mandible Guide: Dr. Basanta K. Shrestha, Assoc. Prof and Head, Orthodontics and Dentofacial Orthopedics Unit Faculty of Dentistry, Institute of Medicine(IOM), Kathmandu Presented by: Dr. Anup Panthee Resident, 1 Department of dentistry, PG programme, IOM 2012
- 2. Introduction Prenatal development Postnatal development Age changes Clinical significances Recent advances Department of dentistry, PG programme, IOM 2012 2 Contents
- 3. Largest and strongest bone of the face. Develops from the first pharyngeal arch. Introduction 3 Department of dentistry, PG programme, IOM 2012
- 4. 4 Department of dentistry, PG programme, IOM 2012 Introduction
- 5. Department of dentistry, PG programme, IOM 2012 5 It has : a horse – shoe shaped body a pair of rami 3 processes - coronoid, condylar & alveolar 2 surfaces - outer and inner 2 borders - upper and lower Introduction
- 6. Muscles attachment 6 Department of dentistry, PG programme, IOM 2012
- 7. PRENATAL DEVELOPMENT 7 Department of dentistry, PG programme, IOM 2012
- 8. 4-5th weeks 8 Department of dentistry, PG programme, IOM 2012
- 9. 9 Department of dentistry, PG programme, IOM 2012 4-5th weeks
- 10. 5-6th weeks 10 Department of dentistry, PG programme, IOM 2012
- 11. 7-10th weeks 11 Department of dentistry, PG programme, IOM 2012
- 12. Intermaxillary segment 12 Department of dentistry, PG programme, IOM 2012
- 13. Meckel’s Cartilage Derived from 1st branchial arch around the 41st – 45th day of IUL. Extends from the cartilaginous otic capsule to the midline or symphysis. Provides a template for guiding the growth of the mandible. 13 Department of dentistry, PG programme, IOM 2012
- 14. Department of dentistry, PG programme, IOM 2012 14 Meckel’s Cartilage
- 15. Fate of cartilage : Incus and malleus Anterior ligament of malleus The mental ossicles Spine of sphenoid bone. Spheno - mandibular ligament 15 Department of dentistry, PG programme, IOM 2012 Meckel’s Cartilage
- 16. Mesenchymal condensation-36-38 days of IUL Osteogenic membrane Ossification centre appear- 6th week Ossification starts- 7th week 16 Department of dentistry, PG programme, IOM 2012 Ossification of Mandible
- 17. 17 Department of dentistry, PG programme, IOM 2012 Ossification of Mandible
- 18. 18 Department of dentistry, PG programme, IOM 2012 Ossification of Mandible
- 19. Secondary accessory cartilages appear between 10th and 14th Weeks of IUL. Endochondral bone formation is seen in : 1. Condylar process 2. Coronoid process 3. Mental region 19 Department of dentistry, PG programme, IOM 2012 Ossification of Mandible
- 20. Department of dentistry, PG programme, IOM 2012 20 Ossification of Mandible
- 21. Condylar process Mesenchymal condensation-5th week of IUL Cone shaped cartilage - 10th week of IUL Starts ossification –14th week of IUL Fuse with ramus –4th month of IUL 21 Department of dentistry, PG programme, IOM 2012
- 22. Department of dentistry, PG programme, IOM 2012 22 Condylar process
- 23. Coronoid process Accessary cartilage - 10th -14th week of IUL Incorporated in to ramus Disappears before birth 23 Department of dentistry, PG programme, IOM 2012
- 24. Mental region Appearance of small cartilage on either side of symphysis Ossify into mental ossicles - 7th month of IUL Incorporated in to symphysis- 1 year post natal life 24 Department of dentistry, PG programme, IOM 2012
- 25. POST NATAL DEVELOPMENT 25 Department of dentistry, PG programme, IOM 2012
- 26. Both endochondral and periosteal activities - growth of the mandible. Appositional growth occurs in all areas of mandible. 26 Department of dentistry, PG programme, IOM 2012 Post Natal Development
- 27. Transverse dimension after the first year - due to the growth in an expanding “v” pattern. 27 Department of dentistry, PG programme, IOM 2012 Post Natal Development
- 28. Scott: divides the mandible into three basic types of bone : basal, muscular (gonial angle & coronoid process) & alveolar. Moss: speaks of the mandible as a group of microskeletal units. 28 Department of dentistry, PG programme, IOM 2012 Post Natal Development
- 29. Enlow’s Counterpart Principle The different parts and their counterparts are : Breadth of the ramus - Middle cranial fossa Mandibular dental arch - Maxillary dental arch Corpus of the mandible - Bony maxilla Lingual tuberosity - Maxillary tuberosity 29 Department of dentistry, PG programme, IOM 2012
- 30. The principal vectors of mandibular "growth" are posterior and superior. 30 Department of dentistry, PG programme, IOM 2012
- 31. Ramus The ramus moves progressively posterior by a combination of deposition and resorption. Function of remodelling 31 Department of dentistry, PG programme, IOM 2012
- 32. Body of the Mandible The relocation of ramus posteriorly - conversion of former ramal bone in to the body of the mandible. 32 Department of dentistry, PG programme, IOM 2012
- 33. Angle of The Mandible On the lingual side Resorption : postero – inferior aspect Deposition : anterio – superior aspect. On the buccal side Resorption : anterio – superior aspect Deposition : postero – superior aspect. This results in flaring of the angle of the mandible as age advances. 33 Department of dentistry, PG programme, IOM 2012
- 34. Major site of growth for the lower bony arch. It moves posteriorly by deposition on its posteriorly facing surface. 34 Department of dentistry, PG programme, IOM 2012 The Lingual Tuberosity
- 35. The Lingual Tuberosity The prominence of the tuberosity is increased by resorption just below it & deposition on its medial facing surface. 35 Department of dentistry, PG programme, IOM 2012
- 36. The Alveolar Process As the teeth develops and increases in height by bone deposition at the margins. It adds to the height and thickness of the body of the mandible. 36 Department of dentistry, PG programme, IOM 2012
- 37. The Chin As age advances the growth of chin becomes significant. Influenced by sexual and specific genetic factors. Its prominence is accentuated - bone resorption occurs in the alveolar region above it. 37 Department of dentistry, PG programme, IOM 2012
- 38. Condylar Process Important site of growth. The presence of condylar cartilage (Secondary cartilage) - adaptation to withstand the compression that occurs at the joint. Growth rate increases at puberty reaching a peak between 12 ½ - 14 years & ceases around 20 years of age. 38 Department of dentistry, PG programme, IOM 2012
- 39. Endochondral ossification 39 Department of dentistry, PG programme, IOM 2012
- 40. Is the condylar cartilage - the principal force that produces the forward and downward displacement of the mandible ??? 40 Department of dentistry, PG programme, IOM 2012
- 41. 1. Growth occurs at the surface of the condylar cartilage and pushed against the cranial base, the entire mandible gets displaced forwards and downwards. 2 School of Thoughts : 41 Department of dentistry, PG programme, IOM 2012
- 42. Carry Away Phenomenon 42 Department of dentistry, PG programme, IOM 2012
- 43. The growth follows the enlarging “ v “ principle. 43 Department of dentistry, PG programme, IOM 2012 Coronoid Process
- 44. Coronoid Process It has a propeller- like twist, so that its lingual side faces 3 general directions all at once, i.e. Posteriorly Superiorly Medially. 44 Department of dentistry, PG programme, IOM 2012
- 45. Timing of growth & rotation of jaws On the average, ramus height increases 1 to 2 mm per year and body length increases 2 to 3 mm per year. 45 Department of dentistry, PG programme, IOM 2012
- 46. Growth in width is completed first, then growth in length, and finally growth in height. Growth in width of jaws - tends to be completed before the adolescent growth spurt. Growth in length and height of both jaws continues through the period of puberty. 46 Department of dentistry, PG programme, IOM 2012 Timing of growth & rotation of jaws
- 47. Mandible comprises of core & functional processes. The core of the mandible rotates - tend to decrease the mandibular plane angle (i.e., up anteriorly and down posteriorly). 47 Department of dentistry, PG programme, IOM 2012 Rotation of Jaws
- 48. By convention, The rotation of either jaw is considered "forward" and given a negative sign if there is more growth posteriorly than anteriorly. The rotation is "backward" and given a positive direction if it lengthens anterior dimensions more than posterior ones, bringing the chin downward and backward. 48 Department of dentistry, PG programme, IOM 2012 Rotation of Jaws
- 49. Internal rotation of the mandible (i.e., rotation of the core relative to the cranial base) has two components: A. Rotation around the condyle, or matrix rotation. B. Rotations centered within the body of the mandible, or intramatrix rotation. 49 Department of dentistry, PG programme, IOM 2012 Rotation of Jaws
- 50. Department of dentistry, PG programme, IOM 2012 50 Rotation of Jaws
- 51. -15 degree internal forward rotation from age 4 to adult life (25% - matrix rotation and 75% - intramatrix rotation) 11 to 12 degrees of external, backward rotation Producing the 3 to 4 degree decrease in mandibular plane angle. 51 Department of dentistry, PG programme, IOM 2012 Average Individual With Normal Vertical Facial Proportions –
- 52. Department of dentistry, PG programme, IOM 2012 52
- 53. Excessive forward rotation of the mandible during growth, resulting from both an increase in the normal internal rotation and a decrease in external compensation. Low mandibular plane angle Deep bite Crowded incisors 53 Department of dentistry, PG programme, IOM 2012 Short face type
- 54. Department of dentistry, PG programme, IOM 2012 54 Short face type
- 55. Long face type 55 Department of dentistry, PG programme, IOM 2012
- 56. AGE CHANGES IN MANDIBLE 56 Department of dentistry, PG programme, IOM 2012
- 57. Infants And Children The two halves of mandible fuse during the first year of life. At birth the mental foramen, opens below the sockets for the two deciduous molar teeth near the lower border. 57 Department of dentistry, PG programme, IOM 2012
- 58. Infants And Children The mandibular canal runs near the lower border. The foramen and canal gradually shift upwards & angle decreases from 175° to 140°. 58 Department of dentistry, PG programme, IOM 2012
- 59. In Adult The mental foramen opens midway between the upper and lower borders. 59 Department of dentistry, PG programme, IOM 2012
- 60. In Adult The mandibular canal runs parallel with the mylohyoid line. The angle reduces to about 110 or 120 degrees because the ramus becomes almost vertical. 60 Department of dentistry, PG programme, IOM 2012
- 61. Old Age Teeth fall out and alveolar border is absorbed, so that the height of the body is markedly reduced. 61 Department of dentistry, PG programme, IOM 2012
- 62. Old Age The mental foramen and the mandibular canal are close to the alveolar bone. The angle again becomes obtuse about 140 degrees because the ramus is oblique. 62 Department of dentistry, PG programme, IOM 2012
- 63. Clinical significance 63 Department of dentistry, PG programme, IOM 2012
- 64. Ankylosis Department of dentistry, PG programme, IOM 2012 64 Fusion across the joint - motion is prevented or extremely limited. Cause 1. Severe infection - destruction of tissues and ultimate scarring. 2. Trauma - soft tissue injury - severe scarring.
- 65. Scar tissue in the vicinity of TMJ Mechanical restriction Impedes translation as soft tissue grow 65 Department of dentistry, PG programme, IOM 2012 Ankylosis
- 66. The Russian surgeon Alizarov discovered in the 1950s. cuts made through the cortex of a long bone of the limbs - lengthened by tension to separate the bony segments. Distraction Osteogenesis 66 Department of dentistry, PG programme, IOM 2012
- 67. External fixation for lengthening the mandible in a child with hemifacial microsomia. 67 Department of dentistry, PG programme, IOM 2012 Distraction Osteogenesis
- 68. Neural Crest Cells Disruption of crest cell development results in severe craniofacial malformations. Vulnerable cell population - easily killed by compounds such as alcohol and retinoic acid. Deficient in superoxide dismutase (SOD) and catalase enzymes - responsible for scavenging free radicals that damage cells. 68 Department of dentistry, PG programme, IOM 2012
- 69. Agnathia Reflecting a deficiency of neural crest tissue in the lower part of the face. Aplasia of the mandible and hyoid bone with multiple defects of the orbit and maxilla. 69 Department of dentistry, PG programme, IOM 2012
- 70. Macrognathia Producing prognathism - inherited condition, hyperpituitarism. Congenital hemifacial hypertrophy, evident at birth - tends to intensify at puberty. 70 Department of dentistry, PG programme, IOM 2012
- 71. Micrognathia Pierre Robin and cat’s cry (cri du chat) syndromes Mandibulofacial dysostosis (Treacher Collins syndrome) Progeria Down syndrome Oculomandibulodyscephaly (Hallermann- Streiff syndrome) Turner syndrome 71 Department of dentistry, PG programme, IOM 2012
- 72. Treacher collins syndrome 72 Department of dentistry, PG programme, IOM 2012
- 73. Robin sequence 73 Department of dentistry, PG programme, IOM 2012
- 74. These disorders are part of a spectrum – CATCH 22 as a result of a deletion on the long arm of chromosome 22. DiGeorge anomaly 74 Department of dentistry, PG programme, IOM 2012
- 75. Facial bones are small and flat. Ear - anotia, microtia Eye - tumors and dermoids in the eyeball Vertebrae - fused and hemivertebrae, spina bifida Cardiac anomalies Hemifacial Microsomia 75 Department of dentistry, PG programme, IOM 2012
- 76. Fetal alcohol syndrome 76 Department of dentistry, PG programme, IOM 2012
- 77. Recent Advances in Growth Study Department of dentistry, PG programme, IOM 2012 77
- 78. Department of dentistry, PG programme, IOM 2012 78
- 79. Department of dentistry, PG programme, IOM 2012 79
- 80. References Contemporary Orthodontics, Proffit, Fields, Sarver, Fourth Edition Essentials of facial growth, Donald H. Enlow, Mark G. Hans Craniofacial development, Geoffrey H. Sperber Text book of Orthodontics, Samir E. Bishara Hand book of orthodontics, Robert E. Moyers, Fourth Edition. Langman’s medical Embryology, Ninth Edition 80 Department of dentistry, PG programme, IOM 2012
Editor's Notes
- a horse – shoe shaped body which lodges the teeth, and a pair of rami which projects upwards from the posterior ends of the body and provide attachments to muscles which bears an anterior coronoid process and posterior condylar process . Each half of body has outer and inner surfaces, upper and lower borders.
- A major portion of this cartilage disappears during growth and the remaining part develops into following structures:
- The mandible is ossified in the fibrous membrane covering the outer surfaces of Meckel's cartilages. These cartilages form the cartilaginous bar of the mandibular arch and are two in number, a right and a left. Their proximal or cranial ends are connected with the ear capsules, and their distal extremities are joined to one another at the symphysis by mesodermal tissue. Meckel’s cartilage has a close, relationship to the mandibular nerve, at the junction between posterior and middle thirds, where the mandibular nerve divides into the lingual and inferior dental nerve. The lingual nerve passes forward, on the medial side of the cartilage, while the inferior dental lies lateral to its upper margins & runs forward parallel to it and terminates by dividing into the mental and incisive branches.
- Ossification grows medially below the incisive nerve and then spread upwards between this nerve and Meckel’s cartilage and so the incisive nerve is contained in a trough or a groove of bone formed by the lateral and medial plates which are united beneath the nerve. At the same stage the notch containing the incisive nerve extends ventrally around the mental nerve to form the mental foramen. Also the bony trough grow rapidly forwards towards the middle line where it comes into close relationship with the similar bone of the opposite side, but from which it is separated by connective tissue. A similar spread of ossification in the backward direction produces at first a trough of bone in which lies the inferior dental nerve and much later the mandibular canal is formed. The ossification stops at the site of future lingula. By these processes of growth the original primary center ossification produces the body of the mandible.
- The condylar cartilage (pink) develops initially as a separate area of condensation from that of the body of the mandible, and only later is incorporated within it. A, Separate areas of mesenchymal condensation, at 8 weeks; B, fusion of the cartilage with the mandibular body, at 4 months, C, situation at birth (reduced to scale).
- In contrast to maxilla, both endochondral and periosteal activities are important in growth of the mandible.some sites are more active than others. The main sites of postnatal mandibular growth are at the condylar cartilages, the posterior borders of the rami, and the alveolar ridges. These areas of bone deposition largely account for increases in the height, length, and width of the mandible.
- Transverse dimension after the first year of life are mainly due to the growth at the posterior border in an expanding “v” pattern.
- Growth of one part relates specifically to other structural and geometric counterparts in the face and cranium. Regional part and its particular counterpart enlarge to the same extent, balanced growth occurs.
- The relocation of ramus posteriorly results in the conversion of former ramal bone in to the posterior part of the body of the mandible.
- The prominence of the tuberosity is increased by the presence of large resorption field just below it & deposition on its medial facing surface.
- Endochondral ossification at the head of the mandibular condyle. A zone of proliferating cartilage is located just beneath the fibrocartilage on the articular surface, and endochondral ossification is occurring beneath this area.
- The mandible was onee viewed conceptually as being analogous to a long bone that had been modified by (1) removal of the epiphysis, leaving the epiphyseal plates exposed, and (2) bending of the shaft into a horseshoe shape. If this analogy were correct, of course, the cartilage at the mandibular condyles should behave like true growth cartilage. Modern experiments indicate that, although the analogy is attractive, it is incorrect. The many arguments about condylar growth focus mostly on one question:
- Bone growth follows secondarily at the condyle to maintain constant contact with the cranial base. The growth of soft tissues carries the mandible forwards away from the cranial base
- Although addition takes place on the lingual side, the vertical dimension of the coronoid process also increases.
- Growth continues at a relatively steady rate before puberty.
- and is affected minimally if at all by adolescent growth changes.
- The mandible can be visualized as consisting of a core of bone surrounding the inferior alveolar neurovascular bundle, and a series of functional processes: the alveolar process, serving the function of mastication; the muscular processes, serving for muscle attachments; and the condylar process, serving to articulate the bone with the rest of the skull.
- Increase in the mandibular plane angle. Anterior open bite Mandibular deficiency The palatal plane rotates down posteriorly. The mandible shows an opposite, backward internal rotation - is primarily matrix rotation, not intramatrix rotation.
- The mental foramen opens midway between the upper and lower borders because the alveolar and subalveloar parts of the bone equally developed.
- It has been known for many years that mandibular growth is gready impaired by an ankylosis Ankylosis : defined as a fusion across the joint so that motion is prevented or extremely limited. Severe infection in the area of the TMJ, leading to destruction of tissues and ultimate scarring. Trauma, which can result in a growth deficiency if there is enough soft tissue injury to lead to severe scarring as the injury heals.
- It has been known for many years that mandibular growth is gready impaired by an ankylosis . Profile view of a girl in whom a severe infection It appears that the mechanical restriction caused by scar tissue in the vicinity of the TMJ impedes translation of the mandible as the adjacent soft tissues grow, and that this is the reason for growth deficiency in some children after condylar fractures. of the mastoid air cells involved the temporomandibular joint and led to ankylosis of the mandible. T h e resulting restriction of mandibular growth is apparent.
- External fixation for lengthening the mandible by distraction osteogenesis in a child with hemifacial microsomia. The Russian surgeon Alizarov discovered in the 1950s that if cuts were made through the cortex of a long bone of the limbs, the arm or leg then could be lengthened by tension to separate the bony segments.
- External fixation for lengthening the mandible by distraction osteogenesis in a child with hemifacial microsomia. Lengthening the mandible via distraction osteogenesis clearly is possible but a number of practical problems still must be overcome before this approach can be used to correct mandibular deficiency.
- One reason for this vulnerability may be that they are deficient in superoxide dismutase (SOD) and catalase enzymes that are responsible for scavenging free radicals that damage cells. crest cells also contribute to the conotruncal endocardial cushions, which septate the outflow tract of the heart into pulmonary and aortic channels
- Mandible - grossly deficient or absent, Ischemic necrosis of the mandible and hyoid bone occurring after the formation of the ear.
- Unilateral enlargement of the mandible, the mandibular fossa, and the teeth - more common is isolated unilateral condylar hyperplasia.
- Malar hypoplasia Mandibular hypoplasia Downslanting palpebral fissures Lower eyelid colobomas Malformed external ear
- Micrognathic mandible Cleft palate Glossoptosis Defects of the eye and ear
- Cardiac defects Abnormal facies – hypertelorism, microstomia Thymic hypoplasia Cleft palate Hypocalcemia
- Oculoauriculovertebral spectrum,
- The characteristic facial appearance of fetal alcohol syndrome (FAS), caused by exposure to very high blood alcohol levels during the first trimester of pregnancy.