PRENATAL AND POSTNATAL GROWTH OF MANDIBLE original (1).pptx

PRENATAL AND POSTNATAL GROWTH OF MANDIBLE original

1. PRENATAL AND POSTNATAL GROWTH OF MANDIBLE ABHIRAMI FIRST YEAR PG DEPT OF PEDODONTICS AND PREVENTIVE DENTISTRY

2. CONTENTS Introduction Anatomy of mandible Attachments and relations of mandible Foramina and relations to nerves and vessels Definition of growth and development Theories of craniofacial growth Prenatal embryology of mandible Meckel's cartilage

3. Process of ossification of mandible Postnatal growth of mandible Growth trends and patterns Growth rotations Age changes in mandible Developmental disturbances of mandible Conclusion References

4. INTRODUCTION Mandible is the largest and strongest bone of the face. The word “mandible” is derived from Greek word “mandere”-to masticate or chew. It is horse-shoe shaped and the only movable bone of the skull.

5. FUNCTIONS OF MANDIBLE Providing mobility to the jaws by the TMJ Mastication by teeth Site of insertion of muscles of mastication Maintenance of airway, ramal width coinciding with pharyngeal width. Textbook of orthodontics-Sridhar premkumar

6. ANATOMY OF MANDIBLE

7. BODY OF MANDIBLE Outer surface presents the following features: The symphysis menti The mental protuberance The mental foramen The oblique line The incisive fossa Inner surface of mandible: The mylohyoid line The submandibular fossa Sublingual fossa Genial tubercle

8. INNER SURFACE OF MANDIBLE

9. ATTACHMENTS AND RELATIONS OF MANDIBLE

10. MUSCLE ATTACHMENTS AND RELATIONS OF INNER SURFACE OF THE MANDIBLE

11. FORAMINA AND RELATIONS TO NERVES AND VESSELS Mental foramen- The mental nerve and vessels. Mandibular foramen- The inferior alveolar nerve and vessels. Mylohyoid groove-The mylohyoid nerve and vessels lie in it. Mandibular notch-The massetric nerve and vessels.

12. GROWTH AND DEVELOPMENT

13. DEFINITION : GROWTH: An increase in size – Todd The entire series of anatomic and physiologic changes taking place between the beginning of prenatal and close of senility-Meredith Self multiplication of living tissues-Huxley Any change in morphology which is within measurable parameter-Moss

14. DEVELOPMENT Progress towards maturity- Todd All naturally occurring unidirectional changes in the life of an individual from its existence as a single cell to its elaboration as a multifunctional unit terminating in death-Moyers A continuum of casually related events from the fertilization of ovum onwards-Melvin Moss

15. THEORIES OF CRANIOFACIAL GROWTH

16. Remodelling theory Given by Brash in 1930’s States that bone only grows appositionally at surfaces and growth of the jaws is characterised by deposition of bone at the posterior surfaces of the maxilla and mandible. Suggest that all of craniofacial skeletal growth occurs exclusively by bone remodelling at its surface

17. Genetic theory By Allan Brodie All growth is controlled by genetic influence and is pre-planned. One of the earliest theories put forward.

18. Sutural theory By sicher According to this craniofacial growth occurs at the sutures The mandible was perceived as essentially a bent long bone, with the mandibular condylar cartilage being equivalent to the epiphyseal plates of long bones whose growth forces the mandible downwards and forward, away from the cranial base

19. Cartilaginous theory By James Scott According to this intrinsic growth controlling factors are present in cartilage and periosteum with sutures being only secondary. The mandible is considered as the diaphysis of long bone, bent into a horse shoe shape with epiphysis removed so that there is cartilage constituting half an epiphyseal plate at the ends, which are represented by the condyles.

20. The functional matrix concept Given by Melvin moss Growth of skeletal components depends on functional matrices or non-skeletal tissues The functional matrices are of 2 types: 1).Periosteal matrices 2).Capsular matrices

21. When applied to the mandibular condyle: It explains the regeneration of the condylar cartilage in response to functional stimulation Condylar cartilage primarily adapts to the demands imposed by the function of surrounding periosteal matrices of the pterygoid and temporalis muscles

22. Multifactorial theory Given by Van Limborgh in 1970. Factors Controlling growth

23. Servosystem theory Developed by Alexandre Petrovic Interaction of series of causal changes and feedback mechanisms determine growth. Activation of jaw protruding muscles acts directly on the cartilage of the mandibular condyle and indirectly through the vascular supply to the TMJ, stimulating the condyle to grow.

24. Enlow’s ‘V’ principle of growth Many craniofacial bones, or their parts have a ‘V’-shaped configuration These bones grew by bone deposition on the inner side of ‘V’, while resorption take place on the outside surface which leads to widening of the ‘v’-configuration. Movement of bone occurring towards the wide end of the v

25. Example : Ramus-to-corpus remodelling With growth there is progressive relocation of the entire ramus in a posterior direction .

26. Enlow’s counterpart principle of growth States that the growth of any given facial part relates specifically to other structural and geometric ‘counterparts’ in relation to it. Examples : middle cranial fossa and width of ramus maxillary and lingual tuberosities

27. PRENATAL EMBRYOLOGY OF MANDIBLE

28. PHARYNGEAL ARCHES AND THEIR DERIVATIVES

29. The 1st – Mandibular arch 2 nd arch- Hyoid arch Each of the five arches contain: A central cartilage rod A muscular component A vascular component A neural element

30. Forms the lower lip and lower jaw

31. MECKEL’S CARTILAGE Derived from first branchial arch around the 41 st -45 th day of intrauterine life Provides template for guiding the growth of mandible

32. Major portion of Meckel’s cartilage disappears during growth Remaining parts develop into: The mental ossicles Incus and malleus Spine of sphenoid bone Anterior ligament of malleus Spheno -mandibular ligament

33. PROCESS OF OSSIFICATION OF MANDIBLE INTRA MEMBRANOUS OSSIFICATION ENDOCHONDRAL OSSIFICATION

34. INTRAMEMBRANOUS OSSIFICATION The first structure to develop in the primordium of the lower jaw is the mandibular division of the trigeminal nerve Followed by the mesenchymal condensation forming the first branchial arch

35. Primary centre of ossification-the ossifying membrane lateral to the Meckel’s cartilage. Ossification spreads below and around the inferior alveolar nerve and its incisive branch and upwards to form a trough for accommodating the developing tooth buds Meckel’s cartilage become surrounded and invaded by bone. Ossification stops at the site that later becomes mandibular lingula.

36. ENDOCHONDRAL BONE FORMATION Seen only in three areas of the mandible: The condylar process The coronoid process The mental region

37. Condylar cartilage: Intra-uterine life 5 th week :An area of mesenchymal condensation seen above the ventral part of the developing mandible. 10 th week :Developed into a cone-shaped cartilage 14 th week :Starts ossification

38. It then migrates inferiorly and fuses with the mandibular ramus by about 4 months Much of the cone-shaped cartilage is replaced by bone by the middle of foetal life but its upper end persists into adulthood .

39. Coronoid process Secondary accessory cartilages appears in the region of the coronoid process by about 10-14 week of IU life; Which is believed to grow as a response to the developing temporalis muscle. They get incorporated into the ramus and disappears before birth.

40. Mental region One or two small cartilages appear on either side of symphysis 7 th month of IU life- they ossify to form variable numbers of mental ossicles in the fibrous tissue of symphysis 1 st year of post natal life-ossicles incorporated into the intramembranous bone when symphysis ossifies

41. POST NATAL GROWTH OF MANDIBLE Mandible has the greatest postnatal growth potential of any component of the craniofacial complex At birth, ramus of mandible is quite short, both in absolute terms and in proportion to the mandibular corpus. During post natal development, ramus become much more prominent , particularly in height but also in width Corpus increases in length

42. Growth of mandible in infancy C hange in overall length (condylion to gnathion) which increases 15 to 18 mm during first year of life. At birth: Two short mandibular rami Minimal condylar development Practically little articular eminence in the glenoid fossa Only a thin fibrocartilage and connective tissue line lies at the symphysis separating right and left bodies of the mandible.

43. 4 months-age 1: Symphyseal cartilage is replaced by bone. Age 1-2: Overall length increases by 8 to 9 m Age 2-3: Length increase by 5mm During these years, condylar growth and modelling of the superior aspects of the ramus are directed posteriorly and superiorly with roughing equal amounts of growth in each direction

44. MECHANISM OF GROWTH OF THE MANDIBLE CONDYLAR GROWTH: Mandibular condyle is an important site for growth. It is a secondary fibrocartilage and is covered with poorly vascularised fibrous connective tissue. Growth occurs by proliferation of the fibrocartilage which subsequently get ossified into bone. Causes an increase in overall length of mandible while displacing the chin downward and forward.

45. RAMUS TO CORPUS REMODELLING: Growth of the ramus occur in all three dimensions: superiorly, posteriorly and transversely. Superior growth : increase in ramus height, primarily due to growth at the condyle . Posterior growth : by cortical drift and surface remodelling at the junction of the ramus and body of mandible. Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

46. Ramus grow posteriorly by selective deposition at the posterior border and resorption at the anterior border. This also lengthens the corpus and provides space for the developing molars Lingual tuberosity remodels backwards by selective resorption at the anterior surface and deposition at posterior surface. Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

47. Transversely: The ramus widens as it grows posteriorly Caused by both growth of corpus as well as by selective deposition and resorption patterns on the posterior and anterior surfaces of the ramus. Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

48. CORONOID PROCESS Also follows the v-principle, just like the ramus Resorption on the buccal side and deposition on the lingual side of the coronoid process under the action of temporalis muscle . Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

49. BODY OF MANDIBLE Increase in length occurs by remodelling at the anterior border of ramus . Increase in height by development of alveolar process in response to tooth eruption. Laterally on buccal surface, mandibular foramen drift backwards and upwards as deposition take place on anterior rim and resorption at posterior rim of foramen. Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

50. Alveolar process: Develops as the teeth erupt in response to the functional demands. Growth at chin: Occurs by surface remodelling in an inconsistent pattern. Generally with age , chin of the humans become more prominent ; due to deposition of bone on the anteroinferior surface and resorption anterosuperiorly at the level of apices of roots of mandibular incisors Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

51. GROWTH TRENDS AND PATTERNS Facial growth pattern can be divided into: Horizontal growth pattern Vertical growth pattern Average growth pattern Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

52. Horizontal growth pattern: There is tendency for mandible to rotate upward and forward. Less lower anterior facial height. Increased tendency for deep bite Squarish face A low mandibular plane angle Well developed jaw elevators Increased biting force Broad dental arches Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

53. Vertical growth pattern Mandible rotates downwards and backwards. Increased anterior facial Dental arches are narrower Jaw bone density is relatively less Tendency for anterior open bite Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

54. GROWTH ROTATIONS As the facial bones grow, they cause downward and backward rotation of mandible. This is compensated by ramus growth and internal remodelling within the corpus. Rotation of mandible occurs as a result of combined interaction between growth of condyles and surface remodelling. Its of 2 types: FORWARD ROTATION BACKWARD ROTATION Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

55. FORWARD ROTATION Characterised by clockwise rotation of mandible Can be of 3 types: TYPE-1: Centre of rotation- TMJ Incisors move superiorly giving rise to deep bite Underdevelopment of anterior face height In severe cases: Reduced depth of antegonial notch Brachycephalic head type Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

56. Type-2 : Centre of rotation-at the incisal edges of lower anterior teeth. Posterior face height increases disproportionately in relation to the anterior facial height. Occurs in 2 conditions: i). Inferior relocation of the middle cranial fossa ii). Disproportionate increase in the ramus height Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

57. . In type 2 and 3 rotators, the mandibular symphysis typically swings forward to reveal a characteristically prominent chin Type -3: Centre of rotation is displaced backwards to the level of premolars. As in patients with large anterior overjet Anterior deep bite Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

58. BACKWARD ROTATION Downward and clockwise movement of mandible. Its of 2 types: Type-1: Centre of rotation-TMJ Increased anterior facial height Seen in cases where: Middle cranial fossa doesnot develop adequately. When bite raising appliances are given. Diagnosis and management of malocclusion and dentofacial deformities-OM PRAKASH KHARNANDA

59. Type -2: Centre of rotation –at the most distal occluding molars Seen when condylar cartilages shows lesser growth Small vertical height of ramus Rotation of chin downwards and backwards making it less prominent. Lower incisors become retroclined over the base, which might lead to anterior open bite.

60. MATRIX VS INTRAMATRIX ROTATION Relocation of mandible occur to maintain the occlusion and harmony with the growing face Brought about by rotation of mandible as a whole, as well as within the corpus. There are 2 types of mandibular growth rotations: 1).Matrix rotation 2). Intramatrix rotation

61. MATRIX ROTATION Rotation of the whole mandible with condyles as the centre Take place in the form of an arc Seen when the bite is opened by tooth eruption or when excessive vertical maxillary growth rotates mandible downwards

62. INTRAMATRIX ROTATION Rotation within the mandibular corpus Mainly by surface remodelling Contributes to the development of angle of ramus , prominence of chin, development of antegonial notch Seen in cases where posterior teeth fail to erupt and centre of rotation shift to the incisor region. The total rotation of mandible is the sum of both matrix and intramatrix rotations which occur in varying intensity and amount

63. AGE CHANGES IN THE MANDIBLE

64. In infants and children The two halves of mandible fuse during the first year. At birth, the mental foramen open below the socket for two deciduous molar teeth near the lower border Bone is made up only of alveolar socket. Mandibular angle is obtuse -140 degree Mandibular canal is of large size

65. In adults: The mental foramen opens midway between the upper and lower borders Alveolar and subalveolar parts of the bone are equally developed. Angle reduces to about 110 or 120 degree; as ramus becomes more vertical.

66. In old age : Teeth fall out and the alveolar border is absorbed Height of the body is markedly reduced Mental foramen and mandibular canal are close to alveolar border The angle again becomes obtuse about 140 degree; ramus is oblique

67. DEVELOPMENTAL DISTURBANCES OF MANDIBLE Agnathia Micrognathia Pierre robin syndrome Macrognathia Mandibulofacial dysostosis

68. AGNATHIA A lethal anomaly characterized by hypoplasia or absence of mandible. Autosomal recessive mode of inheritance Caused by failure of migration of neural crest mesenchyme into the maxillary prominence at 4 th -5 th week of gestation.

69. Micrognathia Means a small jaw Maxilla or mandible can be affected Clinical features: Severe retrusion of chin A steep mandibular angle A deficient chin button Can be apparent or true micrognathia

70. Pierre robin syndrome Congenital defect Classic triad of : -micrognathia/retrognathia -glossoptosis -cleft palate.

71. Macrognathia Condition of abnormally large jaws Can be associated with certain conditions such as : Paget disease Acromegaly Leontiasis ossea Can also be due to generalized increase in size of entire skeleton, as in pituitary gigantism

72. Mandibulofacial dysostosis Also known as : Treacher Collins syndrome Francshetti-zwahlen-klein syndrome Genetic disease of Autosomal dominant inheritance

73. CONCLUSION The craniofacial components grow and develop in an orderly, anticipated, sequential manner throughout lifetime even though broad range of variations exists. The balanced facial forms and their functions are consensus assimilation of these components. During childhood and adolescence, it is necessary to understand and expect the amount of relative growth rate in various parts of face. This knowledge of growth related changes is crucial while planning orthodontic treatment.

74. REFERENCES: Om Prakash Kharbanda, Diagnosis and Management of Malocclusion and Dental Deformities, 2 nd edition,Elsevier;2013 Sridhar Premkumar , Textbook Of Orthodontics, Reed Elsevier india Pvt.ltd;2015 S I Bhalajhi, Orthodontics The Art and Science, 7 th edition,Arya Medi publishing house;2018 Lee.W.Graber, Robert L Vanarsdall JR, Katherine W L, Greg J H uang, Orthodontics current principles and techniques, 1 st south Asia edition, RLEX India pvt limited;2017 B D Chaurasia, Human Anatomy,6 th edition, CBS Publishers;2013 William G Shafer, Maynard K Hine and Barnet M Levy, Shafer’s Textbook of Oral Pathology, 8 th edition, RLEX India Pvt.Ltd;2016