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Gwowth cranial base /fixed orthodontic courses

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Gwowth cranial base /fixed orthodontic courses

  1. 1. PRE-NATAL & POST-NATAL GROWTH OF CRANIAL BASE www.indiandentalacademy.com
  2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  3. 3.  Introduction  Functions of cranial base  Anterior,middle and posterior cranial fossae  Individual bones of cranial base  Pre-natal growth  Various foramina  Ossification in individual basicranial bones  Cranial base flexure  Post-natal growth  Clinical implications  References www.indiandentalacademy.com
  4. 4. INTRODUCTION The cranial base is of considerable importance to the orthodontist as it serves as a reasonably stable reference structure in roentgen-cephalometric analysis. Growth and development of face and the cranial base are intimately related to each other, and has been a focus of interest to many researchers. www.indiandentalacademy.com
  5. 5. For orthodontists, biologists and anthropologists, the patterns of normal development should be known to serve as a basis for comparing and understanding abnormal growth patterns. www.indiandentalacademy.com
  6. 6. FUNCTIONS OF CRANIAL BASE:  Basicranium supports and protects the brain and spinal cord.  It articulates the skull with the vertebral column, mandible and maxillary region.  It acts as an adaptive or buffer zone between the brain, face and pharyngeal region whose growth are paced differently. www.indiandentalacademy.com
  7. 7.  Internal surface of the cranial base shows a natural division into anterior, middle and posterior cranial fossae.  The duramater is firmly adherent to the whole area, and through the numerous foramina and fissures its outer layer, the endocranium is continuous with the periosteum on the exterior of the skull. www.indiandentalacademy.com
  8. 8. www.indiandentalacademy.com
  9. 9. The anterior cranial fossa  Limited in front and on each side by frontal bone. Its floor is formed by: 1. Orbital plate of frontal bone. 2. Cribriform plate of the ethmoid 3. Anterior part of the body and lesser wing of sphenoid. www.indiandentalacademy.com
  10. 10. The anterior cranial fossa www.indiandentalacademy.com
  11. 11. 1. Orbital plate of frontal bone  Forms the greater part of the floor of the fossa on each side of the median plane  Separates the orbit and its contents from the inferior surface of the frontal lobe of the brain.  In its antero-medial part it is split into two laminae to contain part of an airspace, the frontal sinus.www.indiandentalacademy.com
  12. 12. 2. Cribriform plate of ethmoid  Separates the fossa from nasal cavity and forms the roof of the latter.  Anteriorly it presents a median crest like elevation CRISTA GALLI which projects upwards in between the two cerebrals hemispheres (which is a land mark in frontal/anteroposterior cephalograms). www.indiandentalacademy.com
  13. 13.  The numerous small foramina which perforate the cribriform plate of ethmoid transmit the minute olfactory nerves from the nasal mucosa to the olfactory bulb. www.indiandentalacademy.com
  14. 14. 3. The sphenoid bone  Completes the fossa’s floor from behind.Centrally is the anterior part of the upper surface of its body termed the jugum sphenoidale.  This separates the fossae from bilateral air spaces in the body of the sphenoid named the sphenoidal sinuses. www.indiandentalacademy.com
  15. 15.  Lateral to the jugum the floor of the anterior fossa is formed by lesser wing of sphenoid.  Optic canal is located at the junction of lesser wing and body of the sphenoid bone. www.indiandentalacademy.com
  16. 16. The middle cranial fossa  Deeper than the anterior.  In front it is bounded by posterior borders of the lesser wings of sphenoid and body of sphenoid,  Behind by superior borders of the petrous parts of the temporal bone and dorsum sella of sphenoid bone,laterally by the temporal squamae,parietal bone and sphenoidal greater wings. www.indiandentalacademy.com
  17. 17. su fo em for fora Lesser pe Greater pe Teg www.indiandentalacademy.com
  18. 18.  Centrally the floor is narrower and formed by sphenoid body.  Optic canal is present between roots of a lesser wing and lateral to the body of the sphenoid. It contains the optic nerve, ophthalmic artery and meninges.  The chiasmal sulcus connects the optic canals. www.indiandentalacademy.com
  19. 19.  Behind the sulcus the upper sphenoidal surface is the sella turcica,whose ant. slope bears a median tuberculum sellae,behind which is the hypophyseal fossa. Posterior to it the dorsum sellae projects up & forwards. www.indiandentalacademy.com
  20. 20.  Hypophyseal fossa is present in the middle cranial fossa, which contain the hypophysis cerebri.  Laterally the middle cranial fossa is deep and supports the temporal lobe of cerebrum. www.indiandentalacademy.com
  21. 21.  Communicates anteriorly with the orbit through the superior orbital fissure, which is bounded above by the lesser wing ,below by the greater wing and medially by the body of the sphenoid.  Transmits the terminal branches of ophthalmic nerve, ophthalmic veins, occulomotor, trochlear and abducent nerves. www.indiandentalacademy.com
  22. 22.  Foramen Rotundum pierces the greater wing of the sphenoid and leads forwards into the pterygopalatine fossa to which it conducts maxillay nerve.  Foramen ovale lying post. to F.rotundum leads downwards into the infra-temporal fossa and transmits the mandibular nerve. www.indiandentalacademy.com
  23. 23. Foramen spinosum transmits the middle meningeal artery and is located near the posterolateral margin of foramen ovale. Foramen lacerum is located at the posterior end of the carotid groove and posteromedial to the foramen ovale. It contains the internal carotid artery and its accompanying sympathetic and venous plexuses. www.indiandentalacademy.com
  24. 24. The Posterior cranial fossa  The largest and deepest of the cranial fossa.  Surrounded by dorsum sella, posterior part of the body of the sphenoid and basilar part of the occipital bone anteriorly;  Behind by the lower portion of the occipital squamae. www.indiandentalacademy.com
  25. 25.  On each side by the petrous and mastoid parts of temporal bone and lateral parts of occipital  Above & behind by the mastoid angles of the parietal bones.  It contains the cerebellum,pons and medulla oblongata. www.indiandentalacademy.com
  26. 26. The posterior cranial fossa www.indiandentalacademy.com
  27. 27.  The foramen magnum – It is in the floor of the fossa and surrounded by the parts of the occipital bone. Somewhat ovoid in shape communicates with the vertebral canal where the medulla oblongata becomes continuous with the spinal cord. www.indiandentalacademy.com
  28. 28.  The jugular foramen sited at post. end of petro-occipital fissure, provides a passage to the glossopharyngeal, spinal accessory and vagus nerves and internal jugular vein,. www.indiandentalacademy.com
  29. 29.  Above the anterior part of the jugular foramen the internal acoustic meatus runs transversely in a lateral direction. It allows facial and vestibulocochlear nerves, the nervus intermedius and labyrinthine vessels.  Hypoglossal canal is present lateral to the foramen magnum and contains hypoglossal nerve. www.indiandentalacademy.com
  30. 30. BONES FORMING THE CRANIAL BASE www.indiandentalacademy.com
  31. 31. The occipital bone  It forms much of the back and base of the cranium.  Trapezoid in shape,concave internally. Contains 3 parts:  Squamous part.  Basillar part.  Lateral / condylar part. www.indiandentalacademy.com
  32. 32. The sphenoid bone  It is in the base of the skull,wedged between the frontal and the temporal bones and basilar part of occipital bone.  Has a shape of a bird with wings stretched out . www.indiandentalacademy.com
  33. 33. The sphenoid consists of: 1. 2. 3. 4. Central portion or body Greater wings (2) Lesser wings (2) Pterygoid processes (2) Each has: Lateral pterygoid plates (2) Medial pterygoid plates (2) www.indiandentalacademy.com
  34. 34. The temporal bones  This paired bone forms the sides and base of the skull.  Each consists of 4 parts: • • • • Squamous part. Petromastoid part. Tympanic. Styloid process www.indiandentalacademy.com
  35. 35. The frontal bone  It is an irregular cap like bone which forms the region of the forehead  On each side it has a horizontal orbital part which forms most of the roof of the orbital cavity.  The portion of the bone which projects downwards between the supraorbital margins is named as the nasal part. www.indiandentalacademy.com
  36. 36. The ethmoid bone  It is cuboidal and extremely light in build.  Situated at the anterior part of the basicranium and assists in forming the medial walls of orbits, the nasal septum and roof and lateral walls of nasal cavity. It consists of 3 parts:  Cribriform plate (perforated one)  A perpendicular plate  Lateral masses (labyrinths) www.indiandentalacademy.com
  37. 37. The Inferior nasal conchae  These are curved laminae, which lie horizontally in the lateral walls of nasal cavity. www.indiandentalacademy.com
  38. 38. PRENATAL DEVELOPMENT OF CRANIAL BASE www.indiandentalacademy.com
  39. 39. Cranium can be divided into 2 parts:  Neurocranium: It protects and supports the brain and sense organs.  Viscerocranium: Which is related to alimentary, respiratory tracts, face, maxilla and mandible. www.indiandentalacademy.com
  40. 40.  Basicranium or cranial base is related to the both neural and visceral components.  At cellular level, bones of cranial base develop by the following processes:  Hyperplasia (Prominent feature of all forms of growth)  Hypertrophy(sec. Factor) Secretion of extracellular material www.indiandentalacademy.com
  41. 41. Chondrification: Earliest evidence of formation of cranial base is seen in the late somite period i.e. 4th – 8th week of intrauterine life. www.indiandentalacademy.com
  42. 42. Mesenchyme derived from primitive streak,neural crest and occipital sclerotomes condenses around the developing brain “ectomeningeal capsule” basal portion future cranial base . www.indiandentalacademy.com
  43. 43. During this period: The occipital sclerotomal mesenchyme Concentrates around the notochord underlying the developing hindbrain Cephalic extension Floor of the brain. www.indiandentalacademy.com
  44. 44.  Approximately 40th day of intrauterine life mesenchyme starts converting into cartilage marking the onset of cranial base formation.  Chondrification centers form in the following regions: 1. 2. 3. 4. Parachordal Hypophyseal Nasal Otic www.indiandentalacademy.com
  45. 45. Parachordal region  Chondrification centers forming around the cranial end of the notochord are appropriately called the parachordal cartilages.  Fuse with the sclerotomes arising from occipital somites. www.indiandentalacademy.com
  46. 46.  The sclerotome cartilage is considered to be the first part of the skull to develop and it forms the boundaries of foramen magnum, providing the anlagen for basilar and condylar parts of the occipital bone. www.indiandentalacademy.com
  47. 47. www.indiandentalacademy.com
  48. 48. www.indiandentalacademy.com
  49. 49. Hypophyseal region  Oropharyngeal membrane closes off the stomadeum.  Just cranial to this membrane the hypophyseal pouch (Rathke’s pouch) arises from the stomodeum. Anterior lobe of pituitary gland (Adenohypophysis) lying cranial to notochord termination. www.indiandentalacademy.com
  50. 50. Two hypophyseal or polar or post sphenoid cartilages Either side of the hypophyseal stem Sella turcica and posterior part of the body of the sphenoid bone. www.indiandentalacademy.com
  51. 51. Cranial to the pituitary gland fusion of the two presphenoid or trabecular cartilages Precursor to the presphenoid bone Anterior part of the body of the sphenoid bone. www.indiandentalacademy.com
  52. 52. www.indiandentalacademy.com
  53. 53.  Laterally the chondrification centers of the orbitosphenoid (lesser wing) and alisphenoid (greaterwing) contribute later to the sphenoid bone.  Most anteriorly, the fused presphenoid cartilage forms a vertical cartilaginous plate called the mesethmoid cartilage Perpendicular plate of the ethmoid bone and crista galli. www.indiandentalacademy.com
  54. 54.  The capsules surrounding the nasal, otic sense organs chondrify and fuse to the cartilages of the cranial base. www.indiandentalacademy.com
  55. 55. Nasal capsules: Formed around the nasal sense organ Chondrify in the 2nd month IU Box of cartilage with a roof and lateral walls divided by a median cartilage septum. The cartilaginous nasal capsules Ossification www.indiandentalacademy.com Ethmoid and inferior nasal concha.
  56. 56. The chondrified nasal capsules Cartilages of the nostrils & median nasal septum NS remains cartilaginous except posteroinferiorly, Intramembraneous ossification Vomer bone www.indiandentalacademy.com (paired initially,2 halves uniting before birth)
  57. 57. www.indiandentalacademy.com
  58. 58.  In the foetus, the septal cartilage intervenes between the cranial base above and the premaxilla, vomer and palatine processes of maxilla  Postnatally the nasal septal cartilage acts as a functional matrix in the downward and forward growth of the midface.  It helps in transferring compressive forces from incisor region to the sphenoid bone. www.indiandentalacademy.com
  59. 59. Otic capsules:  Formed around the vestibulocochlear sense organs, Chondrify & fuse with the parachordal cartilages Ossification Mastoid and petrous portions ofwww.indiandentalacademy.combones. the temporal
  60. 60. N www.indiandentalacademy.com
  61. 61. Initial separate centers of cranial base chondrification Fusion A single, irregular and much perforated basal plate.  This cartilaginous basal plate has numerous perforations formed by the establishment of blood vessels, cranial nerves and spinal cord between the developing brain and its extracranial contacts. www.indiandentalacademy.com
  62. 62.  The height of cartilaginous skeletal development occurs during the 3rd month IU.  A continuous plate of cartilage extends from nasal capsule posteriorly all the way to the foramen magnum  During the 4th month IU there is an ingrowth of vascular elements into the various points of chondrocranium.  These areas become centers of ossification, at which cartilage is transformed into bone. www.indiandentalacademy.com
  63. 63. Various foramina Related nerves and vessels 1) Perforations in Fibres of olfactory the cribriform plate nerve (I) of ethmoid bone. 2) Optic foramen (Formed by extensions of orbitosphenoid cartilage around II N. fused with cranial part of basal plate) Optic nerve (II) Ophthalmic artery. www.indiandentalacademy.com
  64. 64. 3) Superior orbital fissure (space between the orbitosphenoid and alisphenoid cartilages) Occulomotor (III) Trochlear (IV) Opthalmic (VI) Abducens (VI) nerves and Ophthalmic veins. 4) Foramen rotundum Maxillary (V2) nerve 5) Foramen ovale Mandibular (V3) nerve www.indiandentalacademy.com
  65. 65. 6) Foramen spinosum (Junction between thealisphenoid and polar cartilages) Middle artery meningeal 7) Foramen lacerum (At the junction of alisphenoid and postsphenoid cartilages and otic capsule) Internal artery carotid 8) Internal acoustic Facial (VII) meatus (Nerves Vestibulocochlear passes through otic (VIII) www.indiandentalacademy.com capsule)
  66. 66. 9) Jugular foramen (Passage of nerves and vessels between the otic capsule and the parachordal cartilage) Glossopharyngeal (IX) Vagus (X) Spinal accessory (XI) Internal jugular vein 10) Hypoglossal / anterior condylar canal (Nerve passing between the occipital sclerotomes) Hypoglossal (XII) 11) Foramen magnum nerve Lower end of medulla,meninges, www.indiandentalacademy.com spinal arteries,
  67. 67. Ossification in individual basicranial bones: www.indiandentalacademy.com
  68. 68. Occipital bone:  Ossified from 7 centres, which are 2 intramembranous 5 endochondral.  The supranuchal squamous portion ossifies from a pair of intramembranous ossification centers in the 8th week of intrauterine life. www.indiandentalacademy.com
  69. 69.  The Infranuchal squamous portion ossifies from a pair of endochondral ossification centers at the 10th week.  The basilar part ossifies appearing in 11th wk IU Anterior portion of occipital condyle & ant. boundary of foramen magnum. www.indiandentalacademy.com
  70. 70.  A pair of endochondral ossification centres appears in the 12th wk forming the lateral boundary of foramen magnum & posterior portion of occipital condyles.  An occasional centre appears in the post. Margin of the foramen magnum in 16th wk-KERCKRING’s CENTRE which unites with the rest of squamae before birth. www.indiandentalacademy.com
  71. 71. The temporal bone  Ossifies both endochondrally and intramembraneously from 21 ossification centres.  Squamous and tympanic elements Intramembranous ossification  Petrosal and styloid elements www.indiandentalacademy.com Endochondral ossification
  72. 72.  The squamous portion ossified intramembranously from a single center appearing in the 8 week, the zygomatic process extends from this ossification center.  The tympanic ring surrounding the external acoustic meatus ossifies from 4 intramembranous centers starting in the 12th week I.U. www.indiandentalacademy.com
  73. 73.  The petrosal part ossifies endochondrally in the otic capsule from about 14 centres, these centers start to appear in the 16 th week and fuse during the 6th month I.U. when the contained inner-ear, labyrinth has reached its final size.  Styloid process ossifies from 2 centres in the hyoid (2nd) branchial arch cartilage; the upper center appears just before birth and the lower center just after birth. www.indiandentalacademy.com
  74. 74.  At 22 weeks of I.U. the petrous and tympanic ring fuse incompletely, leaving the petrotympanic fissure.  At birth the tympanic ring fuses incompletely with the squamous part of temporal bone. www.indiandentalacademy.com
  75. 75.  The petrous, squamous and proximal styloid process-parts fuse during the 1 st year of life.  The mandibular (Glenoid) fossa is only a shallow depression at birth facing laterally, deepening with development of articular eminance and ultimately facing downwards. www.indiandentalacademy.com
  76. 76. Ethmoid bone: This wholly endochondral bone, which forms the median floor of the anterior cranial fossa and forms parts of the roof, lateral walls and median septum of the nasal cavity, ossifies from 3 centres. www.indiandentalacademy.com
  77. 77. A pair of centers for the lateral labyrinths appears in the nasal capsular cartilages at the 4th month I.U. A single median center in the mesethmoid cartilage forms the perpendicular plate and cristagalli just before birth. At two years of age the perpendicular plate unites with the lateral labyrinths to form a single ethmoid bone. www.indiandentalacademy.com
  78. 78. Inferior nasal choncha: Single center in the cartilage of lateral part of the nasal capsule (5thmonth I.U) Endochondral ossification Inferior nasal concha Detaches from the capsule www.indiandentalacademy.com Independent bone.
  79. 79. The sphenoid bone:  Sphenoid bone has up to 14 ossification centers (intramembranous and endochondral)  Until the 7th or 8th month IU,sphenoid body has a presphenoid part anterior to tuberculum sellae,with which the lesser wings are continuous ; and a postsphenoid part ,comprising sella turcica and dorsum sellae,and integral with the greater wings www.indiandentalacademy.com & pterygoid processes.
  80. 80.  Lesser wing: Endochondral ossification in the orbitosphenoid cartilage.  Greater wing and lateral pterygoid plate: 2 intramembraneous ossification centres seen in alisphenoid cartilage.A part of G.wing ossifies endochondrally.  Medial pterygoid plate:Ossifies endochondrally from a secondary cartilage in the hamular process. www.indiandentalacademy.com
  81. 81.  Anterior part of body of sphenoid: Ossifies endochondrally from 5 centres(2 paired &1 in midline) in the presphenoid cartilage.  Posterior part of body of sphenoid: Ossifies endochondrally from 4 centres in the postsphenoid cartilage.  The midsphenoidal synchondrosis between the pre and post sphenoid fuses shortly before birth.  The sphenooccipital synchondrosis fuses in www.indiandentalacademy.com adolescence.
  82. 82. CRANIAL BASE FLEXURE  During the embryonic and early fetal periods,the enormous human cerebrum expands around a much smaller enlarging midventral segment(the medulla,pons, hypothalamus,optic chiasma).  This causes a bending of the whole underside of the brain.And the flexure of the cranial base results, in the region of the pituitary fossa,at the spheno-occipital junction,so that the developing face becomes tucked in under the cranium. www.indiandentalacademy.com
  83. 83. Cranial Base Flexure Early embryo (Cranial base straight) Fetus (Cranial base flexed) www.indiandentalacademy.com
  84. 84. Cranial Base Flexure www.indiandentalacademy.com
  85. 85. This relates to two key features: 1. The spinal cord is now aligned vertically,a change that permits upright,bipedal body stance with free arms and hands 2. As the forehead is rotated in a vertical plane with the growth of the frontal lobe,the superior orbital rim is carried with it.This aligns the eyes so that they point in the forward direction of upright body movt. www.indiandentalacademy.com
  86. 86.  The body has become vertical,but the neutral visual axis is still horizontal ,as in other mammals.  This cranial base flexure effectively enlarges the neurocranial capacity and causes downward rather than forward displacement of face during its growth from the cranial base. www.indiandentalacademy.com
  87. 87. Cranial base angulation  The central region of the cranial base is composed of prechordal and chordal parts which meet at an angle at the hypophyseal fossa (sella turcia).  The lower angle, formed by lines from nasion to sella to basion in the sagittal plane varies following the growth of embryo. www.indiandentalacademy.com
  88. 88.  Initially highly obtuse = 150° in 4 week old embryo (precartilage stage).  Reduces approximately = 130° in 7-8 week old embryo (cartilage stage).  Becomes more acute = 115-120° at 10 weeks embryo (pre-ossification stage).  Widens to 125-130° at 10-20 weeks (ossification stage) and maintains this angulation postnatally. www.indiandentalacademy.com
  89. 89. www.indiandentalacademy.com
  90. 90. Uneven nature of cranial base growth  Growth of the cranial base is highly uneven.  The uneven growth of the parts of the brain is reflected in the related parts of the cranial base adapting as compartments or cranial fossae. www.indiandentalacademy.com
  91. 91.  Unevenness is also seen in rate of growth  Eg. the anterior cranial base increases in length and width by evenfold between the 10th and 40th weeks I.U. whereas, The posterior cranial base grows only 5 fold. www.indiandentalacademy.com
  92. 92. www.indiandentalacademy.com
  93. 93. www.indiandentalacademy.com
  94. 94. Postnatal growth of cranial base www.indiandentalacademy.com
  95. 95.  Cranial base has a potent role in the development of structure, dimensions, angles and placement of various facial parts.  Floor of the cranium is a template from which face develops.  Any difference in the development of basicranium will be reflected in the facial growth. www.indiandentalacademy.com
  96. 96.  Growth of the central ventral axis of the brain and of the related body of the sphenoid and basioccipital bones is slow, providing a comparatively stable base.  Laterally,cranially and caudal to this base, the anterior,middle and posterior fossae expand enormously in keeping with the growth of related parts of the brain. www.indiandentalacademy.com
  97. 97.  The cranial base grows postnatally by complex interaction between the following growth processes: 1. Extensive cortical drift and remodelling 2. Growth of the cartilage remnants of the chondrocranium that persist between the basicranial bones. 3. Expansive forces emanating from the growing brain displacing the bones at the suture lines (capsular functional www.indiandentalacademy.com matrix).
  98. 98.  Cortical drift and remodelling  Endocranial surface of cranial floor has a different mode of development when compared with the culvaria because of its complex structure and curvature.  The endocranial or neural surface of the basicranium in contrast to the roof is resorptive in most areas www.indiandentalacademy.com
  99. 99. www.indiandentalacademy.com
  100. 100.  The reason is that the sutures do not have the capacity to provide for the multiple directions of enlargement and the complex magnitude of remodeling required.  Remodeling is required to accommodate the massively enlarged human brain. www.indiandentalacademy.com
  101. 101. Fossa enlargement: The unidirectional sutural growth occurs at locations 1 and 2, which is not sufficient to accommodate the brain expansion. www.indiandentalacademy.com
  102. 102. Fossa enlargement is accomplished by direct remodeling involving deposition on the outside with resorption from the inside. This is the key remodeling process that provides for the direct expansion of the various endocranial fossae in conjunction with sutural growth and growth at synchondrosis. www.indiandentalacademy.com
  103. 103. Various endocranial compartments are separated from one another by elevated bony partitions:  The olfactory fossae are separated by CRISTA GALLI.  Middle and posterior fossae are divided by the petrous elevation. www.indiandentalacademy.com
  104. 104.  Right and left middle cranial fossae are separated by the longitudinal midline sphenoidal elevation.  Right and left anterior and posterior cranial fossae are divided by a longitudinal midline bony ridge. www.indiandentalacademy.com
  105. 105.  All these elevated partitions, unlike of the remainder of the cranial floor are depository in nature because as fossae expand outward by resorption, the partitions between them must enlarge inward by deposition to maintain the proportions. www.indiandentalacademy.com
  106. 106. www.indiandentalacademy.com
  107. 107.  The mid ventral segments of cranial floor grow more slowly than the floor of the laterally located fossae. This accommodates the slower development of the medulla, pons, hypothalamus, optic chiasma in contrast to the massive rapid expansion of the hemispheres. www.indiandentalacademy.com
  108. 108.  A markedly decreasing and tapering gradient of sutural growth occurs as the ventral midline is approached but direct remodeling also occur to provide for the varying extents of expansion required among the different midline parts themselves and much faster growing lateral regions. www.indiandentalacademy.com
  109. 109.  Unlike the roof, the floor of the cranium provides the passage of cranial nerves and major cerebral vessels.  The process of remodeling growth in the basicranium provides for the stability of these nerves and vascular passageways. www.indiandentalacademy.com
  110. 110.  The foramen moves by deposition and resorption keeping pace with corresponding movement of nerve/vessel.  The foramen enclosing each cranial nerve and major blood vessel also undergoes its own drift process to constantly maintain the proper position (Relocation) www.indiandentalacademy.com
  111. 111.  Growth in the posterior cranial fossa is more when compared with growth of the spinal cord and foramen magnum.  Differential remodeling process maintains the proportionate placement of spinal cord, even though the floor of the posterior cranial fossa, which surrounds the spinal cord expands to a considerably greater extent than the circumference of the foramen magnum. www.indiandentalacademy.com
  112. 112.  The resorption occurs from the lining side of the forward walls of the middle cranial fossa (1).  Deposition on the orbital face of the sphenoid and in the sphenofrontal suture (2).  Forward displacement of the anterior cranial fossae occurs as the frontal lobes are displaced anteriorly (3). www.indiandentalacademy.com
  113. 113. www.indiandentalacademy.com
  114. 114.  The petrous elevation (4) increases by deposition on the endocranial surface.  Lengthening of clivus occurs by growth at SOS (5).  The foramen magnum is progressively lowered by resorption on the endocranial surface and deposition on the ectocranial side. Endocranial fossa enlarge by a combination of endocranial resorption and ectocranial deposition. www.indiandentalacademy.com
  115. 115. 2. Synchondroses: The midline part of the basicranium is characterized by the presence of synchondroses. They are the “left over” from the primary cartilages of the chondrocranium after the endocranial ossification centers appear during fetal development. www.indiandentalacademy.com
  116. 116.  By their interstitial growth,the interposed cartilages or “synchondroses” can separate the adjacent bones as appositional bone growth adds to the sutural edges of the bones. www.indiandentalacademy.com
  117. 117.  Different synchondroses seen in cranial base     Spheno-occipital Spheno-ethmoidal Intra occipital Inter-sphenoidal www.indiandentalacademy.com
  118. 118. The sphenooccipital synchondrosis  It is the principal growth cartilage of cranial base During childhood  As all growth cartilages are associated with (directly) bone development, the SOS provides a pressure adapted bone growth mechanism unlike the sutural areas which show tension adapted mechanism. www.indiandentalacademy.com
  119. 119. Pre s Post sphenoid Basi occipital www.indiandentalacademy.com
  120. 120.  Because cranial base supports the mass of the brain and face, SOS in the midline is subjected to craniofacial muscular forces.  As endochondral bone growth occurs at the SOS,the sphenoid and the occipital bones become moved apart by the 1° displacement process. www.indiandentalacademy.com
  121. 121. www.indiandentalacademy.com
  122. 122.  At the same time new endochondral bone is laid down by the endosteum within each bone (Medullary fine cancellous bone). Compact cortical (Intramembranous) bone is formed around this core of endochondral bone tissue. .  Each bone thereby becomes lengthened. Both bones also increase in girth by periosteal and endosteal remodeling. www.indiandentalacademy.com
  123. 123.  The interior of the sphenoid bone eventually becomes hollowed to form the sizable sphenoidal sinus.  Sphenoidal sinus expansion does not push the maxilla. The sinus grows secondarily as the body of the sphenoid bone expands around it keeping constant junction with the moving nasomaxillary complex. www.indiandentalacademy.com
  124. 124.  The synchondrosis has a series of zones like primary cartilage : 1. 2. 3. 4. Familiar reserve zone. Cell division zone. Hypertrophic zone. Calcified zone. www.indiandentalacademy.com
  125. 125.  Similar to an epiphyseal plate, but unlike the condylar cartilage, the chondroblasts in the cell division zone are aligned in distinctive columns that point along the line of growth  Unlike the epiphyseal plate the synchondrosis has 2 major (Bipolar) directions of linear growth.  Structurally the synchondrosis is essentially 2 epiphyseal plates positioned back to back and separated by a common zone of reserve cartilage. www.indiandentalacademy.com
  126. 126.  SOS is the last of all synchondrosis to fuse and starts fusing at 12-13 years in girls, and 14-15 years in boys and completing ossification of the external aspect by 20 years of age.  This prolonged growth period allows for continued posterior expansion of the maxilla to accommodate last erupting molar teeth and provides space for growing nasopharynx. www.indiandentalacademy.com
  127. 127. Spheno-ethmoidal synchondrosis  A cartilaginous band between the sphenoid and ethmoid bones.  Believed to ossify after 5yrs of age. Inter sphenoidal synchondrosis  Between 2 parts of sphenoid  Ossifies at birth Intra occipital synchondrosis  This ossifies by 3-5 yrs of age. www.indiandentalacademy.com
  128. 128.  The size, shape and characteristics of cranial floor have evolved in direct phylogenetic association with the brain it supports, but the basicranium itself has presumably developed a genetic capacity of its own growth that is some how independent of the brain.  Extrinsic control factors are also involved; but to what extent they are involved is not fully understood, since the cranial floor can develop to a greater or lesser extent, www.indiandentalacademy.com even though the brain is malformed or
  129. 129. 3. Expansive forces from brainGrowth at sutures. Some of the sutures of cranial base:  Spheno-frontal  Fronto-temporal  Spheno-ethmoid  Fronto-ethmoid  Fronto-zygomatic www.indiandentalacademy.com
  130. 130. www.indiandentalacademy.com
  131. 131. .  The expansion of the middle cranial fossa and its neural contents  Secondary displacement effect on the anterior cranial floor , underlying nasomaxillary complex and mandible. www.indiandentalacademy.com
  132. 132.  Because the posterior boundary of nasomaxillary complex is developmentally positioned to exactly coincide with the boundary between the anterior and middle cranial fossae some amount of forward displacement of both the anterior cranial fossa and the nasomaxillary complex occurs. www.indiandentalacademy.com
  133. 133.  The temporal and frontal lobes have fibrous attachments to the middle and anterior cranial fossa.  As both lobes expand these 2 fossae are thus pulled away from each other.  This set up tension fields in various frontal, temporal, sphenoidal, and ethmoidal sutures and this also presumably triggers sutural bone responses. www.indiandentalacademy.com
  134. 134.  At about 5 years of age, frontal lobe growth and anterior cranial fossae expansion are largely complete.  The temporal and middle cranial fossa, however continue to enlarge for several more years www.indiandentalacademy.com
  135. 135.  The expansion of each temporal lobe continues to displace the frontal lobe forward and this in turn causes tension in the osteogenic suture systems between these 2 areas.  The anterior fossae and the maxillary complex are carried anteriorly by the frontal lobes, which is moved forward because of temporal lobe enlarging behind it. www.indiandentalacademy.com
  136. 136. Timing of cranial base growth 1. By birth,55-60 % of adult size is attained. 2. By 4-7 yrs,94 % of adult size is attained. 3. By 8-13 yrs,98 % of adult size is attained. www.indiandentalacademy.com
  137. 137. Clinical implications www.indiandentalacademy.com
  138. 138. Study:Cranial base growth for Dutch boys and girls (AJO 1994 November)) - Monique Henneberke and Birte Prahl Andersen In this study growth and development of the cranial base in children who were treated orthodontically were compared with children who were not. www.indiandentalacademy.com
  139. 139. The hypothesis tested was that there is no difference in cranial base growth between children with and without orthodontic treatment. This is a mixed longitudinal study of *153 boys and 167 girls samples for S-N *116 boys and 116 girls for N-Ba and S-Ba, * All were of 7-14 years of age. www.indiandentalacademy.com
  140. 140.  Cephalometric points used in this study. www.indiandentalacademy.com
  141. 141. Results:  The effect of orthodontic therapy on cranial base growth was apparently so limited that no significant differences could be demonstrated between children with or without treatment.  The cranial base displayed sexual dimorphism in absolute size, timing and amount of growth. www.indiandentalacademy.com
  142. 142.  All C.B. dimensions examined in this study were greater in boys than in girls.  Girls did not show adolescent growth spurts, where as all boys showed that for S-N and N-Ba. www.indiandentalacademy.com
  143. 143. Anencephaly  Characterizd by chondrocranium anomalies. a short, narrow with notochordal  Anencephaly patients retain the acute cranial base flexure typical of early fetuses.  This suggests that brain growth contributes to flattening of the cranial base. www.indiandentalacademy.com
  144. 144.  Certain forms of dental malocclusions may be related to defects of the chondrocranium eg. The defects that minimize the space available for maxillary dentition (diminished maxilla) may lead to impacted teeth viz.third molars. www.indiandentalacademy.com
  145. 145.  Afflictions of cartilage growth produce a reduced cranial base resulting in a ‘dished’ deformity of middle 13 of face which is seen in conditions like achondroplasia, cretinism and Down’s syndrome (Trisomy 21).  All these produce a similar characteristic facial deformity by their inhibiting effect on chondrocranial growth. www.indiandentalacademy.com
  146. 146. Achondroplasia: www.indiandentalacademy.com
  147. 147.  The C.B. does not lengthen normally because of deficient growth at the synchondroses; the maxilla is not translated forward to the normal extent, and a relative midface deficiency occurs www.indiandentalacademy.com
  148. 148.  Premature ossification or synostosis of the suture between the presphenoid and post sphenoid parts and of the sphenooccipital suture produces a characteristic apearance.  This is seen in profile, and consists of an abnormal depression of the bridge of the nose www.indiandentalacademy.com
  149. 149.  Hypertelorism. Anomalous development of the presphenoidal elements excessive separation between the orbits and abnormally broad nasal bridge. www.indiandentalacademy.com
  150. 150.  Craniopharyngeal tumours Coalescence of the ossification centers in the body of sphenoid obliterates the orohypopharyngeal track. Persistence of the track as a craniopharyngeal canal in the sphenoid body gives rise to craniopharyngeal tumours. www.indiandentalacademy.com
  151. 151.  Premature fusion of sphenooccipital synchondrosis in infancy results in a depressed nasal bridge and dished face.  Cleidocranial dysostosis patients with CCD exhibit high frequencies of anomalous traits in the cranial base. www.indiandentalacademy.com
  152. 152.  CCD is characterized by abnormalities of the skull, jaws and shoulder girdle as well as by occasional stunting of long bones.  In the skull, frontanelles remain open or atleast exhibit delayed closing.  Frontal, parietal and occipital bones are prominent and the paranasal sinuses are underveloped and narrow. www.indiandentalacademy.com
  153. 153. Study: (AJO May 1981)  Kreiborg,Jensen, Bjork and Skieller conducted a qualitative screening for abnormal morphological traits in the cranial base.  The sample comprised 17 patients with CCD (8 males and 9 females) 1646 yrs of age. www.indiandentalacademy.com
  154. 154. Results:  The anterior and posterior cranial base was significantly shorter and the C.B. angle smaller in the syndrome groups than in the control groups.  Clivus was distorted in 82 % of patients. www.indiandentalacademy.com
  155. 155.  All patients showed bulbous dorsum sellae and many had small pituitary fossae.  The amount of bone resorption was lesser than normal, so abnormalities in remodeling pattern is seen. www.indiandentalacademy.com
  156. 156.  Lateral roentgenocephalometric film of adult male patient with cleidocranial dysostosis.  Poor visualization of posterior cranial base. www.indiandentalacademy.com
  157. 157.  Midsagittal tomogram of posterior cranial base in a patient of CCD.  Bulbous dorsum sellae and flexion of clivus. www.indiandentalacademy.com
  158. 158.  Tracings of the posterior cranial base from midsagittal tomograms of three patients with cleidocranial dysostosis. Note shallow pituitary fossa in Patient 1065Z. All three patients exhibited bulbous dorsum sellae, flexion of clivus, and bulbous anterior margin of foramen magnum. www.indiandentalacademy.com
  159. 159.  Distortion of clivus in the syndrome group could have arisen in a number of ways: • First, it could be related to an abnormal remodeling pattern. • Second, it could be primary anomaly comparable to the other midline anomalies found in the syndrome.. www.indiandentalacademy.com
  160. 160.  Third, it could result from displacement of the bone of the cranial base during the development caused by delayed or defective ossification in the region  It could result from any combination of these mechanisms www.indiandentalacademy.com
  161. 161. References 1. Craniofacial Embryology - G.H.SPERBER 2. Essentials Of Facial Growth - D.H.ENLOW 3. Gray’s Anatomy - Gray 4. Contemporary orthodontics - W.R.PROFFIT www.indiandentalacademy.com
  162. 162. 5. Orthodontics-The art and science-- S.I.Bhalajhi 6.Abnormalities Of Cleidocranial Dysostosis – Kreiborg,bjork& Skeiller (AJO May; 1981) 7. Cranial Base Growth For Dutch Boys & Girls – M.Herneberke,b.P. Andersen (AJO November; 1994) www.indiandentalacademy.com
  163. 163. Thank you www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com

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