Mandible growth / /certified fixed orthodontic courses by Indian dental academy


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Mandible growth / /certified fixed orthodontic courses by Indian dental academy

  2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education
  3. 3. The human mandible has no one design for life. Rather, it adapts and remodels through the seven stages of life, from the slim arbiter of things to come in the infant, through a powerful dentate machine and even weapon in the full flesh of maturity, to the pencil-thin, porcelainlike problem that we struggle to repair in the adversity of old age. D.E. Poswillo.
  5. 5. GROWTH
  6. 6. What is growth ? The very term growth and development is difficult to understand.Development means an increase degree of organizations with increase in complexity and carries an overtone of increasing specialization. There is no universally accepted definition of growth. Various clinicians have defined growth in different ways. Moss: change in morphological parameters which is measurable. Moyers: Quantitative aspect of biological development per unit of time. Todd: An increase in size. Krogman: increase in size change in proportions and progressive complexity J.S. Huxley: The self multiplications of living substance MERIDITH:entire series of sequential anatomic and Physiologic changes taking place from beginning of pre natal life to serenity
  7. 7. ANATOMY OF THE MANDIBLE Mandible is largest, strongest and lowest bone in the face. Body – Horse shoe shaped 2 Parts – Body Pair of Rami Body – Outer aspect Inner aspect Upper border Lower border Outer surface presents the following factors Symphysis menti mental protruberance Mental foramen Oblique line Incisive fossa Inner surface Mylohyoid line Submandibular fossa – lodges submandibular gland. Sublingual fossa – sub lingual gland Genial tubercle Mylohyoid groove
  8. 8. Upper border Socket of teeth Lower border Midline of base is digastric fossa Ramus – quadilateral in shape Coronoid process Condylar process Mandibular foramen Lingula Mylohyoid groove .
  9. 9. Attachments and relations of mandible Oblique line – buccinator muscle Oblique line below mental foramen – depressor labii inferious, depressor anguli oris Incisive fossa – mentalis muscle Mylohyoid line – mylohyoid muscle Posterior end of mylohyoid line – superior constructor muscle Genial tubucle – geniohyoid, genioglossus muscle Digastric fossa – anterior belly of digastric muscle Lateral side of ramus – masseter muscle Lower border – Platysma muscle Postero superior part of lateral surface – Parotid gland muscle Lingula – sphenomandibular ligament muscle Medial aspect of ramus – medial pterygoid muscle Mid surface of coronoid - temporalis muscle Pterygoid fossa - lateral pterygoid muscle Lateral surface of neck – attachment to lateral ligament of TMJ
  10. 10. Age Changes in Mandible Infants 2 halves of mandible fuse during 1st year of age. At birth mental foramen open below sockets for 2 deci molar teeth near lower border (therefore an alveolar part of bone is present). Angle is obtuse (140°) because head is in lie with the body. Coronoid process is large and projects upward above the level of condyle. In Adults Mental for opens midway between upper and lower border. Therefore alveolar and sub alveolar parts are equally developed. Angle reduce to 110° to 120° because ramus becomes vertical. Old Age Teeth fall out and alveolar border is resorbed. Height of body is reduced. Mental foramen and mandible canal are close to alveolar border. Angle becomes obtuse.
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  14. 14. The agnatha, the earliest type of vertebrate, had its mouth opening on the ventral side anteriorly along the vertebral axis. This opening led through an oropharyngeal channel to the gut proper. synarthrosis, which was considered to be the earliest form of a jaw joint. This structure remains as an epiceratobranchial joint in the present-day shark. In the gnathostomes, more highly evolved than the Agnatha, the first and second arches disappeared into the skull, and the third and fourth arches began to function in prey capture: the apparatus of the jaw. As evolution proceeded, a more highly developed moveable jaw joint appeared in the osteichthyes. Formed by gill arches, the cartilaginous jaw was covered by bony dermal plates that formed the second jaws. The teeth developed in the bony plates around the mouth. In the amphibians and reptiles the oral organ was used only for prehension. The amphibia had a dentary bone in the anterior end of the original cartilaginous jaw. At its posterior extremity it articulated with the quadrate bone, a structure of the maxilla. The auditory apparatus also developed in the amphibia. The tympanic membrane moved toward the hyomandibular bone, which was involved in sound transmission by conduction vibrations to the inner ear. http// http//therapsd.htm
  15. 15. In mammals, the dentary-squamosal joint was formed after the completion of the contact between the dentary bone and the skull. This entirely new joint took overjaw function and the original joint decreased in size. The original jaw articulation formed the malleolar-incus joint, making a connection with the hyomandibular bone that was found in the amphibia to form a sound transmitting apparatus. In mammal-like reptiles, the dentary bone increased in size and the quadratoarticulate joint continued to evolve as the sound transmitter. As the function and size of the dentary bone increased, the coronoid process temporal fossa were formed. As mentioned, mammals differ from other vertebrates in the structure of the jaw and ear, and the intimate association between the jaw joint and the ear can be recognized.
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  18. 18. prenatal growth {day1 to 266 day}
  19. 19. It is divided into 3 periods 1) period of ovum (ferti. to 14th day) 2)period of embryo (14th day to 56thday) 3)period of fetous(56th day to birth)
  20. 20. f Endometrium (progestational stage) ., ,.< ---I. ,I
  21. 21. Period of embryo (14th day major development of to 56th day It is the period where It is the period where major development of organ specifically craniofacial structure occur. on 17th day process of gastrulation occurs to form different germ layers. Ectoderm above notochord thickens to form neural plate which forms nervous system . On 21st day embryo is of 3mm now primordial of brain eye are seen in prosenceophalon. On 3rd week otic &optic plocodes are seen. In the same period most inferior part of prosencephalon starts growing to from front nasal process which overhangs future oral cavity which is wide & shallow.
  22. 22. P rimitive pit and neurenteric canal Amnion Wallo! yolk sac Cloacal plate (membrane) A Notochordal plate c E ndoderm Intraembry onic mesoderm Extraembry onic mesoderm E Notochord - ,u :1 I "e+r ~t;n a for ,
  23. 23. ,f/,'~ M. W,'. :~:i: :> "-'.~ , I ~.
  24. 24. on 3-4week oral groove starts deepening. Same time bud for max and man process show their presence lat to oral groove. Deepened oral cavity is now called stomodium and is separated by hind gut with a membranes formed by endoderm and ectoderm called buccopharyngeal membranes . on 4th week the embryo is 5mm . Now frontal elevation shows some ectodermal proliferation which form future nasal placode and olfactory epithelium optic placodes which are formed are placed very widely apart
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  26. 26. Otic placode Lens placode Limb ridge B 28 days
  27. 27. Front nasal process show more growth mesially than laterally which forms medial nasal process. As medial nasal process grows faster, in future it unites with maxillary process to form part of upper lip specifically along line of philtrum . lateral nasal process mainly contribute formation of columella .on 5th week caudal to frontonasal and maxillary process brachial arches show their development they are totally six with 5th one turning to be rudimentary. 2nd brachial arch develop faster than other and covers other brachial arches
  28. 28.
  29. 29. ; Pharyngeal pouch Endoderma! epithelium Nerve 1 st pharyngeal arch Cartilage cleft Ectodermal epithelium. 2nd arch with ner ve, artery, and c<1rtllage Mesenchymal tissue in 4th arch A J
  30. 30. Auditory tube Primitive tympanic cavity External auditory meatus Palatine tonsil Ventral side of phary nx - Foramen cecum f , f I f ! I f , I Superior parathy roid gland , '¥ (f rom 4th pouch) Thy roid gland Inf erior parathy roid gland (f rom 3rd pouch) Ultimobranchial body Foregut
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  32. 32.
  33. 33. same time between and around primordial of brian and eye Mesenchymal condensation appears which gives a shape of skull. Mesenchyma of brachial arch also appears by 5th week. 1st brachial grows faster to become distant .In 6th week mandibular arch show accentuated growth to divide in maxillary and mandibular process both process grows medially . medial nasal process from above also grows downwards and towards midline as a result by the 7th week fusion between maxillary and frontonasal process occurs and this time embryo is 14.5mm in length
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  37. 37. Now eye starts migrating towards midline Mesenchymal of cranial and brachial arch differentiates into cartilage (CHONDRIFICATION) cartilage in the base of skull thins to join with nasal and optic capsules. same time centers for endochondral ossification appears in the cartilage of base of skull, also Mesenchymal condensation in intramembranous bone is seen. At 8th week nasal septum further narrows to become a prominent structure ,also external ear starts its development. nasal pit breaks down to form nostrils. Demarcation seen between lateral nasal and maxillary to form nasolacrimal groove which in future closes to form nasolacrimal duct
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  39. 39. primary palate starts its development at 8th week .so till this time their occurs a direct communication between oral and nasal cavity . lidless eyes increase their movement towards midline .both lateral halves of mandibular process fuse by 8th week. at this time embryo is 18mm in length . Rough head and face shape is almost completed by 8th week . By end of 8th week embryo increases in length almost by 4 times to that of 7th week
  40. 40.  main structures formed in the embryonic period are  neural plate -2  buccopharyngeal membrane -2  mandibular arch –3  hypoglossal muscle—5  median and lateral nasal process-5  lens of eye-5, retina—5  external carotid artery-6  middle ear-6  larynx -6  maxillary process -6  external ear -7  nasal septum-8  palatal shelves-8 *IN WEEKS OF IUL
  41. 41. FETAL PERIOD (56days--9 months ) Eye lid formation occurs .eyes get close . nostrils are formed. This period shows accelerated rate of craniofacial growth resulting in an increase size and proportion In 8th to 12 weeks fetus increases in length by 22—60mm . mandible increases in size and anteroposterior relationship of both jaws develop as it is seen at birth
  42. 42. meckels cartilage it derived from first brachial arch on 41st to 45th day of IUL .extends from cartilaginous otic capsule to sysmphysis .it acts as template and guide for growth of mandible . a major portion of this disappears and remaining part develops in to mental ossicle incus, malleus spine of sphenoid ant. Ligament of malleus sphenomandibular ligament 1st structure that develops in promordia of man. Is mandibular division of 5th nerve this is followed by osteogenesis (neurotropic theory )
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  45. 45. on 6th week of IUL single ossification center for each man. Arise in the region of bifurcation of inferior alveolar nerve in to mental and incisive. ossifying membrane is located lateral to meckels cartilage .IM ossification spreads dorsally and ventrally to form body and ramus of man. Ossification continues till region of future linguala. meckels cartilage continues into middle ear and develops in to auditory ossicle that is malleus and incus and SML
  46. 46. Endochondral bone formation in man. Seen in3 areas condylar process mental region coronoid process condylar process; at 5th week of IUL mesanchymal condensation seen above ventral part of man. By 10th week it develops into cone shaped cartilage. by 14th week it starts ossifying. it then migrates inferiorly and fuse with man. Ramus by4th months . by 6-7 th month of IUL much of cartilage ossifies except upper end which ossifies at adult hood
  47. 47. mental region on either of symphysis 2 small cartilage appears in 7th month of IUL .it then incorporates into body . symphysis ossifies after 1yr after birth coronoid process it is formed by secondary cartilage. appears at 10-14th week of IUL. it grows as response to temporalis muscle. it then join with ramus
  49. 49. It is defined as the first 20 years of growth after birth . Of three periods infancy , childhood and adolesecence .It is divided into 1-6 years midddle phase 6-10years and late phase10 - 15 years .Puberty occurs in late childhoood at about 13 to 14 years and 12 -13 years in female . Adolescence is from 14 to 20 years in males and 13 -20 years in female Timing of growth in width length and height Growth occurs in definite sequence. growth of the mandible occurs three dimensionally . Growth in width is completed first then growth in length and finally growth in height.Growth in width of both jaws including the width of the dental arches tends to be completed before the adolescent growth changes.intercanine width is more likely to decrease than increase after age 12.there is a partial exception to this rule however .As the jaws in length posteriorly they also grow wider. In the case of mandible both the molar and bicondylar width shows small increase until the end of growth in length.Anterior width dimensions of the mandible stabilize earlier.
  50. 50. Growth in length and height of both the jaws continue through the period of puberty.Growth in vertical height of the face continue longer than growth in length with the later vertical growth primarily in the mandible.growth of the mandible continue at 9 .relatively steady rate before puberty.Ramus increase 1 to 2mm per year and body length increases 2 to 3mm per year. Of the facial bones the mandible undergoes the largest amount of growth post natally and also inhibit the largest variability in morphology. One of the most important element of the facial growth process two separate but closely inter related system of movements remodelling and displacement. A bone such as the mandible does not grow simply by generalised,uniform deposition .Of new bone(+)on all the outside surfaces with corresponding resorption on the inside.
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  52. 52. At birth the two rami of the mandible are quite short. Condylar development is minimal and there is practically no articular eminence in the glenoid fossa. A thin line of fibrocartilage and connective tissue exists at the midline of the symphysis to separate right and left mandibular bodies. Between the four months of age and at the end of the first year the symphyseal cartilage is replaced by bone. Although growth is quite general during the first year of life, with all surfaces showing bone apposition, there is apparently no significant growth between the two halves before they unite. During the first year of life, appositional growth is especially active at the alveolar border, at the distal and superior surface of the ramus, at the condyle, along the lower border of the mandible and on its lateral surfaces.
  53. 53. After the first year of extra uterine life, mandibular growth becomes more selective. The condyle shows considerable activity as the mandible moves and grows downward and forward. Heavy appositional growth occurs also on the posterior border of the ramus and on the alveolar border. Significant increments of growth are still observed at the tip of the coronoid process. Resorption is said to occur at anterior border of the ramus thus lengthening the alveolar border and maintaining the antero-posterior dimension of ramus. Cephalometric studies indicate that the body of the mandible maintains a relatively constant angular relationship to the ramus throughout life. The gonial angle changes little after muscle function has become well defined with approaching senescence and a marked reduction of muscle activity there is evidence that the gonial angle tends to become more acute.
  54. 54. Width of the mandible generally shows a subtle change. Actually after the first year of life, during which there is appositional growth on all surfaces, the major width contribution of the mandible is growth at the posterior border. Literally the mandible is an “expanding V” additive growth at the ends of “V” naturally increases the distance between the terminal points. The two ramus also diverge outward from below to above so that additive growth at the coronoid notch and process and condyle also increases the superior inter-ramus dimension continued growth of the alveolar bone with the developing dentition increases the height of the mandibular body. But we are again dealing with a 3dimensional object. The alveolar process of the mandible grows upward and outward on an expanding arc. This permits the dental arch to accommodate the larger permanent teeth. Relatively little increase in mandibular body width is noted after cessation of lateral surfaces appositional growth. Modelling deposition at the canine eminence and along the lateral inferior border is seen.
  55. 55. Scott divides the mandible into 3 basic types of bone basal, muscular and alveolar. The basal portion is a tube-like central foundation running from the condyle to the symphysis. The musculature (the gonial angle and coronoid process) is under the influence of the massetter, internal pterygoid and temporal muscles. Muscles function determines the ultimate form of the mandible in these areas. The third portion, alveolar bone, exists to hold the teeth. When the teeth are lost there is gradual resorption of the alveolar bone. Reduced muscle activity accounts for the flattening of the gonial angle and reduced coronoid process.
  56. 56. Regional Details of Post-Natal Growth of Mandible The Ramus It plays a key role in placing the corpus and dental arch into ever-changing fit with the growing maxilla and the faces limitless structural variations. This is provided by critical remodeling and adjustments in ramus alignment, vertical length and antero posterior breadth. The posterior border of mandibular bony arch has to proceed into a region already occupied by the ramus. This requires a remodeling conversion from ramus to mandibular corpus i.e. the ramus becomes relocated posteriorly. Some of the key anatomic parts participate in the relocation and remodeling process of the ramus and the corpus. One of them is the lingual tuberosity.
  57. 57. Lingual Tuberosity The lingual tuberosity is a major site of growth for the mandible. It grows posteriorly by deposits on its posterior facing surface. The lingual tuberosity protrudes in a lingual direction i.e. towards the midline. The prominence of the tuberosity is increased by the presence of larger resorptive field just below it i.e. the lingual fossa. (the combination of the periosteal resorption in the fossa and deposition on the medial facing surface of the tuberosity itself greatly accentuates the contours of both regions. As the posterior growth of the tuberosity occurs that part of the ramus first behind tuberosity grows medially. This brings the ramus into alignment with the axis of the arch (i.e. corpus) thus eventually becomes a part of the corpus thus lengthening it.
  58. 58. Ramus to corpus remodeling conversion The bony arch length and corpus length has been increased by Deposits on the lingual tuberosity and the contiguous lingual side of the ramus Resultant lingual shift of the anterior part of the ramus to become added to the corpus. The presence of resorption on the anterior border of the ramus not only makes room for the last molar but it progressively relocates the entire ramus in posterior direction from tiny mandible of fetus to attainment of adulthood. The posterior movement of the ramus does not occur in a straight line. This is because the remodeling activity does not occur only on the anterior and posterior border but also on the surfaces between them
  59. 59. Coronoid Process It has a propeller like twist so that its lingual sides faces 3 directions posteriorly superiorly and medially. The growth occurs superiorly thus increasing the vertical dimension. It also brings about posterior direction of growth movement. This is also an example of expanding Vprinciple in horizontal direction. This also contributes to the width of the mandible. Lingual deposits also carry the base of the coronoid in a medial direction to add this part to the lengthening corpus which lies medial to the coronoid process. Buccal side of the coronoid process has a resorptive type of periosteal surface. On the inferior edge of the mandible at the ramus corpus junction, a field of surface resorption is present. This forms the antegonial notch
  60. 60. Mandibular foramenAs the whole ramus grows posteriorly and superiorly the mandibular foramen also drifts backward and upward to maintain a constant position i.e. midway between the anterior and posterior border of ramus.
  61. 61. Mandibular Condyle This is an anatomic part of special interest because it is a major site of growth, having considerable clinical significance. Historically the condyle has been regarded as a kind of cornucopia from which the mandible pours forth. It has believed that condyle was a growth center and which determined the rate of growth amount of growth, growth direction, overall mandibular size and shape. Condylar cartilage: condylar cartilage is a secondary type of cartilage which develops because of the functional and developmental conditions imposed upon the part of the mandible. It is now believed that the condyle is a growth site and its role is to provide regional adaptive growth i.e. it maintains the condylar region in proper anatomic relationship with the temporal bone as the whole mandible is simultaneously been carried forward and downward.
  62. 62. Neck of the condyle As the growth is taking place in the condyle the endosteum and periosteam are actively producing the cortical bone that encloses the medullary core of endochondral bone tissue. This occurs upto the neck of the condyle on which both the anterior margin and posterior margin are both depository unless if mandibular relations occurs where the posterior edge can be resorptive. The lingual and the buccal sides of the neck have resorptive surface. This is because as the condyle moves superoposteriorly hence, what used to be the condyle becomes the neck. This again following the V-principle
  63. 63. Mandibular Corpus Since the mandibular arch relates specially to the bony maxillary arch, the mandibular corpus lengthens to match the growth of the maxilla and it does this by remodeling conversion from the ramus. Chin: Bone is added on the external surface of the basal bone area including the mental protuberance, a reversal occurs at a point where the concave surface contour becomes convex. This results in enlargement of the chin. The process involves a mechanisms of endosteal cortical growth on the lingual surface behind the chin, heavy periosteal growth occurs, with the dense lamellar bone merging and overlapping on the labial side of the chin. The point of periosteal to endosteal contact is variable but usually occurs at a level just superior to the projecting apex of the clip.
  64. 64. Symphyseal region There is periosteal resorption on the labial side of the labial bony cortex and deposition on the alveolar surface of the labial cortex and resorption on the labial side of the lingual cortex and deposition on the lingual side of the lingual cortex. This occurs when the teeth drift lingually and superiorly to bring the upper and lower teeth into occlusion. In the mandibular corpus, except for a resorptive zone on the lingual side there is deposition. This enlarges the breadth on each side of the corpus. But there is only slight increase in width during post-natal growth. The gonial angle is determined largely by the growth direction of the ramus and condyle, but a small extent of downward corpus alignment can be produced by new bone deposition on its antero inferior surface.
  67. 67. Thank you Leader in continuing dental education