Development of the orofacial structures

1. Oro-facial
Embryogenesis
Dr. Fuad M. (OMS R1) PRESENTOR
Dr. Santosh (OMS) MODERATOR
Feb .21,2010 E.C

2. Objectives
Upon completion of this seminar
presentation, the attendants expected to :
Describe the Pharyngeal apparatus
Discuss the development of oro-facial structures
Discuss the development of face
Discuss the development of palate
Discuss the development of tongue
Discuss the development of tooth
Know the major orofascial developemental
anomalies
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3. Content
Introduction
Pharyngeal apparatus
Development of face
Development of Palate
Development of Nasal cavity
Development of paranasal sinus
Development of tongue
Development of tooth
Development of salivary glands
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4. Introduction
 Prenatal growth arbitrarily divided into 3
periods;
1. Period of ovum(0-14d)
2. Period of embryo(14-56d)
3. Period of fetus (57-270d)
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5. Introduction cont..
Period of embryo
The following major events occur
Formation of branchial arch
Development of tongue
Development of perioral region(face)
Development of palate
Formation of nasal pit
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6. Introduction cont..
During the 4th week of
development, the human
embryo consists of a flat
disk that bends down at its
anterior extremity as the
overlying brain expands
and enlarges
A pit develops in the
midline b/n the brain and
the heart and becomes the
oral cavity
Beneath this pit the first
pharyngeal arch forms
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7. Introduction cont…
Below the
mandibular arch four
other pharyngeal
arches or bars appear
during the fourth to
seventh prenatal
week
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8. PHARYNGEAL APPARATUS
4 arches are well developed by 4th week of
gestation
5th and 6th arches are still rudimentary
Development takes place over weeks 4 to 7
Contribute mostly to neck development but the
first arch contributes to facial development
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9. SPMMC
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10. PHARYNGEAL
APPARATUS
 It consists of:
A. Pharyngeal arches
B. Pharyngeal pouches
C. Pharyngeal clefts
D. Pharyngeal membranes
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12. PHARYNGEAL ARCHES
Are most distinctive feature in development of
the head and neck
These arches appear in the fourth and fifth
weeks of development and contribute to the
characteristic external appearance of the
embryo
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13. PHARYNGEAL ARCHES
Consists of a core of mesenchymal tissue
covered on the outside by surface ectoderm and
on the inside by epithelium of endodermal origin
Separated from each other by grooves known as;
 Pharyngeal Cleft: which are external (ectodermal
grooves), 1st-4th(from above downwards)
 Pharyngeal pouches: which are internal (endodermal
grooves) 1st-4th.
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14. PHARYNGEAL ARCHES
 1st pharyngeal arch (Mandibular arch)
 2nd Ph. Arch (hyoid Arch)
 Succeeding arch are called 3rd,4th,5th and 6th
according to their no.
 5th arch is rudimentary and disappears early on
each side, due to degeneration of its blood
supply.
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15. PHARYNGEAL ARCHES
Each arch contains:
A cartilaginous component
A muscular component
An aortic arch (artery)
A nerve
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17. PHARYNGEAL ARCH
Clinical Comment
From the initial development, each pharyngeal
arch has a specific cranial nerve associated with it.
The nerves and the musculature of each arch
emerge together and follow defined pathways to
their functional positions.
These events are closely regulated genetically
during development, and few errors occur.
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18. 1ST PHARYNGEALARCH
Divides early into 2 portions
 Maxillary process dorsally
 Mandibular process ventrally
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19. PHARYNGEAL ARCH
Mesenchyme of the maxillary process gives rise
to the premaxilla, maxilla, zygomatic bone, and
part of the temporal bone through membranous
ossification
Mandibular process contains Meckel’s cartilage
The mandible is also formed by membranous
ossification of mesenchymal tissue surrounding
Meckel’s cartilage.
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20. 1ST PHARYNGEAL ARCH
 Cartilage (Meckel’s Cartilage)
• Dorsal end becomes the malleus and incus
• Intermediate portion regresses, but the
perichondrium forms:
oAnterior ligament of the malleus
oSphenomandibular ligament
• Ventral portion forms the mandible
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21. 1st PHARYNGEAL ARCH
Secondary cartilages
Three secondary (growth) cartilages govern the
further growth of mandible until birth
1. Condylar cartilage(most important)
2. Coronoid cartilage
3. Symphysial cartilage
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22. 1ST PHARYNGEAL ARCH
 Muscular component
 Muscles of mastication (temporalis, masseter,
medial & lateral pterygoids )
Accessory muscles of mastication (mylohyoid,
ant belly of digastric)
Tensor tympani
Tensor veli palatini
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23. 1ST PHARYNGEAL ARCH
 Aortic arch
Maxillary artery
 Nerve
 Trigeminal nerve (CN V)
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24. FIRST ARCH SYNDROME (TREACHER
COLLINS)
Genetic disorder;
Neural crest cells do
not migrate into Arch
1:
Mandibular
hypoplasia
Conductive hearing
loss
Facial malformation
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25. 2ND PHARYNGEAL ARCH
 Cartilage (Reichert’s Cartilage)
Dorsal end becomes stapes (except footplate) and
styloid process
Intermediate portion regresses and perichondrium
forms the stylohyoid ligament
Ventral end forms the lesser cornu of the hyoid
and the upper half of the hyoid bone
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26. 2ND PHARYNGEAL ARCH
 Muscular Component
Migrates over superficial face to form the muscles of
facial expression
Stapedius muscle
Stylohyoid muscle
Posterior belly of digastric
 Aortic Arch
Hyoid artery
Stapedial artery
 Nerve
Facial Nerve (CN VII)
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27. 3RD PHARYNGEAL ARCH
 Cartilage
• Located ventrally and forms the lower half of the body of the
hyoid and the greater cornu
 Muscular Component
• Only one muscle: stylopharyngeus
 Aortic Arch
• Common carotid, external carotid, proximal internal carotid
 Nerve
• Glossopharyngeal (CN IX)
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28. 4TH PHARYNGEAL ARCHE
 Cartilage
• Thyroid cartilage
 Muscular Component
• The 3 pharyngeal constrictors
• Cricothyroid muscle
 Aortic Arch
• Left: Aortic arch
• Right: Right subclavian
 Nerve
• Superior laryngeal branch of vagus (CN X)
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29. 6TH PHARYNGEAL ARCHE
 Cartilage
• Cricoid cartilage, arytenoid, corniculate and
cuneiform
 Muscular Component
• Intrinsic muscles of larynx
 Aortic Arch
• Left: pulmonary artery, ductus arteriosus
• Right: pulmonary artery
 Nerve
• Recurrent laryngeal nerve of vagus (CN X)
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30. Pharyngeal clefts
( grooves)
 4 ectodermal clefts
 The 2nd to 4th clefts become buried by the
overgrowth of the 2nd arch to form the cervical
sinus
 Cervical sinus has disappeared by week 7
 The first cleft persists and invades the
mesenchyme opposite the first pouch
 This becomes the EAC and ectoderm of the TM
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31. SPMMC
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32. Pharyngeal pouches
The human embryo has four pairs of pharyngeal
pouches; the fifth is rudimentary
The epithelial endodermal lining of the pouches
gives rise to a number of important organs
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40. Development of the Face
The dev’t occur b/n the 24th to 38 days of
gestation
On 24th day ,the 1st arch divides into maxillary &
mandibular arches.
Five facial primordia contribute to development
of the face:
The frontonasal prominence
Paired Maxillary prominences
Paired Mandibular prominences
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41. Development of the Face
 4th week: thickening of ectoderm in the
ventrolateral parts of the FNP: Nasal Placodes
 Mesenchyme on the edges of the placodes
proliferates to form: medial and lateral nasal
prominences
As a result the nasal placodes now lie in a
depression called nasal pits which enlarge dorsally to
form the nasal cavities.
These nasal cavities are separated from the oral
cavity by the oronasal membranes
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42. Development of the Face
 Growth of maxillary prominences pushes
medial nasal prominences medially
These fuse to form the nasal bulb, the philtrum,
the premaxillary segment of the maxilla and the
primitive palate
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43. Development of the Face
The lateral nasal prominences, which become
the ala are separated from the maxillary
prominences by the nasolacrimal grooves which
become the nasolacrimal ducts
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44. Intermaxillary segment
Medial growth of the maxillary prominences, the two
medial nasal prominences
Merge not only at the surface but also at a deeper
level.
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45. Intermaxillary segment has 3 parts
1. Labial component: which forms the philtrum of
the upper lip
2. upper jaw component: carries the four incisor
teeth
3. palatal component: which forms the triangular
primary palate
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46. SPMMC
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47. Palate
From 7th to 9th week
Primary and Secondary Palate
Primary Palate
Develops from the fusion of the medial nasal
prominences between the maxillary
prominences
Forms the adult portion of the palate which is
anterior to the incisive foramen
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48. Palate
Secondary Palate
Origin of the hard and soft palate
Develops from internal projections of the maxillary
prominences called the lateral palatine processes
Sixth week two shelflike outgrowths from;the
maxillary prominences of the palatine shelves grow
obliquely downward on each side of the tongue.
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49. Palate
Secondary Palate
As mandible develops, the tongue drops and the
palatine processes grow medially and fuse in the
midline.
They also fuse with the nasal septum and the
primary palate.
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50. SPMMC
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51. Palate
 Seventh week; the palatine shelves ascend to
attain a horizontal position above the tongue and
fuse, forming the secondary palate
Anteriorly, the shelves fuse with the triangular
primary palate
The incisive foramen is the midline landmark
between the 10 and 20 palates.
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52. Nasal cavities
 6th weeks, deepening of the pits due to growth
nasal prominences & partly due to penetration of
the pits into the underlying mesenchyme
And the nasal has a newly formed pit called
primitive choane;
due to the development of secondary palate it is
put at the junction of the nasal cavity and
pharynx to give the definitive choane
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53. Paranasal sinuses
Develop as a diverticula’s of the lateral nasal
cavity into the maxilla, ethmoid, frontal and
sphenoid bones
Start to appear after birth and reaches maximum
size at puberty
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54. Defects of the face and oral region
CLINICAL COMMENT
The face develops during the short span from
the fourth to seventh prenatal weeks.
Environmental factors can cause a facial or
pharyngeal arch defect, which would probably
affect these tissues before the fourth week.
This is the time to be especially careful of
irradiation and chemical, hormonal, dietary, or
stress-related factors.
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55. Defects of the face and oral region
Many facial defects result from a lack of
transformation of the pharyngeal arches to their
adult derivatives.
Pharyngeal cysts and fistulas may appear along the
sides of the neck because the epithelial-lined
pockets remain as a result of the overgrowth of the
arches.
These defects may also open in the pharynx. Cysts
and fistulas may result in swelling or draining of
mucus from an opening on the side of the neck
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57. Development Of Tongue
 4th week: elevation on floor of pharynx, just
rostral to foramen cecum:
 Median Tongue Bud (Tuberculum impar)
 Distal Tongue Bud develop just lateral to median
tongue bud
Distal tongue buds overgrow the median tongue
bud and merge with each other
These form the ant 2/3 of the tongue
Median tongue bud forms no adult structure
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58. Development Of Tongue
 At same time 2 elevations develop caudal to foramen
cecum:
1. Copula: from 2nd arch
2. Hypobranchial emminence: from 3rd & 4th arches
 The hypobranchial emminence overgrows the copula
which disappears
 The post 1/3 of the tongue is formed by the rostral
part of the hypobranchial emminence (Arch 3)
Caudal part of hypobranchial emminence(Arch 4)
forms the epiglottis
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59. SPMMC
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60. Development Of Tongue
Is divided by a V-shaped groove (sulcus
Terminale) into;
Anterior 2/3rd
Posterior 1/3rd
These two parts have different origins and
nerve supply
Special sensory innervation(Taste)
Ant 2/3: chorda tympani branch of facial
nerve
Post 1/3: glossopharyngeal nerve
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61. Development Of Tongue
 Branchial mesenchyme forms the
soft tissue, vascular and lymphatics
of the tongue.
Tongue muscles originate from the
occipital somites which bring with
them innervation (CN XII)
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62. Development Of Tongue
 Most muscles are derived from myoblasts
originating in occipital somites.
 Nerve supply to muscle is CN XII except
platoglossus which is supplied by CN X
 Innervation of mucous membranous of Tongue
confirms its dev’t
 Ant 2/3 supplied by lingual br. of Mandibular
N.
 Post 1/3 supplied by glossopharyngeal N.
 Root & glottis: sup. Laryngeal N.
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63. Development Of Tongue
The lingual papillae appears by the end of 8th
week
Vallate and foliate papilae appear first ,fungi
form & filiform (10-11weeks) papilae appear
later.
Taste buds develop during the 11 to 13 weeks.
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64. Anomalies of Tongue
1. Aglossia: Complete absence of tongue.
2. Microglossia: Small sized tongue.
3. Macroglossia: Large sized tongue.
4. Bifid tongue: due to failure of fusion between
2 lingual swellings.
5. Tongue tie( Ankyloglossia) : due to short
frenulum.
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65. SPMMC
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66. DEVELOPMENT OF TEETH
From the interaction of the oral epithelial cells
and the underlying mesenchymal cells
The first sign of tooth formation is the
development of dental lamina rising from the
oral epithelium
The initiating dental lamina that forms both the
successional and general lamina begins to
function in the sixth prenatal week and
continues to function until the fifteenth year,
producing all 52 teeth
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67. STAGES OF TOOTH
DEVELOPMENT
By the sixth week of development, the basal
layer of the epithelial lining of the oral cavity
forms a C-shaped structure, the dental lamina,
along the length of the upper and lower jaws.
This lamina subsequently gives rise to a number
of dental buds 10 in each jaw, which form the
primordia of the ectodermal components of the
teeth
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68. STAGES OF TOOTH
DEVELOPMENT
 it is characterized by a series of easily
distinguishable stages known as ;
 The bud,
 Cap, and
 Bell stages
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69. Dental buds
This lamina subsequently gives rise to a number
of dental buds, 10 in each jaw, which form the
primordia of the ectodermal components of the
teeth.
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70. Cap stage of tooth development
deep surface of the buds invaginates, resulting
in the cap
cap consists of
 an outer layer, the outer dental epithelium,
 an inner layer, the inner dental epithelium,&
 a central core of loosely woven tissue, the
stellate reticulum
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71. SPMMC
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72. Bell stage
the dental cap grows
and the indentation
deepens, the tooth
takes on the
appearance of a bell
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73. DEVELOPMENT OF TEETH
Mesenchyme cells of the papilla adjacent to the
inner dental layer differentiate into
odontoblasts, which later produce dentin.
The odontoblast layer persists throughout the
life of the tooth and continuously provides
predentin.
The remaining cells of the dental papilla form
the pulp of the tooth .
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74. DEVELOPMENT OF TEETH
In the meantime, epithelial cells of the inner
dental epithelium differentiate into ameloblasts
(enamel formers)
Enamel is first laid down at the apex of the tooth
and from here spreads toward the neck
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75. DEVELOPMENT OF TEETH
Formation of the root of the tooth begins when
the dental epithelial layers penetrate into the
underlying mesenchyme and form the epithelial
root sheath
Cells of the dental papilla lay down a layer of
dentin continuous with that of the crown .
As more and more dentin is deposited, the pulp
chamber narrows and finally forms a canal
containing blood vessels and nerves of the tooth.
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76. DEVELOPMENT OF TEETH
Mesenchymal cells on the outside of the tooth
and in contact with dentin of the root
differentiate into cementoblasts
Outside of the cement layer,mesenchyme gives
rise to the periodontal ligament
With further lengthening of the root, the crown
is gradually pushed through the overlying tissue
layers into the oral cavity
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77. DEVELOPMENT OF TEETH
Buds for the permanent teeth, which lie on the
lingual aspect of the milk teeth, are formed
during the third month of development.
These buds remain dormant until approximately
the sixth year of postnatal life
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78. SPMMC
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79. DEVELOPMENTALDISTURBANCESINVOLVINGTHE
TOOTH
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80. The Embryology of the Salivary
Glands
 is the result of a highly orchestrated complex
interaction between 2 distinct tissues, the oral
epithelium and the underlying mesenchyme.
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81. The Embryologyof the Salivary
Glands
The secretory units (acini) and the ductal system
system of each gland will eventually arise from
these epithelial outgrowths, which are of
ectodermal origin for the parotid glands,
submandibular glands, and sublingual
glands,and are of mixed ectodermal and
endodermal origin for the minor salivary glands
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82. The Embryology of the Salivary
Glands
The mesenchymal cells contain the information
for the branching pattern that eventually will be
the morphologic signature of these glands,
whereas the epithelial cells carry the information
for the type of salivary secretions that will be
produced by each future gland
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83. The Embryology of the Salivary
Glands
The stroma, which comprises the capsule of
each gland as well as the septae that divide the
gland into lobes and lobules will develop from
cranial neural crest cells,which are cells that
originate from the dorsal part of the neural tube
epithelium
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84. Serialdrawingsshowtheprogressivegrowthofadeveloping
salivaryglandthroughitsvariousstages
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85. Serialdrawingsshowtheprogressivegrowthofa
developingsalivaryglandthroughitsvariousstages
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86. Coronaldrawingillustratesthelocationsofthemajorsalivaryglandanlagen
withinthedevelopingoralcavity.
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87. Drawingshowstheparotidsalivaryanlage(green)extendingintotheregionof
thealreadypresentfacialnerve(yellow).Thisresultsinthefacial
nerverunningthroughthesubstanceoftheadultparotidgland.
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88. Period of fetus
B/n 8th-12th week of IUL;
• Fetus triple in length (20 to 60mm)
By 3rd month ; face assume more human
appearances
Eye direct forward
Head erect & bridge of the nose prominent
Ears migrate from lower corners of face to
horizontal plane at level of eye
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89. Period of fetus
Maxillomandibular r/n approaches that of new
born infants
Cranium to face ratio during;
• Embryonic period = 40:1
• 4th month of IUL =5:1
• @ birth = 8:1
• Adulthood =2:1
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90. SPMMC
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91. SPMMC
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92. REFERENCES
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93. THANK YOU
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