Prenatal growth /certified fixed orthodontic courses by Indian dental academy

PRENATAL
FACIAL GROWTH
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

INTRODUCTION
Orthodontists are heavily involved in the
development of not just dentition but the entire
dentofacial complex.
.
The terms growth and development though
closely related are not synonymous. Growth is
largely an anatomic phenomenon, whereas
development is physiologic and behavioral

Development = Growth + Differentiation +
Translocation

THEORIES OF GROWTH
The Genetic theory
Brodie noting the persistent pattern of
facial configuration assumed it was under
tight genetic control.
The assumption was made that the
cartilages, facial sutures were under
genetic control and that the brain
determined the vault dimensions.
Wendell Wylie termed this thinking
“Orthodontic Calvinism”

Scott’s hypothesis
Scott noting the prenatal importance of
cartilaginous portions of the head, nasal
capsule, mandible and cranial base and
feeling that this development was under
intrinsic genetic control, held that they
continued to dominate facial growth postnatally.

Sicher’s hypothesis
Sicher deduced from the many studies
using vital dyes that the sutures were
causing most of the growth. Infact he said
“The primary event in sutural growth is the
proliferation of connective tissue between
the two bones”.


Moss’ hypothesis ( Functional matrix)
Moss felt that bone and cartilage lack growth
determination and grow in response to intrinsic
growth of associated tissues.
Moss divides the skull into a series of discrete
functional components each comprised of a
functional matrix and an associated skeletal unit.
Moss identifies two large, enveloping capsular
matrices the cerebral and the facial,” The effect
is a passive translation of skeletal components in
space.

PRENATAL CRANIO-FACIAL
GROWTH
 Events leading to organization of face in its
normal form are critical and starts during first 4
weeks in utero.
 Till 4th prenatal weeks, the embryo is
isolated from external environment, utilizing its
yolk sac for nourishment and growth.
 The increase in cellular proliferation
enhances the potential for teratogenic
(adverse environmental)
factors to alter development.

PRE NATAL PERIOD
The prenatal life period is divided into
Three periods for the purpose of
understanding :

Period of ovum ( 0- 14 days )
Embryo period ( 15- 56 days )
Fetal period
( 16 – till birth )

Preorganogenesis.
Anomalies produced by teratogens acting during this
period usually result in death of the embryo.
The time table of the events described above is as
follows:
2 days after fertilization embryo is at 2 cell stage.
3 days after fertilization embryo has become a
morula.
On 4th day, the blastocyst has formed.
By 8th day, bilaminar disc has been established.
A round the 14th day, procordal plate and
primitive streak are seen

PERIOD OF OVUM
Fertilization of sperm and ovum results
in formation of zygote (1 cell ) .
 Zygote undergoes a series of
subdivisions called cleavage to form 2
cell stage then 4 cell stage so on till 16
cell stage
.This 16 cell mass is called morula .It has
inner cell mass and outer cell mass .
 It thus forms a cyst called blastocyst.

GASTRULATION
Formation of three layered disc is termed
gastrulation .

First germ layer is endoderm.
Second germ layer is ectoderm .

Third germ layer is mesoderm .
Neural crest cells are termed fourth germ
layer.


EMBRYONIC
PERIOD


TIME TABLE OF THE EVENTS
on the 15th day , the primitive streak
appears & definitive yolk sac is formed
on 16th day embryonic disc is three
layered due to formation of intra
embryonic mesoderm .
on 17th day notochordal process and
heart tube can be seen.
On the 21st day neural groove is seen
and head fold begins to form .

On the 23rd day closure of the neural
tube is seen.
On around 22nd day first branchial arch
appears .
On 24th day bucco-pharyngeal
membrane ruptures & foregut
communicates with stomatodaeum

By 29th day four arches can be seen.

FORMATION OF NEURAL TUBE
 The ectoderm overlying the notochord
undergoes changes that result in formation
of neural tube.
 The neural tube gives rise to the brain and
spinal chord.
 The neural tube is formed from ectoderm
overlying notochord and therefore extends
from prochordal plate to primitive knot.
 In early embryo, the developing brain forms
a large conspicuous mass on the dorsal
aspect.

INTRA EMBRYONIC MESODERM
The intraembryonic mesoderm becomes
subdivided into 3 parts:
The mesoderm on either side of the
notochord , becomes thick and is called
the paraxial mesoderm.
More laterally, the mesoderm forms a
thinner layer called lateral plate mesoderm
Between these 2, there is a longitudinal
strip of mesoderm called the intermediate
mesoderm.

PARAXIAL MESODERM
The paraxial mesoderm now becomes
segmented into cubical masses, called
somatomeres, which give rise to somites.

The first somites are seen on the either
side of midline, a little behind prochordal
plate. More somites are formed caudally
on either side of the developing neural
tube.

The lateral plate mesoderm splits
into:
Somatopleuric or parietal
mesoderm, which is in contact with
ectoderm. It gives rise to peritoneal,
pleural, pericardial cavities.
Splanchnopleuric or visceral
mesoderm in contact with
endoderm. The heart is formed in
the floor of coelom called
cardiogenic area.

FOLDING OF THE EMBRYO
Progressive increase in the size of
embryonic disc.
Head and tail ends are still close together
the increase in length causes it to bulge
upward

With further enlargement, embryonic disc
becomes folded on itself
Parts of the yolk sac become enclosed
within embryo .
In this way a tube lined by endoderm is
formed called primitive gut .

EFFECT OF FOLDING ON OTHER

STRUCTURES
After the folding following changes are seen
Developing pericardial cavity comes to lie
on ventral side of embryo , ventral to the
foregut ..
Septum transversum now lies caudal to the
heart.
The bucco-pharyngeal membrane closes
the foregut cranially
Enlarged cranial part of the neural tube
later forms the brain.

BRANCHIAL ARCHES:Six arches are formed bounded by clefts
and grooves.
The mid and lower facial regions develop
from first two arches named mandibular &
hyoid arch. The third arch also contributes
to base of tongue.
Each branchial arch has skeletal ,
muscular, vascular, epithelial, neural
element that develop in to systems
supplying face & neck.

ARCH

NERVE

MUSCLUAR ELEMENTS

First

Mandibular Nerve

Second

Facial Nerve

Tensor tymani, tensor
palati,
medial
and
lateral
pterygoid,
masseter,
temporalis,
mylohyoid.
Ant.Diagstric stapedius,
stylohyoid,
post.
digastric facial muscles,
occipito-frontalis.

Third

Glossopharyngeal

Stylo pharyngeus

Fourth

Superior laryngeal

Muscles of pharynx

Sixth

Recurrent
Soft palate and larynx
laryngeal

ARCH

First

Derivatives

Cartilage
MECKELS

. Malleus, incus, ant.

Ligament of malleus,
sphenomandibular
ligament

Second

REICHERTS

. Stapes, styloid process,
stylohyoid,
ligament,
superior part of body of
hyoid,smaller corner of
hyoid

Third

Greater corner of
hyoid, lower part of
body of hyoid.

Fourth

Cartilages of larynx

Sixth

Cartilages of larynx


ARTERIAL ARCH:
: A series of arches connecting
dorsal aorta and ventral aorta.
One such arterial arch lies in each
pharyngeal arch.


FETAL PERIOD


DEVELOPMENT
OF CRANIUM
AND CRANIAL
BASE

FETAL SKULL AT 2ND MONTH
CONSISTS OF THREE PARTS :
CHONDROCRANIUM : which is
cartilaginous & made up of base of skull
with otic & nasal capsules.
DESMOCRANIUM :which is membranous ,
forms lateral walls & roof of braincase
APPENDICULAR (visceral part) : which is
cartilaginous , consists of skeletal rods of
branchial arches .

DEVELOPMENT OF
CHONDROCRANIUM
The brain is given support by cartilage
forming along its base, the chondrocranial
elements
The chondrocranium also is important to
the growing face and supports both areas
through the developments of a bar of
cartilage extending uninterrupted along the
midline from the anterior nasal region to
the foramen magnum.

The cartilaginous septum functions in
anterior facial growth as well as in
support

According to Scott, it doubles its
length from 10-14th week, trebles by
17th weeks, and is six times as large
by 36weeks.
Anteriorly, this cartilage forms a
capsule related to olfactory nerve
endings – Nasal capsule.

Posteriorly, the cartilage supports the
pituitary-Hypophyseal capsule.
Laterally otic capsules develop
around the middle and internal ear
structures.
Most posteriorly, it forms the occipital
cartilages around foramen magnum–
parachordal cartilage
The cartilages establish cranial base
by 8th week and are transformed into
bones

Future ethmoid arises from nasal
capsule.
Mastoid and petrous part of temporal
bone from otic capsule.
Parachordal cartilage forms part of
sphenoid, temporal and occipital
bone.
As each of these bones
develops, cartilaginous centers
remain between them, forming the
cranial base synchondroses.

Nasal capsule is large and
important cartilage to developing
face and consists of medial
septum components the
mesethmoid and two lateral
cartilaginous wings


BRAIN ENLARGEMENT,
BASICRANIAL FLEXURE
At 5 weeks the face appears crowded
between the rapidly growing forebrain and
heart,
Even at this stage growth pattern of face is
downward and forward as it grows out from
between these two organs.
Flexures that occur during 4th week in
region of future neck result in brain flexed
ventrally, then dorsally and as a result
head becomes erect (Cranial flexure).

The human cerebrum similarly
expands around a much smaller
enlarging midventral segment
(medulla, pons, hypothalamus). This
causes a bending of whole under side
of brain. The flexure of cranial base
appears.


The expansion of frontal lobes
displaces the frontal bone upward and
outward. This results in bulbous,
upright “forehead” of human face,
although it is really part of
neurocranium and not the face
proper.


The frontal lobes also relate to a rotation of
the human orbits into new position. As
forehead is rotated into a vertical plane by
the brain behind it, superior orbital rim is
carried with it. The eye now point at a right
angle to the spinal cord. The spine is
vertical and orbit is horizontal. Vision is
directed toward forward body movement
Expansion of frontal and particularly, the
temporal lobes of the cerebrum relates to a
rotation of orbits towards midline. The eyes
come closer together.

ENDOCHONDRAL OSSIFICATION
ETHMOID

INFERIOR NASAL CONCHAE


INTRAMEMBRANOUS
OSSIFICATION
FRONTAL
ZYGOMATIC
PARIETAL
VOMER
NASAL
LACRIMAL
MAXILLA
PALATAL

BONES INVOLVING BOTH
PROCESSES :
MANDIBLE
SPHENOID

OCCIPITAL
TEMPORAL

Mandible:
Condyle ossifies by endochondral
ossificaiton
Body and ramus by intramembranous
ossification
Small part of symphysial cartilage
may form mental tubercles by
endochondral ossification


Sphenoid:
Endochondral ossification forms:Body, lesser wings, basal parts of
greater wings lateral plate of pterygoid
process.
Intramembranous ossification
forms:Parts of greater wings, medial plate of
pterygoid process

Temporal
Endochondral ossification:- petrous
part of bone
Intramembraneous ossifications:
Squamous and tympanic parts of
temporal.


Occipital
Endochondral ossification: lower
part of squamous portion .

Intramembranous ossification:
Upper part of squamous portion.

MAXILLARY COMPLEX
Until bone formation occurs , the
nasal capsule is the only skeletal
support of upper face
The nasal ,premaxillary,maxillary,
lacrimal, zygomatic , palatine,&
temporal ossification centers appear
as bones seperated by sutures only.

MAXILLA
ARISES BY INTRAMEMBRANOUS
OSSIFICATION .
FIRST CENTER APPEARS AT AROUND
7-8TH WEEK
SEPARATE CENTER FOR ANTERIOR
PALATE GIVING RISE TO PREMAXILLA
& PALATINE PROCESS OF MAXILLA
BY 14TH WEEK BONY PALATE IS
ESTABLISHED .

MAXILLARY SINUS
IT IS THE FIRST PARANASAL
SINUS TO DEVELOP.
AT AROUND 3RD MONTH OF INTRA
UTERINE LIFE.


PALATAL SHELVES
Two palatal processes .
The primitive palate formed from
frontonasal process.
The definitive palate forms from
fusion of these three processes
During 9-10th week palatine shelves
come in contact & fusion begins .
Initial contact occurs just post. to
primary palatine process & closure
continues both anteriorly and
posteriorly .

MANDIBLE
Rod shaped cartilage known as Meckels
cartilage supports lower face

It extends from midline to otic capsule
where it forms malleus & incus.
Center of ossification appears at around 6th
week
Carrot shaped cartilage appears at 10th
week at site of future condyle

Coronoid process starts ossifying at
around 14th week
Coronoid process develops from
accesory cartilage appearing at
around 10-14th week

It grows as a response to developing
temporalis
Alveolar bone starts developing as a
response to developing tooth buds.

TEMPOROMANDIBULAR JOINT
Malleus & incus function to provide a
movable joint untill temporomandiblar
joint articulation occurs.
From 8-18th this joint is functional .
TMJ develops at around 10th week
and takes over by 19th week

GROWTH OF SOFT TISSUES OF
FACE
FACE , NOSE , LIPS

TONGUE
SALIVARY GLANDS
FACIAL MUSCLES
MUSCLES OF MASTICATION

FACE, NOSE ,LIPS
Face at 5th week is only about one & half
mm wide.
Two small , ovoid raised areas appear just
above the lateral aspects of future nostrils .

These represent future nostrils .
The tissue b/w nasal pits is medial nasal
process & lateral to pits are called lateral
nasal processes

The raised anterior edges of these pits
form the shape of minute horseshoes with
open sides below.
Contact b/w medial border of maxillary
process & lateral border of medial nasal
process forms a lamina nasal fin.
„NF‟ represent a potential site for formation
of cleft lip.
Upper lip is formed by fusion of these
processes
Lower lip is formed by mandibular
processes fusion

In 6th weeks ,upper face appears flat
& broad with nasal pits representing
90% of width of face.

Auricle of ear arises from hillocks of
tissues that cirumscribe the branchial
cleft.
At 6 ½ week the facial proportions
change , due to increase in
dimensions laterally to nasal pits.
Eyes are now rotated to 90 degree
from side to front of face.

In early 7th week face appears
recognizably human as a result of
frontal location of eyes, differentiation
of nose and enlargement of mandible.
At 7th week, furrows separating the
mandibular, maxillary and nasal areas
are les marked.
External ears are also visible at this
stage. Ears are well differentiated by
16th week.

TONGUE
The tongue musculature originates
from the occipital myotomes at
beginning of 4th week.
Develops into oral part (body) and
pharyngeal part (base).
The body arises in part, from
contributions of first arch and base
arises from 2nd, 3rd, 4th arches.

Body of tongue is indicated by paired
lateral lingual swellings and a
centrally located tuberculum impar.
At 5th week base of tongue is
indicated by a median elevation,
copula.
During 6th and 7th week lateral
lingual swellings enlarge and size of
tuberculum impar‟s size reduces.

SALIVARY GLAND
The Parotid and submandibular
salivary glands appear in the
connective tissues of developing
cheek in 6th week.
Sublingual glands develops at
around 8th week


FACIAL MUSCLES
The facial muscles mass, termed
subcutaneous colli, appears in the 4th
week in the ventral lateral position of the
hyoid arch just beneath the surface of
the skin.
In the 5th week, it spreads out,muscle
mass fans out and stylohyoid, diagastric
and stapedial muscle masses appear.

Advancing sheet then separates into
superficial and a deep layer in 7th
week
The superficial form the spread of
platysma muscle over the mandible to
cheek, forehead, , temporal region.
During 7-9th Sphincter colli further
forms orbicularis, caninus and
incisivuslabii.
The quadratus labii inferiors and
mentalis muscles of lower face
appear in 8-9th week

The orbicularis oculi and buccinator
muscles appear from deep fibers of
sphincter colli
whereas triangularis and platysma
from superficial faci
Overlying it buccinator & buccal pad
of fat develop .
By 14th week all facial muscles are in
their definitive position

MUSCLES OF MASTICATION
The muscles of mastication are developing
in the mesenchyme of mandibular arch in
seventh week and nerve fibers are
apparent by 8th week.
these muscle develop in close relation to
Meckel‟s cartilage and cranial base
cartilages
Temporalis muscle begins lateral
development in 8th week, occupying the
space anterior to otic capsule.

Masseter muscle attaches along the
zygomatic arch as it undergoes lateral
growth, providing space for muscle
development.
The pterygoid muscles differentiate in
7th week
Typically the fetal histologic
structure of muscles of mastication
appears by 22nd week.


Respiratory reflexes, jaw closure reflexes,
suckling and infantile swallow are all
developed in a patterned way between
14th –32nd week of intrauterine life.

In human fetus by 8th week, generalized
uniform reflex movement of entire body can
be elicited by tactile stimulation.
14th week movements become much more
individualized
Gag reflex has been demonstrated in
human fetus at about 18½ week

By 25 weeks, respiration is shallow
but may support life for a few hours if
established.
By 29 weeks stimulation of mouth
elicited suckling although complete
suckling and swallowing are
developed at around 32 week.

ORIGIN OF FACIAL
MALFORMATIONS
Malformation: morphologic defect
of an organ or a larger area of body,
resulting from intrinsically abnormal
development e.g. clefts of lip or
palate alone or as a part of
syndrome.


Deformation: abnormal form or
position of a part of body caused by
non-disruptive mechanical forces
e.g. club foot, congenital hip
dislocation, congenital postural
scoliosis.


Disruptions: morphologic defects of
an organ or a larger region of body ,
resulting from a break down of ,or
interferences with originally normal
development . e.g. an amputation of
a digit in utero because of amniotic
band .


The importance of drug induced
impairment in neural crest migration
has been implicated in thalidomide
induced congenital defects and antiacne drug isotretinoin induced
defects.


Fetal alcohol syndrome (FAS):

characteristics facies is due to
deficiency of midline tissues of the
neural plate very early in embryonic
development caused by very high
chronic intoxication in alcoholic
mothers, maxillary and midface
deficiency is seen.

Mandibulofacial dysostosis
(Treacher Collins), Pierre Robbin
syndromes are defects of
branchial arches. Altered neural
crest development has been
implicated.
In treacher Collins syndrome –
lack of development of malar
bones, short curved mandible,
lack of middle ear development
which results in loss of hearing.
.

Hemifacialmicrosomia is primarily
unilateral and characterized by a lack
of tissues on affected side. Typically
external ear is deformed and both the
ramus of mandible and associated
soft tissues are deficient or missing..


Phenytoin when used during
pregnancy also gives rise to
characteristic defects called as
fetalhydantoin syndrome
characterized by hypo plastic
phalanges, cleft palate, hare
lip, microcephaly.


Clefting of lip occurs because of
failure of fusion between median and
lateral nasal processes and the
maxillary prominence which is seen
during 6th week of development in
humans.
Isolated clefts of palate occur when lip
closure is complete and problem
arises after that.

Synostosis syndromes occurs
because of early closure of sutures
between cranial and facial bones.
From early in fetal life, normal cranial
and facial development is dependent
on growth adjustments at the sutures
in response to growth of brain and
soft tissues. Early closure of sutures
leads to distortions depending on
location of early fusion.

Crouzon‟s syndrome is the most
frequently occurring member of this
group. Characterized by
underdevelopment of midface and
eyes that seem to bulge from sockets.
Their is prenatal fusion of superior
and posterior sutures of maxilla, along
the wall of orbit. The early fusion
prevents downward and forward
translation of maxilla as a result of
under development of middle third of
face.

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