Growth and development of jaws

GROWTH AND
DEVELOPMENT OF JAWS:
CAUSE AND EFFECT
www.indiandentalacademy.com

Contents
 Introduction
 Pre natal development
 Post natal development
maxilla
palate
mandible
 Malformation
 Conclusion

The development of the human embryo occurs in
three stages they are:-
Pre-implantation period (1st 7 weeks)
Embryonic period (next 7 weeks)
The fetal period (next 7 calendar months)
During the embryonic period that is from the first
of 8th week,
the first signs of the development of jaw bones occur
1. Pre-somite (8-21 days post
conception)
2. Somite (21-31 days) and
3. Post somite (35-36 days post
conception)
Embryonic period is further divided
into 3 stages:-

During the pre somite period primary germ
layer of the embryo and the fetal
membranes are formed. Somite period is
characterized by the appearance of
prominent dorsal metameric segments and
organs. During the post somite period the
formation of the body’s external features
occurs.
During the late somite period the mesoderm
lateral plate of the ventral foregut region
becomes segmented to form 5 distinct
bilateral mesenchymal swelling called the
branchial arches

The branchial arches are divided by
branchial groove which corresponds to the 5
pharyngeal pouches internally. The first
branchial arch which is other wise called as
the mandibular arch is the precursors of the
jaws, both maxillary and mandibular
The cartilage of the first arch is called as
the meckels cartilage. Meckels cartilage arises
at 41st to 45th day of intra uterine life. Most
of the cartilage disappears in the mandible
development. The mental ossicle is the only
portion of the mandible derived from meckels
cartilage by endochondral ossification

MAXILLA
The maxilla develops from a centre of
ossification in the mesenchyme of the
maxillary process of the first arch which
begins at the 4th week of intra uterine life.
The centre of ossification appears in the
angle between the division of a nerve i.e.
where the anterosuperior dental nerve is
giving off from the inferior branch of infra
orbital nerve. From this centre, the bone
spreads to:-
Posteriorly: - Below the orbit toward the
developing zygoma
Anteriorly: - Towards the future incisor region
Superiorly: - To form the frontal processwww.indiandentalacademy.com

As a result of this pattern a bony trough is
formed for the infra orbital nerve. From this
trough a downward extension of bones forms
the lateral alveolar plate for the maxillary
tooth germs. The medial alveolar plate
develops from the junction of palatal process
and the main body of developing maxilla
which form a trough of bone around the
maxillary tooth germs with its counterpart and
later become enclosed in bony crypts. A
secondary cartilage and zygomatic or malar
cartilage also contributes to the development
of maxilla.

PALATE
Initially there is a common oronasal cavity
bounded anteriorly by the primary palate
and occupied mainly by the developing
tongue. Primary palate develops from the
frontonasal processes. The medial growth
of maxillary process pushes the medial
nasal processes toward the midline where
it fuses with its anatomical counterpart.
The formation of the secondary palate
occurs between the 7th to 8th week of
development and results from the fusion
of shelves formed from each maxillary
processes.

The three elements that makes up secondary
palate are:-
1) Two lateral maxillary swelling
2) A primary palate of the frontonasal
processes.
As the enlarging tongue pushes dorsally into the
nasal cavity the palatal shelves develop in a
wedge shape and because of the presence of
the tongue, grow downward into the floor of
the mouth along either side of the tongue. By
8th week of development movement of the
palatal shelves changes from a vertical position
beside the tongue to a horizontal position
overlying the tongue. This growth will charge
the position of tongue and palatal shelves.

As the shelves roll over the tongue
posteroanteriorly, the tongue may glide
anteriorly to offer les resistance to the shelf
movement. Closure of the palatal shelves
separates the oral and nasal cavities. The
tongue may press upward against the palatal
shelves, helping to bring them in closer
approximation to facilitate their contact in the
mid line. The nerve supply of the tongue and
cheeks are sufficiently developed to provide
some neuromuscular guidance to the intricate
activity of palatal closure.
By 81/2 prenatal week the palatal shelves
appear above the tongue and in near contact
with each other. During 9th and 10th week they
come in contact and the fusion begins.

First the epithelial covering of the shelves join
to form a single layer of cells. Next
degeneration occurs as the connective tissue of
the shelves penetrates this midline epithelial
barrier and intermingles across the area.
In few cases the two shelves have reported
separate after initial fusion, with resulting
epithelially covered connective tissue bands
stretching across the palate between the
shelves.

As the bone form the palate the area along the
midline anteroposteriorly will become a suture.
The entire palate does not contact and fuse at
the same time, initial contact occurs in the
region of the secondary palate just posterior to
the anterior or primary palatine processes and
continues both anteriorly and posteriorly to this
point.
After the initial contact and fusion, further
closure occurs by a process of “merging” which
result in the medial space between the two
processes being eliminated. The anterior
palatal suture and the foramen remain in the
post natal period as an evidence of the early
existence of primary and secondary palate.

MANDIBLE
The cartilage of the first arch forms the jaw in
primitive vertebrates. In human it has a close
relationship to the developing mandible but not
makes much contribution to it. At 6 weeks of
development this cartilage extends a solid
hyaline cartilaginous rod, surrounded by a
fibrocellular capsule, from the developing ear
region (otic capsule) the midline of the fused
mandibular process. The two cartilage of each
side do not meet at the midline but are
separated by a thin rod of mesenchyme. On the
lateral aspect of meckels cartilage, during the
6th week of embryonic development, a
condensation of mesenchyme occurs in the
angle formed by the division of the inferior
alveolar and its incisor and mental branches.www.indiandentalacademy.com

At 7 weeks intramembraneous ossification begins
in this condensation, forming the 1st bone of
mandible. From this centre of ossification, bone
formation spreads rapidly anteriorly to the
midline and posteriorly towards the point where
the mandibular nerve divides into its lingual
and inferior alveolar branches. This spread of
bone formation occurs anteriorly along the
lateral aspect of meckels cartilage, forming a
trough that consists of lateral and medial plates
that unite beneath the incisor nerve. This
trough of bone extends to the midline, where it
comes into close approximation with a similar
trough formed in the adjoining mandibular
processes. The two separate centers of
ossification remain separated at the mandibular
symphysis until shortly after birth.

A backward extension of ossification along
the lateral aspect of meckels cartilage
forms a gutter, later converts into a canal
that contains inferior alveolar nerve this
extends till the division of mandibular nerv
that is the inferior alveolar and the lingual
nerve. From this bony canal, extending
from the division of the mandibular nerve
to the midline, medial and lateral alveolar
plates of bone develops in relation to the
forming tooth germs, so that the tooth
germs will occupy a secondary trough of
bone.

The ramus of the mandible develops by a rapid
spread of ossification posteriorly into the
mesenchyme of the first arch turning away
from meckels cartilage. This point of
divergence is marked by the lingual in adult
mandible. Thus by 10 weeks the rudimentary
mandible is formed almost entirely by
membranous ossification.
The further growth of mandible until birth is
influenced by the appearance of three secondary
cartilages and the development of muscular
attachment; in this the most important cartilage
is the condylar followed by coronoid and
syphyseal cartilages. The histological structure
between the primary meckels primary cartilage
and these secondary cartilages is different.

The condylar cartilage appears during the 12th
week of development and rapidly forms a cone
or carrot-shaped mass that occupies most of
the developing ramus. The mass of cartilage is
quickly converts to bone by endochondral
ossification, so that by 20 weeks only a thin
layer of cartilage remains in the condylar
heads.
The coronoid cartilage appears at about 4 months
of development, surrounding the anterior
border and the top of the coronoid process. The
symphyseal cartilage, two in number appear in
the connective tissue between the two ends of
meckels cartilage, but are entirely independent
of it. They are obliterated within the first year
of birth. The neural, alveolar and muscular
elements and growth is assisted by the
development of these secondary cartilages.www.indiandentalacademy.com

Post natal development of maxilla
A primary intramembraneous ossification centre
appears for each maxilla in the 7th week of I U
L. According to “mills” the maxilla is increased
in size by subperiosteal activity during post
natal growth. The entire nasomaxillary complex
is joined to the cranial vault and the cranial
base by the most complicated suture system of
all. An endochondral bone mechanism for the
long bone growth, as seen in cranium and
mandible is not seen in the mid face. The
growth of cartilaginous part of nasal septum
has been regarded as the source of the force
that displaces maxilla anteroinferiorly. This
theory does not hold well in its entirety at
present. Major part of the bone formation at
the mid face is by intra membranous process

The suture system is the most complicated
system in the body. The maxilla is connected to
the cranial base and the cranium by a number
of sutures. They includes:-
1) Fronto - nasal suture
2) Fronto – maxillary suture
3) Zygomatico – temporal suture
4) Zygomatico – maxillary suture
5) Pterygo – palatine suture
These sutures are all oblique
or parallel to each other. This allows a
downward and forward repositioning of the
maxilla as growth occurs at this sutures.

Surface growth remodeling is very active
providing much regional increase and
remodeling which accompany and adapt to the
additions taking place in sutures, synchndrosis,
condyles and so forth.
Maxilla is joined to the cranial base and the
position of the maxilla is dependent on the
growth at the sphenooccipital and spheno –
ethmodial synchndrosis.
Maxillary post natal growth occurs mainly by two
methods they are:-
Displacement – The shift in position of the
maxillary complex
Surface remodeling – The enlargement of the
complex itself.www.indiandentalacademy.com

Most of the bones in the cranial base are formed
by a cartilaginous process. Later the cartilage is
replaced by bone but certain cartilaginous
bands remain in the junction of various bones
these are called synchondrosis. The area
between the bones consists of growing
cartilage.
Due to the enlargement of bones in the middle
cranial fossa.The dimensions of the middle
cranialfossa increases by the spheno – occipital
synchondrosis providing endochondral bone
growth in the middle of cranial fossa floor by
resorption on the endocranial surfaces and the
deposition on ectocranial side. All cranial and
facial parts lying anterior to the middle cranial
fossa displaced in a forward direction.

This can be proved by the “counterpart
theory” put forward by Enlow.
The theory states: - “Growth of any facial or
cranial part relates specifically to other
structures and geometric part of the face
and the cranium”.
According to the “V” principle put forward by
Enlow and Bang “Growth is a complex
multidimensional and a dynamic process.
Apposition of bone on external surfaces of
maxilla with resorption on the inner aspect
causes an expansion of the maxilla in an
expanding V shape.

Primary displacement can be visualized using two
reference lines
Vertically – Posterior maxillary plane
Horizontally – Functional occlusal plane.
Bone gets deposited on the posterior, facing
cortical plate surface of the maxillary tuberosity.
The endosteal surface within the tuberosity is
having a resorptive field. The amount of anterior
maxillary shift is equal to the amount of bone
deposited on the posterior surface of the
tuberosity. The anterior part of maxilla the pre-
maxilla region is resorptive in nature. There is
an additive growth on the opposite surface of
the resorptive field.www.indiandentalacademy.com

The bone resorption on the nasal side of the palate and
the bone deposition on the inferior oral side produce
a downward growth of the whole palate. In maxilla
the palate grows downward by periosteal resorption
on the on the nasal side and periosteal deposition on
the oral side. This occurs along with the sutural
growth.
The classic implant studies of bjork and skieller
confirm that maxillary height increases because of
sutural growth towards the frontal and zygomatic
bones and positional growth in alveolar process.
Apposition also occurs on the floor of the orbit with
resorptive modeling of the lower surfaces. The nasal
floor is lowered by resorption while apposition occurs
on the hard palate. www.indiandentalacademy.com

Growth of the median suture produces more mm
of width increases the appositional remodeling,
but surface remodeling must everywhere
accompany sutural addition. Alveolar
remodeling contributes to a significant early
vertical growth is also important to attainment
of the width because of the divergence of the
alveolar process. As they grow vertically their
divergence increases the width. Up to the time
that the mandibular condyles have ceased their
most active growth, maxillary alveolar process
increase constitute nearly 40% of the total
maxillary height increases.

Growth in the median suture is more important
than apposition remodeling in the development
of maxilla. Growth increases at the median
suture mimic the general growth curve for body
height and maximum pubertal growth in the
median suture coincides with the time for
maximum growth in the facial sutures. There is
no correlation between growth in width of the
median suture and the sutural growth
contributing to the height of the maxilla. Mutual
transverse rotation of the two maxillae results
in separation of the halves more posteriorly
than anterior.

Different theories of growth have been put
forward to explain the growth of maxilla. There
is no universally accepted theory concerning
the mechanism of growth.
Genetic control theory: - genotype supplies all
information necessary for phenotype expression
Suture-dominance theory: - by siecher
supported by wiemann. This theory states that
sutural growth is the primary mechanism for
forward and downward growth of the maxilla.
Cartilage directed growth theory: - by scott.
It states that cartilage is the primary factor in
the growth of maxilla e.g.: synchondrosis, nasal
septum etc. www.indiandentalacademy.com

Functional matrix theory: - by moss. It
states that the growth of bone is in response to
the functional relationship established by the
sum of all soft tissues operating in association
with that bone.
Servo- system theory: - by stuzmann and
perrovic. It states that the growth occur due
to the influence of somatotropic hormone (S T
H), sex hormone, thyroxine etc.
Increase alveolar processes are closely
correlated with the eruption of teeth. The
increase in overall maxillary height coincides
with the vertical growth in the mandible. There
is general pacing of the growth of maxilla and
mandible and they both are roughly coincident
with the general growth of the body.

The sutural system adapts to posterior
forces (extra oral, cranial and cervical),
anterior forces and transverse process.
Variation in the
maxillary growth and morphology play an
important role in skeletal malocclusion
class ii (extensive mid face growth) and
class iii (decreased mid face growth)

Post natal growth of mandible
The modes, mechanism and sites of mandibular
growth are complicated. Mandible is basically a
slender “U” shaped bone with an endochondral
bone mechanism at each end and
intramembraneous growth between just as in
long bones. Both prenatally and postnatally
very small percentage of the mandible is
endochondrally formed and the majority is
intramembrously developed. Growth and shape
changes of the areas of muscle attachment and
tooth insertion are more controlled by muscle
function and eruption of teeth than by intrinsic
cartilaginous or osteogenic factors.www.indiandentalacademy.com

Condylar cartilage
The condyle is of special interest because it is a
major site of growth. The condylar cartilage is a
secondary cartilage which makes an important
contribution to the overall length of mandible.
It was considered that the condylar cartilage
was the primary growth centre of the mandible.
Proponents of the functional matrix theory
claimed that some mandibles function
adequately and seem to be positioned rather
normally when condyles are absent. They
concluded that soft-tissue development carries
the mandible forward and downward and the
condylar growth fills the resultant space to
maintain the contact with the basicranium.

The growth mechanism of the condylar area is
fairly clear, the main factor being the
mesenchymal cells i.e. periosteum present
above the cartilage. Another significant fact
about the cartilage is that, compared with
other cartilages it reacts faster to outside
stimuli with a lower threshold. The condyle
does not determine how mandible grows,
rather the mandible which determines how the
condyles grows. The growth of mandible is
determined by factors outside the mandible-
muscles, maxillary growth etc.
An endochondral growth mechanism is required
because the condyle grows in the direction of
articulation in the face of pressure, a situation
which pure intramembraneous bone growth could
not tolerate.

An endochondral growth mechanism is required
because the condyle grows in the direction of
articulation in the face of pressure, a situation
which pure intramembraneous bone growth
could not tolerate.
Petrovic et al. have noted the hormonal
influences on condylar cartilage growth.
Koski et al. stated that the periosteal tension
in the condylar neck provides a in-built control
for growth of ramus by way of the cartilage and
the other local factors, such as lateral pterygoid
may induce outside control. The indicate the
periosteal integrity is important for normal
proliferative activity of the connective tissue
cells of the condyle apart from the role of
lateral pterygoid muscle.

The condylar region plays an important
role in mandibular growth because of the
auricular site and because of the
extensive remodeling necessary.
Condylar cartilage plays some role in the
translations of the mandible. The
condylar cartilage as well as the
functioning muscle translates the
mandible and in the absence of one the
other compensate. In either event the
periosteum of the condylar neck region is
important. www.indiandentalacademy.com

Ramus and body
The addition of new bone provided by
the condyle produce a dominant
growth movement (translation) of
the mandible. The posterior border of
the ramus in conjunction with the
condyle also undergoes a major
growth movement (cortical shift)
that follows a posterior and some
what a lateral course

The condylar growth and the ramus growth
bring about the following changes: -
1) A backward transposition of the entire ramus
thereby elongating the mandibular body
2) A displacement of the mandibular body in the
anterior direction.
3) Movable articulation during these various
growth changes.
As the ramus grows and is relocated the
lingual tuberosity also moves posteriorly. The
growth movement of the mandible in general is
complemented by corresponding changes
occurring in the maxilla.www.indiandentalacademy.com

A primary function of corpus displacement is
continuous positioning of the mandibular arch
relative to the complementary growth
movements of the maxilla. As the maxilla
becomes displaced anteriorly and inferiorly a
simultaneous displacement of the mandible in
equivalent directions and approximate extent
occurs. Muscle attachment also play an
important role localized remodeling and
cortical drift accompanying the downward and
forward mandibular displacement. Areas of
muscle attachment coronoid and gonial region
do not develop well if the muscles are removed
very early or if the nerves and vessels serving
severed.

The mandible appears to grow in a forward
and downward manner when visualized in
serial cephalometric tracing. The
predominant trend of the growth is the
posterior and superior but the simultaneous
displacement of the mandible takes place in
the opposite direction i.e. inferiorly and
anteriorly, regardless of the many varying
regional directions of growth, remodeling
and local drift.

Alveolar process
The alveolar process is not present when the
tooth is not present. Its formation is controlled
by dental eruption and it resorbs when the
teeth are exfoliated or extracted. The alveolar
process serves as important buffer zones
helping to maintain occlusal relationship during
differential mandibular and midface growth.
Alveolar process growth is most active during
eruption, plays an unimportant role during
emergence and initial intercuspation, and
continues to maintain the occlusal relationship
during vertical growth of mandible and maxilla.
When corpus growth is essentially over, vertical
alveolar growth persists as the occlusal
surfaces wear thus the occlusal height is
maintained even in adulthood. Adaptive
remodeling of the alveolar process makes
orthodontic tooth movement possible.

Amounts and direction of mandibular growth
1) Height
Ramus height increases correlate well with
corpus length and overall mandibular length.
Anterior process height increases are highly
correlated with eruption. Anterior mandibular
height (mandibular line to incisal edge) is
related to dental development and overall
mandibular growth downward and forward. The
mandibular anterior height id directed to the
facial type and is quite different in a skeletal
deep bite and a long anterior face h

Width
Bigonial and bicondylar diameter
increases are a function of growth in
overall mandibular length and
natural divergence of the mandible.
Width increases occurs because of
lengthening of mandible although
some periosteal deposition occurs.
Mandibular width is generally more
evenly acquired than those of overall
length or height.

Length
Mandibular length is measured in two
ways:
1) Overall length (condyle to gnathion)
2) Corpus length (pogonion to gonion
Both these dimensions show increase in
correlation with ramus height increases and
spurts in mandibular length occurs about the
same time as spurts in stature.

Rotation
Serial cephelometric studies keeping the
cranial base as reference shows that the
mandible is carried away in an anterior
and downward direction. When the
mandible is steeply related to the cranial
base and the anterior facial height
increases are significantly greater than
those posteriorly, the mandible is said to
be rotated posteriorly. In such cases the
increased facial height to a great degree is
contributed by the anterior mandibular
height and also seen that the alveolar
processes is much higher anteriorly than
in posterior region.

Bjork studied this by use of metallic
implants and other methods. There is said
to be two types of rotation
1) Matrix rotation
2) Intramatrix rotation
Matrix rotation the centre of rotation being at
the condyle and forms a pendulum movement.
Intra matrix rotation is the rotation of the
mandibular corpus, inner half of its matrix within
the mandibular corpus not in the condyle. Most
of the time intramatrix rotation accounts for
most of the total so called mandibular rotation.

Timing
Spurts in mandibular dimensions are
common but occurring approximately 11/2
years earlier in girls. The most important
spurt associated with mandibular growth
is that related to puberty. Almost all first
pubertal spurts occur after ulnar sesamoid
ossification and before menarchy. The
prediction of the timing of mandibular
growth spurts according to many research
are not sufficient for clinical application.

Theories of mandibular growth
Genetic theory: - States that growth is
inherited through a genetic code.
Sutural theory: - Proposed by sicher states
that growth takes place by deposition of
new bone at the suture.
Cartilaginous theory: - Proposed by Scott it
states that cartilage is the primary determinant
of growth while bone responds secondarily and
passively.
Functional matrix theory: - Proposed by moss.
Servo system theory: -By petrovic.www.indiandentalacademy.com

Counterpart theory: - By Enlow it states that
growth of any given function or cranial part
relates specifically to other structural and
geometric counterparts in the face and
cranium.
Unloaded nerve theory: - Proposed by moss it
states that mandibular growth is secondary to
the primary growth of the mandibular division of
trigeminal nerve which is the first structure to be
develop in the primodia of the lower jaw.
Trajectories of the jaws: - Proposed by Koch
it states that the bony trabaculae corresponds to
the pathway of maximal pressure and tension
and bony trabaculae are thick there.www.indiandentalacademy.com

Palate
The palate starts its growth between the 7th and
18th week of intra uterine life. After the first
growth the width increases faster than the
length. In early pre natal life the palate is
relatively long but from the 4th month it
widens as a result of mid palatal suture growth
and appositional growth along the lateral
alveolar margins. At the birth the length and
berth of the hard palate is almost equal. The
post natal increase in palatal length is due to
appositional growth in the maxillary tuberosity
region and to some extent at the transverse
maxillo-palatine suture.

Growth of the mid palatal suture occurs between
1 and 2 years of age. Growth in the width of
mid palatal suture is large in its posterior than
in its anterior part, so that the posterior part of
the nasal cavity widens more than the anterior
part. Lateral appositional growth continues until
7 years of age by this time the palate achieves
its maximum anterior width. Posterior
appositional growth continues after the lateral
growth has ceased, so that the palate becomes
longer and wider during late childhood. During
infancy and childhood bone apposition also
occurs on the entire inferior surface of the
palate accompanied by a simultaneous
resorption from the superior surface; this result
in descent of the palate and enlargement of the
nasal cavity. www.indiandentalacademy.com

The appositional growth of the alveolar
processes contributes to deepening as well as
widening of the vault of the boney palate at
the same time adding to the height and
breadth of maxillae. The lateral alveolar
process helps to form an antero posterior
palatal furrow which together with a concave
floor produced by tongue. The anterior palatal
furrow is well marked during the first year of
life and normally flattens out into a palatal
arch after 3 to 4 years of age when sucking
has been discontinued. Persistence of thump
or finger sucking may retain the accentuated
palatal furrow into childhood

Ossification does not occur in the
posterior part of the palate, giving
rise to the region of soft palate.
Myogenic mesenchymal tissues of
the I, II and IV branchial arch
migrates into this facial region
supplying the musculature of facial
and palate.

Congenital malformation
Causes
Genetic factors
Chromosomal disorder.
Single gene disorder.
Multifactoral disorder (polygenic and
environmental) at birth.
Disorder of late life.
Non genetic factors
Maternal infection.
Maternal use of medicine and toxic materials.
Maternal exposure to radiation.
Disturbance of embryonic differentiation and
fetal growth.

Clefts of maxillofacial skeleton
This is the most common defect of the
maxillofacial region. This major congenital
malformation includes: -
 Cleft lip.
 Clefts of primary palate.
 Clefts of secondary palate.
 Clefts of facial skeleton: -
• Oblique facial clefts.
• Mandibular clefts.
 Submucous cleft of palate.
 Bifid uvula.
 Pits in the lips. www.indiandentalacademy.com

Some facial clefts will be so severe and
may result in health hazards out side
the oral cavity also. Early diagnosis
and treatment of these
malformations will help in a better
further development.

Classification of the clefts
Cleft lips: -
 Unilateral cleft lip.
 Bilateral cleft lip.
 Oblique facial cleft and cleft lip.
 Median cleft lip associated with nasal
defects.
 Median mandibular cleft lip.
 Unilateral macrostomia.

Cleft palate
 Unilateral incomplete cleft of primary
palate.
 Complete cleft of the primary palate,
ending at the incisive foramen.
 Bilateral complete cleft of primary
palate.
 Incomplete isolated cleft of secondary
palate.
 Complete cleft of secondary palate; soft
and hard palate.
 Bilateral complete cleft of primary and
secondary palate.
 Incomplete cleft of primary and
incomplete cleft of secondary palate.www.indiandentalacademy.com

Cleft lip
The failure of the facial prominence
to fuse together results in abnormal
development of cleft lip. These clefts are
due to disruption of the many integrated
processes of induction, cell migration,
local growth and mesenchymal merging.
Unilateral cleft of the upper lip is
the result of the medial nasal prominence
failure to merge with the maxillary
prominence on either side of the mid line.
The unilateral is more common on the left
side and have a strong familial tendency
suggesting a genetic background.www.indiandentalacademy.com

The bilateral cleft lip results in a wide mid
line defect of the upper lip and may cause a
protuberant proboscis, which are rarely seen.
The rare median cleft
lip (hare lip) is due to incomplete merging of
two medial nasal prominences and therefore in
most cases, with deep midline grooving of the
nose leading various forms of bifid nose.
Merging of maxillary and
mandibular prominences beyond or short of the
site for normal mouth size result in too small or
too wide (micro or macrostomia). Rarely the
maxillary and mandibular prominences fuse,
producing a closed mouth (astomia).

An oblique facial cleft results from
persistence of the groove between the
maxillary prominence and the lateral
nasal prominence running from the
medial canthus of the eye to the ala of
the nose. Persistence of the furrow
between the two mandibular
prominences produces the rare midline
mandibular cleft.

Cleft palate
Cleft palate occurs due to the lack of fusion
or breakdown of the fusion process of the
palate during the first 6-9 weeks in utero.
These deformities occur about in 750
(Daniel waite) spurber 800. Delay in
elevation of the palate shelves from the
vertical to the horizontal while the head is
growing continuously results in widening of
gap between the shelves so that they
cannot meet and therefore cannot fuse.
This leads clefting of palate.

Other causes of cleft palate are
defective self fusion, medial edge epithelial cell
death, post fusion rupture and mesenchymal
consolidation and differentiation. The least
severe form of cleft palate is the bifid uvula if
the cleft involves the alveolar arch it usually
passes between canine and lateral incisor.
Within the major constraint of
the lack of knowledge on the relative
contribution of genetic and environmental
factors in the pathogenesis of cleft, it is
possible to postulate a number of disturbances
and their consequences for the development of
clefts in the palate.

 Disturbed mesenchymal cell migration or
proliferation. Small facial growth centers or
palatal process impair mesenchymal cell
replacement after palatal fusion.
 Suppressed cell division in associated
structures. Reduced growth of cranial or
meckels cartilage.
 Impaired intrinsic tissue function.
 Reduced tongue mobility and delayed ability
or inability of palatal processes to elevate.
 Disturbance of inductive tissue interactions
aberrant messages leading to failure of
palatal function.
 Suppressed programmed epithelial cell death
following fusion. Incomplete palatal fusion or
opening or fused processes.www.indiandentalacademy.com

Experimental studies and clinical case
reports have shown that certain
substances can be regarded as
teratogenic i.e. they cause deformity
after exposure of the embryo to
which may or may not be above a
therapeutic level. It is thus wise to
avoid all drugs and source of ionizing
radiation during the early months of
pregnancy.

Craniofacial anomalies
Pierre robin syndrome: - Pierre robin (1929)
Features are under developed mandible,
glossoptosis, palatal clefting and respiratory
troubles. The pathogenesis is due the
disturbance of muscular maturation of
nervous origin and the syndrome of Pierre
robin therefore belongs to the category of
muscular dysmaturation which affect the
masticatory muscles, the tongue and the
pharyngeal slings.

Swallowing is disturbed and the airway
is obstructed resulting in the aspiration of
secretion and food. The respiratory difficulties
are further increased by the low and posterior
position of the tongue. A lateral radiograph
shows the tongue positioned below the level of
the mandibular angle, pressing the epiglottis.
Retromandibulism is caused by the
deficient activity of the pterygoid muscle, which
is unable to bring the mandible forward. The
clinical forms of Pierre robin syndrome are
extremely variable. Other mandibular
malformations resemble the syndrome but the
term Pierre robin should not be applied when
there is no abnormal function.www.indiandentalacademy.com

Mandibulo facial dysostosis
(Treacher Collins syndrome)
This is an inherited disorder involving the
structure of the first branchial arch, pouch
and groove. Manifestation includes
fish-like mouth, downward sloping of
palpebral fissure, malar deficiency
receding chin and deformities of the pinna
contribute to the characteristic feature.
Open bite malocclusion, deep palatal and
occasional cleft palate have been reported
as important oral symptoms.

Craniofacial dysostosis
(Crouzon syndrome)
This occurs due to the premature
closure of the cranial and facial
suture. There is severe lack of orbits,
nasal, zygomatic and maxillary bone
components. Mandible will be normal
and they exhibit a class iii
malocclusion with a ‘v’ shaped
palate. In some cases partial
anodontia or peg shaped teeth are
seen.

Hemifacial macrostomia
In this the underdevelopment of the
bony and soft tissue structure of half
of the face, can occur unilaterally or
bilaterally. The patients often having
missing portion of mandible like
condyle, ramus and in severe cases
even the body of mandible.
Malformed ears and zygomatic
arches are the other features.

Cerebrohepatorenal syndrome
(Bowen’s syndrome)
It is occurred in an autosomal recessive way.
 Oral feature includes micrignathia, protruding
tongue and high arched palate.
Trisomy 13 syndrome
This is a chromosomal disorder in which
an extra chromosome number 13 is present.
 Oral signs include cleft lip sometime associated
with cleft palate, small ears and microcephaly.

Cleidocranial dysplasia
This is an autosomal dominant condition.
Oral features: - This includes high arched
palate, with or without clefts, delayed
eruption of teeth, malformed roots, and
supernumerary tooth.
Radiographic features reveals feature like
obtuse mandibular angle and lacking of
cellular cementum in the impacted tooth.

Acrofacial dysostosis (Nagar syndrome)
This is an autosomal recessive condition with
the oral conditions like cleft palate,
micrognathism and malocclusion.
This disorder must be differentiated from
mandibulofacial dysostosis by the absence of
multiple skeletal deformities.
Bowen’s syndrome (Cerebrohepatorenal
syndrome)
This disorder is inherited in an
autosomal recessive way.
Oral features include micrognathia, protruding
tongue and high arched palate.

Chondroectodermal dysplasia (Ellis-van
Creveed syndrome)
This disorder is said to be inherited as an
autosomal recessive trait.
Oral features: - Deciduous teeth show hypoplasia
occasionally and partial anodontia of the
permanent teeth in a common finding.
Craniofacial measurements are not generally
altered but due to the hypoplastic middle third
of the face, relative prognathism of the lower
jaw may be seen. The obliteration of the upper
labial sulcus due to gingival frenal attachments
is a consistent oral mucosal finding of the
chondroectodermal dysplasia.www.indiandentalacademy.com

Growth and development of jaws

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