G & d of mandible

GROWTH AND
DEVELOPMENT
OF MANDIBLE
www.indiandentalacademy.com

MANDIBLE

EVOLUTION

Origin and
homologies of
jaws were
outlined by
GEGENBAUER
(1872)

History of
vertebrates
is history of
jaws

AGNATHA
EARLIEST VERTEBRATES
Sedentary animalwww.indiandentalacademy.com

GNATHOSTOMES
FIRST JAWED VERTEBRATES
More active animal
First gill arch enlarged as first set of
jaws
In both placoderms and chondreichthyans
meckels cartilage continued to serve as jaw
element directly.

OSTEICHTHYES
Meckels cartilage started
covering by dermal bones
Proximal end of cartilage ossified to
form articular bone which continued to
form lower jaw articulation

AMPHIBIANS

HERBIVORES
CARNIVORES

Large temporal
fossa and short
zygomatic
Small temporal
fossa and large
zygomatic
CARNIVOROUS
ADAPTATION
HERBIVOROUS
ADAPTATION

Large
coronoid
Small
coronoid
CARNIVOROUS
ADAPTATION
HERBIVOROUS
ADAPTATION

RamusNo ramus
CARNIVOROUS
ADAPTATION
HERBIVOROUS
ADAPTATION

HOMINID EVOLUTION
OF JAWSwww.indiandentalacademy.com

UPRIGHT LOCOMOTION

INCREASED
BRAIN SIZE
Cranial base flexure

Orbital rotation due to expansion of
frontal and temporal lobes resulting in
binocular vision

Less interorbital space reduces the
nasal base which now cannot support
long snout

•Reduction of
upper jaw
•Downward
rotation of
nasomaxillary
complex
•Reduction of
lower jawwww.indiandentalacademy.com

PROSIMIANS ANTHROPOIDS

EVOLUTION
OF CHIN

It is an
expression of
reduction in
alveolar
segment rather
than increase in
length of body
of mandible.
SCOTT.

Theories of origin as classified
by DUBRUL and SICHER
•Speech theory ( Walkhoff and
Robinson )
•Mechanical effects of reduction and
retrusion of teeth (Weidenrich)
•Shifting theory ( Bolk)
•Effects of muscular activity ( Virchowwww.indiandentalacademy.com

Mandible is derived from
ossification of an osteogenic
membrane formed from
ectomesenchymal
condensation at 36 –38 days
of development

Neural crest
cells arising
from the level of
metencephalon
contributes to
trigeminal
ganglion and
mandibular arch
mesenchyme

PHARYNGEAL ARCHES

MECKEL’S
CARTILAGE
15 mm crl
6th
week
Otic capsule
to mental
regionwww.indiandentalacademy.com

FATE OF MECKEL’S
CARTILAGE

25 mm crl
surface of ventral part erodes and
show signs of replacing bone
30 mm crl
right and left side fuse on ventral
or vestibular aspect
75 mm crl
invasion replacement of ventral
surface
120 mm crl
no longer detectable

Dorsal extremity of cartilage undergo
endochondral ossification at 16 w to
form malleus and incus

Perichondrium proximal to mandibular
foramen persist as sphenomandibular and
malleomandibular ligaments

OSSIFICATION CENTER
Low (1905,1910)
18 mm embryo
Outer Aspect of ventral extremity of
meckel’s cartilage

OSSIFICATION CENTER
Mall (1906)
15mm embryo
Below epidermis towards free
end of first arch

OSSIFICATION CENTER
Symons (1951)
Closely associated with inferior
dental nerve and its branches

OSSIFICATION CENTER
Granstrom (1988)
Anterior to first molar tooth bud
lateral to meckel’s cartilage

OSSIFICATION CENTER
Kjaer (1990)
Area immediately below
mandibular nerve at the site where
mental foramen formswhere fiber
bunch diverge laterally and
frontally from meckels cartilage

24mm crl

95mm crl www.indiandentalacademy.com

Initial woven bone formed along
meckel’s cartilage is soon
replaced by lamellar bone and
typical haversian systems are
already present at 5th
month i.u

This remodelling is earlier than it occurs in
other bones , as is response to early
intense sucking and swallowing which
stress the mandible

Simple
backward
extension of
neural
element
behind and
above
mandibular
foramen
RAMAL ELEMENT
At about 8
weeks appears
as large
mesenchymal
field showing
progressive
differentiation
of muscle
fibres within it
At 40 mm crl
( 10th
week)
coronoid and
angular
processes are
added for
attachment of
muscles of
mastication as
muscular element

CORONOID
PROCESS
differentiate
as separate
entity within
temporal
muscle during
7th
week
Similarly
ANGULAR
PROCESS
also ossifies from
separate center
and both merge
with ramal element
within week of their
first appearance
SECONDARY CARTILAGES

CONDYLAR
CARTILAGE10th
week
50 mm crl stage
Cone shaped mass
with its base at head
of condylar process
and apex reaching
downward and
forward into ramus
as far as level of
By 14th
week ,
bone appears at
periphery of
condylar
cartilage
By mid fetal life ,
replaced by
endochondral
bone
Zone of
cartilage
remains beneath
articular surface
Persist until
growth of
mandible finally
is complete bywww.indiandentalacademy.com

DEVELOPMENTAL UNITS
ATCHLEY AND HALL
‘Those basic structural entities or
regulatory phenomenon necessary to
asssemble a complex morphological
structure’

DEVELOPMENTAL BLOCKS

Initially fetal mandible
has outside surfaces
that are entirely
depository in nature
10 weeks
resorption begins
around rapidly
expanding tooth buds
and is present thereafter

13 weeks
Distinctive resorptive fields on
•Lingual side ramus
•Buccal side coronoid
•Lingual side posterior part of
corpus
By 26 weeks basic growth
and remodelling pattern
that continues on into
postnatal development is
seen except in incisor
region

MANDIBLE AT BIRTH
Short alveolar process
Short
ramus Unformed
chinMore obtuse gonial
angle

Mandible is a membrane
bone , developed in
relation to nerve of first
arch and almost entirely
independent of meckel’s
cartilage…
Mandible has neural,
alveolar and muscular
elements and its growth is
assisted by development of
secondary cartilageswww.indiandentalacademy.com

THANK YOUwww.indiandentalacademy.com

G & d of mandible

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