Growth and development of the mandible /certified fixed orthodontic courses by Indian dental academy

GROWTH AND DEVELOPMENT
OF THE MANDIBLE

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INDIAN DENTAL ACADEMY
Leader in continuing dental education


GROWTH AND
DEVELOPMENT OF THE
MANDIBLE
ANATOMY
 PRE NATAL GROWTH
 POST NATAL GROWTH
 ANOMALIES OF
DEVELOPMENT



Prenatal growth of the
mandible


Neural crest cells

Ist brachial arch
Mandibular process

Mandibular
bone

CT tissue

36 – 38 DAYS
Ectomesenchymal
condensation

mandible

Lateral to Meckels
cartilage

Osteogenic
membrane


6 th week


10 – 12 weeks


Secondary
accessory
cartilages
appear


10 week - condylar cartilage




Appears in the Ramal region

Endochondral bone
(14 week)


Condylar Cartilage
Serves as a growth site
 Brings changes in the mandibular
position and form
 Growth increases during puberty
 Peak 12 – 14 years
 Ceases by 20 years



7 th month IUL






1 or 2 small cartilages appear in the
future mental region
Mental ossicles
Incorporated into the
intramembranous bone of symphsis


Features of neonatal
mandible


Ascending Ramus low and wide

Large Coronoid process
 Body – open shell containing tooth
buds and partially formed
deciduous teeth
 Mandibular canal that runs low in
the body



Features of neonatal
mandible
High
Coronoid
process

Wide
Ramus

Differential growth
During fetal life




8 weeks - mandible > maxilla
11 weeks - mandible = maxilla
13 – 20 weeks maxilla > mandible

At birth



Mandible tends to be retrognathic
Early post natal life
orthognathic

Post natal growth of the
mandible


Main sites of post natal growth
in the Mandible


Condylar cartilage



Posterior border of the Rami Width



Height

length

Alveolar ridges


Symphysis Menti




Limited growth till
fusion
No widening
after fusion


Mental Foramen


Mental Foramen


Vertical relation
within the body
of the mandible


Mental Protuberance




Formed by mental ossicles
from accessory cartilage
and ventral end of Meckel’s
cartilage
Poorly developed in infants

Mental Protruberance
Forms by
osseous
deposition
during
childhood
 Prominence is
accentuated by
bone resorption
above it



Mental Protuberance






Reversal between 2
growth fields
Concave

convex

Reversal line could be
High or low

Alveolar process






Adds to the height and
thickness of the
mandibular body
Teeth absent
fails to develop
Teeth extracted
resorbs

Alveolar process




Acts as buffer zone
Maintains vertical height
Adaptive remodeling makes orthodontic
tooth movement possible


Alveolar process
Lingual movement of anteriors


Condylar cartilage




Secondary cartilage
Important contribution to the overall
length of the mandible


Condylar cartilage



‘ v ‘ principle of
Enlow


Is the Condylar cartilage the
principle force that produces the
displacement of the mandible ?


For many years considered primary growth
center



FMH

-

Condyle absent yet mandible

positioned normally


Considered secondary cartilage -no intrinsic
growth potential



PETROVIC ET AL – role of hormones



Experiments involving transplantation of the condyle



JOHNSTON ETAL

detached condyle from the body

of mandible in guinea pigs


Injection of papain –inhibition of chondrogenesis



RANCHOW MOSS

- Condylectomy – immediate

resumption of growth







Condylar cartilage and functioning muscles
translate the mandible and in the absence of
one the other does best to compensate
Integrity of periosteum is important
When environment is changed compensatory
contributions are enhanced

CURRENT CONCEPT




Condylar cartilage does have a measure of intrinsic genetic
programming
But extra condylar factors are needed to sustain this activity

Physiologic
inductors

Intrinsic and extrinsic
biomechanical forces

ENLOW :



Increase pressure – growth inhibition
Decrease pressure – stimulates growth

based mainly
on animal
experiments

Lingual Tuberosity





Grows posterior and
medial by deposition
Resorptive field
belowLingual fossa


Coronoid Process


POSTERIOR

Lingual surface

SUPERIOR
MEDIALLY



Follows ‘v’ principle


Coronoid Process


‘’V’ PRINCIPLE OF ENLOW


Coronoid Process


Deposition on lingual side
MEDIAL



Resorption

INCREASES
VERTICAL
LENGTH

POSTERIOR
GROWTH

- buccal surface


RAMUS




Posterior
border deposition
Anterior border
resorption


Ramus




Superior part of
ramus below sigmoid
notch

Lower part of ramus
below the Coronoid
process

LINGUAL
-DEPOSITION
BUCCAL RESORPTION
BUCCAL DEPOSITION

LINGUAL RESORPTION

Ramus


Posterior border of Ramus




Depository and keeps pace
with condylar growth
Angle of growth
vertical



horizontal

Posterior margin below
condyle --resorptive field

Ramus Uprighting
Posterior border –
deposition
Inferior > superior
 Anterior border –
resorption
Inferior >superior


Condylar growth
more vertical


Age related differences in
mandibular growth
MARK HANS , DONALD ENLOW
AJO DEC 1995









30 well preserved human mandibles from
dental ages 1 – 13 years
Ground and polished microscopic sections
were obtained from the Ramus
Distribution of various types of resorptive vs
depository surfaces were recorded
2 additional patterns of Ramal remodeling
were noted

Type A – Classical Pattern


Type B – Vertical Variation



Type C - Rotation Variation


Conclusions






All 3 patterns cause downward & forward
displacement but to varying degree
ENLOW’S original description of general
body growth & remodeling type A most
common but one pattern of remodeling is
incomplete
The difference in pattern were large enough
to influence orthodontic treatment

Ramus corpus junction




Inferior Border of
junction resorption

Forms Antegonial
notch

Gonial region


Anatomically variable
B - Resorption



Gonial flares

inwardly
outwardly

L - deposition
B -deposition
L - resorption



Depends upon growth direction of ramus and
condyle

Mandibular foramen






Ramus -- posterior
and superior direction
Mandibular foramen
drifts in backward &
upward direction
Maintains constant
position -[A-P]

Condylar neck








Anterior margin

deposition

Posterior margin
Lingual and buccal
margin
Rotation – posterior
border resorption

Periosteal

resorption
Endosteal
deposition


Ramal growth








Backward transportation of entire ramus –
elongation of mandibular body
Displacement of corpus –anterior direction
Vertical lengthening of ramus as mandible is
displaced
Movable articulation during various growth
changes


Role of muscles in
Mandibular growth
MOSS






CORONOID
GONIAL ANGLE
Medial
CONDYLE

Temporalis
Masseter &
pterygoid
internal pterygoid


Skeletal units of mandible


Role of muscles in Mandibular
growth


Decrease muscle activity

Flattening of
Gonial angle

Reduction of
Coronoid process


Growth of mandible during
pubescence ARTHUR LEWIS , ALEX ROCHE
AJO OCT 1982






Spurts in the mandible were analyzed in 67
subjects from Fels longitudinal study
Spurts in Ar-Go , Ar-Gn , Go-Gn
A spurt was defined as an annual increment
exceeding the immediately preceding annual
increment by at least 1 mm

pubescence


pubescence
conclusion







Spurts in mandibular dimensions are common but not
universal
More common in boys
1.5 yrs earlier in girls
1st pubertal spurt usually occurs before PHV
Almost all 1st pubertal spurts occur one year after US
ossification and before menarche

Anomalies of development


AGNATHIA – deficiency of neural crest
cells in lower part of the face

DOWNS


MICROGNATHIA -

TREACHER COLLINS
PIERRE ROBIN


Anomalies of development


BIFID /DOUBLE CONDYLE



MACROGNATHIA



MICROGENIA



TORUS MANDIBULARIS

References










Craniofacial embryology – SPERBER
Facial growth – ENLOW
Contemporary orthodontics – PROFFIT
Handbook of orthodontics – MOYERS
Principles and practice of orthodontics –
GRABER
Growth of mandible during pubescence –
ROCHE,LEWIS AO OCT 1982
Age related differences in Ramus growth –
ENLOW,HANS AJO DEC 1995

Thank you
Leader in continuing dental education


Growth and development of the mandible /certified fixed orthodontic courses by Indian dental academy

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