Growth and development of mandible / dental crown & bridge courses

GROWTH
AND
DEVELOPMENT
OF
MANDIBLE
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

Under the able guidance of:
• DR. D.N.KAPOOR(M.D.S)DEAN AND
PRINCIPAL
• DR. Y. G.REDDY(M.D.S) PROFESSOR
• Dr D. L. NAIDU (M.D.S) PROFESSOR
• DR.SHRIDHAR KANNAN (M.D.S)
READER
• DR.A.K.CHAUHAN (M.D.S)LECTURER

CONTENTS
• INTRODUCTION
• ANATOMY
• STUDY OF GROWTH OF MANDIBLE
• ROLE OF FUNCTIONAL MATRIX THEORY IN
MANDIBULAR GROWTH
• PRENATAL GROWTH
• POST NATAL GROWTH
• MANDIBULAR GROWTH PATTERN
• MANDIBULAR ROTATION DURING
GROWTH
• GROWTH PATTERN IN SUBJECTS WITH
LONG AND SHORT FACES
• CLINICAL IMPLICATIONS
• DISTRACTION OSTEOGENESIS

INTRODUCTION
• Previously mandible is described as long
bone bent in the shape of a U with cartilage
growth plates at each end that caused growth
and offered articulation.
• If this analogue were correct, the cartilage at
the distal end of the bone should behave like
true growth cartilage, according to modern
concept analogy looks attractive but it is not
correct. www.indiandentalacademy.com

• Mandible is the largest bone of facial
skeleton
• It is the only bone in the body which has
both intramembranous and endochondral
ossification
• Formation of mandible starts from 6th
week
and continue till puberty.

ANATOMY

STUDY OF GROWTH OF
MANDIBLE• The currently accepted concept of upward and
downward growth of mandible was first described by
JOHN HUNTER in 1771.Prior to it was thought that
the mandible grew primarily by deposition of bone at
the chin.
• HUNTER in 1837, demonstrated that bone was
formed on posterior border of ramus, accompanied
by resorption on the anterior border.
• HUMPHREY in 1863, inserted metal rings, into the
anterior and posterior borders of the rami of the pigs
and observed that the rings located on posterior
borders of the rami were more deeply embedded
with continued growth and rings on the anterior

• BRODIE(1946) popularized the idea of pattern as it
relates to facial growth.
• In 1964, ENLOW AND HARRISH mapped the
histologic characteristics of mandible and showed
the areas,where the bone was remodeling out or
growing in.
• MOSS in 1970, advanced the idea that Mandibular
growth does not follow a linear pattern and proposed
that growth follows a ‘logarithmic spiral’.
• RICKETTS(1972) proposed a similar ‘non-liner’
pattern. He thought that mandibular growth follow an
arc.

ROLE OF FUNCTIONAL MATRIX
THEORY IN MANDIBULAR GROWTH
• Based on the functional cranial component,
concept of VAN DER KLAAUW, Moss
supports the concept of role of function matrix.
• Mandible is not a unitary biological object but
rather a composite of several relatively
independent functional matrix(periosteal and
capsular matrices) and skeletal unit.

• According to this concept mandibular growth
is seen to be combination of the morphologic
effect of both capsular and periosteal
matrices.
• The capsular matrix growth causes an
expansion of the capsule as a whole. The
enclosed and embedded microskeletal
unit(the mandible), accordingly, is passively
and secondarily translated in space to
successively new position.www.indiandentalacademy.com

• In normal condition, the periosteal matrics
related to the constituent mandibular
microskeletal units also respond to this
volumetric expansion. Such an alteration in
their spatial position causes them to grow,
that is causes change in their functional
demands. These now cause direct alteration
in the size and shape of their microskeletal
units.
• Thus the sum of translation plus changes in
form comprises the totality of mandibular

PRENATAL DEVELOPMENT
• Development of the mandible begins as a condensation of
mesenchyme just lateral to Meckel’s cartilage and proceeds
entirely as an intramembranous bone formation.
• Ossification of the mandible begins to develop on lateral
aspect of Meckel’s cartilage near the future 1st deciduous
molar during the 7th week and continues until the posterior
aspect is covered with bone.
• Ossified area reaches almost to the symphysis by the 8th
week.
• Posterior elongation from the center of ossification is slower
than anterior elongation and ossification reaches almost to
the region of the mandibular foramen in the 8th week.

• The condylar cartilage develops initially as a
separate area of condensation at 2nd month and
fusion of this cartilage with the mandibular body
occurs at 4 months.
• Ossification of mandible stops at the point of
future lingula and Meckel’s cartilage
disintegrates and largely disappears as the bony
mandible develops.
• Remaining part of Meckel’s cartilage transform
into spehenomandibular ligament, spinous
process of sphenoid and anterior ligament ofwww.indiandentalacademy.com

Fate of meckel’s cartilage
• Most post extremity from malleus of the
inner ear and malleoloalar ligament
• From the sphhenoid to the division of the
nerve into its alveolar and lingual branch
the cartilage is lost completely but its
fibrous capsule persist as
sphenomandibular ligament

• Where the alveolar nerve divide into
incisor and mental branch from this point
to midline the cartilage might make small
contribution to the mandible by
endochondral ossification

prenatal changes of mandible
• Ingham (1932) :-
– the alveolar plate (ridge) lengthens more rapidly
than does the ramus.
– the ratio of alveolar plate length to total
mandibular length is reasonably constant.
– the width of the alveolar plate shows a more rapid
increase than does total width.
– the ratio of the width between the mandibular
angle to the total width is relatively constant during
fetal life.

MANDIBLE AT BIRTH :-
• At birth two rami of mandible are quite short , condylar
development is minimal and there is practically no articular
eminence in the glenoid fossa.
• A thin line of fibrocartilage and connective tissue exists at the
midline of symphysis and this cartilage is replaced by bone
between 4th month of age and the end of 1st year.
• There is no significant growth between the two halves before
they unite.
• During 1st year of life appositional growth is especially active
at the alveolar border, at the posterior and superior surfaces
of ramus ,at condyle, along the lower border of the mandible
and on its lateral surfaces.www.indiandentalacademy.com

POST NATAL GROWTH

RAMUS
• Basic function of ramus of mandible is that it provides an
attachment base for masticatory muscles and it has the key
role in placing the corpus to dental arch into ever charging fit
with the growing maxilla and face in limitless structural
variation.
• As the mandible grows in length, the ramus is extensively
remodeled , resorbtion occurs at the anterior part of the
ramus while deposition occurs on the posterior region.
• Characteristically the labial cortex of the more basal parts of
the ramus is composed of periosteal bone as a result of
periosteal deposition and endosteal resorption. On the other
hand inward moving upper regions are composed of
endosteal bone.
• Remodelling of ramus is so extensive that bone at the tip of
the condylar process at an early age can be found at the
anterior surface of the ramus some years later.

CORPUS OR THE BODY OF
MANDIBLE
• Body of the mandible grows longer as the ramus moves away
from the chin , by removal of bone from anterior surface of the
ramus and deposition on the posterior surface.
• Thus the posterior surface at one time becomes the center
and eventually may become the anterior surface as
remodeling proceeds.
• Continued growth of alveolar bone with the developing
dentition increases the height of mandibular body.
• The alveolar process of the mandible grows upward and
outwards on an expanding arc. This permits the dental arch to
accommodate the larger permanent teeth.

• Width of mandibular body is increased by
appositional growth on lateral surface.
• Modeling deposition occur at the canine eminence
and along the lateral inferior border.
• Measurement between right and left mental foramina
show that little change occurs in this dimension after
six years of life.
• On lingual aspect , anterior to the premolar , lingual
growth occurs in all portions of the body and the
surface is thereafter composed of periosteal bone ,
posterior to the premolar area lingual movement is
mainly in the area of tuberosity, this growth
apparently functions to support the molar teeth in
line with the rest of the dental arch.www.indiandentalacademy.com

THE LINGUAL TUBEROSITY
• Lingual tuberosity is major growth remodeling site and forms
the boundary between the two basic forms of the mandible :
the ramus and the corpus.
• The tuberosity remodels (relocates) in an almost directly
posterior direction , with only a relatively slight lateral shift.
• The posterior growth of tuberosity is accomplished by
continued new deposits of bone on its posterior facing
exposure. Thus the ramus just behind the tuberosity remodels
medially and comes into line with the axis of the arch.
• The lingual tuberosity protrudes in a lingual medial
direction .This prominence is augmented by the presence of a
large resorptive field just below it.
• This resorptive field produces a depression, the lingual fossa.

GONIAL REGION
• The gonial region is anatomically variable and therefore ,
much variation is involved in its pattern of growth.
• Depending on the presence of inwardly or outwardly directed
gonial flares the buccal side can be depository or resorptive
with the lingual side having the converse type of growth.
• A single field of surface resorption is present on the inferior
edge of the mandible at the ramus corpus juction. This forms
the Antigonial notch.
• While the whole ramus grows posteriorly and superiorly the
Mandibular foramen relocates backward and upward by
deposition on the anterior and resorption from the posterior
part of its rim.
• Thus the foramen from childhood through old age maintain a
constant position about midway between the anterior and
posterior borders of the ramus.

CORONOID PROCESS:-
• The growth of coronoid follows the enlarging V principle and
has a Propeller like twist so that its lingual side faces 3
general direction. Posteriorly superiorly and medially.
• As the coronoid processes become higher their termini grow
farther a part at their apices :
– By addition on the lingual surface.
– Contralateral removal from the buccal side.
• The anterior edge of the coronoid processes which faces
away form the direction of growth becomes resorbed by
periosteal resorption and corresponding endosteal deposition
so that only endosteal bone is left in the cortex.
• Finally the base of the coronoid which is oriented medially is
shifted in that direction by the continued lingual bone

CONDYLE AND CONDYLAR NECK
• The hallmark of earlier viewpoint is that the main
growth center of mandibular growth is the hyaline
cartilage in its condyle and growth of the condyle
causes a downwards and forward shift of entire
mandible (Weimmann and Sicher, 1955).
• According to current thinking rather than acting as a
Master growth center it actually performs much
more functional role :
– It provides a pressure tolerant articular contact.
– It makes possible a multidirectional growth capacity in
response to everchanging development conditions and
variations.

CONDYLAR NECK
• Since the circumference of the condyle is
greater than line circumference of neck,
the lingual and buccal sides of the neck
have resorbtive surfaces and the neck is
progressively relocated into areas
previously held by the much wider
condyles.
• In the mandible of an adult both the
outer and inner surfaces of the cortices of
the condylar neck are composed ofwww.indiandentalacademy.com

FEATURES OF CONDYLAR
CARTILAGE
• Zones of condyle
– Zone 1: A layer of dense fibrous connective tissue
layer that coves the hyaline cartilage.
– Zone 2 : Relatively thin transitional zone immature
hyaline cartilage. This layer is composed of densely
packed chondroblast.
– Zone 3 : Layer of prechcndroblast cells this is the
predominant for cellular proliferation.
– Zone 4 : Zone of resorption and deposition of bone
formed by the calcification of deepest part.

CHIN AND SYMPHYSIS
REGION
• Chin is unique to human and man is the only
primate with chin.
• Enlow and Harris (1964) feels that the chin is
associated with a generalized process of cortical
recession in the flattened region positioned
between the canine teeth and the process
involves a mechanism of endosteal cortical
growth.
• Apposition of bone at the symphysis seems to
be about the last change in shape during the
growing period.www.indiandentalacademy.com

MANDIBULAR GROWTH PATTERN
• Growth of the mandible continues at a relatively steady rate
before puberty.
• On the average ramus height increases 1-2 mm per year
and body length increases 2-3 mm per years.
• Mandibular growth is not directly linear in direction but
usually curves and slightly forward or occasionally even
backward. The pattern of mandibular growth is thus generally
characherised by an upward and forward curving at the
condyles and at the same time resorption on the lower aspect
of gonial angle and some appositions below the symphysis.
• One feature of mandibular growth is an accentuation of
the prominence of chin. The increase in chin prominence with
maturity results from a combination of forward translation of
the chin as a part of the overall growth pattern of mandible
and resorption above the chin that alters the bony contours.

Timing of Growth in Width Length
and Height
• For the three planes of spaces there is a definite
sequence in which growth is completed.
• Growth in width is completed 1st then growth
in length and finally growth in height (W>L>H).
• Mandibular intercanine width is more likely to
decrease than increase after age 12.
• Intercanine width is essentially completed by
the end of ninth year in girls and the tenth year
in boys.
• Both molar and bicondylar widths show small
increases until the end of growth in length .

MANDIBULAR ROTATION
DURING GROWTH
Condition Bjork Shudy
Anterior growth greater
than posterior, Posterior
growth greater than
anterior
Forward rotation
Backward rotation
Clockwise rotation
Counterclockwise
Rotation

Bjork Solow
Houston
Profit
Rotation of mandibular
core relative to cranial
base
Total rotation True rotation Internal
Rotation
plane relative to cranial
base (Rotation around
the condyle
Matrix
Rotation
Apparent
Rotation
Total rotation
plane relative to core of
mandible (Rotation
centered within the
body of the mandible )
Intramatrix
Rotation
Angular
Remodeling of
lower border
External
Rotation

• Profit : Total rotation = internal rotation-
external rotation
• Bjork : Matrix rotation = total rotation –
Intramatrix rotation
• Solow: Apparent rotation = true rotation-
angular remodeling of lower border

• For and individual with normal facial
proportion there is about 15 degree
internal forward rotation from age 4 to
adult life (of this about 25% results from
matrix rotation and 75% results from
intramatrix rotation) and 11-12 of external
backward rotation producing 3 to 4 degree
decrease in mandibular plane angle.

Forward Rotation
• Type I : In this there is forward rotation about centers in the
joints which give rise to deep bite . Lower dental arch is
pressed into the upper resulting in underdevelopment of the
anterior face height.
• Type II : Rotation occurs about a center at the incisal edges
of the lower anterior teeth. This type occurs due to the
combination of marked development of posterior face height
and normal increases in the anterior height.
• Type III : Rotation occurs about the center at the level of
premolars.
• The anterior face height becomes underdeveloped and
the posterior face height increases.
• In the growth rotation of types II and III, the mandibular
symphysis swings forwards to a marked degree and the chin
becomes prominent. This is one of the reasons for the chin

Backward Rotation
• Backwards rotation is less frequent than forward rotation. Two
types of backward rotations have been recognized.
• Type I
Centre of backward rotation lies in temporomandibular joint.
In this type underdevelopment of posterior face height leads to a
backward rotation of the mandible with overdevelopment of
the anterior face height and possibly open bite as
consequence.
Type II
Rotation occurs about a centre situated at the most distal
occluding molars. This occurs in connection with growth in the
sagital direction at the mandibular condyle.
In this type symphysis is swung backwards and the chin is
drawn back below the face and a charactheristic double chin
appearance form.

AGE CHANGES IN
MANDIBLE

GROWTH PATTERN IN
SUBJECTS WITH LONG AND
SHORT FACES:-• Long face types persons have excessive lower anterior
face height and the palatal plan rotates down posteriorly
and mandible shows backwards rotation, with an
increase in the mandibular plane angle.
• This type of rotation is associated with an anterior
open bite malocclusion and mandibular deficiency.
• Short face types persons have short anterior lower
facial height and show excessive forward rotation of
mandible and shows excessive forward rotation of
mandible and shows a nearly horizontal palatal plane
and mandibular morphology of “square jaw” type with a
low mandibular plane and a square gonial angle .
• A deep bite malocclusion and crowded incisors
usually accompany this type of rotation.

FACIAL HEIGHT
• Average male face height is approximately 120mm
(nasion to menton) and in the female it is 110 mm
(Meredith 1966)
• In the posterior regionof the face ramus height
(distance between condylar head and gonion is
approximately 42 mm at age 7 (krogman 1943) and 56
mm in early childhood (Goldstein 1956)
• When the ramus height is expressed as percentage
of total face height the posterior height in 42% of the
anterior dimensions at age 7 and increase to
approximately 46% in early childhood (Meredith , 1966)
• This suggests that posterior part of face elongates
more than anterior part.

FACIAL WIDTH
• The lower face width has been determined as the
Bigonial diameter and represents the maximum
width of the body of mandible.
• The average intergumented bigonial diameter is
approximately 57mm at birth (Balinsky 1960) and
increase to 105 mm in early adulthood (Steggarda
1932) and 85% of this bigonal diameter is completed
by the time 1st permanent molar erupt.
• Studies have shown that there is no clinically
significant correlation between lower face width and
mandibular arch width (Merdith 1951) it indicates
that narrow faces do not necessarily have narrower
dental arches.

FACIAL DEPTH
• Facial depth is particularly important in
orthodontics because many malocclusions
have skeletal components in antero
posterior direction.
• From the age 5 to 14 years the depth
of face increased by 22% (Meredith ,1966)

CLINICAL IMPLICATIONS
• In case of pronounced forwards rotation
of mandible there is a major risk of deep
bite developing. This can be prevented
by means of a stabilizing appliance such
as bite plane introduced.
• In case of backwards rotation opening of
the bite is difficult to prevent therefore it
is the policy to postpone treatment until
the pubertal growth spurt is nearly over.

• Majority of childen with class II malocclusion have
mandibular deficiency. Efforts to accelerate mandibular
growth lead to the development of a family of functional
appliance (eg Monobloc Activator). These appliances
forces the patient to close the mouth in function with lower
jaw correct class II malocclusion .
• In cases of class III malocclusion due to mandibular
prognathism extra oral force via a chin cup therapy orients
the line of force application below the mandibular condyle
so that chin is deliberately rotated downwards and
backward. This results in extension of teeth and the force
aimed at the top of condyle might restrain growth there.
• Functional appliance for mandibular prognathism work in
the same manner as the chin cup therapy they create
downwards and backward rotation of the mandible and
create additional vertical space into which eruption of teeth
is guided. www.indiandentalacademy.com

• Growth changes can be an important factor in
retention relapse because active phase of
treatment of many patients is completed while
facial growth is still in progress. If a patient is in
the facial growth some changes in skeletodental
relationship may occur and a principle cause in
continued mandibular growth.
• Downlwards and forward movement particularly if it
is in excess of comparable maxillary movement
can result in lower incisor crowding and a tendency
towards class III occlusal relationship. This may
occur because no overjet is present after treatment
. The mandibular incisor teeth cannot move
downward and forward to a greater extent than the
maxillary teeth because this movement is impeded
by the maxillary dentition.
• In the same manner mandibular growth particularly
in downwards and backwards direction may

• DISTRACTION OSTEOGENSIS :- The Russian
surgeon Elizarov discovered in 1950 that is if cuts
were made through the cortex of a long bone of the
limbs then they could be lengthened by tension to
separate the bony segements.
• The bone of the mandible is quite similar in its internal
structure to the bone of the limbs (Roberts 1994) (even
though its development course is rather different )
Lenghthening the mandible via distraction
osteogenesis is possible . Current research shows that
best results are obtained if segments are separated at
a rate of 0.5-1.5 mm per day.

References
1. Bjork A : Prediction of mandibular growth rotation Am. J Orthod,
1969: 55;589-599,
2. Enlow DH and Hans Age related differences in mandibular ramus
growth : A histologic study Angle Orthod. 1995: 65:335-340.
3. Enlow DH: Handbook of facial growth, ed. 2nd
, Philadelphia W.B.
Saunders Company: 1982.
4. Graber T.M Orthodontics: Principles Practice ed. 3rd
Philadelphia
W.B. Saunders Company: 1988.
5. Moss ML and Rankow R.M. the role of the functional matrix in
mandibular growth Angle Orthod 1968: 38:95-103,.
6. Nanda SK Growth pattern in subjects with long and short faces Am
J. Orothod 98:1990: 247-258.
7. Profit WR. Fields H.W. Contemporary Orthodontics ed 3rd
St. Louis
CV Mosby, 2000.

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