growth and development of mandible

1. Dr SHILPA JOY
V S Dental College
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2. CONTENTS
 Introduction
 Anatomy of mandible
 Evolution of mandible
 Mandibular growth mechanisms-Brief history
 Prenatal growth of mandible
 Postnatal development
 Growth progression-mechanism & site
 Age changes in mandible
 Theories of mandibular growth
 Problems of mandibular growth and orthodontic
significance
 Conclusion
 References 23/1/2017 99

3. INTRODUCTION
The human mandible has no one design for life.Rather it
adapts and remodels through the seven stages of life,from the
slim arbiter of things to come in the infant,through a powerful
dentate machine and even weapon in the full flesh of
maturity ,to the pencil thin,porcelain like problem that we
struggle to repair in the adversity of old age –D.E POSWILLO
It is attached only by ligaments and muscles to immovable
bones of the skull.
The temporomandibular or ginglymo-diarthroidal joints are
the only visible movable articulations in the head. The rest of
the bones of the skull move in union when the head is moved
as a whole.
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4. DEFINITIONS RELATED TO GROWTH
 Moss: change in morphological parameters which is measurable.
 Moyers: Quantitative aspect of biological development per unit of
time.
 Todd: An increase in size.
 Krogman: increase in size change in proportions and progressive
complexity
 J.S. Huxley: The self multiplications of living substance
 Meridith:entire series of sequential anatomic and Physiologic
changes taking place from beginning of pre natal life to serenity
DEVELOPMENT
 Todd:progress towards maturity
 Moyers:All naturally occuring unidirectional changes in the life of
an individual from its existence as a single cell to its elaboration as a
multifunctional unit terminating in death
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5. ANATOMY OF MANDIBLE
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7. Attachments and relations of mandible
 Oblique line – buccinator muscle
 Oblique line below mental foramen – depressor labii inferious,
depressor anguli oris
 Lateral side of ramus- Masseter muscle
 Lower border- Platysma
 Midsurface of coronoid-
Temporalis
 Incisive fossa- Mentalis
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8.  Postero superior part of lateral surface – Parotid gland
 Lingula – sphenomandibular ligament
 Pterygoid fossa - lateral pterygoid muscle
 Mylohyoid line- Mylohyoid muscle
 Posterior end of mylohyoid line-
superior constrictor muscle
 Digastric fossa- Anterior belly
of digastric
 Genial tubercle -Genioglossus &
Geniohyoid
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9. EVOLUTION OF MANDIBLE
 The agnatha, the earliest type of
vertebrate, had its mouth opening on
the ventral side anteriorly along the
vertebral axis. They did not have jaws
 The Placoderms, had 7 arches.The first
arch was lost.Their new first arch
became the Mandibular arch that
formed the jaws.The upper half of
mand.arch became palatoquadrate cartilage
and lower half became the mandibular
or meckels cartilage
 In Elasmobrancs,the jaws were formed by
mandibular arch (arch 1) & hyoid arch(arch 2)
The upper half of hyoid arch became
hyomandibular ligament and lower half
became hyoid cartilage 93/1/2017 99

10. In amphibians the hyomandibular
ligament became the stapes .They had
a dentary bone in the anterior end of
the original cartilaginous jaw. At its
posterior extremity it articulated with
the quadrate bone
In reptiles like early synapsid ,that gave rise to mammals ,the jaw joint is
formed by the articular(lower) & quadrate(upper) bones.The joint was a
simple hinge at the posterior of jaw
In mid and late synapsid reptiles,the dentary bone (lower jaw) increase in
size as muscle and bite force increased,but force on the joint decreased as
the muscle insertion point shifted to allow greater jaw mobility
The articular and quadrate bones at the jaw joint became smaller and was
loosely attached with the dentary
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11.  The coronoid process of dentary bone formed to accommodate these
changing forces
 Ultimately in mammals,the jaw joint shifted from a articular-quadrate
joint to a dentary-squamosal joint.the condylar process formed to create
a new articulating surface
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12. MANDIBULAR GROWTH PATTERNS- A HISTORY
• HUNTER (1771) compared a series of dried mandibles and concluded that in
order to attain space for permanent molar teeth the mandible must grow by
posterior apposition of ramus accompanied by anterior ramus resorption.
• HUMPHRY (1866) studied growth of mandible by inserting metal rings in
the anterior and posterior margins of mandibular ramus in growing pig.Rings
placed on posterior border became more deeply embedded but rings placed
on anterior surface were released
• BRASH (1924) fed pigs the madder plant root(alizarin ) which labeled
appositional growth
 WEINMAN AND SICHER (1940) with the help of longitudinal cephalometrics
and evidence from experiments of animals, focused attention on the
mandibular condyle as a major factor in growth of the mandible.
A STUDY OF POSTNATAL GROWTH OF HUMAN MANDIBLE-DONALD H ENLOW,DAVID B HARRIS
AJODO,JAN 1964
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13.  BRODIE believed that superior and posterior growth of the
condyle along with apposition of the posterior border of the
ramus and alveolar border resulted in development of
mandible.
 RICKETTS(1950)by superimpositions on lower border of the
mandible showed that the condyle followed a superior and
posterior course. He also noted that the mandibular growth
was not same and that the relationship of the mandibular
plane to the Frankfort Horizontal plane was changing about
one degrees every 3 yrs in a typical facial pattern.
 MOSS(1960) envisioned the growth of the mandible as a
logarithmic spiral constructed via the path of the mandibular
nerve.
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14.  BJORK (1963 )conducted a study with tantalum implants and
suggested that
1. Growth in length of the mandible occurs at the condyles.
2. The anterior aspect of chin is extremely stable
3. The thickening of the symphysis takes place by appostion on its
posterior surface and lower border which contributes to
increase in height of symphysis.
4. At the region of the condyles there is upward and forward
curving growth.
5. The mandibular canal is not remodeled and the trabaculae
related to the canal are stationary. Hence the curvature of the
mandibular canal generally reflects the earlier shape of the
mandible
VARIATION IN GROWTH PATTERN OF HUMAN MANDIBLE;A LONGITUDINAL RADIOGRAPHIC
STUDY BY IMPLANT METHOD-ARNE BJORK ;J DENT RES 1963
.
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15. Growth & development of an individual can be divided in to
Pre-natal
Post-natal
Period of Ovum
1-14th day
Period of embryo
14th – 56th day
Period of Fetus
56th – 270th day
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16. PRENATAL GROWTH
PERIOD OF OVUM
Fertilization-Ampulla of uterine tube
zygote
mitosis
Cluster of cells(Blastomere)
mitosis
Morula(16 cell structure)
Blastocyst
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17. BLASTOCYST
Some fluid passes into morula from uterine wall seperating the inner
cell mass (embryoblast) and outer cell mass (trophoblast)
Trophoblast cells become flattened and embryoblast cells get
attached to one side
Now it is called blastocyst and cavity is called blastocoele
The site of attachment of inner cell mass is called embryonic or
animal pole and opposite site abembryonic pole
MORULA
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18. PERIOD OF EMBRYO
PRESOMITE PERIOD(8-20th day)
 Trophoblastic layer differentiate into synctiotrophoblast and
cytotrophoblast layers
SYNCTIOTROPHOBLAST- Outer cells that invades
endometrium and its vessels to establish maternal blood
circulation to developing embryo-UTEROPLACENTAL
CIRCULATION
PRESOMITE SOMITE POSTSOMITE
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19. INNER CELL MASS
Differentiation
BILAMINAR DISC
BLASTOCYSTIC CAVITY is now called as primitive yolk sac
AMNIOTIC CAVITY develops between epiblast and cytotrophoblast
HYPOBLAST
Squamous
/cuboidal
EPIBLAST
Columnar
cells
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20.  Extra embryonic mesoderm(EEM)
formed of loose connective tissue ,
differentiate between developing
embryo and cytotrophoblast
 Chorionic cavity is formed by
fusion of number of lacunae that
develop in EEM
 Expansion of chorionic cavity reduces size of primitive yolk
sac,forming secondary yolk sac, occurs by end of second week
 3rd week- Gastrulation occurs
Bilaminar disc-Trilaminar disc
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21.  Cells of primitive streak grow cranially to reach the prochordal
plate to form notochord which is a solid cylinder of cells,axial
skeleton of fetus forms around notochord
NEURAL TUBE FORMATION
Ectoderm above notochord thickens
Neural plate
Midline of neural plate deepens
Neural groove
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22. Elevated margins on either side-Neural folds
Neural folds grow towards each other
Fuse to form Neural tube- CNS
Edges of neural tube on either side-neural crests
Anterior end of neural tube-fore,mid,hind brain
Certain elevations called rhombomeres in area of hind brain-cells
that proliferate from neural crests
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23. NEURAL CREST CELLS
Forms from neuro ectoderm
Migrate & differentiate extensively with in the developing embryo
Spinal & cranial sensory ganglia, Sympathetic neurons, Schwann cells, pigment
cells & meninges
Most of the connective tissue of the head is formed
Migration is essential for development of teeth & face
All the tissues of teeth (except enamel) & its supporting apparatus are derived
directly from these cells
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24. SOMITE PERIOD(21ST -31ST day of IUL)
 Rapid growth of cranial end of embryo,caudal end lags
behind- CEPHALOCAUDAL GRADIENT OF GROWTH
Head-1/2 of total embryonic disk length
BRANCHIAL /PHARYNGEAL ARCHES
 In specific areas,the migrating and rapidly proliferating
ectomesenchyme cells develops elevation between ectoderm and
endoderm
 4th week of IUL Elevations seen in ventral foregut
5th arch perishes Formation of 6 pharyngeal arches
(bilaterally)
Finally 5 arches remain
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25. Separated externally by small clefts called branchial grooves
(Ectodermal clefts)-4 in number
On the inner aspect of pharyngeal wall are corresponding small
depressions called pharyngeal pouches-5 in number
In aquatic vertebrates both branchial grooves & pharyngeal
pouches fuse to form gill slits
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26. 263/1/2017 99

27. DEVELOPMENT OF MANDIBLE
Develops from the mandibular process of 1st branchial arch
The cartilage of the 1st arch
(Meckle’s cartilage) forms lower jaw
in the primitive vertebrates
In human beings Meckel’s cartilage
has close positional relationship to
the developing mandible but makes
no contribution to it
The mandibular nerve has close relationship to the Meckel’s
cartilage, beginning 2/3 of the way along the length of cartilage
At this point mandibular nerve divides in to lingual and inferior
alveolar branches 273/1/2017 99

28. At around 36-38 days of IUL there is
ectomesenchymal condensation
Some mesenchymal cells enlarges,acquire a
basophilic cytoplasm and form osteoblasts
Osteoblast secrete a gelatinous matrix called osteoid
and results in ossification of osteogenic membrane
The resulting intramembranous bone lies lateral
to meckels cartilage of mandibular arch
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29. In sixth wk ,a single ossification centre for each half arises in the
bifurcation of inferior alveolar nerve into mental and incisive
7th wk-bone begin to develop lateral to meckels cartilage and
continues until the postr aspect is covered with bone
Between 8th & 12th wk ,mandibular growth accelerate ,as a
result mandibular length increases
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30. Ossification stops at apoint,which later become lingula,the
remaining part of meckels cartilage continues to form
sphenomandibular ligament &spinous process of sphenoid
Secondary accessory cartilage appears between 10th &14th wk to
form head of condyle,part of coronoid process & mental
protuberance
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31. FATE OF MECKELS CARTILAGE
Posterior extremity forms malleus, incus &
sphenomandibular ligament
Most of the cartilage is absorbed except for some
portion in midline which may cause endochondral
ossification
FETAL PERIOD
Endochondral bone formation seen only in 3 areas
• Condylar process
• Coronoid process
• Mental region
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32. Condylar process
 About 5th week of I.U.L. area of
mesenchymal condensation above
the ventral part of developing mandible
 About 10th wk develops into cone shaped
cartilage
 By 14th week starts ossification
 By 4 months migrates inferiorly and fuses with ramus
 4th month onwards replaced by bone but proximal end persists into
adulthood acting as
Growth cartilage & Articular cartilage
 Condylar head separated from temporal bone by thin disc of connective
tissue – future articular disc
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33. Coronoid process
 By 10th to 14th week of I.U.L. secondary cartilages seen in region
of coronoid
 This cartilage becomes incorporated into expanding
intramembranous bone of ramus and disappears before birth
Mental region
 Secondary cartilages seen on both sides -- ossify by 7th wk
I.U.L.
 They ossify to form mental ossicles in fibrous tissue of symphysis
and later on gets incorporated into it.
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34. POST NATAL DEVELOPMENT
MANDIBLE AT BIRTH
MANDIBULAR
GROWTH-FIRST YEAR
GROWTH
PROGRESSION AFTER
FIRST YEAR-
MECHANISM & SITE
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35. MANDIBLE AT BIRTH
 2 rami of mandible are quite short,wide and the condyles are poorly
developed
 The alveolar process not yet formed
 The body of mandible is like a shell of
bone with tooth follicles and developing
crowns of teeth which are covered by
occlusal gum pads
 The angle of the mandible is about 175 degree with condyle nearly
in line with the body
 Initial separation of the two mandibular halves by fibrocartilage and
connective tissue which is eliminated gradually as ossification occurs
between 4th month to 1st year.
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36. MANDIBULAR GROWTH DURING FIRST YEAR
Appositional growth especially active at
 Alveolar border
 Distal and superior surface of ramus
 Condyle
 Lower border of mandible
 Lateral surface of mandible
 After first year growth becomes more selective,condyle shows
considerable activities , mandible moves and grows forward and
downward
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37. GROWTH PROGRESSION-MECHANISM & SITE
MANDIBULAR CONDYLE
 It is a major site of growth
Historically, the condyle has been
regarded as a kind of cornucopia
from which the whole mandible
itself pours forth.
 During mandibular growth ,the
condyle functions as regional
field of growth that provides an
adaptation for its own localized
growth circumstances
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38.  The condylar cartilage is a secondary type of cartilage
 Its real contribution is to provide regional adaptive growth
 Main functional role of condyle is
(1) provides a pressure tolerant articular contact
(2) it makes possible a multidimensional growth capacity in
response to ever-changing, developmental conditions and
variations.
 The condylar growth mechanism itself is a clear-cut process.
Cartilage is a special non-vascular tissue and is involved
because variable levels of compression occur at its articular
contact with temporal bone
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39.  An endochondral growth mechanism is required ,because the
condyle grow in a direction towards its articulation in the face of
direct pressure
 Intramembranous type couldn’t operate because the periosteal
mode of osteogenesis is not pressure adapted
 In Figure the endochondral bone tissue (b) , formed in association
with the condylar cartilage (a) is laid down only in medullary portion
 The enclosing bony cortices (c) are produced by periosteal-
endosteal osteogenic activity
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40. HISTOLOGICALLY
Articular zone
Resting zone
Proliferative zone
Hypertrophic zone
Erosive zone
• In secondary cartilage like condyles,the prechondoblast are not
surrounded by cartilaginous matrix ,thus they are exposed to
environment and are moldable to external influences
•Codylar cellular arrangement is multidirectional unlike primary
cartilage where its arranged in rows
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41.  Anterior margin of condylar neck is
depository, this surface is part of sigmoid notch
 Posterior edge which grades into posterior
border of ramus is also depository
The lingual and buccal sides of neck characteristically have a
resorptive surface. This is because condyle is quite broad and
neck is narrow
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42.  The neck is progressively relocated into areas previously held by the
much wider condyle,and it’s sequentially derived from the condyle as
condyle moves in superoposterior course
 Explained another way, the endosteal surfaceof the neck actually
faces the growth direction; the periosteal side points away from the
course of growth.
 This is another example of the
V principle, with the V-shaped cone
of the condylar neck growing toward
its wide end.
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43. What is the physical force that produces the forward and
downward primary displacement of mandible ???????
For many years it was presumed that
 Cartilage is pressure adapted type of tissue & creates a thrust of
mandible against its articular bearing surface
 proliferation of cartilage towards its contact thereby pushes the whole
mandible away from it.
But,Bilaterally condyle- lacking mandibles occupy an essentially
normal anatomic position and the mandible functions in
movements
These observations suggested 2 conclusions.
1. Condyles may not play the kingpin role of a “master center”.
2. The whole mandible can become displaced anteriorly and
inferiorly into its functional position without a "push" against the
basicranium
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44.  The current thinking is that condylar cartilage does have a
measure of intrinsic genetic programming .
 The cartilage cells are coded and geared to divide ,but
extracondylar factors are needed to sustain this activity
 So overall mandibular length can be clinically increase or
decrease depending on class II or class III if this were done during
period of active condylar growth
Physiologic
indicators
Extrinsic & intrinsic
biomechanical
factors
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45. CORONOID PROCESS
 The coronoid process has propeller
like twist, so that its lingual side
faces three general directions all at
once posteriorly, superiorly and medially.
 When bone is added onto the lingual side of the coronoid process ,
growth thereby precedes superiorly and this part of ramus increases
in vertical dimension
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46.  These same deposits of bone on the
lingual side also bring about a
posterior direction of growth
movement .
 Produces backward movement of
two coronoid process even though
deposits on the inside (lingual) surface.
 These same deposits on the lingual
side also bring about medial direction
of growth in order to lengthen corpus
 Area occupied by anterior part of ramus
in mandible 1 becomes relocated and
remodeled into posterior part of corpus
in mandible 2.
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47. CORPUS / BODY OF MANDIBLE
 Outer surface-depository & medial surface(inferior aspect)-
Resorptive,remodelling is in the form of ‘L’
 Depository area -from the superior half of medial surface of
corpus to anterior half of medial surface of ramus(below coronoid)
 Resorptive area –from inferior half of medial surface of corpus to
posterior half of medial surface of ramus (below condyle)
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48. RAMUS
 At birth the two rami of mandible are
quite short, they grow by the process
of direct surface apposition and
remodeling.
 THE PRINCIPLE GROWTH VECTORS ARE IN POSTERIOR & SUPERIOR
DIRECTION
 Resorption occurs on the anterior
surface of ramus while bone deposition
occurs on posterior surface.
 Bone growth occurs at the mandibular condyle and along the
posterior part of ramus to the same extent as anterior part has
undergone resorption
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49.  The lower part of ramus below the coronoid process also has a
twisted contour.
 Its buccal side faces posteriorly toward the direction of
backward growth and thus characteristically has a depository
type of surface.
 The opposite lingual side, being away from direction of
growth, is resorptive.
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50. IMPORTANCE OF RAMUS
 It positions the lower arch in occlusion with the upper.
 It is continuously adaptive to the multitude of changing
craniofacial conditions.
 Attach the mastication muscle and must accommodate the
increasing mass of masticatory muscle inserted into it.
 Bridges the pharyngeal compartment.
 The horizontal breadth of ramus determines the
anteroposterior positioning of lower arch.
 Height of ramus accommodates the vertical dimension and
growth of nasal and masticatory components of face.
 Remodeling and relocation give space to accommodate
erupting permanent molar.
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51. RAMUS UPRIGHTING
 Greater amounts of bone additions
on the inferior part of the posterior
border than on the superior part.
 A correspondingly greater amount
of matching resorption on the anterior
border takes place inferiorly than
superiorly.
 A "remodeling" rotation of ramus
alignment thus occurs.
 In diagram the pharynx enlarges
horizontally from a to a’ .
 The ramus enlarges correspondingly from b to b’
 Angle c is reduced to c’ to accommodate the vertical
increase,which allows for considerable extent of vertical
nasomaxillary growth 513/1/2017 99

52.  Vertical lengthening of the ramus continues to take place after
horizontal ramus growth slows or ceases
 Resorption takes place on the upper part
of the posterior border.
 A forward growth direction can occur
on the anterior border in the upper part
of the coronoid process.
 A posterior direction of remodeling takes place in the lower part of the
posterior border,this result in more upright alignment and longer vertical
dimension of ramus without increase in breadth
In fig mandible a is superimposed
over b remodeling changes outlined
above serve simply to alter the ramus
angle without increasing its breadth
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53. • The growth and remodeling changes of both ramus and middle cranial
fossa produces lowering of mandibular arch .This accommodate vertical
expansion of nasomaxillary complex .
• A vertical imbalance thus occurs ,this ‘opens’ anterior bite,only the first
and second molars are in occlusal contact
• The amount of upward mandibular tooth drift is much less than the
downward drift and displacement of maxillary teeth.
• This is one of the several reason why
orthodontic purpose, often attack maxillary
dentition ,eventhough given malocclusion
can be largely based on improper positioning
of mandible
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54. MANDIBULAR FORAMEN
 The mandibular foramen likewise drift backward and upward
by deposition on the anterior and resorption on the posterior
part of its rim.
 The foramen maintains a constant position about midway
between the anterior and posterior borders of ramus.
 Even when the ramus undergoes
marked alterations associated with
edentulism ,the foramen usually
sustains midway location
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55. ANTEGONIAL NOTCH
 A single field of surface resorption is present on the inferior
edge of mandible at the ramus corpus junction.
 This forms the antegonial notch by remodelling from the ramus
just behind it as the ramus relocates posteriorly
 The size of the notch can be increased whenever a downward
rotation of corpus relative to the ramus takes place
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56. ANTEGONIAL NOTCH –CLINICAL
SIGNIFICANCE
 Deep notched subjects have retrusive mandible with
shorter corpus, less ramus height and increase gonial
angle.
 Mandibular growth directions in deep notched patients
were more vertically directed as measured by facial axis
and the mandibular plane angle.
 Deep notched subjects had longer total facial height and
longer lower facial height,Smaller saddle angle
 Deep notch patients required a longer duration of
orthodontic treatment.
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57. THE LINGUAL TUBEROSITY
 Important structure as it is
direct anatomic equivalent of
the maxillary tuberosity
 Major site of growth for mandible
 Effective boundary between basic
parts of the mandible ; ramus and corpus.
 Grows posteriorly by deposits on the
posterior facing surface.
 The prominence of tuberosity is increased
by presence of large resorptive fields
just below it which produces a sizable
depression, the lingual fossa.
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58.  The combination of resorption in the fossa and deposition on the
medial facing surface of tuberoisty itself greatly accentuates the
contours of both regions
 Deposition on the lingual surface of the ramus just behind the
tuberosity produces a medial direction of drift that shifts this part
of the ramus into alignment with the axis of corpus.
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59. THE RAMUS TO CORPUS REMODELLING CONVERSION
 The whole ramus is being relocated in the posterior direction
 Bony arch length has been increased and the corpus has been
lengthened by
-Deposits on the posterior surface of lingual tuberosity and the
contiguous lingual side of the ramus.
- A resultant lingual shift of this part of ramus to become added to
corpus.
 The presence of resorption on the anterior border of ramus is
usually described as ‘MAKING ROOM FOR THE LAST MOLAR’
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60. THE CHIN
 Man is one amongst two species having a chin
 During the descent of the maxillary
arch and the vertical drift of the
mandibular teeth, the anterior
mandibular teeth simultaneously
drift lingually and superiorly
The remodelling process involves
a)periosteal resorption on the labial
bony cortex
b)Deposition on the alveolar surface of
the labial cortex
c)Resorption on the alveolar surface of the lingual cortex
d)Deposition on the lingual side of the lingual cortex
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61.  At the same time, bone is progressively added onto the external
surface of the mandibular basal bone area , including the mental
protuberance (chin).
 The reversal between these two growth fields usually occurs at
the point where the concave surface contour becomes convex.
 The result of this two way growth process is a progressively
enlarging mental protuberance
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62. AGE CHANGES IN MANDIBLE
ANATOMICAL
LANDMARK
AT BIRTH ADULT OLD AGE
Mental foramen Near the lower
border (b/w 2
deciduous molars)
Midway between
upper and lower
border
Near upper border
Ramus Vertical in direction Oblique in direction
Mandibular canal Runs little above
mylohyoid line
Runs parallel with
mylohyoid line
Runs close to the
upper border
Angle Obtuse (175˚) 110-120 Obtuse(140˚)
Coronoid process Large and project
above the condyle
condyle Positioned nearly in
the line of body
Condyle above
coronoid
Extreme old age-
bent backwards
Symphysis menti Present;2 halves
united by fibrous
tissue
Represented by
faint ridge- only in
upper part
Not recognizable or
absent
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63. THEORIES OF MANDIBULAR GROWTH
GENETIC THEORY:-
This theory states that all growth is compelled by genetic
influence ie: genetic encoding of mandible determines its
growth.
CARTILAGENOUS THEORY
 This theory states that the cartilage is the primary
determinant of skeletal growth while bone responds
secondarily & passively.
 According to this theory, the condyle by means of
endochondral ossification deposits bone, which tends to
grow the mandible.
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64. ENLOW’S EXPANDING ‘V’ PRINCIPLE
 This theory states that many facial bones or a part of the bone
follows a ‘v’ pattern of enlargement.
Deposition is in the inner surface of of ‘v’ .
Resorption is seen along the outer surface of ‘v’.
CORONOID PROCESS: Deposition –lingualsurface,
Resorption-buccal
CONDYLE PROCESS: Deposition-ant. & post. Margins,
Resorption-buccal & lingual surfaces
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65. ENLOW’S COUNTERPART PRINCIPLE
This principle states that growth of any given facial or cranial
part relates specifically to other structural & geometric
counterpart in the face & cranium
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66. UNLOADED NERVE CONCEPT
The skeletal units &growth fields fulfill the
demand of protection of mandibular nerve
by formation of bone around
The basal tubular portion of mandible
serves as a protection for the mandibular
canal & follows a logarithmic spiral in its
downward & forward movement from
beneath the cranium
The most constant part of mandible is
the arc from foramen ovale to the mandibular
foramen and mental foramen.
The U.N.C. also accounts for stress trajectory alignment & trabecular
structure from condyle to symphysis . The mandi. canal & nerve are
protected by this concentration of trabaculae
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67. SERVO SYSTEM THEORY
 Control of primary cartilages takes a cybernetic form of ‘command’ whereas
control of secondary cartilage like condyle is comprised of both direct effect
of cell multiplication and also indirect effects
Theories of craniofacial growth in the postgenomic area ;semin ortho 2005 ,11:172-83
MUSCLE
FUNCTIONS
actuator
ANTERIOR GROWTH
OF MIDFACE
Reference input
OCCLUSAL
DEVIATION
comparator
Regulation of
inputs-CNS
controller
TRIGGERS –
PROPRIOCEPTIVE
RECEPTORS(MUSCLES &
PERIODONTIUM
CONDYLAR
GROWTH
HORMONAL
FACTORS-
Command
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68. GNOMONIC GROWTH & LOGARITHMIC SPIRAL
A mathematical model was proposed by Moss that describes
mandibular growth along a logarithmic spiral
This was based on D’Arcy Thompsons study on sea-shells
( Nautilus)
Chambered Nautilus
The characteristics of its growth are
 Original shape remains constant,
with increase in size.
 Gnomonic growth can be described
by a curve called as equiangular or
logarithmic spiral
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69. “Gnomon” – that portion or increment
which when added doesn’t alter the shape
but only produces an increase in size
Equiangular or Logarithmic spiral – The growth of the nautilus
follows a particular spiral.
 The important feature of the spiral is
movement of point away from pole along
the radius vector with velocity increasing
with distance from pole
 The angles formed with pole are equal
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70. LOGARITHMIC GROWTH OF MANDIBLE
 Moss found it reasonable to speculate that the pathway of the
inferior alveolar nerve follows a logarithmic spiral
 These foramina (foramen ovale ,mandibular foramen,mental
foramen) are aligned on a curve that fits them all.
 The corpus stays in essentially a horizontal position. At the
same time, the mandible moves down the logarithmic spiral
course of the inferior alveolar nerve.
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71.  The logarithmic spiral formulated
by moss, which coincide with three
foramina of inferior alveolar nerve
and describes path of mandibular
growth.
 Mandible moves to a position where
there is less curvature of spiral
because as the bone lengthens with
growth,the distance between the
foramina increases
 As mandible increase in size, it does
not actually grow up and out ,the
whole spiral rotates clockwise and
corpus remains horizontal
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72. FUNCTIONAL MATRIX THEORY
According to the functional Matrix theory Logarithmic growth is
related to active and passive processes:
Active transformative skeletal growth process occurring at the
level of the skeletal units (histologically discernible).
Passive translative - primary expansive growth of their capsular
functional matrices by an alteration in their spatial position.
As the orofacial capsule expands the embedded mandible is
passively lowered in space. The capsular matrix expansion is
not haphazard but involves postnatal rotation of the inferior
alveolar nerve about an axis passing through fixed axis
(foramen ovale).
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73.  This suggests that anterior positioning of the mental foramen
must be a passive growth event. But the mandibular foramen
actively grows up back and out.
 Hence the distance between the mandibular and mental foramen
increases, as does the distance between Ovale and Mandibular
foramina. All these increases however are allometric.
 The position, angulation, resting lengths and tensions of the
masseter and medial pterygoid muscles tend to be altered by the
passive expansion of the orofacial capsule as a consequence of the
rotation of the logarithmic curve.
- Neuromuscular adaptation
- Neurotrophic regulation
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74. passive growth of oro-facial capsule
primary alterations in resting length
contractile and passive
tension, and /or angulation of
the related muscles
change in the growth of the skeletal units
alter the muscle activity vectors
Active mandibular skeletal growth
CNS
Membrane
conduction
Neuromuscular
Adaptation
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75. PROBLEMS OF MANDIBULAR GROWTH AND THEIR
ORTHODONTIC SIGNIFICANCE
HYPOGNATHISM
Agnathia - mandible may be grossly deficient or absent which
reflects deficiency of neural crest cell tissue in lower part of the
face.
First arch and second arch syndrome – Aplasia of mandible
and hyoid bone.
Micrognathia - a diminutive mandible, occurs in
Pierre Robin’s syndrome
Cat cry syndrome
Mandibulofacial dysostosis
Progeria
Down’s syndrome
Oculo-auriculo vertebral syndrome
Turner’s syndrome
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76. Pierre Robin’s syndrome
 PRS is a sequence, i.e. a chain of certain
developmental malformations, one entailing the
next.
The three main features are cleft palate,
Retrognathia and glossoptosis (airway obstruction
caused by backwards displacement of the tongue)
Hemifacial microsomia
(Goldenhar’s syndrome)
Rare congenital defect characterized by
incomplete development of the ear, nose,
soft palate, lip, and mandible.
It is associated with anomalous development
of the first and second branchial arch
 Clinical manifestations –limbal dermoids,
preauricular skin tags, and strabismus
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77. 773/1/2017 99

78. PROGNATHISM
 Common in males and in conditions like acromegaly
 Anterior and posterior crossbite will be present
 Increased mandibular corpus length on ceph
 Dental and skeletal class III malocclusion
TMJ ANKYLOSIS
 Limited mouth opening
 Unilateral/bilateral OR Osseous /fibrous
 Crossbite on affected side
 Deviation of jaw to affected site while opening
 Flatness or fullness of affected side
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79. CONDYLAR HYPERTROPHY
 Mostly due to genetic or hormonal causes
 Common in males
 Usually expressed in late teen age when the growth of mandible
continues at condyle
 More likely to be a high angle case
 Unilateral-chin divergent on side opposite to hypertrophy
facial assymetry
buccal crossbite on unaffected side
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80. EXCESSIVE TRANSVERSE GROWTH
 Due to genetic reasons
 Common in prognathic patients
 Brachiofacial appearance
 Bilateral crossbite
 Anterior divergent face
 In severe cases there can be total lingual non occlusion-Crocodile bite
POOR TRANSVERSE GROWTH
 Common in hypognathic patients
 Usually class II cases
 Posterior divergent patients
 In severe cases there is complete buccal non occlusion-Brodie’s Bite
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81. PROBLEMS OF RAMAL GROWTH
 EXCESSIVE VERTICAL RAMAL GROWTH
Brachiofacial patients
low angle cases
anterior deep bite
 POOR VERTICAL RAMAL GROWTH
dolichofacial patients
high angle cases
anterior open bite
 EXCESSIVE HORIZONTAL RAMAL GROWTH
More broad oropharynx
 POOR HORIZONTAL RAMAL GROWTH
Narrow oropharynx
Chances of airway embarassment
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82. PROBLEMS OF CHIN GROWTH
PROMINENT CHIN
Common in males
Due to late gonial deposition
Excessive mental bone resorption
Can be treated with genioplasty in adults
DEFECTS DUE TO FAILURE OF FUSION OF PROCESSES
MANDIBULAR CLEFT; Rare condition due
to persistence of furrow between 2
mandibular processes
MICROSTOMIA/MACROSTOMIA;Determined by fusion of maxillary and
mandibular process at their lateral extent 823/1/2017 99

83. SIGNIFICANCE
 Timely identification of growth disturbances helps in
interception of developing malocclusions and other
orthodontic and esthetic facial problems
 Knowing the timing of development of different facial
structures gives you idea about the long term facial
apppearence of the patient
 Timely diagnosis of growth problems gives you a chance to
treat the problem with functional appliances
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84. Role of functional appliances in the growth of mandible
MANDIBULAR DEFICIENCY
A skeletal Class II relationship could be either due to a small
mandible or a normal mandible in posterior position.
 One possibility of treatment is to restrain the growth of maxilla
with extra oral force and let the mandible continue to grow
more or less normally
 Enhancement of mandibular skeletal growth and this is done
with the help of functional appliance which hold the mandible
forward from its retruded position and enhances growth.
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85.  For most mandibular deficient patients: a standard bionator or
activator appliance is used as it is a simple, durable and readily
acceptable appliance.
 If transverse expansion is needed ,buccal loops attached to bionator
or buccal shields of Frankel appliance shields the cirumoral
musculature away and thus helps in transverse expansion
 Twin block appliance comprising of upper and lower acrylic blocks
which works together and helps in positioning lower jaw forward
 The Herbst appliance ,a fixed functional appliance can also be used
to correct class II malocclusion due to retrognathic mandible
 Mandibular anterior repositioning appliance , Forsus appliance,
Cemented twin block can also be used 853/1/2017 99

86. MANDIBULAR EXCESS
 Class III malocclusion because of excessive growth of mandible
are extremely difficult to treat.
 For growth modification, treatment of mandibular excess both
functional appliance and chin cup have been used before and
throughout the adolescent growth spurt.
1.Class III functional appliance (Bionator)
It was designed to rotate the mandible down and back and
produce proper occlusal relation by allowing max.posterior
teeth to erupt down and forward while restraining eruption of
mandibular teeth.
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87.  These appliances also tip the mandibular teeth (incisors)
lingually and maxillary incisors facially.
2.Extra oral force: Chin cup treatment
 Chin cup is attached to head gear for anchorage.
 Extra oral force directed against the mandibular condyle would
restrain growth at that location.
 Chin cup therapy does accomplish lingual tipping of lower
incisors as a result of pressure of the appliance on the lower lip
and dentition and a change in direction of mandibular growth,
rotating the chin down and back.
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88. A study was conducted to evaluate the dental and skeletal effects of chin
cup using two different force magnitudes
 Fifty growing class III patients were divided into three groups.
Patients in group 1 (n = 20) - 600 g of force per side.
Patients in group 2 (n = 20) - 300 g of force per side.
Group 3 (n = 10) no treatment was performed
Lateral Cephalograms were traced and analyzed before treatment and after one year
They concluded that;
 The use of a chin cup significantly improved the mandibular and maxillary
relationship, but with only minor skeletal effects.
 Reduced ramus height and increased the anterior facial height, mandibular
plane angle, and retroclination of the mandibular incisors.
 Use of 600g force had a more pronounced effect in the reduction of ramus
height.
Chin cup effects using two different force magnitudes in the management of Class III
malocclusions,
Yasser L. Abdelnaby and Essam A. Nassar THE ANGLE ORTHODONTIST;SEP.2010 :VOL.8 ,ISS. 5883/1/2017 99

89. ENVELOPE OF DISCREPENCY (william R Proffit ,Ackerman J. L)
It has three envelopes .The perimeter of each envelope gives the
maximum range of movements possible by different methods
INNER ENVELOPE- Only orthodontic treatment
MIDDLE ENVELOPE- Orthodontic &growth modification
OUTERMOST ENVELOPE- Orthodontic & surgical treatment
893/1/2017 99

90. 10
6
5
5
903/1/2017 99

91. CHANGES IN CONDYLAR REGION DURING MYOFUNCTIONAL
APPLIANCE THERAPY
DIFFERENTIATES SOX 9 regulates
FGF-8,BMP 2 type II
collagen syn.
OSTEOGENESIS MATURE
SECRETE
DIFFERENTIATES EXPRESS TYPE X
RECRUITS COLLAGEN
FUNCTIONAL APPLIANCE THERAPY ACCELERATE AND ENHANCE CONDYLAR GROWTH –A.B.M
RABIE,AJODO 2003;123-40-8
Undifferentiated
mesenchymal cells
SOX9
CHONDROBLAST
CARTILAGE MATRIX
CHONDROCYTES
HYPERTROPHIC
CHONDROCYTES
VEGF
NEW BLOOD
CELL
INVASION
OSTEOPROGENITOR
CELLS
OSTEOBLAST
OSTEOCYTES
ENDOCHONDRAL
OSSIFICATION
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92. Different surgical procedures
(I) Mandibular advancement
 Bilateral sagittal split osteotomy: can be used to set back or advance the
mandible
 Inverted L. osteotomy
 C Osteotomy
 Sub apical surgery
BSSO INVERTED ‘L’ SUBAPICAL
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93. (II) Mandibular set back
 BSSO
 Trans oral vertical oblique ramus osteotomy (TOVRO)
 Body ostectomy
 Segmental surgery
TOVRO ANTERIOR BODY OSTECTOMY
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94. Correction of Mandibular Retrognathia and Laterognathia by
Distraction Osteogenesis: Follow up of 5 cases-EUR J DENT2009
Oct; 3(4): 335–342.
 The procedure was carried out in 5 subjects (3 males and 2 females)aged
between 14 years and 27 years.3 Patients had undergone bilateral
distraction osteogenesis and remaining 2 ,unilateral distrctn.osteogenesis
 In patients treated with bilateral mandibular distraction, it was observed
that the ANB angle decreased by a mean of 5°, the mandibular corpus
length increased by a mean of 14.5 mm and the overjet decreased by a
mean of 12.2 mm after treatment.
 In patients treated with unilateral mandibular distraction, a mean of 3.5°
reduction was achieved in ANB angle, the mandibular corpus length
increased by a mean of 5.5 mm and a mean of 7 mm correction was
achieved in relation to craniofacial midline with treatment.
 It can be concluded that distraction of the deformed mandible is a
feasible and effective technique for treating mandibular retrognathia and
laterognathia and that long term relapse is within acceptable limits. 943/1/2017 99

95. Mandibular Growth, Remodeling, and Maturation During Infancy
and Early Childhood(Yi-Ping Liu, Rolf G. Behrents, and Peter H.
Buschang) The Angle Orthodontist-vol.80 Jan 2010
 In a study lateral cephalograms of 24 females and 24 males, taken
between birth and 5 years of age, as well as early adulthood, were
traced and digitized. Five measurements and nine landmarks were used
to characterize mandibular growth, remodeling, and degree of adult
maturity.
Ramus height (Co-Go),Overall length (Co-Gn),Corpus length (Go-Gn),Condylion
angle (Go-Co-Me),Gonial angle (Co-Go-Me)
They concluded that
1. Mandibular size increased 18.2 mm to 34.7 mm between 0.4 and
5.0 years of age.
2. Males displayed greater growth increases for ramus height (Co-Go)
than for corpus length (Go-Gn), and females showed similar changes
3. Gonial angle decreased 2.8° and 2.0° in males and females,
respectively. 953/1/2017 99

96. Regulation of the Response of the Adult Rat Condyle to
Intermaxillary Asymmetric Force by the RANKL-OPG System(Yue
Xua; Tuojiang Wub; Yangxi Chenc; Zhiguang Zhangd) The Angle
Orthod. 2009;79:646–651.
 The mandibular rami of 160 Sprague-Dawley rats (3 months old) were
subjected to unilateral traction in the anterior-superior direction using
an elastic force. (120 & 40 g ,then traction removed after28 days.
 The expression of RANKL and OPG in the subchondral bone of the
condyles was analyzed by semiquantitative immunohistochemistry.
Results:
- Different force levels induced similar changes in the expression of the
OPG protein by28 days.
-The effect of a 120-g elastic force on the expression of RANKL was
stronger than that of a 40-g force. Because of the asynchrony of RANKL
responses to external forces of different values, the values of
RANKL/OPG ratio showed characteristic variation
963/1/2017 99

97. CONCLUSION
Bone growth in mandible is a remodelling process
represented by apposition and resorption.
Knowledge of general facial growth provides a
background to the understanding of the etiology
and development of of malocclusion, such an
understanding is in turn an important part of
diagnosis and treatment planning.
973/1/2017 99

98. REFERENCES
1.HANDBOOK OF FACIAL GROWTH,SECOND EDTN-ROBERT E MOYERS
2.THE HUMAN FACE-DONALD H ENLOW
3.HUMAN EMBRYOLOGY,EIGHTH EDITION-INDERBIR SINGH
4.ORTHODONTIC CURRENT PRINCIPLES & TECHNIQUE,FIFTH EDITION-
T.MGRABER
5.CONTEMPORARY ORTHODONTICS,FIFTH EDITION-WILLIAM R PROFITT
6.DENTOFACIAL ORTHOPEDICS WITH FUNCTIONAL APPLIANCES-
GRABER,RAKOSI,PETROVIC
7.CRANIOFACIAL DEVELOPMENT-GEOFFREY H SPERBER
8.PRENATAL DEVELOPMENT OF HUMAN MANDIBLE.THE ANATOMICAL
RECORDS 263:314-325(2001)
9.GROWTH OF MANDIBLE DURING PUBESCENCE-ROCHE,LEWIS AO OCT
1982
10.AGE RELATED DIFFERENCE IN RAMUS GROWTH-ENLOW,HANS AJO
DEC.1995
.
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99. 11. VARIATION IN GROWTH PATTERN OF HUMAN MANDIBLE;A
LONGITUDINAL RADIOGRAPHIC STUDY BY IMPLANT METHOD-
ARNE BJORK ;J DENT RES 1963
12.CORRECTION OF MANDIBULAR RETROGNATHIAAND
LATEROGNATHIA BY DISTRACTION OSTEOGENESIS-EUR J DENT
2009 OCT:3(4);335-342
13. MANDIBULAR GROWTH,REMODELLING AND MATURATION
DURING INFANCYAND CHILDHOOD-ROLF G BEHRENTS,PETER H
BUSCHANG-AO JAN.2010
14.THEORIES OF CRANIOFACIAL GROWTH IN POSTGENOMIC
ERA;DAVID S CARLSON: SEM ORTHO ,2005 11:172–183
15. REGULATION OF THE RESPONSE OF THE ADULT RAT CONDYLE TO
INTERMAXILLARY ASYMMETRIC FORCE BY THE RANKL-OPG
SYSTEM-YUE XUA,TUOIJANG WUB.THE ANGLE ORTHODONTIST
2009;79,646-651
16.FUNCTIONALAPPLIANCE THERAPY ACCELERATE AND ENHANCE
CONDYLAR GROWTH –A.B.M RABIE,AJODO 2003;123-40-8
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