Growth and development of the mandible/prosthodontic courses

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

CONTENTS
 Introduction
 Definitions
 Importance of growth and development
 Mechanism of bone formation
 Theories of growth
 Prenatal and postnatal growth of maxilla
 Age changes in maxilla
 Prenatal and postnatal growth of mandible
 Age changes in mandible
 Developmental disturbances of jaws
 Prosthodontic considerations
 Conclusion
 biblography www.indiandentalacademy.com

INTRODUCTION
 A thorough background in craniofacial growth and
development is necessary for every dentist. It is
difficult to comprehend conditions observed in adults
without understanding the developmental processes
that produced these problems.
 It is also important to distinguish normal variation
from the effects of abnormal or pathologic process.
 Since dentists are heavily involved in the
development of not just the dentition but the entire
dentofacial complex, a through understanding of not
only the pattern of normal growth but also of the
mechanisms that underlie it is very essential

DEFINITIONS OF GROWTH
 “Growth refers to increase in size” - Todd.
 “Growth usually refers to an increase in size
and number” – Proffit.
 “Change in any morphological parameter which is
measurable”- Moss
 “Self multiplication of living substance”-
J.S.Huxley.

DEFINITIONS OF DEVELOPMENT
Development is a progress towards maturity”
– Todd
“Development refers to all naturally occurring
progressive, unidirectional, sequential changes in
the life of an individual from it’s existence as a
single cell to it’s elaboration as a multifunctional
unit terminating in death” – Moyers

Importance of growth and
development :
 To determine the growth deviation of particular individual, we
study normal health variations.
 In order to make accurate description of growth observations,
corresponding precise information about the normal state
must be available.

 Changes in the pattern of growth that occur over a
period of time within representative samples of
population are valuable indicators of changes in
general health and nutritional status of the
populations.
 It would not be possible to design and conduct
investigation regarding control mechanism of growth,
if no precise data were available describing the
resultant somatic effect.

MECHANISMS OF BONE
GROWTH
 Cortical drift : It is the
growth movement (relocation
or shifting) of an enlarging
portion of a bone by the
remodeling action of its
osteogenic tissues towards
the depository surface.

 Displacement : It is the movement of the whole
bone as a unit. Displacement can be of two types.
 Primary displacement : If a bone gets displaced
as a result of its own growth, it is called primary
displacement.
 Secondary displacement : If the bone gets
displaced as a result and growth and enlargement of
an adjacent bone, it is called secondary displacement

OSTEOGENESIS
 Intramembranous ossification
 Endochondral ossification

INTRAMEMBRANEOUS
OSSIFICATION
 At site of bone formation mesenchymal cells become
aggregated
 Mesenchymal cells lay down bundles of collagen
fibres
 At initial site of ossification mesenchymal cells
differentiate into osteoblasts
 Osteoblasts deposit osteoid
 By deposition of calcium salts osteoid converts into
bony lamella(primary trabecular bone)

Through reorganisation primitive trabecular
bone & compact bone converted to mature
bone.

ENDOCHONDRAL OSSIFICATION
 Formed by transformation of cartilage “bone models.”
 Mesenchymal condensation –some differentiated
cells become chondroblasts and lays down
cartilage,cells on surface of cartilage form
perichondrium.
 Intercellular substance surrounding cartilage calcify ,
nutrition cut off , cells die ,PRIMARY AREOLAE.

 Periosteal bud eats away the
calcified matrix- large cavities –
SECONDARY AREOLAE.
 Osteogenic cells become
osteoblasts , lay down osteoid.
 Bone deposited– lamellar bone
– primary ossification centre.

THEORIES OF GROWTH
 Genetic theory :Brodie in 1941 This theory states
that all growth is controlled by genetic influence and is
pre-planned. This is one of the earliest theories put
forward.

 Sicher’s hyposthesis of sutural dominance :
(Sicher in 1947) Sicher deduced from the many
studies using vital dyes that the sutures were causing
most of the growth. The primary event in sutural
growth is the proliferation of the connective tissue
between the two bones.
 If the sutural connective tissue proliferates, it creates
the space for oppositional growth at the borders of
the two bones. Replacement of the proliferating
connective tissue was necessary for functional
maintenance of the bones.

 Scott’s Hypothesis of nasal septum :
(Cartilaginous theory) (Scott in 1948)
According to scott, intrinsic growth controlling
factors are present in cartilage and periosteum with
sutures being only secondary. He viewed the
cartilaginous sites throughout the skull as primary
centres of growth.
 Ex : Growth of the maxilla is attributed to the nasal
septal cartilage. According to scott, the nasal septal
cartilage is the pacemaker for growth of the entire
naso – maxillary complex.

 Moss Hypothesis of functional matrix :
(Melvin Moss in 1960)
 Most felt that bone and cartilage lack growth
determination and growth in response to intrinsic
growth of the associated tissues, noting that the
genetic coding for craniofacial skeletal growth is
outside the bony skeleton. He terms the associated
tissues “functional matrices”
 Moss argues the skeletal tissues grow only in
response to soft tissue growth. The effect is a
passive translation of skeletal components in
space.

 Van Limborgh’s Theory (1970) : A multi-
factorial theory was put forward by van limborgh he
explains the process of growth and development in
a review that combines all the 3 existing theories,
the functional matrix theory of moss, sichers theory
and Genetic theory.

PRENATAL GROWTH OF
MAXILLA
 Around the 4th
week of
intrauterine life a shallow
depression corresponds to
future mouth appears –
stomodeum.
 Five branchial arches form in
region of future head and neck.
 1st
branchial arch is called the
mandibular arch and place an
important role in development
of naso-maxillary region.
 Stomodeum is overlapped
superiorly by frontonasal
process.

 The mandibular arches of both sides form lateral
walls of stomodium.
 Mandibular arch gives off a bud from its dorsal end
called maxillary process.
 Maxillary process grows ventro-medio-cranial to
mandibular arch to form mandibular process.
 The mandibular process grow medially and fuse to
form the lower lip and lower jaw.

DEVELOPMENT OF PALATE
 Palate is formed by contribution of –
1. Maxillary process.
2. Palatal shelves given off by maxillary process.
3. Frontonasal process

POSTNATAL GROWTH OF
MAXILLA
 Post – natal growth of maxilla :
the growth of the naso-maxillary complex is
produced by the following mechanisms

Displacement

Growth at sutures

Surface remodeling

Primary displacement
A primary type of
displacement is seen in a
forward direction by growth of
the maxillary tuberosity in a
posterior direction. This results
in the whole maxilla being
carried anteriorly. The amount
of this forward displacement
equals the amount of posterior
lengthening. This is a primary
type of displacement as the
bone is displaced by its own
enlargement.www.indiandentalacademy.com

A passive or secondary
displacement of the naso-
maxillary complex occurs in a
downward and forward direction
as the cranial base grows. The
nasomaxillary complex is simply
moved anteriorly as the middle
cranial fossa grows in that
direction.

GROWTH AT SUTURES
 The maxilla is connected to the cranium
and cranial base by a number sutures which
include
 Fronto – nasal suture
 Fronto – maxillary suture
 Zygomatico – temporal suture
 Zygomatico – maxillary suture
 Pterygo – palatine suture

 These sutures are all oblique and more or less
parallel to each other. This allows the downward and
forward repositioning of the maxilla as growth occurs
at these sutures.
 As growth of the surrounding soft tissue occurs,
the maxilla is carried downwards and forwards. This
leads to opening up of space at the sutural
attachments. New bone is formed on either side of
the suture. Thus the overall size of the bones on
either side increases. Hence a tension related bone
formation occurs at the sutures

SURFACE REMODELLING
 In addition to the growth occurring at the sutures
massive remodeling by bone deposition and
resorption occurs to bring about
 Increase in size
 Change in shape of bone
 Change in functional relationship

BONE REMODELLING CHANGES SEEN
IN THE NASO MAXILLARY COMPLEX
 The floor of the orbit faces
superiorly, laterally and
anterioirly . surface
deposition occurs here
resulting in growth in a
superior, lateral and
anterior direction.
 Bone deposition occurs
along the posterior margin
of the maxillary tuberosity
causing lengthening of the
dental arch and
enlargement of the A-P
dimension of the entire
maxillary body. This helps
in accommodating the
erupting molar.

Bone resorption
occurs on the lateral
wall of the nose
leading to an
increase in size of
the nasal cavity.
Bone resorption is
seen on the floor of
the nasal cavity. To
compensate this,
there is bone
deposition on the
palatal side. Thus a
net downward shift

The zygomatic bone
moves in a posterior
direction. This is achieved
by resorption on the
anterior surface and
deposition on the
posterior surface.
The face enlarges in
width by bone formation
on the lateral surface of
the zygomatic arch and
resorption on its medial
surface. www.indiandentalacademy.com

 As the teeth starts erupting, bone deposition
occurs at the alveolar margins which increases the
maxillary height and the depth of the palate.
 The entire wall of the sinus except the mesial wall
undergoes resorption, resulting in increase in size
of the maxillary antrum.

AGE CHANGES IN MAXILLA
 At birth
 The transverse and sagital maxillary dimension
are greater than the vertical
 The frontal process is prominent
 The body consists of little more than alveolar
process, its alveoli reaching almost to the orbital
floor
 Maxillary sinus is a mere furrow on the lateral
nasal wall.

 In Adults : The vertical diameter is greatest owing
to the development of the alveolar process and
enlargement of the sinus
 In the old age
If all teeth are lost, the bone reverts to the infantile
shape. Its height diminishes, the alveolar process is
absorbed and lower parts of the bone contracted and
reduced in thickness at the expense of the labial wall

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

Prenatal growth of the
mandible

Neural crest cells
I branchial arch
Mandibular
process
Mandibular
bone
CT tissue

Ectomesenchymal
condensation
Lateral to Meckels
cartilage
Osteogenic membrane
mandible

6th
week
Ossification centre

10th
– 14th
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

 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
 8 weeks - mandible > maxilla
 11 weeks - mandible = maxilla
 13 – 20 weeks maxilla > mandible
At birth
 Mandible tends to be retrognathic
 Post natal life - corrected
During fetal life

Post natal growth of the
mandible

Main sites of post natal growth
in the Mandible
 Condylar cartilage
 Posterior border of the Rami
 Alveolar ridges

Symphysis Menti
 Limited growth till
fusion
 No widening
after fusion

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

Condylar cartilage
 Secondary cartilage
 Important contribution to the overall
length of the mandible

Lingual Tuberosity
 Grows posterior
and medial by
deposition
 Resorptive field
below-
Lingual fossa

Coronoid Process
 Lingual surface
 Follows ‘v’ principle
POSTERIOR
SUPERIOR
MEDIALLY


‘ v ‘
principle of
Enlow
CORONOID PROCESS

Coronoid Process
 ‘’V’ PRINCIPLE OF ENLOW

Coronoid Process
 Deposition on lingual side
 Resorption - buccal surface
MEDIAL POSTERIOR
GROWTH
INCREASES
VERTICAL
LENGTH

RAMUS
 Posterior border -
deposition
 Anterior border -
resorption

Ramus
 Superior part of
ramus below sigmoid
notch
 Lower part of ramus
below the Coronoid
process
BUCCAL -
DEPOSITION
LINGUAL -
RESORPTION
LINGUAL
-DEPOSITION
BUCCAL -
RESORPTION

Ramus

Posterior border of Ramus
 Depository and keeps pace
with condylar growth
 Angle of growth
 Posterior margin below
condyle --resorptive field
vertical horizontal

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

Classical Pattern

Ramus corpus junction
 Inferior Border of
junction - resorption
 Forms Antegonial
notch

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

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
 CORONOID Temporalis
 RAMUS and
GONIAL ANGLE Masseter & Medial
pterygoid
 CONDYLE internal pterygoid
Tongue, perioral muscles --- Over all growth
MOSS

Skeletal units of mandible

Role of muscles in Mandibular
growth
 Decrease muscle activity
Flattening of
Gonial angle
Reduction of
Coronoid process

AGE CHANGES IN
MANDIBLE
AT BIRTH :
 The two halves of the mandible are united by a
fibrous symphysis menti.
 At this stage the body is a mere shell, enclosing
imperfectly separated sockets of deciduous teeth.
 The mandibular canal is near the lower border
 The mental foramen opens below the first deciduous
molar and is directed forwards.
 The coronoid process projects above the condyle
 The angle of the mandible is obtuse (above
140degrees or more) because the head is in line with
the body.

IN ADULTS :
 The mental foramen opens midway between the
upper and lower borders as the alveolar and sub-
alveolar regions are about equal in depth.
 The mandibular canal nearly parallels the mylohyoid
line
 The angle between the lower border of the body and
a plane touching the posterior surface of the condyle
above and ramus below diminishes as ramal height
increases with age (about 110 –120degrees)

In OLD AGE :
 Bone is reduced in size as teeth are lost and alveolar
region resorbed
 The mandibular canal and the mental foramen are
nearer the superior border
 The ramus becomes oblique as angle becomes
obtuse (140degrees) and the neck inclined
backwards.

Developmental disturbances
of the jaws
 Agnathia : Agnathia is an extremely rare
congenital defect characterized by absence of
the maxilla or mandible. More commonly only a
portion of one jaw is missing.
 Micrognathia : It likely means a small jaw.
Many cases of apparent micrognathia are due
not to an abnormally small jaw in terms of
absolute size, but rather to an abnormal
positioning or an abnormal relation of one jaw to
the other or to the skull which produces the
illusion of micrognathia.

 Macrognathia : It refers to the condition of
abnormally large jaws. It may be associated with
 Pagets disease
 Acromegaly
 Leontiasis ossea, a form of fibrous dysplasia.
 Facial hemihypertrophy :- Here there is a very mild
degree of facial asymmetry. The etiology is
unknown, but it may be due to
 Hormonal imbalance
 Incomplete twinning
 Chromosomal abnormalities
 Vascular abnormalities and
 Neurogenic abnormalities

 Here there is enlargement of one half of the head.
This disproportion may be seen with birth and may be
maintained throughout life.
 The dentition of the hypertrophic side, is abnormal in
three respects.
 Crown size
 Root size and shape
 Rate of development
 There is no specific treatment except for cosmetic
repair.

 Facial hemiatrophy : (Parry-Romberg syndrome;
romberg syndrome; Hemifacial atrophy)
 It is a progressive atrophy of some or all of the
tissues on one side of the face, occasionally
extending to other parts of the body. The etiology is
unknown.
 As the dental effects the hemiatrophy of the lips
and the tongue is reported, the roots of the teeth may
exhibit deficiency of root development and reduced
growth of the jaws on the affected side. Eruption of
teeth on the affected side may also be retarded.
There is no specific treatment.

 Cleft lip and cleft palate
cleft lip occurs due to failure of fusion of maxillary
process with the medial and lateral nasal process.
cleft palate is due to failure of fusion between
maxillary process and frontonasal process.
they can be treated by surgical management or by
fabrication of passive obturator.

PROSTHODONTIC
CONSIDERATIONS
BOUCHER :
 During 1st year after extraction, the reduction of
residual ridge height in the midsagittal plane is about
2-3 mm for maxilla and 4-5 mm for mandible. After
healing resorption continues but with decreased
intensity. Rate of reduction in maxilla annually is
generally 4 times less than mandibular (about 0.1-0.2
mm).


 One of the dental problem in an aged is excessive
bone resorption. The supporting bony tissue
undergoes resorption to a greater or lesser degree.
The crest of the residual alveolar ridge is usually
found to be concave or flat and can terminate in a
knife edge. In extreme cases the layer of bone
overlying mandibular canal may be resorbed
completely leaving a thin layer of oral epithelium as
the only protection to the exposed canal.

 A potential source of discomfort in marked senile
atrophy is compression of nerve ending between
sharp vertical bony projections & thin mucosal
covering by a hard denture base particularly in the
anterior mandibular region. The soft tissue is unable
to distribute forces during mastication.
 The presence of denture on an exposed mental
nerve emerging form mental foramen can cause pain
and paresthesia of lower lip and chin. Pressure on
mandibular canal by a prosthesis can also be most
annoying to the patient. Best treatment is careful
relief.

 A case report presented at the university of pittsburgh
where dental treatment of 4year old boy included
extraction of deciduous teeth and construction of
immediate complete denture. absence of primary
teeth effected the development of jaws.
 During three years edentulous period general growth
pattern of facial component was within normal limits.
 By end of edentulous period both jaws demonstrated
deficiency in the growth in vertical plane. mandible
appeared to be prognathic and longer antero-
posteriorly .

 Reduced height of face was attributed to the
presence of complete denture which resulted in
certain amount of resorption or lack of alveolar
growth.
 So this case report support that the dynamic
equilibrium of the patients bones, joints and muscles
have established and it should not be violated

CONCLUSION
 “Life is change; for when you are through changing,
you are through” – BRUCE BARTON
 As moyers defined growth as the normal
changes in the amount of living substance and
development as the normal sequential events that
encompass between fertilization and death. A
knowledge of growth and development is the
precious key to grasp and the form and direction of
anatomical structures. It is a vital key to the mastery
of the aberrant as well as the normal.

References

Human Embryology : Inderbir singh, 7th edition
 Oral Histology and Embryology : Orbans
 Oral Histology : Richard tencate, 5th edition
 Oral Pathology : Shafer, 3rd edition
 Prosthodontic Treatment For Edentulous Patients :
Boucher’s 11th edition.
 Craniofacial Embryology : G.H. Sperber, 2nd edition
 Orthodontics : S.I. Bhalajhi, 1st edition
 Contemporary Orthodontics : Profitt, 2nd edition
 Facial Growth : Enlow, 3rd edition
 Handbook of Orthodontics : Moyers, 2nd edition

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