Controlling factors in craniofacial growth /certified fixed orthodontic courses by Indian dental academy

CONTROLLING FACTORS IN CRANIOFACIAL
GROWTH

INDIAN DENTAL ACADEMY

Leader in continuing dental
education
www.indiandentalacademy.com

www.indiandenatalacademy.c
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INTRODUCTI
ON

It is commonly said that growth is
strongly influenced by genetic factors.
also by

 Environment
 Nutritional status
 Degree of physical activity
 Health or illness
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Since need for orthodontic
treatment is created by
disproportionate growth of the
jaws,
in order to understand the the
etiological processes of
malocclusion,it is necessary to
learn how facial growth is
influenced and controlled
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Lot of effort has been put in recent
years in understanding growth
control.
Exactly what determines the growth
of the jaws,however remains unclear
and continues to be the subject of
intensive research
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genetic factors
The basic control of growth both in magnitude &
timing, is located in genes.
Studies of twins have shown that

body size
body shape
deposition of fat
patterns of growth
are all more under genetic control
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Samir bishara

Genetic factors most likely play a
leading role in male- female
growth differences

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Neural control
It is thought that a growth center
exists in the region of the
hypothalamus, which keeps children on
their genetically determined growth
curves.
There is also evidence that the
peripheral nervous system plays a
part in growth control.
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Samir bishara

Hormonal control
Probably all of the endocrine glands influence
growth.
Growth hormone maintains the growth from
the birth onwards.
Excess of growth hormone – pituitary giant.
Pituitary deficiency – dwarf.

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moyers

Nutrition
Sufficient in take of nutritious food is
essential for normal growth.
Malnutrition involves deficiency in
calories and required food elements.
Under nutrition tends to accentuate the
normal differential growth of the body
tissues.
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Secular Trend
There is considerable evidence that
Children today have growing faster
than they grew in the past.
Although Children are growing at a
faster rate, they are stopping growth
sooner.
moyers
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Season and circadian
Rhythm
Growth in height is faster in the spring
than in the autumn.
There is evidence that growth in height
and eruption of teeth is greater at night
than in the day time.
The reason for this differences is
probably related to fluctuations in the
hormone release.
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Samir bishara

Disease
The effects of disease are similar to those
of malnutrition.
After an illness, a catch up growth period
usually brings the child back to the
predetermined growth curve.

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Cultural factors
Males of Japanese born near the
middle of the century in the
united States grew taller on
average than groups born in Japan
because of different cultural
influences.
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Samir bishara

According to moyers

Controlling
factors
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Controlling factors
NATURAL
 Genetics
 function
 general body
growth

neurotrophis
m

DISRUPTIVE
FACTORS

• orthodontic
forces
• surgery
• malnutrition
• malfunctions

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NATURAL FACTORS

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Genetic factors

One can often say that all resemblances in
families are genetic & structural.
Facial expression,mode of laughter,way of
speaking may be learned as a result of living
together.
The old argument about heredity versus
environment has changed from the question of
which is more important,how,when,and in what
way does the environment alter the original form
laid down by heredity
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Intrinsic genetic factors

primary

secondary
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There are primary controls for
initiation & formation of facial
structures.
Primary genetic control
determines certain initial
features:
Tooth buds calcify in the jaws,&
mandible forms in face,not legs
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Secondarily,there are
inductive local feedback &
inner communication
mechanisms between cells
& tissues
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Although it is argued
whether or not there is
simple genetic
control,the end result
appears to be
multifactorial or poly
genic.
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function
Normal function plays a role in
skeletal growth.
Altered function hampers growth
like
 TMJ Ankylosis
 Aglossia
 Neuromuscular disorder
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general body
Biological maturity growth role in all
plays a general
aspects of maturation of individual.

All maturational events are influenced in
individuals by a combination of factors
 Genetic
 Climatic
 Racial
 Nutritional
 socioeconomic

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neurotrophism

It is known that neural activity
controls muscle activity & growth.
Nervous control of skeletal growth,
assumedly by transmission of a
substance through the axons of the
nerves has been hypothesized for
years and is called neurotrophism.
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DISRUPTIVE FACTORS

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Disruptive factors in facial growth
are those which do not routinely
contribute to normal variation but
when they appear in the individual
may be important.
They may be
elective,environmental, or
congenital in origin.
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a) Orthodontic forces

Orthodontic forces
are utilized to affect
growth & alter tooth
positions.
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b) surgery
Orthognathic surgeries are undertaken
for,
To correct a craniofacial anomaly
To improve aesthetics in nonanomalous
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Modern surgical
techniques have improved
surgeons ability
• Relapse of the surgical
result ,even in non growing
• Effects of surgery on
subsequent growth
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C) malnutrition

Gross malnutrition affects
craniofacial growth

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D) malfunctions
The altered malfunction can play a
role in craniofacial morphology &
well documented.
(Harvold,Petrovic,Mcnamara and
Carlson)
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Controlling factors

According to Ranly

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Local epigenetic factors
General epigenetic factors

Local environmental factors
General environmental factors
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Genetic factors
inherent to the
osseous tissues
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bone

nucleus

Form
of
osseous
tissue

Genetic
material
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Local epigenetic factors

Genetically
determined influence
originating from
adjacent structures
and spaces
Brain eyes etc

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eyeball

orbit
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General epigenetic factors

Genetically
determined
influences
originating from
distant structures
Sex hormones

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Local environmental factors
Local non-genetic influences
originating from the
external environment
(local external pressure
muscle forces etc)
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Morphology of bone
gets altered
according to the
functional demands
placed on it
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General environmental factors

General non-genetic
influences
originating from
the external
Food & oxygen supply etc
environment
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Determinants
of facial
growth
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Three major theories
in recent years have
attempted to explain
the determinants of
craniofacial growth
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1
Bone like other tissues is the primary
determinant of its own growth.
That is genetic control is expressed at
the level of the bone,& therefore its
locus should be the periosteum.
Dominant view until the 1960’s has
largely been discarded.
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2

Cartilage is the primary
determinant of skeletal
growth,while bone responds
secondarily and passively.

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3
The soft tissue matrix in which
the skeletal elements are
embedded is the primary
determinant of growth,& both
bone and cartilage are secondary
followers.
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Site versus center
A site of growth is merely a location at
which growth occurs.
Center is a location at which independent
(genetically controlled) growth occurs.
All centers of growth also are sites,but
the reverse is not true.
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Bone ,suture, & periosteum were considered as
growth centers.
It is clear now that sutures & the periosteal
tissues, are not primary determinants of
craniofacial growth.
Evidence which lead to this conclusion
(1) When an area of the suture ,between two facial
bones is transplanted to another location,the
tissues does not continue to grow.
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Lack of innate growth potential

(2) It can be seen that growth at the sutures will respond
to outside influences under a number of circumstances.

If facial bones are mechanically pulled
apart at the sutures,new bone will fill in.

distraction osteogenesis
If a suture is compressed, growth at
that site will be impeded
use of head gear
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THUS SUTURES MUST BE
CONSIDERED AREAS THAT
REACT-NOT PRIMARY
DETERMINANTS

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Cartilage as a
determinant of
craniofacial
growth
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For many bones, cartilage does the growing
while bone merely replaces it making this
theory attractive for jaw bones.
If cartilaginous growth were the primary
influence,the condylar cartilage could be
considered pacemaker for growth of that
bone.
Remodeling of ramus & other surface
change-----secondary to primary cartilaginous
growth.
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visualize the mandible like diphysis
of long bone bent into horse shoe
shape with epiphyses removed.
cartilage at the end should behave
like a growth center.

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Long bone bent as horse
shoe-shape

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Growth of the maxilla
 More difficult but not impossible
to explain on a cartilage theory basis.
 There is no cartilage in the maxilla
itself,but there is a cartilage in the
nasal septum.
 Proponents of cartilaginous theory
hypothesize that the cartilaginous
nasal septum serves as a pacemaker.
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The cartilage is so located that the its
growth could easily lead to a downward and
forward translation of the maxilla.
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two kinds of experiments have been
carried out to test the idea that
the cartilage serves as a true
growth center.
 transplanting the cartilage
 removing the cartilage at an early
age
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Transplantation experiments
demonstrate that not all skeletal
cartilage acts the same when
transplanted.
If a piece of the epiphyseal plate of
long bone is transplanted,it will continue
to grow in a new location or in
culture,indicating that these cartilages
do have innate growth potential.
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 Cartilage from spheno-occipital
synchondrosis of the cranial base also
grows when transplanted,but not as
well
 It is difficult to obtain cartilage
from the cranial base,particularly at
an early age when the cartilage is
actively growing

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In experiments,transplanting
cartilage from the nasal septum
,sometimes it grew ,sometimes it
did not
 In precise recent experiments
,nasal septal cartilage was found to
grow nearly as well
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Little or no growth was observed when the
mandibular condyle was transplanted.
From these experiments,the other cartilages
appear capable of acting as growth
centers ,but the mandibular condyle does not

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Experiments to test to the effect of
removing cartilage.
The impact on a growing rabbit of
having a segment of cartilaginous
nasal septum removed.

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 In summary, it appears that epiphyseal
cartilages and the cranial base
synchondroses can & do act as growing
centers, as can the nasal septum.
 Neither transplantation experiments nor
experiments in which the condyle is
removed lend any support to the idea that
the cartilage of the mandibular condyle is
an important center.
 Growth at the mandibular condyle is
more like growth at the sutures of the
maxilla
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Functional matrix theory
growth

 If neither bone nor cartilage were the
determinant for growth of the craniofacial
skeleton, it would appear that the control
would have to lie in the adjacent soft
tissue.
 This was put forward by moss in 1960

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 He theorizes that growth of the face
occurs as a response to functional
needs & neurotrophic influences, & is
mediated by the soft tissue in which
the jaws are embedded.
 The soft-tissue grow & both bone &
cartilage react.

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example
The growth of the cranial vault is a direct
response to the growth of the brain.
Microcephaly: when the brain is very
small,the cranium is also very small
Hydrocephaly: reabsorption of CSF is
impeded ,intracranial pressure builds up
which impedes development of the brain.
Another excellent example is size of the eye
& size of the orbit
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normal

Anencephaly

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conclusion
Growth is a interplay between
heredity and environment.In coming
years we are going to witness intense
research in this field ,which may lead
us to control growth at will ?
om

www.indiandentalacademy.com
Leader in continuing dental education

www.indiandenatalacademy.com

Controlling factors in craniofacial growth /certified fixed orthodontic courses by Indian dental academy

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