Theories of growth /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


Why - Since we deal most of the times
with treatment of disproportionate
jaws, it is necessary to learn how
skeletal growth is influenced and
controlled.


Scientific revolution –
Carlson
the
representation
of
changes in normal
science wrought by
the introduction of
new paradigms.
Normal science – Kuhn the research findings
generally agreed to
be basic to a scientific
field.
Paradigm - the current
conceptual
frame
work of a research
field.

INDEX
Relevant terminologies
Remodeling theory
Genetic concept
Sutural dominance hypothesis
Scott’s hypothesis
Functional matrix hypothesis
FMH revisited
Van –Limborgh’s concept
Petrovics hypothesis
Modern Composite

Terminologies
Growth site:
All surfaces of bones are covered by irregularly
arranged growth fields. These can be either
resorptive or depository. Growth fields having a
special role in the growth of particular bones are
C/as growth sites (e.g. mandibular condyle).
Growth center:
Growth centers are locations where growth takes
place
independently
(mostly
genetically
controlled). They grow even when transplanted to
other areas. They produce a tissue separating
force, that facilitates bone deposition until the
stretch is relaxed (tension created on the adjacent
bones).

All growth centers are growth sites but the
reverse is not true.

Remodeling theory
Remodeling theory was proposed by Sanstedt
(1980). It postulated that all of the craniofacial
skeletal growth occurs exclusively by selective
addition and resorption of bone.


The scientific basis :
Bone grows appositionally at surfaces.
Jaw growth characterized by deposition of bone
on the posterior surfaces.
Calvarial growth by deposition on ectocranial
surface and resorption on endocranial surface.


Support
Belchier, Duhamel, Hunter performed experiments
involving vital dyes and concluded that growth
of the maxilla and mandible takes place primarily
by means of the addition of bone on their
posterior aspects

Against
Stressed on the nature of bone growth rather than
on craniofacial growth


Genetic concept
This concept originated with the advent of classical
Mendelian genetics. Later with the blending of
data from vertebral paleontology, the neoDarwinian synthesis was created, a currently
accepted paradigm of phylogenetic regulation.


Genetic concept stipulates that the genotype
supplies all the information required for
phenotypic expression.

Moss also stated in his thesis that the whole plan
of growth, the various operations carried out, the
order and site of growth and their co-ordination
with other systems are all embossed in the
nucleic acid message.


Support
Brodie (1940) noted the persistent pattern of
facial configuration and assumed it was under
tight genetic control.
Consistent with the above is the observation
that it is possible to predict features of children
from cephalometric data of parents.
This was also supported by Weinmann and
Sicher.


However Moyers maintained that there are
primary controls for the initiation and formation
of facial structures.
Van Limborgh reports after conducting
experimental studies on chick embryos that the
intrinsic genetic information necessary for the
differentiation of cranial cartilages and bone is
supplied by neural crest cells.
Bony initiation and formation
neural
crest cells
Intrinsic genetic information
Bony initiation and formation
genes of
muscles
extrinsic genetic information

Against
the highest correlation between parents and
progeny is
r=0.5
prediction of only
25% of variability
“ Not more than 1/4th of the variability of any
dimension in children can be explained by
considering that dimension in parents.
( R.E.Moyers)

After the general assumptions were found to be
flawed it was believed that some parts are
genetically controlled while some are not or that
certain parts are more controlled by heredity
than the others.
Later research was focused on identifying the
growth sites under the genetic control. The
sutures, craniofacial cartilages and periosteum
were thought to be under the genetic control
and act as growth sites


It was believed that the cartilages were under
genetic control but the vault sutures were
passive or the brain determined the vault
dimensions. This thinking was termed as

“Orthodontic Calvinism” by Wendel Wylie


These ideas were contested by Moyers via
experiments with
Electromyography studies of craniofacial
musculature
Animal studies carried out in neonatal rats


At the end of all this it is concluded that “ the
inheritance of facial dimensions is polygenic”
(R.E.Moyers)
It is also pointed out that “ it is fallacy that the
genome, the totality of DNA molecules, is the
main repository for the developmental
information i.e. there exists a genetic program
or a blueprint theoretically capable of creating
an entire organism” (A.J.O. 1995)


Sutural Dominance
Theory
This theory was proposed by Sicher and supported
by Weinmann.


Sicher called it the sutural theory even though he
held
sutures
cartilages
periosteum
responsible for facial growth and assumed that
all these were under tight intrinsic genetic
control.


“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 appositional growth at the
borders of the two bones”.
After his many studies using vital dyes he
maintained that
sutures have autonomous growth potential
Are growth centers
Act as independent growth centers

Support
Sicher and Weinmann explained that growth of
nasomaxillary complex in a downward and
forward direction is due to growth at sutures
which attach the complex to cranium which are
parallel and oblique
Sutures:
Frontomaxillary
Zygomaticomaxillary
Zygomaticotemporal
Pterygopalatine

Against
1.Sutures and periosteal tissues are not primary
determinants of growth
Transplantation studies
When the suture was transplanted into a different tissue the
suture doesn’t continue to grow as assumed earlier that
they had an innate growth potential.

Growth at sutures responds to outside influences
Microcephaly
Hydrocephaly
Anencephaly

Sutures must be considered areas that react not
primary determinants.

2. Sicher’s theory that bones are pushed apart by
connective tissue growth at the sutures was
contested by Babula, Dixon and Smiley.

Bone membrane is pressure sensitive
Bone-bone push causes compromised blood supply
Necrosis of osteogenic membrane

Actual stimulus for bone growth is the tension
created by functional matrices which are
expanding and hence deposition takes place at
the sutures which are tension adaptive and
responds by bone deposition.

3. Rumlink (1988) pointed out that all the sutures
are not parallel and oblique.


Cartilaginous
Dominance Theory
Proposed by James Scott an Irish Anatomist


Intrinsic growth controlling factors are
present in
Cartilage
Periosteum

And sutures are only secondary and
dependent on extrasutural influence


Cartilaginous parts of skull are responsible for cranial
growth
Nasal septum a major contributor in maxillary growth
Condyle determines growth of the mandible

Cranium

Nasomaxillary

Cranial base
Synchondroses
Nasal septum

Complex Mandible

Condyle


Pacemakers/
Growth Centers

In case of the mandible
this can be explained
by visualizing it as the
diaphysis of a long
bone bent into a
horse shoe shape
with the epiphysis
removed, so that
there is cartilage
representing half an
epiphyseal plate at
the ends representing
the mandibular
condyles.

Support
Pressure and tension have little effect on
cartilaginous
growth.
On
the
contrary,
intramembranous bone is immediately responsive.
Hunter and Enlow – growth equivalent theory relatively lesser response of the endochondral
cranial base as opposed to immediate response of
the intramembranous cranial vault to external
influences
Experimental research on rats by Ohyama removal of cartilage produces significant effect on
growth.
Also supported by research of Sarnat, Burdi,
Baume, Petrovic et al

Expt. by Sarnat, Burdi, Baume and Petrovic


Achondroplasia
Cebocephaly
Henrichson’s
research on
palatal splitting

Midface deficiency
Severe Midface def.
Largely adjusted and
adaptive compensatory
reaction of sutural
connective tissue and
immediate and sensitive
response of membranous
bone to tensional forces


Against
Two studies were carried out by Gilhus-Moe and
Lund in Scandinavia in 1960’s showed that
there are excellent chances that condylar process
would regenerate to approx. its original size after
trauma
In a few there was even a overgrowth of condyle.
In a few children there is a reduction in growth after
injury maybe due to the trauma to the soft tissues /
scarring

Therefore Scott’s hypothesis does not hold true
completely.

Experiments
Transplantation:
Not all skeletal cartilages act the same when
transplanted
Epiphyseal cartilage
Synchondroses

independent growth
centers

Nasal septum

less independent
growth potential

Mandibular condyle

little or none


Evaluation of effect of removal of cartilage
on growth:
The impact on a growing rabbit of removing a
segment of cartilage is a deficit in midface
growth
Setback
The surgery itself
Accompanying interference with blood supply


Inference from these experiments

Except the mandibular condyle all other
cartilages act as growth centers


Functional Matrix
Theory
Melvin Moss based on original concept of
Van Der Klaaus. (1969)


Succintly stated the theory is as follows:
“There is no direct genetic influence on the size
and shape, or position of skeletal tissues, only
the initiation of ossification. All genetic
skeletogenic activity is primarily dependent upon
the embryonic functional matrices”


Concept

Circumstances
appropriate

Environmental
influence

DNA of bone cells
set into motion

Genetic
influence

ossification

Effect


Tissues
and
functions

Differentiation

Functional Cranial Component
One function

Skeletal tissue

Neural tissue

Muscle tissue


Vascular tissue


Tissues and spaces that
completely perform a function

A related skeletal unit that
acts biomechanically to
protect and/or support its
functional matrix

Functional matrix


Skeletal cranial
component

Periosteal Matrix
Relates the matrix to those tissues that influence
the bone directly through the periosteum
Muscles
Blood vessels and nerves lying in grooves or entering
or exiting through foramina

Affects a microskeletal unit, sphere of influence
is usually limited to a part of one bone
Temporalis – coronoid process
Tooth
- alveolar bone

Capsular Matrix
Included in this matrix are those masses and
spaces that are surrounded by capsules.
Neural mass with scalp and dura.
Orbital mass with supporting tissues of the eyes.

Capsules tend to influence macroskeletal units
which means portions of several bones are
simultaneously affected
Inner surface of calvarium. This sharing of reaction
by several adjacent bones constitutes a macroskeletal
unit.

Moss contends, then, that all loci of new bone
formation
Sutures
Periosteum
Spheno-occipital synchondrosis
Nasal cartilage
Condyles

are all growth sites and not growth centers.
None of these sites contains genetic information
that can determine their ultimate form; they are
at the disposal of the functional matrices related
to them.

Support
Anencephaly
Microcephaly
Hydrocephaly
Normal growth manifested by patients from
whom the condyles have been removed due
to
trauma
pathology
Experimental studies with cast gold bite planes
contd.

Natural
translation
Growth
site

Cartilage cells have genetic
information
that enables them to be
responsive to pressure
only

Experimental
displacement

Capacity to determine
its own size

FUNCTIONAL MATRIX


Against
Spheno-occipital synchondrosis
Demonstrates autonomous growth

Nasal cartilage
Scott- midfacial growth not responsive to external
influence
Removal - deficient growth
Destruction of cell proliferation potential without
cicatrization – Deficient growth

Craniostenosis – premature stenosis of sutures
inhibits growth – sutures have some capacity to
regulate the activity of functional matrix

Clinical applications of Moss’s theory


Clinical practices that reflect functional
matrix modification
Enucleated orbit.
Widening midpalatal sutures
Repositioning of maxillary segments of cleft
patients
Bilateral condylectomy
Oblique bite planes
Monobloc functional therapy


Van Limborgh’s
Compromise theory
Three major viewpoints considered:
Sicher’s
Scott’s
Moss’s


New concepts

Anatomic Division
Factors that control Growth


Anatomic Division
Endochondral
ossification

Chondrocranium

Cartilaginous
base

Desmocranium

Intramembranous
ossification

Calvarium

Nasal
capsule

Middle face
Otic
capsule


Mandible

Sicher’s view
Cartilage
Sutures
Periosteum

Are all growth centers


Scott postulates
Intrinsic genetic factors affect
Cartilage
Periosteum

while sutures are passive n reactory.


Moss is felt to have erred
in denying any intrinsic genetic factors in
the control of chondrocranial growth and…
restricting the control of sutural growth to
local epigenetic and environmental
factors.


Fails because
Microcephaly and Hydrocephaly
Orbital response
Primordia of eye can be manipulated
Eye enucleation without replacement ceases
expansion

contd.

Van Limborg’s Compromise
Chondrocranial growth is controlled by intrinsic genetic
factors
Desmocranial growth is controlled mainly by local
epigenetic factors
Desmocranial factors is also controlled by local
environmental factors
General epigenetic and general environmental factors
have very little role to play.


Independence of skull growth cannot be
consistently demonstrated


Modern Composite
Because Van Limborgh used a few terms to
describe embryologic entities that are novel, and
he fails to classify the controlling factors for the
mandible a ‘Modern Composite’ of craniofacial
growth is offered by Ranly


Embryologic Classification

Desmocranium

Cranial vault

Middle face
Splanchnocranium
Mandible

Spheno-occipital
syn.
Chondrocranium
Nasal

cartilage

Modern Composite


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Theories of growth /certified fixed orthodontic courses by Indian dental academy

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