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

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


Genetic
Epigenetic
Sutural
Cartilagenous
Servosystem


INTRODUCTION
Over many years various theories of growth have been
proposed for the craniofacial complex.
The Genetic theory, Epigenetic theory,Scott’s
Cartilagenous Hypothesis, Sicher’s Sutural Dominance theory,
attempt to explain the growth of the craniofacial complex with
different growth determinants and have their own limitations.
The Servo system theory of growth is based on a factorial
qualitative analysis which takes into account various factors
which determine a coordinated growth of the craniofacial
complex as a whole.
The Servo system theory attempts to explain craniofacial
growth and the modus operandi of Functional appliances.

How does growth affect Orthodontics?
Malocclusion

Orthodontic
Therapy

Abnormal Growth
Of Craniofacial
bones

Malfunction of
The Orofacial
neuromusculature

Malocclusion

•Impaired Mastication
•Unfortunate Esthetics

Abnormal Growth
Of Craniofacial
bones
Malfunction of
The Orofacial
neuromusculature

•Dysfunction of the TMJ
•Susceptibility to
Periodontal diseases
•Susceptibility to Dental
Caries
•Impaired speech due to
malpositions of teeth

GROWTH THEORIES
GENETIC CONTROL THEORY:

• Genotype supplies all the
information required for
phenotype expression.
• Does not address the question
of local and general factors
modifying gene expression.


MENDEL’S GENETIC THEORY
Mendel, the father of genetics stated that the
diploid expression of the chromosome is derived
from two monoploids; one each from both the
parents.
The acquired characters are expressed by the
offsprings due to mutations.
The dominant characters are expressed where as
the recessive are carried and expressed less often
Unfortunately the undesired characters are
dominant more frequently.

THEME OF GENETIC THEORY

•Changing complexity
•Shift from competent to fixation
•Shift from dependent to independent
•Ubiquity of genetic control modulated by environment
at all levels the genetic control of development is
constantly being modified by environmental interactions
which persist through life.

GROWTH THEORIES
EPIGENETIC THEORY
Epigenetic factors are those which are determined genetically, and
are effective outside the cells and tissues in which they are
produced
These occur only indirectly, due to reactions of the structures
which they influence
Van Limborg- they can have an effect on the adjacent structures
such as local epigenetic factors (eg: embryonic induction
influences brain,eyes,inner ear) or are produced at distance and
exert a general epigenetic influence (eg: Sex and growth
harmones)

GROWTH THEORIES
SICHER’S SUTURAL DOMINANCE THEORY:
• He believed that craniofacial
growth occurs at sutures.
• Paired parallel sutures which attach
the facial bones to the cranial base
and skull push the nasomaxillary
complex forwards to compare with
mandibular growth.
• Acknowledges the genetic influence
on growth at the sutures.
• Transplantation of sutures to
another site showed that there was no
innate growth potential.
•Doesn’t justify cases of
Microcephaly and Hydrocephaly.

GROWTH THEORIES
CARTILAGE DIRECTED GROWTH THEORY:
• James Scott- 1953, 1954, 1967
• Cartilage has intrinsic growth potential.
• Role of Periosteum and sutures are only
secondary.
• All cartilages through out the skull are
primary centres of growth.
• Growth of the maxilla is attributed to the
growth of the Nasal septal cartilage.
•Nasal septal cartilage is the pacemaker of
growth for the nasomaxillary complex.
•The mandible is like the diaphysis of a
long bone bent with epiphyseal cartilages
at both ends.

GROWTH THEORIES
CARTILAGE DIRECTED GROWTH THEORY:
• Epiphyseal cartilages transplanted to a
different area will continue to grow - innate
growth potential.
• Nasal septal cartilages also grow when
transplanted to another site.
•Removal of nasal septal cartilages gives
rise to retarded midface development.
• Petrovic’s studies have shown that only
primary cartilages grow in organ culture and
not secondary cartilages.


SERVOSYSTEM THEORY AND CYBERNETICS
Craniofacial growth is a multifaceted
process where the connections and
interrelationships are complex with
interactions and feedbacks.
The Servo system theory uses the
Cybernetic language of information and
communication as a tool to explain the
influence of various factors - extrinsic and
intrinsic on Craniofacial growth.
“Cybernetics” derived from a greek word
meaning ‘steersman’ by Dr.Rosenbleuth and
Norbert Weiner and others in 1947.

CYBERNETICS:
• Used to explain Systems and
Circuit analysis.
• Can also be used in biomedical
sciences to explain negative and
positive feedback loops, self
regulation, gain and in the process
explain physiological processes.



CYBERNETICS:
• A Cybernetically organized system
operates through signals transmitting
information.
• Signals can be physical, chemical or
electromagnetic in nature and of low
energy.

NorbertTr - RH
Weiner
TSH
THYROXINE
T3,T4


Petrovic 1977
• Demonstrate qualitative and quantitative
relationship between observed and experimental
findings.
• Broader understanding of orthodontic problems,
and action of appliances
• Familiarity of orthodontists with cybernetics

Cybernetics

Transfer of Information

• Cybernetic systems operate through transfer of
information
• Physical, Chemical, Electromagnetic


Input

Input

Process

Cybernetic
System
Transfer Function

Output

Output

Physiological cybernetic systems

Open loop

Closed loop

Regulator

Servosystem

Comparator

Feedback


Peripheral
Central
Positive
Negative

Open Loop
Output has no affect on the input


Closed Loop
Relationship maintained between input and output

Input

Comparator

Feedback
Loop

Transfer function

Output


Regulation Type of Closed Loop
Input is constant
Any change of the input will initiate a “regulatory
process”
Input

Comparator

Regulation of input

Transfer function

Servosystem Type of Closed Loop


Components of a Servosystem
COMMAND

Reference Input Elements

Actuator, Coupling System,
Controlled System

COMPARATOR
Output
(Controlled Variable)

Central Comparator
(sensory engram)

Reference Input

Deviation Signal

Performance
Analyzing
Elements

Performance

Growth of the Face
According to the
Servosystem Theory

Types of Cartilage
Primary


Types of Cartilage
Secondary


Primary Cartilage:
Epiphysis, Synchondrosis, Nasal Septum, Ethmoid
Sphenoid
Secondary Cartilage:
Condyle, Coronoid, Mid Palatal Suture,
Fracture Callus

Factors influencing Primary
Growth
Cartilage

Secondary
Cartilage

Hormones

Yes

Yes

Local Factors

No (Chondroblasts

Yes (Pre-

surrounded by
matrix)

chondroblasts not
surrounded by
matrix)

Only Direction

Direction and
Amount

Orthopaedic
appliances

Charlier, Petrovic, Stutzmann
Strasburg, France


Role of Lateral Pterygoid and Retrodiscal Pad

•Blood Supply

•Bio-mechanic


Relationship Between Lateral Pterygoid,
Retrodiscal Pad and Condyle

MENISCUS

LPM
RDP


Stutzmann and Petrovic

Proper function of Lateral Pterygoid and
retrodicsal pad:
• Excision of Lateral Pterygoid
• Reduced function of the Retrodiscal pad
(Rat experiments)


The Face as a Servosystem

Input – Maxillary dental arch

Output – Adjustment of the position of mandibular
dental arch

Growth of the maxilla

Growth in
Length

Growth in
Width


Growth in Length:

Traction
SeptoPremaxillary
ligament

Induction

Growth of
Nasal Septum

Biomechanical

Labio narinary
Muscles
Release of
STH
Somatomedin

Thrust

Growth of
Pre
Maxillary
extremity

Anterior shift
Of premaxillary
bones

Growth of
PremaxilloMaxillary
suture

Protrusion of
Upper Incisors
Increased size
Of Tongue

Thrust
Protrusion of
Lower Incisors
Direct Action

Growth of
Maxillo
Palatine
suture

Growth in Width:
Growth of
Lateral cartilaginous
masses of Ethmoid

Release of
STH
Somatomedin

Transverse
Separation of
premaxillae
Outward growth
Of maxillary
bones

Growth of cartilage
B/w greater wings
& body of sphenoid

Increased size
Of Tongue

Outward shift of
Alveolus and
molars


Direct effect

Growth of
inter Pre
Maxillary
suture

Transverse
Seperation of
Horizontal
Maxilla and
Palatine plates

Growth of
mid
Palatine
suture

Outward
Appositional
Bone
growth

The Face as a Servosystem
Release of
Hormones (Command)

LPM & RDP
(Coupling system)

Position of Maxillary
Dental arch (Ref Input)

Hormones

Growth at condyle
(Controlled System)

OCCLUSION
Output

Periodontium,
Teeth
Musculature
Joint

Actuating
signal

Actuator (Motor Cortex)
Brain
(sensory engram)

(Comparator)

Deviation Signal

Mastication
(Performance)

Growth at the Posterior Border of the Ramus


Other Terms Related to a Servosystem
Gain

=

Output
Input

Enhancement (Gain>1)

Attenuatation (Gain <1)

1. Large amounts of
TESTOSTERONE
2. Small or large amounts of
2. Small amounts of
OESTROGEN
TESTOSTERONE
3. Large amounts of
3. Very small amounts of
CORTISONE
OESTROGEN
1. STH – Somatomedin


Attractor

Cusp to fossa relation

Repeller

Cusp to cusp relation

Disturbances

Abnormal tooth position
Occlusal interferences
Arthritis
Muscle Inflammation
Periodontitis, Pulpitis

Peripheral Comparator
Before development of Occlusion:•Sensory engram not developed
•Servosystem does not operate
•Genetic influence on mandibular
growth
•Anodontia is not explained

After Development of Occlusion:•Sensory engram forms
•Peripheral comparator controls
growth

Failure of Servosystem to Control Growth
• Peripheral comparator faulty – Caries,
Mutilated dentition.
•Discrepancy between rotation pattern (Anterior
or Posterior) and location of comparator.


Discontinuities
• DISCONTIUITIES as seen above are important
points in control of cranio-facial growth, and
should always be taken into consideration during
growth prediction, treatment planning and
decision making. As mentioned earlier, a given
occlusal pattern can be formed due to any number
of causes. But once it is established, it remains
relatively stable, as any local changes are
minimized by the regulatory process

Discontinuities

Stable

Unstable

Catastrophe Theory

Stable

Importance of Discontinuities

•Growth prediction , treatment planning , decision making
•Stability of occlusion after it is established
•Genotype does not directly influence the phenotype


Bifurcation


Catastrophe Theory
• Another characteristic of the peripheral
comparator is the existence of
DISCONTINUITIES. Between two stable points
(intercuspation) there is an area of instability (cusp
to cusp relation).
• So a stable phase can never be changed to another
stable phase without an unstable phase.
• This forms the basis of the CATASTROPHE
THEORY

Catastrophe Theory


The Sensory Engram

• Collection of feedback loops
• Blueprint of ideal muscular function/position
• CNS tends to operate along these feedback loops


Optimality of Function

•Minimum deviation signal
•CNS always tries to revert back to optimal position
•Observation of Chain gang prisoners by Jacobs (1968)


Development of Skeletal Malocclusion
According to the Servosystem Theory


For every unit of Growth hormone released,
the amount of growth in the maxilla is less than
that in the mandible.


Increase in length

LPM(max)
LPM(norm)
LPM(min)
MAX

Retrognathism

Prognathism

L1

N


L2

Hormone levels

Action of Functional
Appliances


Two Types of Functional Appliances:

1) Activator, Postural hyperpropulsor, Frankel
appliance, Twin block, Bionator, Class II Elastics(?)
2) Herren activator, LSU activator, Harvold-Woodside
activator, Extra oral traction on the mandible.


FIRST GROUP:
Position mandible
Forward

Increased activity of
LPM and RDP

Less fatigable fibres in LPM
•Oudet et al (1988)
•Carlson et al (1990)

LPM “helped to contract more” by
Functional appliances.

CELLULAR LEVEL
1. Precursor
Skeletoblast –
pleuripotent,
fibroblast like.
2. Prechondroblast –
faster cell cycle,
matures into
Chondroblast

Chondroblasts lost

Increased
multiplication of
prechondroblasts

(hypertrophy, surgically removed)

Local
control
prechondroblasts

over

multiplication

of

Originates from chondroblastic layer
•Stutzmann and Petrovic
(1982, 1990)

Functional appliances (especially Class II elastics)

Increased activity of RDP
Increased nutrients and growth factors supplied
and inhibitors removed.
Increased mitoses and earlier hypertrophy of
chondroblasts.

Reduced negative feedback
signal reaching
prechondroblasts
Increased growth at the
condyle


Cytoplasmic junctions between skeletoblasts reduce.

Transmission of inhibitory factors reduce.

Increased mitotic rate and rate of differentiation into
prechondroblasts.

SECOND GROUP:
Position mandible forward , open in beyond rest
position.
No increase in activity of LPM
•Herren (1953)
•Auf der Maur (1978)

Yet there was an increase in growth

wo steps:

) While appliance is worn:Forward position
Reduction of length of LPM
New sensory engram

) While appliance is not worn:New sensory engram
Functioning in anterior position
Increased activity of RDP

Action of first group

while appliance is worn

Action of second

while appliance is not worn

group


CLINICAL IMPLICATIONS
1) Principle of optimality of function :Less relapse tendency if post orthodontic
treatment muscular activity produces a lower
deviation signal.

2) Removal of functional appliance – when growth
is complete.

3) If removed when growth not complete – Proper
intercuspation will be hindered.


4) Understanding of when, and for how long a
particular functional appliance should be worn.
First group – Full time
Second group – Part time


5) Proper functioning of LPM and RDP important for
growth – Proper parent counseling.
6) Sensory engram poorly developed in younger
children.

7) Utilization of high hormonal activity at puberty.

Drawbacks
1) Lot of importance on condyle:

Fracture?

2) Peripheral comparator (occlusion) discrepancies may be overcome by Dentoalveolar
changes.
3) Occurrence of Class II end on relation is seen often?
4) Action of reverse pull headgear on maxilla
(primary cartilage)


APPLICATION OF THE SERVOSYSTEM THEORY IN
CLINICAL ORTHODONTICS
FUNCTIONAL APPLIANCES
INCREASED CONTRACTILE ACTIVITY OF LPM
INCREASE IN GROWTH STIMULATING FACTORS
ENHANCEMENT OF LOCAL MEDIATORS
REDUCTION IN LOCAL REGULATORS
ADDITIONAL GROWTH OF THE CONDYLAR
CARTILAGE
ADDITIONAL SUBPERIOSTEAL OSSIFICATION
SUPPLEMENTARY LENGTHENING OF THE
MANDIBLE

POSTURAL HYPERPROPULSOR:
• Simulates a more anterior position of the upper dental arch.
• A deviation signal is produced which increases LPM and
retrodiscal pad activity.
TWIN BLOCK:
• Alters the occlusal inclined planes.
• 70 degree inclined planes alter the sensory engram and
provide a horizontal component of force.

CLASS II ELASTICS:
• Act primarily through the
retrodiscal pad rather than the LPM.
• Alters the intrinsic regulation of
prechondroblast multiplication .
• Enhance the rate of hypertrophy of
Functional chondroblasts so that the
decreased amount of Functional
chondroblasts enhance
prechondroblast replication.

• Similar to the effect of Thyroxine.


HERREN(L.S.U.) ACTIVATOR:
• Acts when the appliance is not worn.
•Action not mediated to through the LPM but
through the Retrodiscal pad.
• Shortening of the LPM when the appliance is
worn when compared to other muscles.
• A new sensory engram is produced.
• The mandible closes in a more anterior
position.
•Stimulation of the retrodiscal pad and alteration
of intrinsic regulation of the cartilage similar to
the Class II elastics.

EFFECT OF CHIN CUP THERAPY:
• Retropulsion of the mandible results
in reduction in the number of dividing
cells.
• Dividing cells if any are found
anteriorly.
• Resulting in anterior growth rotation
and decreased mandibular length.


CLINICAL VERSUS BIOLOGIC APPROACH
INPUT
Orthodontic,
Functional and
Orthopedic appliances
to correct disturbances

BLACK BOX
Genetically determined and
cybernetically organized biologic
features of phenomena
characterizing, inducing or
controlling spontaneous and
appliance-modulated growth
relative primarily of the following:
•Maxilla lengthening and
widening
•Mandible lengthening
•Teeth movements

OUTPUT
Correction of
malocclusion and
intermaxillary
malrelation

CONCLUSION
Understanding growth is difficult, yet fruitful to the
Orthodontist.
A better treatment is rendered by predicting,modifying,correcting or
intercepting growth. At times Orthodontist takes advantage of
growth. All this is beneficial to the patient which would otherwise
cause delay or produce a different outcome.


References
• Hand book of facial growth

Enlow

• Dentofacial orthopedics
• Orthodontics; Current
principles and Techniques

Petrovick

Graber& Vanersdall

• Hand book of Orthodontics

Moyer

• Contemporary Orthodontics

Proffit

•Color atlas of Dental Medicine
Orthodontic Diagnosis

Rakosi

References
•

Craniofacial Growth Series – Monograph 23

(Craniofacial Growth Theory and Orthodontic Treatment – Edited by Carlson)

•Treatment objectives and case retention: Cybernetic and
myometric considerations
R.M. Jacobs Am J Orthod, 58:552-564, 1970
•Grant’s Atlas of Anatomy

THANK YOU


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

Recomendados

Recomendados

Más contenido relacionado

La actualidad más candente

La actualidad más candente (20)

Destacado

Destacado (15)

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

Similar a Theories of growth /certified fixed orthodontic courses by Indian dental academy (20)

Más de Indian dental academy

Más de Indian dental academy (20)

Último

Último (20)

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

Notas del editor