Cybernetics

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Nov 30, 2013 (3 years and 11 months ago)

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CYBERNETICS


Dr.Ameet.V

ORIGIN



Greek word
KYBERNETES
(steersman)


Plato & Ampere



Norbart

Weiner 1948


“ Science of control &


communication in animal &


machine”


Cybernetics is the science that studies the
abstract principles of organization in
complex systems. It is concerned not so
much with what systems consist of, but
how they function.



Cybernetics focuses on how systems use
information, models, and control actions
to steer towards and maintain their goals,
while counteracting various disturbances.



The cybernetic theory postulates
that everything affects everything
& therefore organized living
systems never operate in an open
-
loop manner




There is a dynamic motor control of
receptor sensitivity, receptor
orientation, stimulus selection &
sources of environmental stimuli

Black Box

Output

Input

Black box is the physiologic system under study

Black box concept

Input

Transfer function

Output

Black Box

Input

Output

Genetically determined &

cybernetically organized

biologic features of

Phenomena characterizing,

inducing, or controlling

spontaneous & appliance
-

modulated growth relative

To the following:


Max. lengthening &


Widening


Mandible lengthening


Teeth movements

Orthodontic,

Functional,

& orthopedic

appliances

Correction of

malocclusion &

Intermax.

malrelation

Pavlovian concept of
accommodation in biological
systems


Conditioning



Reinforcement



Habituation

Living animals respond passively to stimuli

Open Loop

Output has no effect on the input

Refutations

1. Steiner & Brown


“The North
Carolina chain
gang”


2. Post retention
Relapse

Principle of optimality

Laws of Energetics





Mechanical/Functional efficiency


Energy expenditure


Gravitational work


Kinetic energy

Prof. Alexandre G. Petrovic


National Institute Of Health &
Medical Research, Strasbourg,
France



1977



1982

Morphophysiologic systems

Open loop

Closed loop

Regulator

Servosystem

Comparator

Feedback

Central

Peripheral

Positive

Negative

Closed Loop systems

Input

Measure of effect

Regulation of effect

Return of modified information


Closed Loop systems

Regulator Type of Closed Loop


Input is constant







Input varies across time




Servosystem Type of Closed
Loop

Components of a Servosystem

COMMAND

Reference Input Elements

Reference Input

COMPARATOR


(peripheral)

Performance

Analyzing

Elements

Performance

Deviation Signal

Central Comparator


Actuator, Coupling System,

Controlled System

Output

(Controlled Variable)

Growth of the craniofacial
region & the servosystem

Cartilage & its types

Primary




Secondary

Types of Cartilage

Primary

Types of Cartilage

Secondary

Primary Cartilage:

Axial skeleton

Epiphysis, Synchondrosis, Nasal Septum,

Ethmoid(lat masses
),
Sphenoid



Secondary Cartilage:

Condyle, Coronoid, Sutures,

Fracture Callus


Factors
influencing

Growth

Primary

Cartilage

Secondary
Cartilage

Hormones

Yes

Yes

Local Factors

No
(Chondroblasts
surrounded by
matrix)

Yes
(Pre
-
chondroblasts
not

surrounded
by matrix)

Orthopaedic
appliances

Only Direction

Direction and
Amount

Condylar cartilage

Sarnat


Akin to Epiphyseal



Stutzmann & Petrovic


secondary




-

Response to local factors


-

Phylogenetic success


-

Fine tuning of occlusion

Cell types in condylar cartilage

1.
Precursor

Skeletoblast


pleuripotent,
fibroblast like.

2.
Prechondroblast


faster cell cycle,
matures into
Chondroblast

3.
Preosteoblast

Double differentiating potential of
skeletoblasts

Relationship Between Lateral Pterygoid,

Retrodiscal Pad and Condyle

RDP/

MTMF

LPM

MENISCUS

Somatomedin & LPM Interaction

Evidence supporting the role of
LPM

Resection

EMG in monkeys

Microelectric stimulation of LPM

Post hyperpropulsor


Non fatigable fibers


Serial sarcomeres


Goret
-
Nicaise, Awn & Dhem

Voudouris

Retrodiscal Pad / MTMF

Jeanne J Stutzmann


1.Biomechanic role


2.Metabolic role

Biomechanic role


Posterior growth rotation


Supplementary lengthening



Paulsen, 1996

Metabolic role



Increase



Blood & Lymph flow



Open loop nutritive factors



Decrease



Cell catabolites


-
ve feedback factors

The Face as a Servosystem

Input


Maxillary dental arch


Output


Adjustment of the position of mandibular


dental arch

The Face as a Servosystem

Release of

Hormones
(Command)

Labionarinary muscles

Septal cart,Premax
-
frenum

Position of Maxillary

Dental arch
(Ref Input)

OCCLUSION


( P.Comparator)


Periodontium,

Teeth

Musculature

Joint

Mastication

(Performance)

Deviation Signal

Brain

(sensory engram)

Actuator (Motor Cortex)

Output

Actuating

signal

LPM & RDP

(Coupling system)

Growth at condyle

(Controlled Variable)

Growth in

Length

Growth in

Width

Growth of the maxilla

Growth in Length:

Release of

STH


Somatomedin

Growth of

Nasal Septum

Increased size

Of Tongue

Septo
-

Premaxillary

ligament

Labio narinary

Muscles

Traction

Protrusion of

Lower Incisors

Protrusion of

Upper Incisors

Thrust

Growth of

Maxillo

Palatine

suture

Growth of

Pre

Maxillary

extremity

Induction

Growth of

Premaxillo
-

Maxillary

suture

Biomechanical

Direct Action

Anterior shift

Of premaxillary

bones

Thrust

Growth in Width:

Release of

STH


Somatomedin

Growth of

Lateral cartilaginous

masses of Ethmoid

Increased size

Of Tongue

Growth of cartilage

B/w greater wings

& body of sphenoid

Outward growth

Of maxillary

bones

Outward shift of

Alveolus and

molars

Outward

Appositional

Bone

growth

Transverse

Separation of

premaxillae

Transverse

Separation of

Horizontal

Maxilla and

Palatine plates

Growth of


inter Pre

Maxillary

suture

Growth of

mid

Palatine

suture

Direct effect

Condylar cartilage growth

Peripheral comparator


Confrontation



Output

Intrinsic regulation of condylar
growth

Other Terms Related to a Servosystem

Gain

= Output


Input

Attenuation (Gain <1)

Amplification (Gain>1)

1.
STH


Somatomedin


2. Small amounts of


TESTOSTERONE

3. Very small amounts of


OESTROGEN

1.
Large amounts of


TESTOSTERONE

2.
Small or large amounts of


OESTROGEN

3.
Large amounts of


CORTISONE


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


After Development of Occlusion:
-


Sensory engram forms


Peripheral comparator controls
growth

Discontinuities

Catastrophe Theory

Stable

Stable

Unstable

Bifurcation

Importance of Discontinuities



Growth prediction , treatment planning , decision making



Genome partially determines the phenome



Supports mixed dentition therapy


Mode of action of functional
Appliances

Functional appliance

LPM

Retrodiscal Pad

Growth stimulating factors

Lengthening of mandible


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
.

Two Types of Functional Appliances:

FIRST GROUP:



Position mandible Increased activity of

Forward 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



(surgically removed)

Local

control

over

multiplication

of

prechondroblasts

Originates

from

chondroblastic

layer


Stutzman

&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

Two steps:


1)
While appliance is worn:
-







Forward position






Reduction of length of LPM






New sensory engram


2)
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.

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) 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 end on relation is seen often


4) Action of reverse pull headgear on maxilla



References

Auxologic categorization & chronobiologic
specification for the choice of appropriate
orthodontic treatment


Alexander
Petrovic AJODO 1994 Feb.


LPM, TMF & postural hyperpropulsor in
growth of mandible


J.J Stutzmann & A.J
Petrovic; Am J Orthod Dentofac Orthop
May 1990;97;381
-
92

Treatment objectives & case
retention:Cybernetic & “myometric”
considerations


Richard M. Jacobs;
AJO 1970;58:552
-
56


Dentofacial orthopedics with
functional appliances


Graber,
Rakosi, Petrovic; 2
nd

edition,1997,Mosby
-
year Book
Inc.:13
-
73