Cybernetics /certified fixed orthodontic courses by Indian dental academy

CYBERNETICS
INDIAN DENTAL ACADEMY
Leader in continuing dental education

www.indiandentalacademy.com

Greek word KYBERNETES (art of
steering)
Plato & Ampere
Norbart Weiner 1948
“ Science of control & communication
in animal & machine”
ART OF ENSURING THE EFFICACY OF
ACTION.
Once regarded as pointless
sophistication in accounting for
biologic & biomedical findings.

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

• Based on communication & information
theory : particularly on feedback
control system.
• Has bought new concepts eg –ve & +ve
feedback,self regulation,reference
input ,open & close loop


CYBERNETICS
The science of control and
communication in biological,
electronic and mechanical systems.
This includes analysis of feedback
mechanics that serve to govern or
modify the actions of various
systems.
TABER’S CYCLOPEDIC MEDICAL
DICTIONARY 16TH ED

• Permits display of qualitative and
quantitative relationship between
observed and experimental findings
(what I see is what I report)
• Broader understanding of
orthodontic problems, and action
of appliances
• Rigorous language of cybernetics
is the most app way to lead to the
current use of computers

Cybernetic features:
1 Placing observations next to each
other
2.diagram displaying qualitative
relations b/w observations.
3.mathematical language to describe
interactions among various parts of
morphophysiologic system.
4.cybernetics based on communication &
information theory : mainly on
feedback control system is also a
useful research approach

Cybernetics

Transfer of Information

• Cybernetic systems operate through
transfer of information
•

Physical,

Chemical,

Electromagnetic


Black box concept
Input

Black Box

Output

Input

Transfer function

Output

Black box is the physiologic system under study

Input
Orthodontic,
Functional,
& orthopedic
appliances

Black Box
Genetically determined &
cybernetically organized
biologic features of
Phenomena characterizing,
inducing, or controlling
spontaneous & appliancemodulated growth relative
To the following:
•Max. lengthening &
•Widening
•Mandible lengthening
•Teeth movements


Output
Correction
of
malocclusion
&
Intermax.
malrelation

• Identification & analysis of
feedback loops are among main tasks
in craniofacial growth .
• So far, cybernetic language has been
the best tool to render accurately
the intricacy & complexity of
craniofacial morphogenesis & the
means to influence it clinically.


Pavlovian concept of
accommodation in biological
systems
 Conditioning
 Reinforcement
 Habituation
Living animals respond passively to stimuli

Morphophysiologic system
Open loop

closed loop


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
Feedback controlled behavioral
Pattern is assessed.
Deviation b/w given state of
system + desired optimal state
of system is fed back as input
: system then take action to
reduce this deviation to a min.

Closed Loop
Relationship maintained between
input and output


Closed Loop systems
Input

Regulation of effect

Measure of effect

Return of modified information

Closed Loop


Morphophysiologic systems

Open loop

closed loop
Regulator


Servosystem

These concepts of cybernetics :
1.Mechanism of craniofacial Growth
2.Method of operation of orthopedic
& orthodontic appliance.


• Theory of facial growth based
on these concepts of
cybernetics is servosystem


Control of
maxillary growth
• Direct effect : STH
preosteoblast
• Indirect effect : thr
intermediaries

Types of Cartilage
Primary


Types of Cartilage
Secondary


Double differentiating
potential of skeletoblasts


Primary Cartilage:
Epiphysis,

Synchondrosis,

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

Factors
influencing
Growth

Primary
Cartilage

Secondary
Cartilage

Hormones

Yes

Yes

Local Factors No

Yes (Pre-

(Chondroblasts
surrounded by
matrix)

Orthopaedic
appliances

chondroblasts
not surrounded
by matrix)

Only
Direction

Direction and
Amount

Charlier, Petrovic, Stutzmann
Strasburg, France

Growth of the maxilla

Growth in
Length

Growth in
Height


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
Separation of
Horizontal
Maxilla and
Palatine plates

Growth of
mid
Palatine
suture

Outward
Appositional
Bone
growth

Growth in height


Control of Mandibular Growth
Role of Lateral Pterygoid & Retrodiscal Pad
Two roles :
•Blood
Supply
•Biomechanic


Metabolic role
Increase
• Blood & Lymph flow
• nutritive factors
Decrease
• Cell catabolites
• -ve feedback factors

Biomechanic role


Relationship Between Lateral Pterygoid,
Retrodiscal Pad and Condyle

MENISCUS

LPM
RDP


Somatomedin & LPM
Interaction


• Definitions
• Command : signals established
independent of feedback system
under scrutiny.
• Reference input elements:
establish r/lship b/w command &
reference input
• Reference input : signal
established as a standard of
comparison.
• Controller : located b/w
deviation & actualling signal

•Actuating signal :corresponds to
output signal of the controller
• Controlled system : b/w actualing
signal & directly controlled
variable.
• control variable : output signal of
the system.


Components of a Servosystem
Reference Input Elements

Reference Input

COMMAND
Actuator,
Coupling
System

Controlled system

(Controlled Variable)
Performance
Analyzing
Elements

Central Comparator
(sensory engram)

Output COMPARATOR

Deviation Signal


Performance

The Face as a Servosystem
Input –

Maxillary dental arch

Output – sagittal position of the
mandible.


The Face as a Servosystem
Release of
Hormones(Command)

LPM & RDP

(Coupling system)
Actuating
signal

Hormones

Growth at
condyle
(Controlled
System)

Position of Maxillary
Dental arch (Ref Input)

Output

Actuator (Motor Cortex)
Brain
(sensory engram)

Deviation Signal

OCCLUSION

(Comparator)
Periodontium,
Teeth
Musculature
Joint

Mastication
(Performance)

The Sensory Engram

• Blueprint of ideal muscular
function/position
• Collection of feedback loops

• CNS tends to operate along these
feedback loops

Other Terms Related to a Servosystem

Gain

=

Output
Input

Amplification

(Gain>1)

Attenuation

(Gain <1)


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

Stable

Unstable

Stable

Catastrophe Theory
So , a class II molar r/l will never spontaneously revert

to class I

Bifurcation


Importance of Discontinuities
Facial growth should be accounted for by
using unpredetermined & discontinous
models rather continous & deterministic
ones.
Stability of occlusion after it is
established
• Genotype does partially influence the
phenotype


Cybernetics
Dr.Rekha

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

and location

of comparator.

Action of Functional
Appliances


Mode of action of
functional Appliances
Functional appliance

LPM
Retrodiscal Pad
Growth stimulating factors
Lengthening of mandible

Two Types of Functional Appliances

1) Activator, Postural hyperpropulsor,
Frankel appliance, Twin block,
Bionator, Class II Elastics(?)

) Herren activator, LSU activator,
Harvold-Woodside activator,
Extra oral traction on the mandible.


FIRST

GROUP:

Forward Position

mandible:

Increased activity of
LPM and RDP
LPM “helped to contract more” by
Functional appliances.

i.e myotactic reflex & isometric
contractions


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

Chondroblasts lost
removed)

(hypertrophy, surgically

Increased
multiplication of
prechondroblasts
Local
control
over
multiplication
of
prechondroblasts
Originates
from
chondroblastic layer
•Stutzmann and Petrovic
(1982, 1990)

Functional appliances (especially Class
II elastics)
Increased activity
of RDP

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

Cytoplasmic junctions between
skeletoblasts reduce.

Transmission of inhibitory factors reduce.

Increased mitotic rate and rate of
differentiation into
prechondroblasts.

Reduced negative feedback
signal reaching
prechondroblasts

Increased growth at the
condyle


SECOND GROUP:
Position mandible forward , open in
beyond rest position.
Viscoelastic property of muscle is imp
No increase in activity of LPM
•Herren (1953)
•Auf der Maur
(1978)
•Yet there was an increase in growth


• Proponents contend that the use
of myotactic reflex should be
largely ignored.
• Alveolar remodelling is
obtained from the inherent
elasticity of muscle,tendinous
tissue, skin without motor
stimulation.

wo steps:

)While appliance is worn:Forward position
increase in 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 group
while appliance is not worn


A New Parameter for
estimating condylar growth
direction

• Growth direction of condyle
coincides in general with the axes
of individual trabeculae ,located
just inferior to the central part of
the condylar cartilage.
• Stutzmann’s angle : trabecular
alignment with mandibular plane.


Stutzmann’s angle increases
at the beginning of
treatment(only a transient
remedial event).
Closes: horizontal growth
pattern.
Opens : vertical growth
pattern.


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) Sensory engram poorly developed
in younger children.
7) Utilization of high hormonal
activity at puberty.


Drawbacks
Lot of importance on condyle:
Fracture?

)Peripheral comparator (occlusion)
itself is unstable.
discrepancies may be overcome by
Dentoalveolar changes rather than
growth of Mandible.


) Occurrence of Class II end on
relation is seen often?

) Action of reverse pull headgear
on maxilla (primary cartilage)


References
Dentofacial Orthopedics with Functional
Appliances
Graber, Rakosi, Petrovic

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


Treatment objectives and case retention:
Cybernetic and myometric considerations
1970

R.M. Jacobs Am J Orthod, 58:552-564,

Grant’s Atlas of Anatomy

Leader in continuing dental education


Cybernetics /certified fixed orthodontic courses by Indian dental academy

Recommended

Recommended

More Related Content

What's hot

What's hot (13)

Similar to Cybernetics /certified fixed orthodontic courses by Indian dental academy

Similar to Cybernetics /certified fixed orthodontic courses by Indian dental academy (20)

More from Indian dental academy

More from Indian dental academy (20)

Recently uploaded

Recently uploaded (20)

Cybernetics /certified fixed orthodontic courses by Indian dental academy