CYBERNETICS INDIAN DENTAL ACADEMY Leader in continuing dental education
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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 www.indiandentalacademy.com biologic & biomedical findings.
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ďƒ˜ 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 www.indiandentalacademy.com
• 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
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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 www.indiandentalacademy.com
• 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 www.indiandentalacademy.com
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 www.indiandentalacademy.com
Cybernetics
Transfer of Information
• Cybernetic systems operate through transfer of information •
Physical,
Chemical,
Electromagnetic
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Black box concept Input
Black Box
Output
Input
Transfer function
Output
Black box is the physiologic system under study www.indiandentalacademy.com
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
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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.
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Pavlovian concept of accommodation in biological systems Conditioning Reinforcement Habituation Living animals respond passively to stimuli www.indiandentalacademy.com
Morphophysiologic system Open loop
closed loop
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Open Loop Output
has no effect on the input
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Refutations 1. Steiner & Brown “The North Carolina chain gang�
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2. Post retention Relapse
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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. www.indiandentalacademy.com
Closed Loop Relationship maintained between input and output
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Closed Loop systems Input
Regulation of effect
Measure of effect
Return of modified information www.indiandentalacademy.com
Closed Loop
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Morphophysiologic systems
Open loop
closed loop Regulator
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Servosystem
These concepts of cybernetics : 1.Mechanism of craniofacial Growth 2.Method of operation of orthopedic & orthodontic appliance.
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• Theory of facial growth based on these concepts of cybernetics is servosystem
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Control of maxillary growth • Direct effect : STH preosteoblast • Indirect effect : thr intermediaries www.indiandentalacademy.com
Types of Cartilage Primary
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Types of Cartilage Secondary
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Double differentiating potential of skeletoblasts
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Primary Cartilage: Epiphysis,
Synchondrosis,
Nasal Septum, Ethmoid Sphenoid Secondary Cartilage: Condyle, Coronoid, Mid Palatal Suture, Fracture Callus www.indiandentalacademy.com
Factors influencing Growth
Primary Cartilage
Secondary Cartilage
Hormones
Yes
Yes
Local Factors No
Orthopaedic appliances
Yes (Pre-
(Chondroblasts surrounded by matrix)
chondroblasts not surrounded by matrix)
Only Direction
Direction and Amount
Charlier, Petrovic, Stutzmann www.indiandentalacademy.com Strasburg, France
Growth of the maxilla
Growth in Length
Growth in Height
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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
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Direct Action
Growth of Maxillo Palatine suture
Growth in Width: Growth of Lateral cartilaginous masses of Ethmoid
Release of STH Somatomedin
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
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Direct effect
Transverse Separation of premaxillae
Growth of inter Pre Maxillary suture
Transverse Separation of Horizontal Maxilla and Palatine plates
Growth of mid Palatine suture
Outward Appositional Bone growth
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Growth in height
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Control of Mandibular Growth Role of Lateral Pterygoid & Retrodiscal Pad Two roles : •Blood Supply •Biomechanic
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Metabolic role Increase • Blood & Lymph flow • nutritive factors Decrease • Cell catabolites • -ve feedback factors www.indiandentalacademy.com
Biomechanic role
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Relationship Between Lateral Pterygoid, Retrodiscal Pad and Condyle
MENISCUS
LPM RDP
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Somatomedin & LPM Interaction
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• 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 www.indiandentalacademy.com
•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.
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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
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Performance
The Face as a Servosystem Input –
Maxillary dental arch
Output – sagittal position of the mandible.
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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 www.indiandentalacademy.com
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 www.indiandentalacademy.com
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Other Terms Related to a Servosystem
Gain
=
Output Input
Amplification
(Gain>1)
Attenuation
(Gain <1)
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Attractor
Cusp to fossa relation
Repeller
Cusp to cusp relation
Disturbances
Abnormal tooth position Occlusal interferences Arthritis Muscle Inflammation Periodontitis, Pulpitis
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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 www.indiandentalacademy.com
Discontinuities
Stable
Unstable
Stable
Catastrophe Theory So , a class II molar r/l will never spontaneously revert www.indiandentalacademy.com
to class I
Bifurcation
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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 â&#x20AC;˘ Genotype does partially influence the phenotype
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Cybernetics Dr.Rekha www.indiandentalacademy.com
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 www.indiandentalacademy.com
OCCLUSION
(Comparator) Periodontium, Teeth Musculature Joint
Mastication (Performance)
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Failure of Servosystem to Control Growth • Peripheral comparator faulty – Caries, Mutilated dentition. •Discrepancy between rotation pattern (Anterior or Posterior)
and location
of comparator. www.indiandentalacademy.com
Action of Functional Appliances
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Mode of action of functional Appliances Functional appliance
LPM Retrodiscal Pad Growth stimulating factors Lengthening of mandible www.indiandentalacademy.com
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.
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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
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CELLULAR LEVEL 1. Precursor Skeletoblast â&#x20AC;&#x201C; pleuripotent, fibroblast like. 2. Prechondroblast â&#x20AC;&#x201C; faster cell cycle, matures into Chondroblast www.indiandentalacademy.com
Chondroblasts lost removed)
(hypertrophy, surgically
Increased multiplication of prechondroblasts Local control over multiplication of prechondroblasts Originates from chondroblastic layer â&#x20AC;˘Stutzmann and Petrovic (1982, 1990) www.indiandentalacademy.com
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Functional appliances (especially Class II elastics) Increased activity of RDP
Increased nutrients and growth factors inhibitors removed. Increased mitoses and earlier hypertrophy of chondroblasts. www.indiandentalacademy.com
Cytoplasmic junctions between skeletoblasts reduce.
Transmission of inhibitory factors reduce.
Increased mitotic rate and rate of differentiation into prechondroblasts. www.indiandentalacademy.com
Reduced negative feedback signal reaching prechondroblasts
Increased growth at the condyle
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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
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â&#x20AC;˘ Proponents contend that the use of myotactic reflex should be largely ignored. â&#x20AC;˘ Alveolar remodelling is obtained from the inherent elasticity of muscle,tendinous tissue, skin without motor stimulation. www.indiandentalacademy.com
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
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Action of first group while appliance is worn
Action of second group while appliance is not worn
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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.
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Stutzmannâ&#x20AC;&#x2122;s angle increases at the beginning of treatment(only a transient remedial event). Closes: horizontal growth pattern. Opens : vertical growth pattern.
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CLINICAL IMPLICATIONS 1)Principle of optimality of function : Less relapse tendency if post orthodontic treatment muscular activity produces a lower deviation signal.
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2) Removal of functional appliance â&#x20AC;&#x201C; when growth is complete. 3) If removed when growth not complete â&#x20AC;&#x201C; Proper intercuspation.
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4) Understanding of when, and for how long a particular functional appliance should be worn. First group â&#x20AC;&#x201C; Full time Second group â&#x20AC;&#x201C; Part time
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5)
Proper functioning of LPM and RDP important for growth â&#x20AC;&#x201C; Proper parent counseling.
6) Sensory engram poorly developed in younger children. 7) Utilization of high hormonal activity at puberty.
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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.
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) Occurrence of Class II end on relation is seen often?
) Action of reverse pull headgear on maxilla (primary cartilage)
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References Dentofacial Orthopedics with Functional Appliances Graber, Rakosi, Petrovic
Craniofacial Growth Series – Monograph (Craniofacial Growth Theory and Orthodontic Treatment – Edited by Carlson)
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Treatment objectives and case retention: Cybernetic and myometric considerations 1970
R.M. Jacobs Am J Orthod, 58:552-564,
Grant’s Atlas of Anatomy www.indiandentalacademy.com
www.indiandentalacademy.com Leader in continuing dental education
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