Servosystem

SERVOSYSTEM
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Introduction
Craniofacial growth has been the ground for research for
several years, starting from Genetic theory, Sutural
theory, Cartilaginous theory, Functional matrix theory,
Van Limborg’s theory and now the Cybernetic theory.
The Servosystem is a part of the cybernetic theory which
describes the craniofacial growth mechanism
systematically and also explains the functioning of the
various appliance system

Genetic theory
 Genotype supplies all the information required for the
phenotypic expression
 The influence of the general, regional and local factors
modifying the gene expression
How does the modification occurs

Sicher’s Sutural dominance theory
 Craniofacial sutures are responsible for the growth
 This theory acknowledge the importance of Genetic
theory
 Sutures, cartilage and and Periosteum are growth centers
 Sutures carry the genetic potential of the growth
pattern,thus sutural patterns were predetermined
 Disapproved
Transplantation of the sutures
Moss’ experiment on rats
Hydrocephaly and microcephaly

Cartilage directed theory of growth
 Proposed by James Scott – 1953, 1954, 1967
 Cartilage and periosteum as active and primary growth
centers
 Sutures play a passive and secondary role
 Cartilage have the intrinsic genetic potential
 Nasal cartilage and mid face
Transplantation
 Mandible and condylar cartilage
 Achondroplasia
 Disapproved
Condylar cartilage www.indiandentalacademy.com

Cartilage directed growth theory

Functional matrix
 Proposed by Melvin Moss 1960, 1962, 1997
 Original concept of Functional cranial component by Van
Der Klaaw
 The origin, form, position ,growth and maintenance of
the skeletal tissue is secondary and compensatory to the
responses that occur in the specifically related non
skeletal tissues, organs or functioning spaces
 Could not explain the control of the epigenetic factors
 Functional matrix hypothesis revisited – 1997 AJO DOwww.indiandentalacademy.com

Functional matrix
Functional cranial component
Functional matrixSkeletal unit
Micro
Skeletal
unit
Macro
Skeletal
unit
Capsular
matrix
Periosteal
matrix
Transformation
Translation

Mechano transduction
Collagen fibres
Trans membrane
protein Integrin
Actin
Cytoplasmic
membrane
Nuclear membrane

Cybernetic and control theory
 Demonstrates the quantitative and qualitative relationship
between the observationally and experimentally collected
findings
 Petrovic was the first to propose a cybernetic model to
account for the physiological phenomena involving
facial growth and functioning of the functional and
orthopeadic appliances
Observation findings Experimental finding

Epistemplogic features
 Branch of philosophy that deals with the possibility,
nature, origin, structure and validity of knowledge
Hypothesis
Refute
FAIL
Corroboration Strengthening
of the theory
Popper1963,
Science is not a
static
acceptance of
truth but rather
the permanent
search for truth

Cibernetically organized biologic features
Orthodontic
functional , and
orthopaedic
appliances
o Maxillary
lengthening and
widening,
o mandibular
lengthening and
widening,
oTeeth movements
Correction of
malocclusion
and
intermaxillary
relation
INPUT BLACK BOX OUTPUT

Classification of the loop systems
Physiologic systems
Closed loop system Open loop system
Regulator
system
Servosystem
Input
Not a
constant
constant
No comparator
No feed back
mechanism

Command
Reference
input element
Constantly
changing reference
input
x
PerformancePerformance
analyzing elements
Controller
Actuator
Coupling
system Controlled
system
Output
Controlled variable
Xx
Comparator

Command
 Signal established independent of the feedback system
 Affects the behavior of the control system without being
affected by the consequences
 Eg. Growth hormones,testosterone, and estrogen
CONTROLLER
ACTUATOR
REFERENCE INPUT
ELEMENT
COMPARATOR
COMMAND
PERFORMANCE
ANALYSING
ELEMENTS
CONTROLLED
SYSTEM
PERFORMANCE
AMPLIFIER
REFERENCE
INPUT
OPUTPUT

Reference input element
 Between the command and the reference input
 Septal cartilage, septopremaxillary frenum, labionarinari
muscle and premaxillary and maxillary bone
REFERENCE INPUT
ELEMENT
COMPARATOR
COMMAND
PERFORMANCE
ANALYSING
ELEMENTS
CONTROLLED
SYSTEM
CONTROLLER
ACTUATOR
PERFORMANCE
AMPLIFIER
REFERENCE
INPUT
OPUTPUT

Reference input constantly changing variable
 Signal established as a standard of comparison
 Independent of the feedback mechanism
 Sagittal position of the maxilla
REFERENCE INPUT ELEMENT
COMPARATOR
COMMAND
PERFORMANCE
ANALYSING
ELEMENTS
CONTROLLED
SYSTEM
CONTROLLER
ACTUATOR
PERFORMANCE
AMPLIFIER REFERENCE
INPUTOPUTPUT

Control of the maxillary growth
Direct effect Indirect effect
STH -
stomatomedin
Spheno occipital synchondrosis
Nasal septal cartilage
Lateral masses of ethmoid
Body and greater wing of sphenoid
Forward
growth of
septal
cartilage
Outward
growth

Forward growth of septal cartilage
 Thrust effect
Anterior extremity of the
nasal septal cartilage
Spreads laterally in
antero inferior direction
Penentrates into the
premaxillary bone
Premaxillomaxillary
suture
Maxillopalatine
suture
Thrust
effect

 Septopremaxillary ligament traction
 Traction of the labionarinari muscle
Traction of the premaxillary bone through this muscle
Biomechanic promotion of the forward growth of the upper jaw
Absence of labial muscle attachment on the nasal septum –
cleftlip- bone deformation
Growth of the nasal
septal cartilage
Traction effect on the
premaxillary bone through
the Septopremaxillary
ligament

Outward growth
Outward growth of the lateral cartilaginous
masses of the ethmoid and the cartilage
between the body and greater wings of
sphenoid
Produces a lateralization of the right and left
alveolar ridges
Stimulates the growth of the midpalatal suture
Outward growth of the
maxilla

Performance and the performance
analysing elements
REFERENCE INPUT ELEMENT
COMPARATOR
COMMAND
PERFORMANCE
ANALYSING
ELEMENTS
CONTROLLED
SYSTEM
CONTROLLER
ACTUATOR
PERFORMANC
E
AMPLIFIER
REFERENCE
INPUT
OPUTPUT

The controller and the actuating signal
 The central nervous system
 Controls the activity of the lateral pterygoid muscle and
the retrodiscal pad
 The A.signal is the response of muscle and the
retrodiscal pad
REFERENCE INPUT
ELEMENT
COMPARATOR
COMMAND
PERFORMANCE
ANALYSING
ELEMENTS
CONTROLLED
SYSTEM
CONTROLLER
ACTUATOR
PERFORMANCE
AMPLIFIER
OPUTPUT

Role of lateral pterygoid & retrodiscal pad
I CONTROL- INTACT LPM AND
RETRODISCAL PAD
NORMAL
II BILATERAL RESECTION OF LPM DECREASED NO OF DIVIDING
CELLS
DECREASED GROWTH RATE
OPENING OF STUTZMANN’S
ANGLE
DECREASED WIDTH OF MITOTIC
COMPARTMENT
III TMF CLAMPED BILATERALLY SAME AS II BUT LESS
INTENSE
IV TMF CLAMPED
LPM RESECTED
SAME AS II AND V
V TMF RESECTED SAME AS A II
VI LPM AND TMF RESECTED
BILATERALLY
NO CHANGE

Retrodiscal pad
 Partly a mediator of LPM as the blood supply is through
this muscle
 Surgical resection causes diminished rate of growth of
condylar cartilage and lengthening of mandible
 Blood circulating effect
 Biomechanic effect

Controlled system
 Is the final outcome of the system
 The sagittal position of the mandible
REFERENCE INPUT
ELEMENT
COMPARATOR
COMMAND
PERFORMANCE
ANALYSING
ELEMENTS
CONTROLLED
SYSTEM
CONTROLLER
ACTUATOR
PERFORMANCE
AMPLIFIER
REFERENCE
INPUT
OPUTPUT

The Attractor
 Structurally stable steady state in a dynamic system
 Full interdigitation of the teeth be it class I, Class II or
Class III, with cusp to fossa relationship thus eliminating
 The servosystem strives to achieve this stable form

The Repeller
 Unstable equilibrium state
 Cusp to cusp type of occlusal relationship
 The comparator detects this deviation signal and tries to
achieve the cusp to fossa relationship through the
servosystem

Comparator
Central comparator Peripheral comparator
Detects the
disturbances in
periphery
Periodontal receptors
Repetitive
posturing of the
mandible
Sensory engram

Functioning of functional appliances
Functional appliances
Increased contraction
of LPM
Additional growth of
condylar cartilage
In growth stimulating factors
Change in the condylar
trabecular orientation
Iterative activity of the
retrodiscal pad
Enhancement of local mediators
Reduction of local regulators
Additional subperiosteal
ossification of the posterior
border of mandible
Supplementary
lengthening of
the mandible

Postural hyperpropulsor
Upper dental arch in a more
anterior position
Confrontation
between arches
Supplementary
lengthening of mandible
Contractile activity
of LPM
Reduced by fwd posturing
of mandible
Deviated signal
Reduced intensity
of the deviated
signal
Reduction in
anatomic
repositioning of
the mandible

Class II elastics
 No increase in the contractile activity
 Action through the retrodiscal pad
 Intrinsic regulation of the prechondroblasts multiplication
 Biologic activator for stimulating effect of class II
elastics seem to be retrodiscal pad and its role as a
metabolic pump
Functional prechondroblast
stimulated growth rate
Restriction of the
prechondroblast multiplication

Herren Activator
 Two step effects
When the appliance is
worn
Reduced length of the
muscle as the mandible is
positioned forward
When the appliance is not
worn
The retrodiscal pad is
more stimulated
Early onset of hypertrophy
of the prechondroblasts
Growth rate of condylar
cartilage is increased
No stimulating effect on
the condylar cartilage
Effect similar to class II elastics

Chin cap therapy
 The number of dividing cells in the condylar cartilage is
decreased
 Vertical growth direction and closing of the Stutzmann
angle
 Decrease in the length of the mandible
 Complete immobilization and the use of chin cap induces
the greatest decrease in the growth rate of condylar
cartilage and the lengthening of the mandible

Upper jaw
growth
control by
STH

Effect of hormone - maxilla and mandible

Lavergne and Petrovic,1983
 Growth categories - taken both maxilla and mandible
into consideration
 Three level arborization
I
l
e
v
e
l
2
l
e
v
e
l
3
L
e
v
e
l

Petrovic growth categories
Growth inequality of bases
1 Mandible equal to maxilla
2 Mandible smaller than maxilla
3 Mandible greater than mandible
Rotation of the mandible
R Neutral
P Posterior rotation of mandible
A Anterior rotation of mandible

Petrovic growth categories
Posteroanterior state
N Normal
D Distal
M Mesial
Vertical state
N Normal overbite
OB Open bite
DB Deep bite

Growth categories

I LEVEL
Mandible
greater than
maxilla
Mandible
less than
maxilla
Mandible equal to maxilla
Quantitative
determination of
difference between
maxilla and mandible
70%
3%25% Cell and molecular
biology level

II LEVEL
PosteriorAnterior
Neutral
Relates to the
growth
rotation and growth
inclination
of both maxilla
and mandible
Partly on respiration,
phonation and deglutition

III LEVEL
MesialDistal
Normal
Based on the
occlusal relationship
Unstable occlusion
Functional discontinuities

 Tissue level growth potential – level of subperiosteal
ossification rate and the level of alveolar bone turnover
rate
 Tissue level growth responsiveness – the degree of
augmentation of the alveolar bone turnover resulting
from orthodontic treatment
 Morphogenetic rotation – the change in the shape of the
mandible
 Positional rotation – the change in the position of the
mandible with relation to adjacent structures

Lavergne and Gasson, 1977
 Six auxologic categories of the mandible
 Depends on – tissue level growth potential
- tissue level growth responsiveness to
orthodontic, orthopaedic and functional appliances
 helps define the biologic, inter individual variation of the
growing mandible
 Clinicians must give more importance to tissue level
growth responsiveness than just determining the growth
direction

Auxologic groups

Local factors affecting the condylar
cartilage
Cytoplasmic junction
between the skeletoblasts
become quantitatively
reduced
Inhibitory intercellular
stimulations are reduced
Cell division rate
increases
Rate of differentiation of
skeletoblasts to
prechondroblasts increases

 Consistent transmembrane ion flux variation
•Intra cellular Na ion concentration increased
•Intracellular K ion concentration is decreased
•Discharge of H ion from blasts cell is increased
•Increased pH
•Intracytoplasmic Ca concentration is low
Local factors affecting the condylar
cartilage

Local coupling mechanism
Open loop part of the
system
Stimulating effect on the
cell multiplication
Growth hormone and
growth promoting factors
acting primarily by
inhibition of the restraining
signal
Closed loop part of the
system
Inhibitory effect on the
cell multiplication and
consists of regulators of
local origin

Bifurcation
Cusp to cusp unstable position
corresponds to functional
discontinuity
Lack of interdental contacts
correspond to the absence of
both stable and bifurcation
situation

Occlusal development
First phase
Morphogenetic process
leading to stable occlusion
Stable occlusal
development capable of
serving as a peripheral
comparator is not achieved
Creation of an engram is
not possible
Second phase
First phase coincides with
the establishment of the
occlusion to serve as the
peripheral comparator
Thus the creation of an
engram
Minimizes the possible
deviation to achieve
stable occlusal
adjustment

Malfunctioning of the servosystem
Morphologically defective
Morphologically acceptable
Multiple caries
Extreme bruxism
Inadequate reference bases
Anterior rotating mand with
distal jaw basal relationship
Or a posteriorly rotating mand
with mesial interjaw basal
relation ship
The control system operates
faultlessly but is unable to
correct the discrepancy between
the growth rates of the upper
and lower jaw
Seen in anteriorly rotating mand
associated with mesial basal
interjaw relationship and in
posteriorly rotating mand
associated with distal basal inter
jaw relationship

Conclusion
 The treatment of dentofacial malrelations requires
considerable insight into the modalities of craniofacial
growth which is adequately understood only with a
knowledge of mechanisms controlling it,so far the
cybernetic language has been the best tool to render
accurately the intricacy and complexity of the
craniofacial growth and means to influence it clinically

Thank you

Servosystem

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