Functional appliances philosophy and various studies, servo system theory

FUNCTIONALAPPLIANCES : PART-I PHILOSOPHY ANDFUNCTIONALAPPLIANCES : PART-I PHILOSOPHY AND
VARIOUS STUDIES,VARIOUS STUDIES,
SERVOSYSTEM THEORY, FUNCTIONALANDSERVOSYSTEM THEORY, FUNCTIONALAND
CEPHALOMETIC ANALYSISCEPHALOMETIC ANALYSIS
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Contents
 Introduction
 Cybernetics
 Components of a servosystem
 Primary and secondary cartilages
 Condylar cartilage
 Control of maxillary growth
 Control of mandibular growth
 Three level arborization
 Bifurcations
 Studies of functional appliance therapy
 Mode of action of functional appliances
 Cephalometric analysis
 Functional analysis
 Conclusion
 References

INTRODUCTION
 Last 20 years have seen an increasing awareness of the potential
of functional appliances as a valuable tool in the armamentarium
of orthodontists.
In late 1960’s Petrovic & co-workers produced first rigorous
demonstration that condylar cartilage’s growth rate & amount
can be modified by using appropriate functional & orthopedic
appliances.
Later he employed the model of cybernetics & control theory to
describe craniofacial growth patterns & method of operation of
functional & orthopedic appliances.

The term “CYBERNETICS” (Greek kybernetes means steersman)
was coined by mathematician Norbert Wiener in 1948 to
encompass the entire field of control and communication theory,
whether in the machine or in the animal.
Cybernetics is concerned with scientific investigation of
systematic processes of a highly varied nature, including
phenomenon such as regulation, information processing, storage,
adoption, self organisation and strategic behavior.

It grew out of Shannon's information theory – designed to
optimise transmission of information through communication
channels and the Feed back concept used in engineering
control systems.
 The concept of cybernetics and control theory was put forth
by Petrovic (1977,1982) to describe craniofacial growth
mechanisms and the method of operation of functional and
orthopedic appliances.

The theory refines orthodontic concepts by demonstrating a
qualitative and quantitative relationship between observationally
and experimentally collected findings.
Helps in a broader understanding of orthodontic problems as the
language of cybernetics is compatible with the rapidly expanding
use of computers among clinicians.

According to Symons, in mammalian embryo, the condylar
cartilage develops independently of the chondrocranium.
The response of the condylar cartilage growth to local factors
may explain the extraordinary success of the phylogenetically
new mammalian joint between the skull and the lower jaw.

Condylar cartilage growth is integrated into an organised
functional whole that has the form of a servosystem and is able
to modulate the lengthening of the condyle so that the lower jaw
adapts to the upper jaw during growth.
In the absence of such an adjustment the forces of occlusion
would expose the pdl structures to repeated trauma and loss of
teeth.
This adjustment hence allows proper mastication and facilitates
high basic metabolism.

CYBERNETICS

Cybernetics is based on the communication of information.
 Any cybernetically organized system operates through signals
that transmit information (which may be physical, chemical or
electromagnetic in nature).
 Any cybernetic system, when provided an input (or stimulus),
processes such an input and produces an output. The output is
related to the input by a transfer function that characterizes the
physiologic system.

Transfer functionInput Output

PHYSIOLOGIC SYSTEM
OPEN LOOP CLOSED LOOP
REGULATOR THE SERVO SYSTEM
No feedback loop
Or Comparator
Main input constant
Comparator detects
disturbances
It is –ve feedback
system
or follow up system
Main input not constant

In an open loop, the output does not affect the input. There are
no feed back loops or comparators.
In a closed loop system, a specific relation is maintained between
the input and output and are characterized by a feedback loop
and a comparator.

INPUT TRANSFER FUNCTION OUTPUT
INPUT COMPARATOR TRANSFER FUNCTION
OUTPUT
Feed back loop

The input is fed into a comparator which analyses the input and
judges the degree to which the transfer function needs to be
carried out to obtain a certain output.
The output is fed back to the comparator (through a feed back
loop) and is analyzed for its adequacy. If found inadequate, the
transfer function is carried out once again.
The feed back loop can have a positive or enhancing affect or a
negative or attenuating affect.

A regulator type of closed loop is one in which the input is
constant. Any disturbance in the input will cause the comparator
to initiate a regulatory feedback system, which will restore the
input to its normal state.
Eg. The temperature regulation system of the body-Any change
in body temperature acts as the input into the comaparator (the
hypothalamus), which causes an action (pilorection and
shivering) which ultimately brings the body temp back to
normal.

Servosystem in this the main input is constantly changing with
time and the output is constantly adjusted in accordance to the
input.

WHY CYBERNETICS?
Craniofacial growth is an extremely complex process involving a
multitude of factors.
The connections between constituents are complex, although the
constituents themselves are not.
The identification and analysis of the feed back loops (regulation
processes) is among the main tasks in the field of craniofacial
growth.

Cybernetic language has been the best to accurately describe the
intricacy and complexity of craniofacial morphogenesis and the
means to influence it clinically.
The following set of approaches may be useful in relating
scientific findings and the method of operation of orthopedic and
orthodontic appliances.

COMPONENTS OF A SERVOSYSTEM

COMMAND :a signal established independent of the
servosystem and is not affected by the output of the system. It
tells the system what has to be done.
REFERENCE INPUT : is a signal established as a standard of
comparison.
REFERENCE INPUT ELEMENTS :establish the relationship
between command and the reference input.

COMPARATOR (PERIPHERAL) :It is a component that
analyses the reference input and judges the performance of the
system through performance analysing elements.
CENTRAL COMPARATOR : the performance judging elements
then transmits a deviation signal to the central comparator
which sends a signal to various components – the actuator,
coupling system and the controlled system.
This ultimately brings about an output/controlled variable.

THE PRIMARY AND SECONDARY CARTILAGES.

Stutzman (1976) emphasized the following -
PRIMARY CARTILAGE - dividing cells, differentiated
chondroblasts, are surrounded by a cartilaginous matrix
synthesized by them, that isolates them from local factors able to
restrain or stimulate cartilaginous growth. Chondroblasts
undergo maturation and are later transformed into hypertrophied
chondroblasts.
Deeper in the cartilaginous matrix, calcium is deposited and
endochondral ossification begins.

Seen in
1. Epiphysial cartilages of long bones
2. Cartilages of synchondroses of cranial bones.
3. Nasal septal cartilage.
4. Lateral cartilaginous masses of ethmoid
5. Cartilage between greater wings and body of sphenoid

 SECONDARY CARTILAGES the dividing cells,
prechondroblasts, do not synthesize a cartilaginous matrix,
hence are not isolated from local factor influences. Once they
mature into chondroblasts, they become surrounded by
cartilaginous matrix and do not divide.
 Seen in
1. Coronoid and condylar cartilage
2. Mid palatal suture cartilage
3. Post fracture callus

According to studies carried out by Chartlier, Petrovic and
Stutzmann on organ cultures-
Dividing chondroblasts (in primary cartilages) are more
susceptible to general extrinsic factors, especially growth
hormone, stomatomedin, and sex hormones. The cartilaginous
matrix surrounding the mature chondroblasts, isolates them from
the effects of local factors.
Local biomechanical factors can only modify the direction of
growth and not the amount of growth at these sites.

In the secondary cartilages, where prechondroblasts are the
dividing cells, general and local extrinsic factors can affect the
growth.
The amount of growth of these cartilages can be affected by
altering the local extrinsic factors.

Condylar Cartilage
Adaptive to both extrinsic & local biomechanical & functional
factors.
Condylar cartilage growth is integrated into an organized
functional whole that has form of Servosystem & able to
modulate lengthening of condyle so that lower jaw adapts to
upper jaw during growth

Specific features of condylar cartilage
1. Fibrous capsule -fibroblasts and type I collagen.
2. Zone of growth (mitotic compartment) –skeletoblasts and
prechondroblast type II, not surrounded by the cartilaginous
matrix with type I collagen.
3. Zone of maturation - functional and hypertrophied
chondroblasts.
4. Zone of erosion
5. Zone of endochondral ossification.

Correlation between growth direction of condyle & sagittal
distribution of dividing cells in condylar cartilage

Anatomic, microscopic and histologic studies have shown that
the growth direction of the condyle coincides in general, with the
axis of individual trabeculae, located just inferior to the central
part of condylar cartilage.
Hence the condylar growth direction can be determined by
measuring the main axis of endochondral bone trabeculae in the
condyle and the angle it forms with the mandibular plane.

A histologic & radioautographic study was made of distribution
of dividing cells in a sagittal section of condylar cartilage of
juvenile rats.
Condylar cartilage divided into 4 equal sections from anterior to
posterior & cells counted.
Each experimental group was subjected to specific orthopedic
treatment.

Results showed that both treatment with the postural
hyperpropulsor & with the growth hormone produced significant
increase in growth rate of condylar cartilage compared to
control group (Charlier et al, 1968, 1969; Petrovic et al , 1975)

Condylar growth is not exclusively a result of the lengthening of
pre-existing endochondral bone trabeculae under condylar
cartilage but also a result of growth of bone trabeculae
(mesenchymal cells) that are formed in parallel & posteriorly
oriented in condylar cartilage.

Stutzmann angle- the angle formed between main axis of
endochondral bone trabeculae in condyle with mandibular plane as
viewed on lateral cephalogram.
In anterior growth rotation there is closing of angle as seen in
treatment with growth hormone.
In posterior growth rotation there is opening of angle as seen in
treatment with postural hyperpropulsor

1. Lateral pterygoid muscle & retrodiscal pad tissue
2. Effect of hormones
3. Intrinsic regulation of condylar cartilage growth rate
4. Other hormonal & humoral factors
5. c-AMP
FACTORS AFFECTING CONDYLAR
CARTILAGE GROWTH

TEMPOROMANDIBULAR JOINT

Retrodiscal pad

Resection of LPM & retrodiscal pad
Experimental studies on juvenile rats were carried out in which
LPM were resected.
The interruption of circulatory dependence on the blood supply
originating directly from LPM & indirectly through retrodiscal
pad may contribute to inhibited differentiation of skeletoblasts.
It was observed that growth of condylar cartilage & lengthening
of mandible continued but significantly decreased.

Intrinsic regulation of condylar cartilage growth rate
A “negative feed back signal” originates from the proximal part
of the chondroblastic zone and exerts a restraining effect on the
prechondroblastic multiplication rate.
This concept can help explain the effects of some orthopedic and
orthodontic appliances and of a hormone such as thyroxine.

The earlier commencement of chondroblastic hypertrophy and
the subsequent decrease in the prechondroblastic division-
restraining signal are important intermediary steps in growth
stimulating effects of class II elastics, mandibular hyperpropulsar
etc.
The acceleration of the chondroblastic maturation rate is
similarly an intermediary step for the growth rate –stimulating
effect of thyroxine. (Stutzmann, Petrovic, 1975, 1979)

CONTROL OF MAXILLARY GROWTH

Increase in length of maxilla
Is caused by growth at the premaxillomaxillary and
maxillopalatine sutures and by subperiosteal deposition of bone
in the anterior region.
Increase in width of maxilla
Is due to growth at the mid palatal suture and bone deposition
along lateral areas of alveolar ridge.
Mid palatal suture - secondary cartilage.

Mechanisms controlling growth of the upper jaw
STH-somatomedin, testosterone and estrogen play primary roles
in extrinsic control of post natal growth of the upper jaw.
They have direct and indirect effects.

Direct effects
Represents almost the entire influence of the hormones on
growth of spheno-occipital synchondrosis and nasal septal
cartilage.
 Small part of the effect of hormones on growth of cranial
sutures is direct. Effects the responsiveness of preosteoblasts to
regional and local factors, stimulating the skeletal cell
multiplication.
In secondary cartilage - effect seen in multiplication and
responsiveness of prechondroblasts

Indirect effect
 Forward growth of nasal septal cartilage.
1. Thrust effect
2. Septomaxillary ligament traction effect.
3. Labionarinary muscle traction effect.

CONTROL OF MANDIBULAR GROWTH

The variation in direction and magnitude of condylar growth is
partly a quantitative response to changes in maxillary length.
Variation in maxillary growth can be induced through resection
of nasal septal cartilage or administration of growth hormone or
testosterone or by orthopedic appliances.
As long as growth alteration does not exceed a certain limit, no
significant changes in saggital relationship of dental arches
occurs.

The physiologic adaptation of mandibular length to maxillary
length occurs through a variation in both growth rate and
direction of growth of condylar cartilage.
Growth hormone- somatomedin affects the lengthening of
mandible (through condylar growth) to a greater extent than its
affects on the lengthening of maxilla.
 If this hormonal effect remains within physiological limits, the
occlusion is not significantly altered, as concomitant reduction
an angle between ramus and corpus of mandible, decreases the
length of the mandible.

The release of somatomedin represents the command (command
to grow).
Reference input elements are the nasal septal cartilage,
septopremaxillary frenum, labionariary muscles and
premaxillary and maxillary bones. The position of maxillary
dental arch is constantly changing reference input of the
servosystem.
Lower arch is controlled variable.
The “operation of confrontation” between the upper and lower
dental arches is the “ peripheral comparator” of the
Servosystem.

Owing to the forward and outward growth of maxilla, there is
obvious change in relation of the teeth. What was originally a
cusp to fossae relationship becomes a cusp to cusp relationship.
Hence the peripheral comparator (occlusion), senses this, due to
change in performance or efficiency of mastication. Due to
improper mastication there is increases force on periodontium,
teeth, muscles and TMJ, which serve as performance analysing
elements. The performance analyzing elements send signals to
the central comparator (controller) represented by the CNS.
The CNS is equipped with a SENSORY ENGRAM.

The sensory engram is a collection of feedback loops, which
record the activity of masticatory muscles corresponding to a
particular habitual mandibular position.
It operates on the principle of OPTIMALITY OF FUNCTION.

Any particular muscle action or mandibular position that gives
the minimal deviation signal is recorded in the sensory engram. i.
e. when any new mandibular position is dictated to the patient,
unless the newer position causes a smaller deviation signal than
the older position, the CNS will tend to make the mandible
relapse to its older position, where in function was more ideal.
The CNS compares the present muscular position with the ideal
position stored in sensory engram and sends a deviation signal to
an actuator-motor cortex to correct this discrepency.

The actuator then sends an actuating signal to the coupling
system of the lateral pterygoid muscle and retrodiscal pad.
The LPM positions the mandible forward and the activity of
retrodiscal pad induces mandibular growth at the condyle.
The resultant output or controlled variable is the forward growth
of mandible which results in an ideal cusp to fossa relationship.
 Once growth at the condyle occurs, the posterior border of the
mandible becomes more concave in shape, causing a negative
piezoelectric effect to develop at the posterior border of
mandible and bone apposition occurs.

At the same time anterior border becomes more convex, positive
piezoelectric current resorption of bone.
Thus length of mandible increases.

THREE LEVEL ARBORIZATION

It is a morphogeneticic classification of human facial
development.
By Lavergne and Petrovic (1983).
The first level, based on the quantitative determination of the
difference between maxillary and mandibular sagittal growth,
has three main branches.

The second level based on variations in the direction of
mandibular and maxillary growth, relates to growth inclinations
and growth rotations of both maxilla and mandible.
The third level, based on the occlusal relationship that functions
as the peripheral comparator of the Servosystem, has
subdivisions representing either an aggravation or a melioration
of malocclusions resulting from the first two arborizational
levels.

BIFURCATIONS DURING FACIAL GROWTH

Occlusal relationships play a significant role in the process of
controlling facial growth.
The peripheral comparator has several stable positions, each
corresponding to some type of class I, II or III intercuspations.
Any given occlusal relationship is stable with respect to limited
fluctuations and disturbances.

Each cusp to cusp unstable position corresponds to a functional
discontinuity-a topologic bifurcation type instability, described
by Thom(1972)and Zeemann(1976).
The concept of discontinuity connotes that at critical points, the
servosystem behavior goes through some basic switch, implying
the existence of continuous quantitative variations that appear
qualitative.

Occlusal development involves two phases.
First phase consists of all morphogenetic process leading to a
stable occlusion, during this phase all the parts of the
servosystem are already existent and functional, but stable
occlusal relationship capable of serving as a peripheral
comparator has not yet been achieved.
A reference point for the development of sensory engram is
not possible
Hence mandibular morphogenesis cannot be regulated through
information originating from occlusal relationships.

The beginning of the second phase coincides with the
establishment of a stable occlusion to serve as a peripheral
comparator – required for the development of a sensory engram.
The subsequent morphogenesis of the face is regulated to
minimize possible deviations from achieved stable occlusal
adjustment, regardless of whether this corresponds to a class I, II
or III intercuspation.

Depending on the relationship of maxilla to mandible, the
dentition as a whole or in part (peripheral comparator may be
located near molars or incisors, sometimes near canines.) may be
operating as a peripheral comparator of the servo system.
 In posterior rotating mandible - molars
In anterior rotating mandible - incisors and canines.
The action of the peripheral comparator is an important part of
both orthodontic and orthopedic treatment.

STUDIES OF FUNCTIONAL APPLIANCE THERAPY

A total of 13 studies carried out in recent years have
provide some of the concepts influencing the
functional appliance therapy at university of
Toronto.
1ST
STUDY (WOODSIDE 1975) : - The effect of
activator treatment applied during the evening and
night on mandibular length .

THE 2ND
AND 3RD
STUDIES (ALTUNA
,WOODSIDE 1977 , 1985 ) : These studies
attempted to clarify the experimental conditions
necessary to achieve increased mandibular length .
In this studies the mandible was opened 2mm , 4mm
, 8mm , and 12mm through the use of posterior
occlusal bite blocks with out any attempt to advance
the mandible .

These 2 studies support the hypothesis that a
continuous change in condylar stress with out any
active attempt to advance the mandible consistently
results in a large increase in mandibular length.

THE 4TH
STUDY (WOODSIDE 1975 ) : - The effect
of activators with wide vertical openings in the
construction bite ( 8 mm beyond the rest ) by
comparing them with appliances with small vertical
openings (3 to 4 mm).
Activators were used for short periods in patients
with flaccid and hypotonic lips to induce a rapid
increase in lip strength.

5th
STUDY ( SHAPERA 1975 ) : - Demonstrated a
recovery from midface restriction with in 5 years of
treatment who had all experienced this restriction
during their treatment.

THE 6TH
STUDY ( WOODSIDE 1985) : - This study
was conducted to compare differences in
electromyographic activity generated in the lateral
pterygoid muscles by the Frankel function regulator
and activator.
The activity in these muscles was associated with
proliferation of condylar tissue .some researchers
suggested that the function regulator could produce
this proliferation but that the activator could not .

THE 7TH
STUDY( SESSLE 1990) : - Six juvenile
female monkeys (macaca fascicularis ) was studied
to test the longitudinal effect of functional
appliances on jaw muscle activity . The EMG
activity of masticatory muscles was monitered
longitudinally with permanently implanted EMG
electrodes to determine whether functional
appliances produce a change in postural EMG
muscle activity .

The insertion of herbst and functional protrusive
appliances to induce mandibular protrusion was
associated with a statistically significant decrease in
postural EMG activity in the superior and inferior
heads of the LPM , superficial masseter and anterior
digastric muscles .
This decreased postural EMG activity persisted for
approximately 6 weeks gradually returning to
preappliance levels during a subsequent 6 week
observation period.

8th
AND 9th
STUDIES (SECTAKOF1992,YAMIN
1991) : - These studies tested functional activity in
the muscles of mastication after the insertion of a
functional appliances, because increased muscle
activity was absent in the studies, this activity could
not promote the condylar growth.

10TH
STUDY (ORGAN 1979) : - Tested the
hypothesis that extension of the buccal shields into
the soft tissues of the oral vestibule results in
increased arch width and bone formation at the
apical base.

THE 11TH
STUDY(WOODSIDE 1987) : - A sample
of juvenile monkeys was studied to assess the
remodeling changes in the condyle and glenoid fossa
after a period of progressively activated and
continuously maintained mandibular advancement
using the herbst appliance .
This mandibular advancement produced extensive
remodeling and anterior relocation of the glenoid
fossa, which contributed to anterior mandibular
positioning and lateral jaw relationship .

12TH
STUDY ( VOUDOURIS 1988 ) : - Found
similar changes in mixed dentition animals .
13TH
STUDY ( ANGELOPOULOS,1991) : - These
changes are stable .

EARLIER CONCEPTS OF FUNCTIONAL APPLIANCES –
MODE OF ACTION
The theoretical basis of functional treatment was the principle that “a
new pattern of function” brought about by functional appliance, leads to
a “new morphologic pattern”. New pattern of function are brought by
tongue, lips, facial muscles, ligaments and periosteum.
 New morphologic pattern includes different arrangement of the teeth
within jaws, improvement of the occlusion and altered relation of the
jaws. It also includes changes in the amount and direction of growth of
the jaws and differences in facial size and proportions.

While, others believe that functional appliances only
accelerate growth of the mandible, by helping it reach its final
size, and not by increasing the size of the mandible
(Johnston .L.E).
Though these studies recognized the possibility of modifying
growth of the condylar cartilage, due to methodological
proteins, their explanations are open to criticism and have
sparked controversy.

One of the earliest functional appliances was called as the
Activator because it was supposed to activate the masticatory,
facial, lip and tongue musculature.
Andresen believed that the protractor muscles of the mandible
were stimulated by activator.

To meet the bulkiness of activator and its limitations to night
time wear, a number of modifications of this appliance have
been made which have been called as “open activators”.
Bionator is one of these less bulky appliances.
According to Balters, the equilibrium between the tongue and
circumoral muscles is responsible for the shape of the dental
arch and for the intercuspation.

Other example of Frankel developed Functional Regulator,
which is worn in lingual and dental regions and uses the
vestibule as operational base in contrast to all previously
mentioned functional appliances. Shields
of Frankel’s appliance stimulate bone growth in the apical
subperiosteal areas and provide a guidance of eruption of
teeth.

Changes in our understanding
1. At cellular level
2. Clinical studies

CELLULAR LEVEL
 a) Factors regulating mandibular condylar growth:
In the past years, natural growth of condyles and growth
changes using orthopedic appliances on experimental animals
have been reported. Petrovic & Stutzmann hypothesized that
“there must be a negative feedback-signal originating from the
proximal part of the chondroblastic zone and exerting a
restraining effect on the prechondrobastic multiplication rate.

Which means condylar growth is regulated in part by factors
that are intrinsically expressed. As of today, most of these
regulatory factors have not been identified in the condyles.

Several differentiation factors, growth factors & angiogenic
mediators have been found to play important roles during
endochondral ossification of long bones. Similarly, condylar
growth must be regulated by various growth factors.

Master transcription factor which controls the differentiation
of mesenchymal cells into chondrocytes during development
of long bones, it was identified that transcription factor Sox 9
is required for chondrocyte differentiation. It was also
required for expression of a series of cartilage specific marker
genes including types I, X, XI collagens.

The expression of Sox 9 function during differentiation of
mesenchymal cells within the condyles, it should be identified
and correlated with the cellular events occurring during
endochondral ossification of the condyles. Once mesenchymal
cells differentiate into chondrocytes in the condyles, they
mature, form cartilage, & express type II collagen which is a
major component of the condyles.

Chodrocytes later undergo hypertrophy and express type X
collagen. Type X collagen has been used as a marker for
endochondral ossification of long bones & condyles.
Rabie & Hagg in their study correlated the temporal
expression of type X collagen on molecular and protein levels
in growing condyles to the amount of bone expressed during
condylar growth.

Rabie & Hagg identified cellular and molecular events which
are responsible for key processes governing condylar growth.

ROLE OF VEGF, SOX 9 & TYPE II COLLAGEN IN BONE
FORMATION OF THE CONDYLE AND GLENOID FOSSA
Functional appliances have been used to induce mandibular
growth by changing muscle function and condyle - glenoid
fossa relationships.

It has been shown that the glenoid fossa remodels anteriorly in
response to mandibular protrusion and corrects skeletal class
II div I malocclusion. Regarding the response of the glenoid
fossa to functional appliance therapy we have to understand
the mechanism of growth of glenoid fossa on a cellular and
molecular level and then compare these changes with those
occurring during forward mandibular positioning.

 They found highest level of VEGF expression in posterior
region of glenoid fossa when compared with middle and
anterior regions during natural growth.
 The highest level of new bone formation during natural
growth was also found in the posterior region of glenoid
fossa. This suggests a close correlation between angiogenesis
and osteogenesis during growth of glenoid fossa .

Forward mandibular positioning led to a significant increase
in the expression of VEGF in the posterior region when
compared with middle and anterior regions. The highest
amount of bone formed in response to forward mandibular
positioning also occurred in the posterior region .

In summary, the mechanical strain caused by forward
mandibular positioning stimulated the cells of the chondroid
layer to secrete VEGF. VEGF enhances neovascularization
and the perivascular connective tissues surrounding the new
blood vessels are depository sites of mesenchymal cells.

VEGF also stimulates vascular endothelial cells to secrete
growth factors and cytokines that influence the differentiation
of mesenchymal cells to enter the osteogenic pathway and
engage in osteogenesis.

ROLE OF SOX 9 AND TYPE II COLLAGEN
 Chondroid bone in the glenoid fossa a unique calcified tissue
that possess morphological and structural properties
intermediate between those of cartilage and bone.
Morphologically, chondroid cells look similar to the
chondrocytes, but they are surrounded by a bone like matrix.
This extracellular matrix consists of cartilage, type II and X
collagens and also type I collagen, osteocalcin which are
components of bone.

Though the bone formation in the glenoid fossa is intra
membranous, the growth of the chondroid bone layer is highly
responsive to mechanical stimuli which contribute to growth
adaptation in response to masticatory function. Rabie et al, in
their study found cellular changes which expresses Sox 9 and
type II collagen synthesis in glenoid fossa in response to
forward mandibular positioning .

ROLE OF PTHRP IN MATURATION OF CONDYLAR
CARTILAGE
Parathyroid-hormone-related protein (PTHrP) belongs to the
parathyroid hormone (PTH) family. PTH is a circulatory
hormone where as PTHrH is a local messenger with multiple
functions in many tissues. During skeletal growth, the
physiologic action of PRHeP in cartilage is to regulate
endochondral bone formation by controlling the pace of
chondrocytes differentiation and maturation.

REPLICATING MESENCHYMAL CELLS IN THE CONDYLE
AND GLENOID FOSSA
DURING MANDIBULAR FORWARD POSITIONING
An important factor that influences bone growth is the number
of osteoblasts involved in the synthesis of bone matrix. The
number of osteoblasts is directly proportional to the number of
mesenchymal cells. Hence number of mesenchymal cells will
determine the osteogenic potential.
Rabie, Louise Wong, Marjorie Tsai. AJODO 2002; 123: 49-57

ward mandibular positioning resulted in significant increase in
ber of replicating cells in posterior areas of condyle and glenoid f
O-DO Rabie, Louise Wong, Marjorie Tsai. JAN 2003 ; 123 ;49-57 .www.indiandentalacademy.com

In the condyle and glenoid fossa, the pathway of
mesenchymal cells differs because of the two mechanisms of
bone formation. The glenoid fossa forms by intramembranous
ossification, here mesenchymal cells directly differentiate into
osteoblasts before forming bone.

 Whereas the condyle develops by endochondral ossification
and here mesenchymal cells must first undergo a transitory
stage of cartilage formation before being replaced by bone
after vascular invasion. In condyle, these cells are located in
the proliferative layer and in glenoid fossa, beneath the
articular layer.

FUNCTIONAL APPLIANCE THERAPY ACCELERATES
AND ENHANCES
CONDYLAR GROWTH
Whether functional appliance accelerates and enhances
condylar growth, continues because of lack of tissue markers
to distinguish between two processes:
1) Acceleration of growth
2) Actual growth.
Recently, Rabie and Hagg identified some cellular and
molecular events which are responsible for condylar growth.

Developing condyles
Mesenchymal cells
Chondrocytes
Type II collagen
Framework
Cartilage matrix
Hypertrophic chondrocytes
Regulated by Sox 9 trancription factor
Type 2
collagen
Activate gene expression for
differntiated
Chondrocytes mature
secretes

Type X collagen
Endochondral ossification
Hypertrophic cartilage matrix
Replaced by
Bone
onset

These above mentioned molecular events give us the baseline
data of condylar growth in response to functional appliance
therapy. If the effect of functional appliance therapy on
condylar growth is acceleration, then these factors should be
accelerated when compared with their expression during
natural growth.

 If the effect of functional appliance therapy is actual growth,
then the cartilage matrix and amount of bone formed during
mandibular advancement should be more than the amount of
bone formed during the same period of natural growth.

GROWTH RELATIVITY HYPOTHESIS
Enlow and Hans presented an excellent overall perspective suggesting
that mandibular growth is a combination of regional forces and
functional agents of growth control that interact in response to specific
extra condylar activating signals. These extrinsic signals are the main
foundation of the growth relativity hypothesis.

Growth relativity refers to the growth that is relative to the
displaced condyles from actively relocating fossae.
Viscoelasticity is conventionally applied to elastic tissue,
which are primarily muscles and non calcified tissues. More
specifically, viscoelasticity explains the viscosity and flow of
the synovial fluids, elasticity of the retrodiscal tissues, fibrous
capsule, TMJ tendons, ligaments and body fluids.

MAIN FOUNDATIONS FOR GROWTH RELATIVITY
HYPOTHESIS
The glenoid fossa promotes condylar growth with the use of
orthopedic mandibular advancement therapy. Condylar
displacement affects the fibro-cartilaginous lining in the
glenoid fossa to induce bone formation locally which is
followed by the stretch of non muscular viscoelastic tissues.

 New bone formation occurs some distance from the actual
retrodiscal tissue attachments in the fossa. Condylar
displacement
affects fibro-cartilaginous lining of glenoid fossa
induce bone formation
followed by stretch of non muscular viscoelastic tissues

The glenoid fossa and the displaced condyle are both
influenced by the articular disc, fibrous capsule and
synovium. These all are related anatomically and functionally
with the viscoelastic tissues. Therefore, condylar growth is
affected by viscoelastic tissue forces via attachment of the
fibro-cartilage that blankets the head of the condyle.

There are posterior, anterior and 2 collateral soft tissue
attachments between retrodiscal tissues and condyle along
with the fibrous capsule and synovial fluid. These attachments
use the articular disk and fibro-cartilage to communicate
between glenoid fossa and condyle.

THREE GROWTH STIMULI
Displacement + viscoelasticity + referred force
The concept that viscoelastic tissue forces can affect growth
of the condyle suggest
that modification occurs
result
Anterior displacement
Condyle
Affected by posterior viscoelastic tissues
Stimulate (or turn on the light switch)

Transduction of forces over
On fibrocartilage cap of condylar head
Growth of the mandible
Condylar growth is also mediated by intrinsic and extrinsic
biofeedback factors that are present and active even when the
mandible is not distracted.

CORRELATION OF REPLICATING CELLS AND
OSTEOGENESIS IN THE GLENOID
FOSSA DURING STEPWISE ADVANCEMENT
Mandibular advancement leads to an increase in the number
of mesenchymal cells in the glenoid fossa, which in turn
shows more bone formation. Theoretically, this response
should occur every time when we advance the mandible.
Pancherz et al and Du et al, reported stepwise mandibular
advancement elicited a more favourable response in the
mandible compared with its one-step advancement.

In stepwise mandibular advancement when compared with
one-step mandibular advancement led to more replicating
mesenchymal cells and more bone formed in the glenoid
fossa.
 Each advancement should exceed the minimum threshold
intensity, to maximize the potential growth of the glenoid
fossa, so that it can contribute to the correction of skeletal
malrelationship.

Various diagnostic exercises :
 An assessment of the mandibular position as determined by
the musculature.
 Examination of TMJ and mandibular movements.
 Examination of tongue and its functions.
 Examination of respiratory function.
 Examination of lips.
 Assessment of speech.
 Analysis of smile.

I)An assessment of the mandibular position as determined by the
musculature.
Under this we measure
1. Postural rest position
2. Inter occlusal clearance
3. Evaluation of the path of closure from rest to occlusion in:
sagittal plane
vertical plane
transverse plane

Postural rest position
 The postural rest position is a relatively unchanging
neuromuscularly derived relationship of the lower jaw to the
upper.
 It is the position of the mandible when the elevator and
depressor muscles of the mandible are in a state of minimal
tonic contraction.

When the mandible is in postural rest position, it is usually 2-3mm
below and behind the centric occlusion (recorded in canine area)
The space between the teeth, when the mandible is at rest, is referred
to as the freeway space or interocclusal clearance.

I. The mandible now has to be brought into postural rest
position. There are several methods for doing this.
i)Command methods
Phonetic method
ii) Non command method
iii) Combined method

2)Registration of the postural rest position of the mandible
 Direct intra oral method.
Direct extra oral methods.
 Indirect extra oral method.

Indirect extra oral method
1. Cephalometry - the clinician takes two or three lateral cephalograms
under identical exposure and patient position conditions

 Kinesiographic registration of the rest position, the recording unit

Evaluation of the path of closure from postural rest to occlusion in
vertical plane
True deep bite

Pseudo deep overbite

Evaluation of the path of closure from postural rest to occlusion in
sagittal plane

• Evaluation of the path of closure from postural rest to
habitual occlusion in the transverse plane.
LATEROCCLUSION LATEROGNATHY

Examination of TMJ and mandibular movements

Examination of TMJ and jaw movements
Clinical significance
Malocclusion and TMJ
TMJ dysfunction symptoms
Examination

EXAMINATION OF TEMPOROMANDIBULAR DISORDERS IN
THE ORTHODONTIC PATIENT: A CLINICAL GUIDE(J Appl
Oral Sci. 2007;15(1):77-82)
Examination of TMJ is a very important aspect of functional
analysis for the following reasons:
Early diagnosis of TMJ dysfunction and its elimination can
prevent or eliminate incipient TMJ structural problems.
Another reason is during functional therapy the condyle is
displaced and dislocated to achieve a remodeling of the TMJ
structures.

I)Acute muscle disorders are the most common symptoms of TMJ
disorder.
 Spasm of the inferior lateral pterygoid causes this muscle to
contract resulting in disclusion of the posterior teeth on the
same side and premature contact of the anterior teeth on the
opposite side.

II. Joint sounds
1.clicking-single joint sound of short duration , if it is loud it is
referred to as a ‘pop’.
2.crepitation-rough gravel like sound described as grating.

When Auscultation is carried out with a stethoscope, clicking
and crepitus in the joint may be diagnosed during
anteroposterior and eccentric movements of the mandible.

I. Initial clicking
II. Intermediate clicking
III. Terminal clicking
IV. Reciprocal clicking

Examination of TMJ and related structures
Lateral palpation of the TMJ Posterior palpation of the TMJ

Temporalis- The anterior region is palpated above the zygomatic
arch and anterior to the TMJ.

Palpation of anterior and posterior temporalis muscle
The middle region is palpated directly above the TMJ and
superior to the zygomatic arch.

Medial pterygoid: palpated at their insertions on the medial
surfaces of the mandibular angles. The finger tips are placed at
the inferior borders of the mandible and lightly rolled medially
and superiorly.

Masseter: the fingers are placed on the zygomatic arches (just
anterior to the TMJ) They are then dropped down slightly to the
portion of the masseaters attached to the zygomatic arches just
anterior to the joint.

Lateral pterygoid:

Maximum incisal distance
Normal range of mandibular opening when measured
interincisally is between 53 and 58 mm. The patient is asked to
open slowly until pain is first felt. This is the maximum
comfortable opening.

The patient is next asked to open maximally. This is the recorded as
maximum opening. Opening less than 40 mm is considered to be
restricted.
Lateral and protrusive movements
 Any lateral movement less than 8 mm is recorded as a restricted
movement.

Examination of tongue and its functions

Examination of the tongue and its function
Evaluation of the tongue
Size
Shape
Posture
Evaluation of tongue in function
Swallowing
Cephalometric analysis of tongue

Palatographic machine

Examination of tongue posture
Cephalometric analysis Use of radio opaque coating such as barium
paste on the tongue enhances visualization.

Cephalometric analysis of the tongue

Class II DIV I (Left) Class III (Right)

Evaluation of tongue in function- swallowing
Swallowing is examined in the following manner .
1. The patient is seated upright with the Frankfort horizontal
parallel to the floor.
2. Observe unnoticed several unconscious swallows.
3. Small amount of tepid water is placed beneath the patients
tongue tip and the patient is asked to swallow. Mandibular
movements, facial muscle contractions are noted.
4. Hand is placed over the temporal muscle and swallowing
exercise is repeated to feel for contractions for the muscle.

5. A tongue depressor or mouth mirror is placed on the lower lip to
hold it lightly. While the patient is asked to swallow.
6. Unconscious swallow may be examined more specifically as
follows.
Some more water is placed in the patents mouth and the hand on the temporal muscle. The patient is
asked to swallow for the last time.

Normal infantile swallow

Normal mature swallow

Retained infantile swallow- persistence of infantile swallow even
after eruption of permanent teeth. Tongue thrusts strongly
between the teeth on all sides.
Strong contraction of the lip and facial muscles, inexpressive
face, low gag thresh hold and occlude only on one molar in each
quadrant.
The prognosis for conditioning such a primitive reflex is very
poor.

Abnormal tongue habits
 Simple tongue thrust Complex tongue thrust

Clinical significance of abnormal swallowing
1. Simple tongue thrust corrects itself with correction of the
open bite.
2. Complex tongue thrust requires occlusal stabilization by
orthodontic treatment followed by tongue training with
exercises.
3. Retained infantile swallow is a primitive reflex and correction
is difficult . Poor prognosis.

Examination of respiratory function
Research has proved that mouth breathing or interference in
nasal respiration can have important effects on the craniofacial
growth and the positions of the teeth.

Adenoid facies

Mouth breathers do not change the shape or size of the external nares and occasionally contract the nasal
orifices on inspiration.
Even nasal breathers with temporary nasal congestion will demonstrate reflex alar contraction and dilation of
nares during voluntary inspiration.
Methods of examination

Mirror test
Cotton test

Scope of functional therapy with respiratory problems
1. In habitual mouth breathing with little or no respiratory resistance,
functional therapy is indicated:
– Lip exercises-holding a sheet of paper between the lips to
improve lip seal.
– Oral screen with breathing holes.
1. If structural problems occur with excessive adenoid tissues etc,
ENT consultation and possible treatment should be sought. After
the resolution of the problem orthodontic treatment can begin.

Examination of lips

Examination of the lips
The lips must be carefully examined as a part of the functional
assessment. The lips should be examined at rest and during
swallow and mastication.
LIP DYSFUNCTIONS
COMPETENT LIPS
INCOMPETENT LIPS

POTENTIALLY COMPETENT LIPS

EVERTED LIPS- These are hypertrophied lips with redundant
tissue but weak muscular tonicity.

Various diagnostic exercises
 An assessment of the mandibular position as determined by the
musculature
 Examination of TMJ and mandibular movements
 Examination of tongue and its functions
 Examination of respiratory function
 Examination of lips
 Assessment of speech.

Speech Analysis
In malocclusions with malposed teeth, malposition of the tongue may also
occur impairing normal speech. Usually tongue with its inherent flexibility
is able to compensate for atypical morphologic relationships.

There are two processes in the production of speech
1] Phonation –it is the production of airflow and the
establishment of frequency
2] Articulation- it is the modification of airflow by
resonance or various degree of stoppage to produce
vowels and consonants

Speech problems which may be improved by orthodontics are those of
faulty articulation.
• What are articulatory valves ?
• The articulatory valves are
Velopharyngeal valve
labiodental
linguodental, and
linguoalveolar valve

Labiodental {upper teeth and lower lip} ‘F’ & ‘V’
Bilabial {lips} ‘P’ ‘B’ ‘W’ & ‘M’
Linguo –dental {tongue tip and upper teeth} ‘TH’
Linguo –alveolar {tongue tip alveolar ridge} ‘T’ & ‘D’
Linguo-velor-pharyngeal {tongue back, velum and
pharyngeal wall} ‘K’ & ‘G’
Glottal {glottis} ‘H’

Cephalometric for functional appliance therapy

Analysis for facial skeleton
1.Saddle angle (N-S-Ar)
Normal 123±5º
Less than 118º -Antr post gl.fossa- favorable
Greater than 128º-postr post gl.fossa -favorable
Look for –
1.Articular angle - less than 143±6º- favorable
2.Ramal length- Long - favorable
Uncompensated:
Greater saddle angle + greater articular angle + Lesser
ramal angle-unfavorable

2.Articular angle-
S-Ar-Go angle Upper and lower parts of the posterior contours of facial
skeleton
Large art in retrognathic mandible
Small art angle in prognathic mandible
Can be altered by orthopedic and orthodontics
Reduction in the Ar angle
1.Anterior repositioning of Md
2.Closing the bite
3.Mesial migtratin of molars
Between 9-15 years:
Decreases by 2.5* for vertical growers and
2.9* in horizontal growth

3.Gonial angle
 Shows –
1. Form of the md.
2. Direction of mandibular growth - where functional appliance
indicated.
 Small lower gonial angle -horizontal grower – favorable
 Large lower gonial angle-vertical grower - unfavorable if growth is
considered during appliance fabrication, then it can be used as
initial therapy but finally – surgery
9yr – gonial angle 125.5º Lr gonial angle - 69.5º- hor
133.4º 78.3º-ver
 Decreases 2.89º-horizontal growth
2.42º-vertical growth

4. Jarabak ratio:
Postr face ht×100 = 62 to 66%
Antr facial ht
9yrs 9-15yrs
H V H V
Post facial ht. 69.5 64.1 11.05 10.8
Antr facial ht. 103 106.6 12.18 12.71
 Hor 67.5%-69.9%
 Ver 60.1%-62.7%

5. Antr cranial base length (Se-N)
 Horizontal growth 68.8mm at 9 yrs and increases by 4.46mm
between 9- 15 yrs
 Vertical growth 63.8mm and increases 3.52mm between 9- 15 yrs.
Therefore greater antr cranial base length in horizontal & lesser in
vertical growth
6.Postr cranial base length (S-Ar)
 Depends on posterior face ht and position of gl.fossa
 Short postr cranial base is seen in
1. Vertical growers
2. Skeletal open bite
 Hor – 32.2mm 9.16mm (in 6yrs) 9-15 yrs
 Ver -30mm 4.47mm

Analysis of jaw bases
1.SNA- Sagittal relation of the antr limit of the maxillary apical base
Average 82.2 ± 2º - if larger than 84º functional appliance is
contradicted
SNA doesnt change significantly with functional appliance
9yrs 15yrs
 Avg 79.5 81.28
 Hor 79.73 81.57
 Ver 79.0 80.57
 Functional appliance can decrease SNA to a moderate extent.
 A significant decrease is possible by H activator(7-8mm sagittal & 2-
3mm vertical) or a twin block

2.SNB- Smaller indicative of retrognathic mandible - Functional
appliance is indicated
Hor- 77.2º-80.5º (3.2º)
Ver- 74.3º-75.9º (1.6º)
Therefore growth directions and greater increments make the success of
the functional therapy.
3.Basal Plane Angle (pal-mp)
Hor – small 23.4º-20.5º (-3º)
Ver – larger 32.9º – 30.9º (-2º)

4.Inclination angle 85º(PP-Pn)-
Anteinclination is seen in horizontal growers and mouthbreathers
Retroclined palatal plane is present in compensated ver growers
Doesnt correlate with growth pattern or facial type
But maxillary base inclination changes with fnl appl therapy
Therefore mid treatment evaluation is indicated periodically

5. Rotation of the jaw bases:
A) Intermatrix rotation
B) Matrix rotation = total rotation is what we see cephalometrically.
 Remodelling of mandible at the gonial and symphyseal area
 Horizontal – apposition at gonial, resorption at symphysis.
 Vertical – apposition at the gonial, and resorption at genium.
 Matrix rotation – neurovascular envelope
 Functional appliance and growth can influence the mandibular
rotation
 Maxillary base is not altered by growth, but environmental factors
like neuromuscular dysfunction, occlusal forces, gravity and
nasorespiratory malfunction.

6. Mutual rotation of jaw bases:
Horizontal rotation – deep bite – convergent rotation
Vertical rotation – open bite – divergent rotation
Cranial rotation of both bases – offset deep bite
Caudal rotation both bases – offset open bite
Therapeutic control of vertical dimension is not possible and
therefore compensatory treatment is indicated.

7. Linear measurement of the jaw bases:
 The length of mandibular and maxillary bases and ascending ramus is
measured relative to Se – N.
 Ideal dimensions can be calculated using the ratios:
N-Se:Md base 20:21
Asecending ramus:Md base 5:7
Max base: Md base 2:3
Mandibular base:
The mandibular base should be 3 mm longer than Se-N until 12th
year and 3.5 mm longer after 12th
year. A length 5mm less than this
average is considered normal until 7 years and length 5mm or more is
considered normal until 15 years.
9 yrs 15 yrsHorizontal pattern 67.59 mm 77.35 mm
Vertical pattern 65.23 mm 73.5mm

Extent of maxillary base:
 It is the distance between PNS and Pt A projected perpendicular to
palatal plane.
 Growth potential of mandible is greater than that of maxilla hence
SNB angle increases and ANB decreases.9 years 15 years
Horizontal patterns 44.56 mm 48.6 mm
Vertical patterns 44.0 mm 47.16 mm

Evaluation of the length of the jaw bases
1. Mandibular base:
 Md base = N-Se + 3mm indicates an age related normal
mandibular length and an average growth increment.
 If the base is shorter the growth increment is larger, if the
base is longer the growth increment is shorter.
 Retrognathic mandible may have short or longer base.
Short base – retrognathism is due to growth deficiency
Long base
1) functional retruded position because of overclosure or
occlusal guidance
2) the mandible is morphologically built into the facial
skeleton in a posterior position.

Length of ascending ramus:
 Measured from gonion to condylion. Condylion is
constructed by the intersection of FH plane on the tangent
to the ramus.
 Ideal FH plane is also constructed “distance between soft
tissue nasion and palatal plane is bisected along the Pn line.
From this point a straight H line is drawn paralel to Se-N
plane.”
 Ramal length determines the posterior facial height.
 It is longer in horizontal growers with 48.9mm at 9 years
increasing to 68.6 7mm at 15 years.
 It is shorter in vertical growers 44.47 mm at 9years 51.7
mm at 15 years.

2. Maxillary base:
It is related to N-Se and to the Md base. Deviation from
the Md base indicates that the Mx base is too short or too
long.
3. Ascending ramus:
If the ramus is too short, a large amount of growth can
be expected because the growth pattern is not vertical.
4. Morphology of the mandible:
 Orthognathic type – width of ramus is equal to ht of body of
mandible including ht of alveolar process and incisor. The
condyle and coronoid are almost on same plane.
 Retrognathic – the ramus is narrow and short, the symphysis
narrow and long. The coronoid process is shorter than condyle
and the gonial angle is acute or small.
 Prognathic – ramus is wide and long, symphysis is wider in
saggital plane, the gonial angle is acute or small.

Analysis of dentoalveolar relationship
Axial inclination of the incisors:
1. Upper incisors:
Upper incisor to SN angle:
a. 94 -100* until 7th
year
b. 102* in the permanent dentition
c. larger angle indicates incisor procumbancy
2. Lower incisors:
Incisor to mandibular plane angle:
90* - average
smaller angle – lingual tipping of incisors – advantageous for
functional appliance treatment. Activators are more effective in
the saggital plane and tend to tip the lower incisors labially.
if lower incisors are already labially tipped anterior
repositioning of mandible and uprighting of incisors is
necessary.

3. Positioning of the incisors:
Maxillary incisor to N-Pog line: 2 to 4mm
Mandibular incisor to N-Pog line: -2 to +2 mm
Proclined incisors are tipped, if the axial inclination is correct, then
bodily movement is required.
Mandibular incisors behind this line can be moved labially because
space is available and anterior to this line should be moved lingually.

Cephalometric evaluation of treatment progress in mixed dentition

Cephalometric evaluation of A-P discrepancies

Steiner’s anaylsis:
An ANB angle of 2 ± 2° was considered Class I.
Angles greater than 4° were considered Class II.
Angles less than 0° were considered Class III.

Wits appraisal in Class I patients with 0 ± 2 mm.
greater than 2 mm indicated a Class II skeletal relation, and
measurements less than – 2 mm indicated a Class III skeletal
relation.
The Wits analysis is a function of the inclination of the occlusal
plane
So standardization was attempted on the basis of an inclination of the
occlusal plane of 8° to the palatal plane (NL). (AJO-85, Williams)

McNamara analysis:
The relationship of either A or Pog to nasion perpendicular of
0 ± 2 mm was considered Class I.
For differences greater than 4 mm between points A and Pog,
If A is anterior to Pog, it is considered Class II.
If Pog is anterior to A, it is considered Class III.

Cephalometric assessment of sagittal relationship using palatal
plane - 1994 Apr AJO - Ram Nanda and Merrill
 the first part evaluated changes in the inclination of palatal
plane and in the linear distances from the age of 6 to 24 years
and indicated the inclination of the palatal plane was stable
throughout the growth period studied.
 The second part established acceptable adult norms by
evaluating in non-orthodontically treated with good facial
balance.
 The third part evaluated the proposed measures in
pretreatment radiographs in malocclusions to compare the
results of various diagnostic criteria for assessment of sagittal
jaw relationships.
 The distance between projections from points A and B on the
palatal plane (App-Bpp) was found to be the best indicator of
sagittal jaw relationship when compared with the angle ANB,
the Wits appraisal and N perpendicular,

Changes in palatal plane inclination
The growth changes in the inclination of the palatal plane were
measured relative to the pterygomaxillary vertical plane
on an average Pp decreased by 0.16° in the female subjects and
increased 2.22° in male subjects from age 6 to 24 years.
The correction factor iwas found to be less than 0.01 mm, which was
considered insignificant.
This confirmed the observations that the palatal plane remains
relatively stable throughout growth.
This stability over time validates use of the palatal plane as a
reference plane for measurement.

Changes during growth
Mean changes in the measurements App-Bpp, App-Pogpp, Mpp-
Dpp, and Mpp-Pogpp from age 6 to 24 years showed that those
persons who are at the extremes at age 6 years may remain at or near
the extremes. In some cases they move closer to from the average
than they were at age 6 years.
The measures using point Pogpp were more negative than the
measurements based on points B and D, and the range was larger.
The range for App-Pogpp was 13.66 mm for the women and 24.66
mm for the men. For Mpp-Pogpp the range was 13.94 mm for the
women and 24.87 mm for the men.

The advantages of using palatal plane are
(1) growth changes of point N do not influence the result
(2) rotation of the jaws does not influence the result
(3) inclination of the occlusal plane by dental effects is excluded
(4) vertical effects of points A and B are decreased in comparison to
other methods of analysis.
(5)Palatal plane is to be preferred over the FOP because the occlusal
plane changes its inclination during growth and with orthodontic
treatment.

(6)Palatal plane is desirable since this skeletal plane is in close
proximity to the areas under consideration.
(7)The proximity of palatal plane to the dentitions and their apical
bases in both the maxilla and the mandible allowed an evaluation of
the maxillomandibular complex by relating the mandible to the
maxillary plane and not by how the maxilla and the mandible related
to nasion, cranial base, functional occlusal plane, or any other distant
reference point.
(8)Palatal plane was also selected because it is stable throughout life.
 The palatal plane appeared to maintain a parallel relation over the
growth range Broadbent.
The palatal plane maintained a constant angular relationship with the
anterior cranial base –(Brodie, Bjork) and to the pterygomaxillary
vertical plane (Riolo)

REFERENCES
DENTOFACIAL ORTHOPEDICS WITH FUNCTIOBNAL
APPLIANCE - GRABER AND PETROVIC
CURRENT PRNCIPLES AND TECHNIQUES
GRABBER ,VANARSDALL AND VIGG
TWINBLOCK FUNCTIONAL APPLIANCE THERAPY –
WILLIAM.J.CLARK
CONTEMPORARY ORTHODONTICS – WILLIAM.R
PROFFIT
REMOVABLE ORTHODONTIC APPLIANCES – GRABER
AND NEWMANN

Osteogenesis in the glenoid fossa in response to mandibular advancement:
Rabie, Zhihe Zhao. AJODO 2001; 119: 390-400
Growth and treatment changes in patients treated with a headgear-
activator appliance. Margereta Bendeus, Urban Hagg, Rabie AJODO
2002; 121: 376-84
Effects of headgear Herbst and mandibular step-by-step advancement
versus conventional Herbst appliance and maximal jumping of the
mandible.- Xi Du, Hagg and Rabie; EJO 24 (2002)
VWGF and bone formation in the glenoid fossa during forward
mandibular positioning. Rabie, Lily Shum, Chayanupatkul. AJODO
2002; 122: 202-9

Factors regulating mandibular condylar growth - Rabie, Hagg-
AJODO 2002;122: 401-4
The correlation between neovascularization and bone formation
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Functional appliance therapy accelerates and enhances condylar
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PTHrP regulates chondrocytes maturation in condylar cartilage:
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Functional appliances philosophy and various studies, servo system theory

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