Contemporary views on functional appliances

GOOD MORNING
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CONTEMPORARY VIEWS ON
FUNCTIONAL APPLIANCE

CONTENT
 Introduction
 The Road to dicovery: masters of functional appliance
 Classification of functional appliances
 A view and ideas : based on clinical studies
1) How Do The Functional Appliances Work ?
2) Do Functional Appliances have an Orthopedic Effect
3) What Bite Registration Technique Should We Follow ?
4) Stepwise Advancement of Mandible V/S Maximal Jumping Of Bite ?
5) Is Early Treatment Beneficial ?
6) Are The Treatment Changes Stable ?
7) Do Functional Appliances Cause Temporo Mandibular Disorders ?
8) Epiphysis of long bone vs condyle?
 REASONS FOR INDIVIDUAL VARRIATION IN RESULT
 conclusion www.indiandentalacademy.com

INTRODUCTION

Functional appliance , the most interesting ,
fascinating part of mechano therapeutic
armamenterium available to orthodontist.
 Since the inception of the idea of functional jaw
orthopedics, it has always been surrounded with
numerous views regarding its mode of action,
the outcomes of such treatment, the stability, the
timing, the appliance and its effects on the
skeletal pattern.

MASTERS OF FUNCTIONAL
APPLIANCES AND THERE
VIEWS

In 1880, Kingsley
introduced the term
and concept of
“jumping the bite” for
patients with
mandibular retrusion.

He inserted a vulcanite palatal plate
consisting of an anterior incline that
guided the mandible to a forward position
when the patient closed on it.

The valcanite plate
was fastened to the
maxillary arch with
silk threads and its
action was enhanced
by a vestibular plate
connected with silk
binding to the palatal
plate to move the
anterior teeth
backward. www.indiandentalacademy.com

The purpose was not only to push the
mandibular incisor forward but also to
modify the entire articulation

The real goal of functional orthopedics
had not yet been fully understood , that is
shifting the mandible to provoke the
phenomenon of bone and cartilage
remodeling that would change its structure
and position.

Hotz modified the Kingsley plate and
called it vorbissplatte. It was used in cases
of deep bite retrognathism, when the
overbite was likely to cause a functional
retrusion and the lower incisors were retro
inclined by the hyperactivity of the
mentalis muscle and the lip musculature.

In 1902, Pierre Robin of France
introduced the Monobloc as a passive
positioning device. It was used in
neonates with micromandibular
development, particularly infants with cleft
lips and palates, to prevent glossoptosis.
This Monobloc was a single vulcanite bite
jumping appliance which was used to
position the mandible forward in patients.

In 1908 viggo andresen experimented
with a removable retention device for his
daughter, following active multiband
therapy , and was surprised to achieve
further clinical improvements that is
correcting of distocclusion.
He called this retainer as biomechanical
retainer.

When Andresen
moved from Denmark
to Norway , he
became associated
with Haupl.
Andresen and Haupl
teamed up and
renamed this
appliance as
Activator.. because
its ability to activate
muscle forces.

They believed that the repetition of the
new mandibular closure pattern induced a
musculoskeletal adaptation and resulted
in the reeducation of the oro-facial
musculature.

The appliance advanced the mandible
and generated a biomechanical force as
the muscles attempted to return the
mandible to its normal position.

Since it was designed to be loose fitting
and required the patient to actively hold
the appliance in place, it was often
described as an exercise appliance.
Valuable contributions were made by
numerous authors to modify the activator
appliance like, Harvold, Woodside, Herren
etc.

The bulkiness of the activator and its
limitations to nighttime wear caused the
development of many similar appliances.

The Activator was
modified by Balters in
1960, and he called it
the Bionator.
 It is a less bulky
appliance and its
lower portion is
narrow, and its upper
has only lateral
extensions, with a
crosspalatal
stabilizing bar.

The palate is free for
proprioceptive contact
with the tongue; the
buccinator wire loops
hold away potentially
deforming muscle
action.
Balter’s Bionator

The principle of
treatment with the
Bionator is not to
activate the muscles
but to modulate
muscle activity,

Thereby enhancing normal development
of the inherent growth pattern and
eliminating abnormal and potentially
deforming environmental factors.

At the same time
Bimler in 1946 was
working towards
developing an
appliance that
consisted of wire
elements that were
fixed to each other by
acrylic, which is
known as the Bimler’s
Appliance. www.indiandentalacademy.com

The patient were supposed to wear it all
day and night except during meal time.

Perhaps the most
significant
development in
removable appliances
is the Funktionsregler
(Functional
Regulator) of Rolf
Frankel in 1967.
The Functional
regulator (FR) is
designed to be an
exercise device. www.indiandentalacademy.com

Its conceptual method
of action is based on
medical orthopedic
principles – exercise
and muscle training
are important training
factors in the normal
development of
osseous tissues.

Frankel believed that poor postural
behaviour of the orofacial musculature is
the primary etiologic factor in Class II
malocclusions. Therefore, correction of a
Class II is achieved by permanently
advancing the position of the mandible
through muscular exercise.

All the above functional appliances shared
the disadvantage of being made in one
piece due to which the patient could not
eat, speak or perform other normal
functions with the appliance in the mouth.
This led to the development of the Twin
Block Appliance by William J. Clark in
1977 as a two piece appliance .

The appliance was
designed for full time
wear and thus could
correct the maxillo-
mandibular
relationship through
functional mandibular
displacement
because of the
presence of the
inclined planes in the
upper and the lower
plate.

The patients found this appliance very
simple, comfortable and aesthetically
acceptable. The use of the appliance
during eating harnesses the full occlusal
forces for the facial and dental
development and maximize the functional
response to treatment.

Classification of Functional
Appliances :

Classification No. 1
1 All functional appliances were grouped together,
where they were considered to be sub-class of
removable appliances.
2 Removable – Frankel appliance, Activator, Bionator
etc
 Semifixed – Holtz appliance ,Bass appliance etc.
 Fixed - A) Flexible fixed functional appliance
eg. Jasper Jumper, Forsus etc.
 B) Rigid fixed functional appliance eg.
Herbst Appliance, Bio- pedic appliance, etc.

A) Tooth borne
Active (Myodynamic) : Jasper Jumper
Bimler’s appliance
Headgear + activator
Passive (myotonic) : Activator
Bionator
Catalan’s appliance
Twin block appliance
Kinetor
B) Tissue borne :
Vestibular screen
Frankel Appliance

Group A – Tooth Supported eg- Catlan’s appliance
Group B – Teeth / Tissue Supported eg - activator
Group C – Vestibular position appliances eg: Oral Screens, Frankel
Appliances.

According to Graber Neumann
Group I – Consists of inclined planes and oral screens
which transmit muscle forces directly to teeth.
Group II – is made up of activator and its various
modifications permitting daytime as well as night time
wear. They all reposition the mandible downward and
forward activating the attached and associated
musculature.
Group III – also refers an mandibular positional changes
but its major area of operation is vestibule. Supporting
bone and teeth influenced by changing the muscle
balance through cheek shield and lip pads.

A views and ideas : Based on different
studies

From the time functional appliances
achieved wide spread usage, it has been
surrounded by numerous controversies.
Many clinicians look at these appliances with
suspicion and have never been assured
about its efficiency while many others just
love to put them into usage. In the following
section some of the myths and uncertainties
surrounding the functional appliances will be
dealt with.

How Do The Functional Appliances
Work ?
Over the years several theories have
emerged attempting to shed light on
mechanism of action of functional
appliances.

Genetic theory :
It suggests the condyle is under strong
genetic control that causes the entire
mandible to grow downward and forward.
Although this may be related more to
development of prenatal than postnatal
condylar growth, this theory does indirectly
question the effectiveness of orthopedic
appliances in condylar growth.

Myotactic reflex hypothesis
 According to the original Andresen-Haupl
(1955) concept, the forces generated in activator
therapy are cause by muscle contraction and
myotatic reflex activity. A loose appliance
stimulates the muscles, and the moving
appliance moves the teeth. The muscles
function with kinetic energy, and intermittent
forces are clinically significant.

Successful treatment depends on:
 Muscle stimulation,
The frequency of movements of the
mandible, and
 The duration of effective forces.
Activators with a low vertical dimension
construction bite function this way.

Viscoelastic tissue forces :
 Grude (1952) gives one explanation for
the continuing controversy suggesting that
the activators mode of action,
According to him, the appliance is
squeezed between the jaws in the
splinting action. The appliance exerts
forces that move the teeth in this rigid
position.

The stretch reflex is activated, inherent
tissue elasticity is operative, and strain
occurs without functional movement. The
appliance works using potential energy.

For this mode of action an over
compensation of construction bite in
sagittal or vertical plane is necessary. An
efficient stretch action is achieved by over
compensation and the viscoelastic
properties of the contiguous soft tissues.

Twin-block effect :
 The occlusal inclined plane is the
fundamental functional mechanism of the
natural dentition. Cuspid inclined planes
play an important part in determining the
relationship of the teeth as they erupt into
occlusion.

If the mandible occludes in a distal
relationship to the maxilla, the occlusal
forces acting on the mandibular teeth in
normal function have a distal component
of force that is unfavourable to normal
forward mandibular development.

Twin block appliance was developed in
1977 as a two piece appliance .This
appliance modifies the occlusal inclined
plane and use the forces of occlusion to
correct the malocclusion. The mandible is
guided forward by the occlusal inclined
plane.

Lateral Pterygoid Hypothesis :
 The influence of muscle function on
bone structure, formation, and function
has been recognized.
 The masticatory muscles, particularly the
lateral pterygoid has aroused considerable
orthodontic interest.

Petrovic et al (1975) raised the possibility that
the lateral pterygoid activity increased the
proliferation of condylar tissue.
 Later Mcnamara (1978-80) also confirmed
the hypothesis by implanting electrodes in the
muscles of monkeys in his longitudinal study of
the effects of permanently placed mandibular
protrusion appliances on the electromyographic
(EMG) activities of lateral pterygoid and other
masticatory muscles.

He reported that a qualitative increase in
postural activity of the superior and inferior
heads of the lateral pterygoid muscle was
associated with an increased proliferation
of condylar tissue.

Attachment of lateral
pterygoid muscle to the
condylar head or articular
disk may expected to
cause condylar growth
but an atomic research
has not found evidence
that significant
attachments actually
exist. Tissue contiguous with the TMJ

The lateral pterygoid
muscle tendon is
observed attaching
however to the
anterior border of
fibrous capsule.

More recently permanently induced
implanted longitudinal muscle monitoring
technique have found that the condylar
growth is actually related to decreased
postural and functional lateral pterygoid
muscle activity. This notion was also
supported by human studies by Autder
Manr, Pancherz and Anehus, that
reported decreased muscle activity.

The Frankel Philosophy
Frankel has based his appliance on the
following principles :
Vestibular arena of operation :
 According to Frankel, the dentition is
influenced by perioral muscle function.
Abnormal perioral muscle function creates
a barrier for the optimal growth of the
dento-alveolar complex.www.indiandentalacademy.com

Thus the Frankel appliance is designed to
hold away the muscles (buccal and labial)
from the dentition, so that the dento-
alveolar structures are free to develop. In
addition, the frankel appliance acts as an
exercise device or an oral gymnastic
device that aids in correction of the
abnormal perioral muscle function.

Sagittal correction via tooth born maxillary
anchorage :
 The Frankel appliance is anchored firmly in
the maxillary arch by means of grooves in the
molar and canine regions. The mandible is
positioned anteriorly by means of an acrylic pad
that contacts the alveolar bone behind the lower
anterior segment. This lower lingual pad acts
more as a proprioceptive trigger for postural
maintenance of the mandible.

Differential Eruption Guidance :
 The Frankel appliance is free of the
mandible teeth. This allows selective
eruption of the lower posterior teeth, which
aids in correction of the discrepancy in the
vertical dimension and also helps in
saggittal correction of class II
malocclusion by allowing upward and
forward movement of only the mandibular
teeth.

Minimal maxillary basal effect :
 It has been noted that in most class II
malocclusions, the maxillary position is
close to normal while the mandible is
retruded.
The frankel appliance has relatively little
retrusive saggittal effect on the maxilla in
contrast to the marked protrusive change
in mandible.

Periosteal pull by buccal shields and lip pads
 The buccal shields and lip pads are
extended to bring about outward periosteal pull.
This aids in bone formation at the apical base.
 The buccal shields and lip pads hold the
buccal and labial musculature away from the
teeth and investing tissues, eliminating any
possible restrictive influence from this functional
matrix.

Growth Relativity Hypothesis
Enlow and Hans (2000) presented an
excellent overall perspective suggesting
that mandibular growth is a composite of
regional forces and functional agents of
growth control that interact in response to
specific extracondylar activating signals.
They are the foundation of growth relativity
hypothesis.

Activity during growth relativity refers to
growth that is relative to the displaced
condyles from actively relocating fossas.
Viscoelasticity refers to all non calcified
tissue. Specifically the viscoelasticity
addresses the viscosity and flow of the
synovial fluid, the elasticity of the
retrodiskal tissues, TMJ tendons and
ligament other soft tissues and body fluids.

Viscoelastic changes :
During orthopedic mandibular
advancement, there is an influx of
nutrients and other biodynamic factors into
the region through the engorged blood
vessels of the stretched retrodiscal tissue
that feed on the fibrocartilage of the
condyle.

 Another promising area is the alteration of
synovial fluid dynamics that occurs with
orthopedics.
 Nitzan used disoccluding appliances in human
beings to demonstrate low subatmospheric
intra-articular pressures within the TMJ in the
open position.
 The low intra-articular pressures were
significant in altering the joint fluid dynamics or
flow of synovial fluid.

The TMJ pump may act similar to a
suction cup placed directly on the
displaced condylar head to activate
growth.
 These negative pressures initially below
capillary perfusion pressures permit the
greater flow of blood into glenoid fossa
region.

 Three Growth Stimuli (A/C to Voudoris et. al )
 (Displacement + Viscoelasticity + Referred Force)
The concept that viscoelastic tissue forces can affect growth of the
condyle suggests that modification first occurs as a result of the
action of anterior orthopedic displacement.
Second the condyle is affected by the posterior viscoelastic tissues
anchored between the glenoid fossa and the condyle, inserting
directly into the condylar fibrocartilage.
Finally, it is hypothesized that displacement and viscoelasticity
further stimulate (or turn on the light switch for) normal condylar
growth by the transduction of forces over the fibrocartilage cap of
the condylar head.

Decrease in
intra-articular
pressure

Thus ensuring increase in new
endochondral bone formation that appears
to radiate as multidirectional finger-like
processes beneath the condylar
fibrocartilage, and significant appositional
(periosteal) bone formation is seen in the
fossa.

 Light bulb analogy of the
condylar growth and retention.
 When the condylar growth is
continuously advanced, it
lights up like a light bulb.
 When the condyle is released
from the anterior
displacement, the reactivated
muscle activity dims the light
bulb and returns it close to
normal growth activity.

In the boxed area , the
upper open coil shows
the potential of the
anterior digastic muscle
and other peri-mandibular
connective tissues to
reactivate and return the
condyle back into the
fossa once the
advancement is released.
The lower coil in the box
represents the shortened
inferior LPM.

2) Do Functional Appliances have an
Orthopedic Effect ?
 The influence of functional appliances
on mandibular growth is a controversial
issue. The primary question is whether
treatment with a functional appliance can
induce a clinically significant increase in
mandibular growth. Much of the work
demonstrating the ability of functional
appliances to stimulate mandibular growth
is based on animal experimentation.

Whether these findings on animal models
are applicable to human beings during
routine clinical treatment is debatable.
Discrepancies between animal and
human studies are expected since animal
experimentation frequently involves the
use of continuous forces.

These types of forces usually are
impractical and often undesirable in most
clinical situations; therefore treatment
results can be expected to be less
dramatic and more variable.

Mc Namara evaluated the results
obtained in his laboratory and those of
Petrovic and concluded that a maximum
of 5% - 15% increase in mandibular length
can be expected in experimental animals
under controlled laboratory conditions and
during periods of active growth.

Johnston, after renewing series of
experimental studies, concluded that
condylar growth can be altered by
unloading or distracting the condyle

Stockli and Willert also reported an
increase in the size of the condylar head
with significant proliferative activity in the
intermediate zone.

Rabie et aI investigated the temporal
pattern of expression of VEGF (vascular
endothelial growth factor) and new bone
formation in the condyle during forward
mandibular position. Sagittal sections
were cut and stained with VEGF
antibodies

Results showed there was significant
increase in both vascularization and
mandibular bone growth upon forward
mandibular positioning and highest
amount of both were expressed in
posterior region of the condyle.

VEGF expression with mandibular
Forward positioning
VEGF expression with normal
growth

The highest acceleration of
vascularization preceded that of new bone
formation. Thus forward mandibular
positioning resulted in increased
vascularization and enhanced condylar
growth.

CHONDROCYTES
V.G.F.
Blood Vessels

The results of the animal studies seems
encouraging but whether such results can
be expected in humans is questionable.

3) What Bite Registration Technique
Should We Follow ?
 The construction bite determines the
sagittal and vertical displacements of the
mandible and therefore the degree and
direction of appliance activation. The
determination of a proper construction bite
is critical for a functional appliance to
succeed.

Andersen and Haupl increased the
vertical dimension between the molars by
3-4 mm.
Thus the appliance was loosely fitting
appliance that would induce “myotactic
reflex” which would encourage the patient
to bite into the appliance.

Harvold increased the vertical dimension 9-
11mm .
Harvold believed that a small increase was
ineffective because the vertical dimension
normally increase during sleeping which
permitted the mandible to slip out of the
appliance.
 Therefore he increased the vertical dimension
5-6 mm beyond 4-5mm rest position.

He also increased the horizontal displacement of
the mandible beyond the advancement to a
Class I molar relationship to an end to end
incisor relationship.
 The overextended activator, stretching the soft
tissues like a splint, induces no myotactic reflex
activity but instead applies a rigid stretch and
creates a buildup of potential energy.

Herren over extends in a saggital plane, moving
the mandible anteriorly into an incisal cross bite
relationship.
The bite registration most commonly used in
North America registers the mandible protruded
to a point approximately 3mm distance to the
most protrusive position,
 where as vertically the bite is registered
approximately 4mm beyond the rest position of
the mandible.

According to Graber, if the forward
positioning of the mandible is 7-8mm, the
vertical opening should be 2-4 mm.
 and if the forward positioning is 3-5mm
the vertical opening should be 4-6 mm.

Variation in the construction bite
Bjork
Wieslander and Lagerstrom
5mm increase
5mm increase
Class I molar
Class I molar
Harvold and Vargervik
Pancherz
Vargervik and Harvold
5 to 6 mm increase
beyond rest position
5 to 7 mm increase
7 to 8 mm incease
beyond rst position
End to end incisor
Class I molar or
greater
_________
Birkebaek, Melsen, and Terp Greater than 2mm
End to end incisor
Luder
Williams, and Melsen
3 to 5 mm increase
2 o 3 mm increase
3-4mm
End to end incisorwww.indiandentalacademy.com

4) Stepwise Advancement of Mandible
V/S Maximal Jumping Of Bite ?
The term “jumping the bite” was
introduced by Kingsley regarding his
maxillary plate.
It refers to the advancment of the
mandible to a class I relationship during
bite registration.

McNamara and Petrovic (1981)
suggested that a progressive activation
method to bring the mandible gradually
forward :
placing less stress on the investing soft
tissue matrix, and
 might reduce the undesirable dental
effect while maintaining the skeletal effect.

Anehas and Pancherz advocated the
multistep approach to be a more
physiologically favourable effect in terms
of muscular response.

Rabie et al investigated the number of
replicating mesenchymal cells to correlate
it to the amount of bone formation in the
condyle during stepwise advancement of
the mandible Vs single step advancement.

In single step advancement group, the posterior
region of the condyle contained twice as many
as replicating cells as those present in response
to the initial advancement in the stepwise group.
During stepwise group, the level of new bone
formation in response to the initial advancement
was half as much as the level of new bone
formed in the one step advancement .

After single step advancement Initial advancement in stepwise
Advancement group

The maximum level of bone formation in the single step
group was reached 30 days after advancement followed
by decline to levels equal to those expressed during
natural growth between days 40 to 60..
Such a pattern can be explained on the basis that , in the
single step advancement , the differentiation of
mesenchymal cells to chondroblasts or osteoblasts
curtails the population size because , once
differentiated , they loose their replication ability.
Therefore they go back to the levels of bone formation
expressed during natural natural gaowth.

In contrast , the second advancement in
the step wise manner recruits more
mesenchymal cells leading to more blood
vascules, thus lead to more bone
formation, compare to single
advancement and normal growth.

The inference is that the more
mesenchymal cells in a given site, the
more is the bone forming capacity at that
site. Such a correlation was the foundation
of auto-transplantation of mesenchymal
cells for the repair of bone defects when
other clinical strategies failed. The number
of mesenchymal cells significantly
increase when the mandible is positioned
forward..

Mandibular advancement produces
stretching of the posterior fibers and the
net effect of this mechanical strain brings
about an increase in the number of
replicating mesenchymal cells to the site.
Therefore, growth of the mandible could
be influenced to a greater extent by
advancing the mandible forward in a
stepwise manner to recruit a greater
number of replicating cells to the site

Thus stepwise advancement of the
mandible seems to be a better option
when compared to the maximal bite
jumping. The former is also a more
comfortable and physiologically
acceptable mode of treatment for the
patient.

Cellular changes in posterior region of condyle. (A) control group , B) 1 step advancement C) stepwise
advancement on day 7
A B C

5) Is Early Treatment Beneficial ?
 It has always been very confusing for
the orthodontist to decide when exactly to
begin treatment of growing patients.
Whether to initiate treatment immediately
or to allow the patient to complete his / her
growth and then proceed with the
treatment has become a nerve-wrecking
issue.

It is believed that an early phase of
treatment will present the need for
treatment at a later stage and or reduce
the severity of the malocclusion, which
can be corrected with a phase II treatment
thus reducing treatment time and yield
better results.

One view is that:
A major problem in assessing the efficacy
of early treatment is that it take place
during a growth period. Since we work
without a control it is difficult to determine
whether correction is the result of
treatment or of normal growth that would
happened anyway.

Pancherz assessed the long term effects
of functional appliance in patients who
were treated early and late (after peak
velocity of growth)and showed that the
post treatment relapse in overjet was 36%
in early cases and 8% in late cases ; and
sagital molar relationship relapse was
29% of early cases but none in late cases.

Thus concluded that the main cause of
relapse seems to be unstable post
treatment occlusal and persisting lip
tongue dysfunction habit and the best
treatment time would be in the a period
after the peak height velocity of pubertal
growth.

Ghafari et al proposes that treatment in
late childhood may be more practical and
cost-effective, because it reduces the total
length of time a child has to be seen by an
orthodontist.

Tullcoh et al who evaluated the benefit of
early class II treatment by using a
randomized controlled trial and concluded
that for children with moderate to severe
class II problems, early treatment followed
by later comprehensive treatment on an
average does not produce major
differences in jaw relationship or dental
occlusion compared with one later stage
treatment.

But O’Brien et al in a multi center
randomized controlled trial using Twin-
Block appliance concluded that early
treatment with the Twin Block is effective
in reducing overjet and severity of
malocclusion. The skeletal change was
small and not clinically significant

Despite the rising popularity of a
functional phase of treatment, the
literature contains little support for the
notion that it produces “extra” mandibular
growth .

6) For How Long Do We Treat ?
For how long should the treatment be
carried out is a prime consideration during
functional appliance treatment.
Chen et al while reviewing the various
articles to analyse the efficacy of
functional appliances noticed that the
treatment duration differed widely among
the studies, ranging from 6-24 months.

Studies have suggested that maximum
condylar prechondroblastic and
chondroblastic response to be 6 weeks
after initial activation, which is used as a
guide for planning the treatment.

Chayana et al monitored the amount of
bone formed after early and later removal
of bite jumping devices and compared it
with that of normal growth. Appliances
were fitted to position the mandible
forward in the experimental groups.

On day 30, the device was removed in 2
groups (early removal) and the day 44 and
60. The full time wear and control animals
were sacrificed at different points in time.
The results showed that in the condyle,
early removal of the appliance resulted in
less bone formation when compared with
that of natural growth. Late removal of the
appliance resulted in bone formation
similar to that of natural growth.

In conclusion, early appliance removal
results in subnormal growth of the
posterior condyle but not of the glenoid
fossa. Increasing the length of mandibular
advancement secures normal levels of
mandibular growth in post treatment
periods.

7) Are The Treatment Changes Stable ?
 One of the most frustrating aspect
of functional appliance therapy has
been the ability to predict the stability
of the changes after the removal of the
appliance.

Angelopaoulos (1991) showed that the
glenoid fossa changes that occurred
during mandibular advancement were
stable. Thus glenoid fossa relocation has
been shown to be a powerful tool in the
correction of class II dysplasia.

Voudouris observed that the active return
of the condyles to the fossa post treatment
appears to deactivate the modifications by
compressing the condyle against the
proliferated retrodiskal tissues.
Any additional bone induction appears to
be clinically insignificant at the condyle in
the long term.

Orthopedic advancement
has been associated with
reduced muscle activity,
while stimulating condylar
proliferation. However,
after long-term retention
when the appliances
have been removed, the
majority of the condylar
growth stimulation has
been shown to be
minimal in human beings.

Pancherz and Fischer studied stability, the amount and
direction of condylar growth, glenoid fossa displacement
and “effective” TMJ changes by analyzing 35 class II,
division I malocclusion treated with functional appliance.
The results revealed that during the treatment period
condylar growth was directed posteriorly about twice the
amount as in the control subjects, and the fossa was
displaced in an anterior inferior direction.
The effective TMJ changes showed a pattern similar to
condylar growth but were more pronounced.

During the first post treatment period, all TMJ
changes revealed, the glenoid fossa was
displaced backward; the amount of condlyar
growth and effective TMJ changes was reduced,
and the changes were more superiorly directed.
During the second post treatment period all TMJ
changes were considered physiological. Hence
they concluded that during treatment the amount
and duration of TMJ changes (condylar growth,
fossa displacement and effective TMJ changes),
were only temporarily affected favourably by
treatment.

8) Do Functional Appliances Cause
Temporo Mandibular Disorders ?

 It has often been argued whether the
Bite – Jumping produced by the various
functional appliances causes any kind of
damage to the TMJ.

Larsona and Ronnerman patients who
were treated with the Functional appliance
They concluded that extensive orthodontic
treatment can be performed without fear of
creating complications of TMD. They also
suggested that orthodontic treatment may
prevent TMD.

Pancherz evaluated the effects of the
functional appliance in the treatment class
II division I malocclusions and reported
that the number of subjects with
tenderness to palpation doubled during
the initial 3 months of treatment. However,
after appliance removal, most muscle
symptoms disappeared in 12 months.

9. Epiphysis of long bone vs condyle
Epiphysis of long bone is a primary
cartilage.
Where as condyle is a secondary
cartilage.
Lets look the histological picture of these
cartilage:

SCAN

Stutzmann emphasis that primary
cartilage exists in the skull base , and the
limbs
The dividing cells , differentiated
condroblasts ,are surrounded by a
cartilagenous matrix that isolates them
from local factor able to restrain or
stimulate cartilagenous growth.

Where as in secondary cartilage exists in
condylar and coronoid process and some
times in sutures
The dividing cells , prechondroblasts , are
not surrounded by a cartilagenous matrix
and thus are not isolated from local factor
influence.

REASONS FOR INDIVIDUAL
VARRIATION IN RESULT

Patient compliance varies
Time of wear: some clinician advocate
night time wear of these appliances ,
where as others recommend full time
wear. If a long term effect is to applied to
the growing facial infrastructure, it might
be beneficial to work with appliances that
can be worn full- time.

Mandible grows in a wave like fashion,
with multiple acceleration in mandibular
growth followed by quiescent periods. If
orthodontic treatment is applied during
quiescent period , significant orthopedic
changes may not occur.

Improper diagnosis : we simply cannot
expect growth control to exceed certain
limits. The true nature of many
malocclusion is comouflage by downward
and backward mandibular rotation or by
upward and forward mandibular rotation
into an over closed position.

Thus a truly prognathic class III mandible
may be rotated downward and back into a
modrate class II relationship with
excessive lower face height . The clinician
in error , applies a class II functional
appliance to what is in fact a camouflaged
class III malocclusion , result may not be
correct .

Age variation in the experimental group.
It is difficult to find untreated class II div I
control sample , so experimental results
are often compared with those of
untreared normal subject.

Variation in appliance design : such as the
amount of mandibular advancement ,
types of construction bites , and
prescribed time of wear –are so common
that practically no to investigators use
similar appliance design.
Duration of treatment varies from study to
study.

Cephalometric studies:
Some ceph studies involve angular
measurement such as SNA , SNB , ANB,
to show skeletal changes. However these
angles may increase or decrease when
the incisor position changes , although no
skeletal changes occurs , rendering the
result invalid.

Some ceph landmarks used for the
measurement of mandibular length are
difficult to locate . eg: condylion.

Mandibular length measurement: some
studies take mand length from Ar to Gn.
They cannot distinguish between true
mandibular length increase and functional
condylar displacement. As in functioal
treatment condyle is positioned anteriorly
in glenoid fossa.

The assessment for increased condylar
length is sometimes made from
superimposition of lateral ceph on
anatomical structures. This procedure is
subject to considerable error because the
radiographic images are often obscured
by other cranial structures.
Mandibular is a angular bone, measuring
its length in linear direction is itself faulty.

Histologic studies :these studies itself
having technical and analytical problems.
Problem exist in quantifying new bone
formation
The plane of section must be identical to
make accurate comparisons of the new
bone formation.

Despite all these problems there is still
convincing evidence supporting the
concept that the functional appliances do
create an orthopedic effect.
Efficiency of functional appliances no
longer needs to be “proved” unless one is
ignoring thousands of case reports.

The missing link in all these studies
appears to be lack of consideration of
GLENOID FOSSA RELOCATION. well
controlled animal studies show large
amount of downward and forward glenoid
fossa relocation in appliance worn 24
hours a day. EVIDENCE FROM HUMAN
STUDY YET TO COME.

CONCLUSION

we realize that the principles of functional
appliance – which had their initial
epicenter in europe –later spread
throughout the world. The seeds of
functional thinking so generously and
enthusiastically scattered for about 100
years , took root more or less broadly
depending on the fertility on the ground
they fell on.

Today we are able to evaluate the results
of these teachings and gather their fruits.
In facts , we can see that interest in
functional therapy is increasing and that it
has admires throughout the scientific
world.
Still in this field there is lot much to know
and explore.

“ The orthodontics must not be a slave
to one method”
by,
Rudolf hotz

 Graber, Rakosi, Petrovic. Dentofacial
orthopedics with functional appliances.
 The masters of functional orthodontics
by Aurelio and Lorenzo.
 Do functional appliances have an orthodontic
effect ? AJO JAN 1998 VOL 113 NO. 11
 Graber vanasdrall : THIRD EDITION.
 William Proffit. Contemporary orthodontics.
Mosby. 3rd Edition

References
 John C Voudouris and Miaden M. Kuftinec. Improved clinical use of Twin
Block and Herbst as a result of radiating viscoelastic forces on the condyle
and fossa in treatment and long term retention : Growth Relatively. Am J
Orthod 2000 ; 117 : 247-266.
 A.B.M Rabie, Lily Shum, Atinooch Chayanupatkul. VEGF and bone formation
in the glenoid fossa during forward mandibular positions. Am J of Orthod and
Dentofacial Orthop 2002; 122 : 202-209.
 A.B.M Rabie, Ming Ju Marjorie Tsai, Urban Hagg, Xi Diu, Bing-Wu Chou. The
correlation of replicating cells and osteogenesis in the condyle during
stepwise advancement. Angle Orthodontist 2003 ; 73 : 457-465
 Rabie A.B.M & Hagg U. Factors regulating mandibular condylar growth. Am J
Orthod Dentofacial Orthop 2002;122:401-9.
 McNamara and Brudon. Orthodontics and Dentofacial Orthopedics.
Needham Press, Inc. 1st edition
.

THANK YOU

Referencs :

Contemporary views on functional appliances

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