Modus operandi

SEMINAR ON
MODUS OPERANDI OF
FUNCTIONAL APPLIANCES
www.indiandentalacademy.com

INTRODUCTION
Functional appliances or myofunctional appliances
are used for growth modification procedures that are aimed
at intercepting and treating jaw discrepancies that depend
upon the orofacial musculature for their action.
The theoretical basis of functional treatment in general
is the principle that a new pattern of function dictated by the
appliance leads to the development of a corresponding new
morphologic pattern. The treatment outcome of functional
appliance depend on proper case selection, diagnosis and
proper appliance selection.
To select the proper appliance, it is necessary to know
about the mode of operation of functional appliances. This
seminar mainly focusses on the mode of operation of
functional appliance. www.indiandentalacademy.com

DEFINITION
Functional appliances are defined as loose fitting or
passive appliances which harness natural forces of the oro-
facial musculature that are transmitted to the teeth and the
surrounding structure through the medium of the appliance.

CLASSIFICATION OF FUNCTIONAL APPLIANCES
I. a. Tooth borne passive appliances (E.g., Activator, Bionator)
b.Tooth borne active appliances (E.g., Appliance incorporated
with active springs and screws)
vestibule. (E.g., Frankel`s functional regulator)
II. a. Myotonic appliances- that depend on muscle mass for
their action.
b. Myodynamic appliance - depend on muscle activity
for their action.
III. a. Removable functional appliance
b. Fixed functional appliance - (E.g., Herbst, Jasper
Jumper appliances)

IV. a. Group I appliance - that transmits muscle forces
directly to teeth.
E.g., Oral screen, Inclined plane
b. Group II appliance - that reposition the mandible and
the resultant force is transmitted
to the teeth and other structures
c. Group III appliance -these also reposition the
mandible but their area of
operation is the vestibule
(E.g,, Frankel`s functional appliance)

BIOLOGICAL COMPONENTS INVOLVED IN THE
MODE OF ACTION OF FUNCTIONAL APPLIANCES
a. Condyle
b. Articular disc
&
Retrodiscal pad
c. Glenoid fossa
Muscles
Mainly
Lateral pterygoid
muscle
TMJ Masticatory

CONDYLE
Condyle comes under
secondary cartilage variety.
The zone of growth includes
a. skeletoblasts &
b. prechondroblasts, cells that
divide but do not synthesize
a cartilaginous matrix as seen
in primary cartilage. SO
LOCALLY EXTRINSIC
FACTORS MAY MODIFY
THE GROWTH RATE OF
CONDYLAR CARTILAGE.

SIGNIFICANCE OF LATERAL PTERYGOID MUSCLE
& RETRODISCAL PAD
Increased contractile
activity of LPM
Increased of the repetitive
activity of retrodiscal pad
Condylar growth &
remodeling

GLENOID FOSSA
When the condyles are
brought into a new forward
and downward position by
the functional appliances
glenoid fossa remodel and
adapts to the new condylar
position.

MYOTACTIC REFLEX OR
STRETCH REFLEX
When a muscle is
stretched, it causes reflex
contraction of that muscle.
When the mandible is
opened and advanced sagittally
it stretches the elevator muscles
of mastication and the leads to
reflex contraction of the same.
This contractile activity of the
muscles brings about condylar
growth.www.indiandentalacademy.com

BASIC STEPS INVOLVED IN THE MODE OF
OPERATION OF FUNCTIONAL APPLIANCES
FUNCTIONAL APPLIANCE
Increased contractile activity of LPM
Intensification of the repetitive activity of the retrodiscal pad
(bilaminarzone)
Increase in growth stimulating factors.
(e.g., Growth hormone, testosterone)
(a) Change in condylar trabecular Orientation
(b) Additional growth of condylar cartilage
(c) Additional subperiosteal ossification of the posterior border of
the mandible
Supplementary lengthening of mandiblewww.indiandentalacademy.com

ACTIVATOR
MODE OF ACTION
The activator
induces musculoskeletal
and condylar adaptation
by introducing a new
pattern of mandibular
closure.

I. ANDRESEN & HAUPL CONCEPT
According to Andresen & Haupl, the bite is not
opened beyond the postural rest position (i.e. no more than
4mms)
Forward positioning of mandible induces
Myotactic reflex actively and
Isometric muscle contraction.
These muscle contraction forces Stimulate the LPM & retro-
are transmitted by the appliance discalpad thus bring about
to move the teeth. bone remodeling & condylar
adaptation.
Thus activator rely mainly on the muscle activity
during biting & swallowing & thus works by using
KINETIC ENERGY.

CRITICISM ABOUT ANDRESEN & HAUPL CONCEPT
Activator is mainly a night time wear appliance.
During sleep the frequency of biting & Swallowing decreases
and also the freeway space is almost double what it is when
the patient is awake. This reduces the myotactic reflex
activity & muscle contraction. So some authors argue that the
efficiency of the activator is questionable.

II. HEREN, HARVOLD & WOODSIDE CONCEPT
Bite is opened approximately 12-15mm beyond the
postural rest position
It induces stretching of soft tissues & the viscoelastic
pull of the soft tissues are responsible for the appliance
action. The power to produce alveolar remodeling is
obtained from inherent elasticity of muscle, tendinous tissues
& skin. Thus the appliance works by POTENTIAL ENERGY
rather than kinetic energy (i.e. Myotactic reflex activity).
III. The third concept is a combination of above 2.www.indiandentalacademy.com

DENTAL, SKELETAL &
ORTHOPAEDIC EFFECTS
OF ACTIVATOR
These effects are mainly
produced by
a. Sagittal repositioning &
Vertical opening of the
mandible.
b. Selective unidirectional
trimming of the activator or
incorporating certain wire
elements, screws & springs
that bring about the desired
changes. By selective
unidirectional trimming, the
teeth are guided and allowed
to erupt or migrate in desired
direction.

The effects produced are :
Promote or redirect the condylar growth & there by
lengthening the mandible.
Restrict the sagittal growth of maxilla
It causes downward tipping of maxillary base (activator
with high construction bite).www.indiandentalacademy.com

Labial tipping of lower
incisors, can be prevented by
incisor capping.
Lingual tipping of upper
incisors, due to the reciprocal
effect.
It causes intrusion of teeth by
preventing normal eruption.
Leveling of mandibular
occlusal plane.

CORRECTION OF CL III
MALOCCLUSION- REVERSE
ACTIVATOR
Here the restraining effect
is directed towards the mandible
instead of maxilla & the
maxillary teeth are directed
mesially and the in mandibular
teeth distally. The condyles are
restricted from the normal
growth.www.indiandentalacademy.com

MODIFICATIONS
OF ACTIVATOR
They are modified to
reduce its bulkiness and to
increase patients cooperation.
Certain wire elements, springs,
screws and acrylic components
are added to bring about desired
tooth movement, to prevent
unwanted tooth movement and
to increase the efficiency of the
activator e.g. (a)Herren activator
(b) The bow activators of
A.M Schwarz. (c) the reduced
activator or cybernator of
Schmuth. (d) the Karwetzky
modification. (e) the propulsor
appliance (f) the palate free
activator and (g) the elastic open
activator.

BIONATOR
According to Balters, the equilibrium between the
tongue and circumoral muscles and the functional space for
the tongue are essential to the normal development of the
orofacial systems.
MODE OF ACTION
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.www.indiandentalacademy.com

THE APPLIANCE DOES THE
FOLLOWING ACTIONS:
Due to sagittal repositioning
of mandible, the appliance
increases the oral functional
space.
This appliance induces
myotactic reflex activity with
isotonic muscle contraction.
The appliance exerts a
constant influence on the
tongue by means of palatal
arch which promotes anterior
positioning of tongue.
The appliance prevents the
external unfavourable muscle
forces by means of vestibular
arch and its buccal extension.
Intrusion and extrusion of
teeth can be achieved by
loading or unloading the teeth
with acrylic.

OPEN BITE APPLIANCE
The appliance is constructed in
such a way,
The interocclusal bite blocks
prevent the extrusion of
posterior teeth.
INHIBITION OF TONGUE
MOVEMENTS the acrylic
potion of the lower lingual part
extends into the upper incisor
region as a lingual shield,
closing the anterior space
without contacting the upper
teeth.
Vertical strain on the lips
tends to encourage the extrusive
movement of the incisors after
eliminating the adverse tongue
pressures.

CL III OR REVERSED
BIONATOR
The palatal arch configuration
runs forward instead of
posteriorly so that the tongue is
stimulated to remain in a
retracted position in its proper
functional space and contact the
anterior portion of the palate,
encouraging forward growth of
maxilla.
The labial arch runs on the
labial aspect of the lower incisors
rather than the labial aspect of
the upper incisors.

FRANKEL’S FUNCTIONAL REGULATOR
Functional Matrix Theory
Frankel’s philosophy is based on the functional
matrix hypothesis.
The functional matrix hypothesis claims that the
origin, form, position, growth and maintenance of all
skeletal tissues and organs are always secondary and
compensatory to the events or processes that occur in
specifically related non-skeletal tissues, organs or
functioning spaces.

FRANKEL’S PHILOSOPHY AND MODE OF ACTION
VESTIBULAR ARENA OF OPERATION
According to Frankel, the dentition is influenced by
peri-oral muscle function. Abnormal peri-oral muscle
function creates a barrier for the optimal growth of the dento-
alveolar complex.

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 BONE
MAXILLARY ANCHORAGE
The appliance is anchored
on the maxillary dentition
both in the molar and canine
region. And there is no tooth
contact in the lower arch.
The mandible is positioned
anteriorly by means of a
lingual contact more of a
proprioceptive trigger for
postural maintenance than a
pressure bearing area.

DIFFERENTIAL ERUPTION GUIDANCE
The maxillary teeth are withheld whereas the
mandibular teeth are free to erupt upwards and forwards.
This not only corrects vertical dimension but also helps
in the sagittal correction of Cl-II malocclusion.
MINIMAL MAXILLARY BASAL EFFECT
Relatively little retrusive sagittal effect is seen on the
maxilla in contrast to the significant forward change of the
mandible.
It is possible to activate the maxillary labial wire to close
spaces, but this is usually a secondary treatment objective.www.indiandentalacademy.com

BUCCAL SHIELD LIP PADS
AND PERIOSTEAL PULL
There will be outward
periosteal pull by maximal
extension of the shield and
pads into the depth of the
buccal and labial vestibule to
the point at which the depth of
the sulcus is under tension.
This cause an outward
growth of membranous bone,
plus relief of any restrictive
changes in the posterior
segments and bone formation
at the apical base.

Frankel-Ia is used for
class I malocclusion where there
is minor to moderate crowding
and also in cl-I deep bite cases.
Frankel-Ib is used for
class II, division 1 malocclusion
where overjet does not exceed
5mm.
Frankel-Ib is quite similar
to 1a, the difference being the
use of a lingual acrylic pad
instead of lingual wire loops to
contact the lingual mucosa of
the lower incisor segment.

Frankel-Ic is used for
cl - II division 1 malocclusion
in which the overjet is more
that 7mm. Frankel-Ic differ
from Frankel-Ib in that the
buccal shields are split
horizontally and vertically into
two parts permitting the
movement of the free position
in a forward direction by
pulling the anterior section
forward.

Frankel-II is used for cl-II
and division 2. Frankel-II is
modified by adding a stainless
steel protrusion bow behind the
maxillary incisors, which serves
to maintain the pre-functional
appliance alignment that was
achieved and stabilize the
appliance by helping to lock it on
the maxillary arch.

Frankel-III - is used in the
treatment of cl-III malocclusion.
Here the lip pads are situated
in the maxillary, instead of
mandibular vestibular labial
sulcus.
Labial bow rests against the
mandibular teeth and not on the
maxillary incisors.
There is a protrusive bow
similar to that of Frankel-II
behind the upper incisors to
stimulate the forward movement
of these teeth.

Effects of Frankel -III
FRANKEL-III gives both skeletal and dental changes
(a) maxilla is moved in a forward and slightly downward
direction.
(b) The mandibular is redirected vertically in its vector of
growth with little evidence of antero-posterior repositioning
of the chin.

Frankel-IV
Primarily used in correction
of open bite and to a lesser
extent in bimaxillary
protrusion. In open bite cases,
Frankel-IV redirect the
mandibular growth from a
downward and backward
growth rotation to a upper
and forward rotation.
With lip seal exercises, lip
contact takes over, reducing
tongue protrusion and
causing tongue to move back
into its normally raised
position.

TWIN BLOCK APPLIANCE
Occlusal inclined plane is
the fundamental functional
mechanism of the natural
dentition. Cuspal inclined plane
play an important role in
determining the relation of the
teeth as they erupt into
occlusion.
In case of class I relation
the distal slope of the lower
posterior teeth slide with the
mesial slope of the upper
posterior teeth creating a mesial
component of force which is
favourable for the normal
mandibular development.www.indiandentalacademy.com

In case of distoocclusion,
the mesial slope of the lower
posterior teeth slide with the
distal slope of the upper
posterior teeth creating a distal
component of force that is
unfavourable to normal forward
mandibular development.

MODE OF ACTION OF TWIN
BLOCK
Twin block modify the
occlusal inclined plane and use
the forces of occlusion to correct
the malocclusion.
The unfavourable cuspal
contacts of the distal occlusion
are replaced by favourable
proprioceptive contact on the
inclined plane of Twin block to
correct the malocclusion and to
free the mandible from its locked
distal functional position. Due to
the inclined plane effect a mesial
component of force is created that
is favourable for the normal
mandibular development.

I. ACTION OF TWIN BLOCK
IN CL-II DIV. 1 DEEP BITE
The bite is opened by
sequential trimming of upper
bite block occluso distally that
allows the lower posterior teeth
to erupt.

II. IN OPEN BITE
The posterior bite blocks
remain unreduced and intact
through out treatment.
This results in intrusive
effect on the posterior teeth,
where as the anterior teeth
remain free to erupt.

III. CL-II DIVISION 2
In addition to the sequential trimming of upper bite
block the twin block is modified by the addition of two
sagittal screw set.
The activation of the screw expand the arch by
advancing the upper incisor and at the same time, drive the
upper buccal segment distally and buccally along the line of
the arch. www.indiandentalacademy.com

IV. IN CL-III
MALOCCLUSION
Treatment of class-III
malocclusion is achieved by
reversing the occlusal inclined
plane to apply a forward
component of force to the upper
arch and a downward and distal
force to the mandible in the lower
molar region.

FIXED FUNCTIONAL
APPLIANCES
Fixed functional appliances
also work in the same way as other
removable functional appliances.
They produce extensive
remodeling and anterior relocation
of glenoid fossa, which contributed
to anterior mandibular positioning
and altered jaw relationship.
In contrast to removable
appliances, fixed functional
appliances maintain a continuous
alteration in condylar relationship.

FUNCTIONAL AND ORTHOPAEDIC APPLIANCE
COMBINATION
They are used together when both the orthopaedic as
well as the functional effects are needed. They can be used
in combination with head gear, chin cap and face mask.
a. When used in combination with head gear, it restricts or
redirect maxillary growth.
b. When used in combination with chincup, it restricts
mandibular growth.
c. When used in combination with face mask it augments
maxillary growth.

The concorde facebow apply
both intra oral intermaxillary and
extra oral orthopaedic traction to
restrict maxillary growth and at the
same time to encourage mandibular
growth in combination with
functional mandibular protrusion.www.indiandentalacademy.com

THE MAGNETIC FUNCTIONAL SYSTEM
The magnetic functional system works under :
Spatial magnetic force system
Centripetal spatial orientation
The Spatial Magnetic Force System
It refers to the dissociation of the attractive magnetic
forces in to three vector components i.e.,
Vertical force – acting craniocaudally.
Lateral shearing force – acting along the transverse
plane.
Sagittal shearing force – acting anteroposteriorly.

Centripetal Spatial Orientation
It describes the attraction of mobile mandibular
magnet by a stationary maxillary magnet towards the
constructive protrusive closure position.
The above mentioned functional system enables
normal physiologic oral activity during active periods (e.g.
mastication, deglutition, speech) and constraint of the
mandible in constructive protrusive closure position
during rest periods (i.e. sleep) by means of attractive
magnetic force. www.indiandentalacademy.com

MAGNETIC TWIN BLOCK
The inclined plane of the twin block uses either
Attracting magnet ie the poles of the magnet attract each
other.
or
Repelling magnets ie the poles of the magnets repel each
other.
There are logical reasons to support the use both
systems. The attracting magnets pull the appliance together
and encourages the patient to occlude in a forward position
that trigger proprioceptive Reponses.

The repelling magnetic force
is intended to apply
additional stimulation to
forward posture as the
patient closes into occlusion.
Magnets should be
used only where speed of
treatment is an important
consideration or where the
response to non magnetic
appliances is limited.

LIP BUMPER
Lip bumper is mainly
indicated in case of lower lip
habit that flattens and crowds
the lower anteriors.
MODE OF ACTION
The lip bumper keeps the
lower lip away from the lower
anterior teeth and there by
eliminating the action of
hyperactive mentalis and the
tongue will then stimulate the
lower anteriors to move labially,
which increases the arch length
and eliminate crowding.

CATALAN’S APPLIANCE
This appliance is used for
the correction of single tooth in
cross bite or a segment of upper
arch in cross bite.
MODE OF ACTION
The inclined plane
transmits muscle forces directly
to the teeth that are in cross bite
and cause labial tipping of the
teeth.www.indiandentalacademy.com

ORAL SCREEN
MODE OF ACTION
The lip exert pressure through
the plastic against the anterior
part of the dentition and bone
support which leads to the
correction of proclination.
The buccal part of the screen
is wide enough to keep the
pressure off the posterior teeth
(2-3mm clearance on each side in
the first deciduous molar area),
the tongue’s active function
moulds the posterior segments
and helps to expand the narrow
dental arches.www.indiandentalacademy.com

Thus, the anterior segment is influenced directly by the
appliance through muscle pressure against the plastic,
whereas the posterior segments are influenced by the actual
keeping away of the cheek muscles, allowing tongue posture
and function to expand the posterior areas.

CONCLUSION
Though different authors suggest different mode of
action for each appliance, the effects produced by these
appliances are similar with some difference. Still controversy
exist regarding the mode of action of functional appliances.
Many researches are going on to know about the changes that
occur in the oro-facial structures to the functional and
orthopaedic forces.

Modus operandi

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