removable functional appliance 1

Part 1
dr Maher FOUDA
Faculty of Dentistry
Mansoura Egypt
Professor of orthodontics
Removable functional
appliance

The term ‘functional appliance’ refers to a
variety of removable appliances designed
to alter the arrangement of various muscle
groups that influence the function and
position of the mandible to transmit forces
to the dentition and the basal bone.
Functional or Twinblock Appliance

Typically, these muscular forces are generated
by modifying the mandibular position in
vertical and sagittal direction, thereby resulting
in orthopedic and orthodontic changes.
The Twin Block appliance
design used in this case.
class II division 1

1. Functional appliances are appliances that alter
the posture of the mandible, holding it open or
open and forward or backward (Proffit).
2. Functional appliances are loose removable
appliances designed to alter the neuromuscular
environment of the orofacial region to improve
occlusal development and/or craniofacial skeletal
growth (Moyers).
3. Functional appliances are appliances that act by
either harnessing the muscular forces or by
preventing aberrant muscular forces from acting
on the dentition.
VA R I OUS D E F INI T I ONS F O R
FUNC T I ONA L A P P L I ANC E S

A major reason for the development of functional
appliances was the recognition that function
affects the ultimate morphologic status of the
dentofacial complex.

The history of the functional appliance can be
traced back to 1879, when Norman Kingsley
introduced the ‘bite-jumping’ appliance.
Cl II Malocclusion Treatment, Using the Modified
Twin Block Appliance Coordinated with Fixed Orthodontics in
a Postmenarche Patient
Twin Block appliance: maxillary part (A): (a) modified ball clasps used instead of
conventional clasps to coordinate with fixed
appliance; Twin Block appliance (B): (b) block A, (c) block B, (d) labial bow, (e)Cclasps,
and (f)Adam’s clasp;mandibular part (C);mandibular
part mucosal surface (D); mandibular part occlusal surface (E); maxillary part mucosal
surface (F); maxillary part occlusal surface (G).

Alfred Paul Rogers (1873–1959), sometimes called the
father of myofunctional therapy, wrote: “It is a well-
recognized biological fact that structural form is influenced
by pressures due to abnormal neuromuscular
Intraoral photographs with
Twin block appliance.
Post twin block facial
photograph.
Class II div 1 malocclusion Effect of Twin Block Appliance on a Growing Patient – A
Case Report
activity; the converse being true that normal
pressures, due to function, tend toward normal form
in the osseous structures.”

The monobloc, developed by Robin in 1902, is
generally considered the forerunner of
removable functional appliances, but the
activator developed in Norway by Andresen in
the 1920s was the first functional appliance to
be widely accepted, becoming the basis of the
‘Norwegian system’ of treatment.4
The Basic Activator is a mono-block appliance (solid block of
acrylic) designed to be loose fitting in the patient’s mouth.

HISTORICAL HAPPENINGS IN
DENTOFACIAL ORTHOPEDICS
• In De Epidemicis, by the great doctor
Hippocrates, the first scientific description of a
malocclusion appeared relating anatomical
characteristics to functional ones.
• In 1880, Kingsley, designed an upper plate with
a plane inclining backward that embraces the
lingual surface of the lower incisors. The
purpose was not to push these teeth forward but
to modify the whole articulation. This was the
birth of functional orthodontics.

• In 1887, Angle gave great importance to
the influence of orofacial musculature on
the shape of dental arches. He also
believed that the Class II division 1
malocclusion was primarily caused by
mouth breathing. He was thus able to arrive
at a conclusion of purely functional nature.
• In 1888, Wilhelm Roux worked out the
theory of functional adaptation.

• In 1892, Julius Wolff stated that the adaptive capacity
of bones enable them to take a shape best suited to the
required purpose. With Roux, he made an important
theoretical contribution to orthopedics.
• In 1902, Pierre Robin designed the monobloc, a
vulcanite device to cure mandibular retrusion.
• In 1908, Viggo Andresen experimented with a
removable retention plate following multibanded therapy
and was surprised to obtain further clinical
improvement.
• In 1909, Emil Herbst designed a piston worked fixed
appliance for forced mandibular advancement.

• In 1918, Alfred Paul Rogers defined
muscles as living orthodontic appliances
and also described his fundamental theories
of myofunctional therapy.
• In 1937, Selmer Oslen held that the
activator’s mechanism of action lay in
stretching of soft tissues and in the potential
energy that accumulated. He recommended
high construction bite to overcome
mandibular repose position.

• Bimler in 1949, modified activator and created the
elastic occlusal modeler.
• In 1949, Edmundo Muzj modified the activator
eliminating the palatal part and introducing a metal
slide curved on the mandibular part to expand the
arch.
• In 1950, Martin Schwarz attributed the activator’s
effect to microstimuli exerted by the device after
observing that the mandible is immobile at night.

• In 1950, Wilhelm Balters began to modify the
activator to develop the bionator.
• In 1952, Hans Muhlemann introduced the
propulsor, a device similar to the activator but
without metal components.
• In 1953, Herren concluded that the activator
worked like a repositioning splint, altering the
balance between the protractor and retractor
muscles.
• In 1953, Hugo Stockfish introduced the kinator,
an elastic activator.

• In 1954, Oscar Hoffer studied the increase in
mandibular growth produced by the activator.
• In 1960, Klammt, student of Bimler, altered his
teachers’ appliance as he felt Bimler’s appliance is
too fragile.
• In 1960, Melvin Moss formulated functional matrix
theory together with his wife Letty Selentin.
• In 1960, Rolf Frankel devised the functional
regulator.

• In 1960, Ahlgren studied EMG responses to activator.
• In 1967, Alexander Petrovic formulated his fundamental theories
on different types of cartilages involved in osteogenesis and
individuated the peculiarities of condylar cartilage, which also
responds to local stimuli.
• In 1969, Stockli and Teuscher used activator with cervical
traction.

• In 1971, Harvold proposed an activator with high construction bite. His ideas
were shared by Woodside.
• In 1972, Van Limborgh criticized Moss’s theory giving greater importance to
epigenetic control in craniofacial growth.
• In 1977, William Clark developed the twin block.
• In 1979, Herren presented the results of monozygotic twin study that the
mandible grew 5 mm more in those treated with functional appliances than in
those who were not treated.
Sub and Upper Parts of the Twin-block Appliance.

CLASSIFICATION OF FUNCTIONAL
APPLIANCES
There are many methods of classification of functional
appliances. A few of them are as follows.
Proffit’s Classification
• Tooth-borne passive: Appliances have no intrinsic
force-generating capacity, e.g. bionator, twin block,
Herbst, activator.
• Tooth-borne active: Appliances have intrinsic force-
generating capacity due to incorporation of spring or
screws, e.g. activator modifications.
• Tissue-borne: Frankel appliances.
bionator twin block activator.
Frankel

CLASSIFICATION OF FUNCTIONAL
APPLIANCES
Graber’s Classification
• Group 1: Transmit muscle force directly
to the teeth, e.g. inclined plane, oral
screen.
• Group 2: Transmit force to teeth as well
as other structures, e.g. activator.
• Group 3: Operate from vestibule, e.g.
Frankel appliance.
inclined plane oral screen activator Frankel

Based on the Nature of Removability
• Removable functional appliances:
Activator, Twin block, bionator, Frankel.
• Fixed functional appliances: Herbst,
jasper jumper, Forsus.

Based on the Way Muscle is Used
• Myotonic appliances: Rely on muscle mass for
action, e.g. activator, bionator.
• Myodynamic appliances: Rely on muscle
movements or dynamic properties, e.g. Bimler.
• Frankel appliance does not fit into any of these two
groups.

PRINCIPLES OF FUNCTIONAL
APPLIANCES
The goal of functional appliances is to use functional
stimulus, channeling it to the greatest extent that the
tissues, jaws, condyles and teeth allow. The forces
that arise are purely functional and intermittent.
U bow activator, an alternative functional orthodontic
appliance

influence the facial skeleton of the growing child in the
condylar and sutural areas. However, these appliances
also exert orthodontic effects on the dentoalveolar area.
Functional appliances are considered to be
orthopedic tools to
The Hybrid Aesthetic Functional (HAF) Appliance: A Less
Visible Proposal for Functional Orthodontics

APPLIANCES
The uniqueness of functional appliances lies in
the mode of force application. They do not act
on the teeth in the similar manner to
conventional appliances, which uses mechanical
elements, such as springs, elastics, or ligatures,
but rather transmit, eliminate and guide natural
forces. The natural forces are those of muscle
activity, growth and tooth eruption.

APPLIANCES
The most important principle underlying the functional
appliance therapy is the adaptation between form and
function. Functional appliances induce change either
in form or function. Neuromuscular adaptation allows
the form and function to get adjusted.
Teuscher-type activator with torquing
spurs and headgear tubes

Functional appliances work by two principles: (1)
force application and (2) force elimination .
Principle of functional appliance. (A) Force
elimination. (B) Force application.

Appliance wear by patients produces the following effects:
• Force applied to dentition and underlying basal bone
induces change in form or shape.
• Secondary adaptation of function to the form takes place.
• Most of the removable appliances and fixed appliances work
by this principle.
• Subsequent to change in form, the neuromuscular response
brings about adaptation in function to the new form.
Modified Balters Bionator with lower
incisor capping
Force Application

• Abnormal and restrictive muscular forces are prevented from
acting on the developing dentition and jaws.
• Function is rehabilitated or changed. This is followed by
secondary adaptation in form according to the new rehabilitated
function.
• Vestibular shields, Frankel appliances act by this principle.
Force Elimination
A modified functional regulator (FR 2)
appliance with lower incisor capping

The success of functional appliance treatment depends on
the neuromuscular response. Functional appliance
treatment induces change in either form or function.
Secondary adaptation of form to function or adaptation of
function to form occurs due to the neuromuscular response.
Neuromuscular Response
The Dynamax appliance. Mandibular
protrusion is achieved by lingual springs or
spurs that rest behind shoulders on a lower
fixed lingual arch

EFFECTS OF FUNCTIONAL APPLIANCES
AND THEIR MODUS OPERANDI/ COMMON MECHANISMS BY WHICH
FUNCTIONAL APPLIANCES WORK
Though the functional appliances is considered as a part of
contemporary orthodontic practice, yet their mode of action is still
controversial. The capability of the functional appliances to
reduce overjet by modifying incisor angulation and position is not
debatable. The controversy surrounds the capability of the
appliances in increasing the mandibular growth resulting in long-
term change in the skeletal pattern. The mandibular growth aspect
is of particular interest as most skeletal Class II patterns have as
their main component mandibular retrognathia.
A Twin Block appliance

Several types of functional appliance have been introduced.
Although they differ in detail, their action falls into three
categories:
1. Utilizing the forces of the muscles of mastication
2. Utilizing the forces of the circumoral musculature
3. Reducing the forces of the circumoral musculature.
A Herbst appliance

Almost all functional appliances use the principles
embodied in two basic appliances, the Andresen
appliance or activator, and the oral or vestibular screen.
Many appliances combine the principles of these two
basic appliances. The different mechanisms by which
the functional appliances produce their effects are
analyzed here.
FORSUS® spring

AND THEIR MODUS OPERANDI/ COMMON MECHANISMS BY
WHICH FUNCTIONAL APPLIANCES WORK
Dentoalveolar Changes
Differential Eruption
Eruption pattern is modified as per the need by placing
molar stops and by providing acrylic guide planes. The
divergent directions of eruption of the maxillary and
mandibular molars can be altered by the functional
appliances.
Treatment of Class II division 1 malocclusion with
functional and fixed appliances. Upper
left panel shows the presenting malocclusion in late
mixed dentition. Upper right panel shows
the occlusion following 9 months treatment with a
Twin Block functional appliance: note the
lateral open bites. Lower left panel show fixed
appliances being used to settle and detail the
occlusion. Lower right panel shows final occlusion
following removal of appliances

Treatment of a Class II divison 2-type
malocclusion with a Twin Block appliance and
a sectional fixed appliance to decompensate
the upper labial segment
In Class II treatment, the acrylic platform can
be adapted to arrest maxillary molar eruption,
yet allow concomitant mandibular molar
eruption into Class I relationship. In Class III
treatment, the converse would be applied.8

The vertical eruption of the maxillary teeth is prevented by acrylic
occlusal stops and the intrusive forces created by the appliance.
Incisal acrylic coverage prevents the eruption of the mandibular
and maxillary anteriors. Functional appliances can also correct
deep bite by relative intrusion.
Modified Andresen activator. The
original design did not have lower incisor
capping or Adams cribs, which have both been
added for retention

Tipping Movements
Reduction in overjet takes place through a combination of
retroclination of upper incisors and proclination of mandibular
incisors. This needs to be prevented or minimized as this could
impede skeletal or orthopedic correction. Functional appliances
seem to have an uprighting effect on the erupting canines and
premolars during eruption.
Picture showing the Bimler Type A
appliance with is
components: (a) acrylic plates; (b)
coffin spring; (c) lower shield;
(d) buccal bow; and, (e) dorsal arches

AND THEIR MODUS OPERANDI/ COMMON MECHANISMS BY WHICH FUNCTIONAL
APPLIANCES WORK
Skeletal Changes
Maxillary Growth Restriction
A restraining effect on the maxilla has also been reported with use
of functional appliances. The maxillary change is generally
measured to ‘A’ point, which is a dentoalveolar point rather than a
true skeletal landmark.
Cephalometric
superimposition of the pre-
treatment
cephalometric (green color)
and post-treatment
cephalometric tracing
(red color) with Sella -nasion
as a reference plane

Functional appliances harness the passive
tension arising from the inherent elasticity in
muscle, skin and tendinous tissue and transmit
to the maxillary teeth engaged to the appliance.
Transduction of viscoelastic force:
Various intra oral views of twin block appliance.

Increased Rate of Mandibular Growth
Functional appliance is claimed to cause increased
forward growth of the mandible. With regard to the
nature and method by which the mandibular growth is
stimulated, there is a lot of controversy.
Initial start photo After Ph. I Bionator ( removable appliance)
Functional Orthopedic Removable Bionato

Lateral Pterygoid Muscle Stimulation
Mandibular growth stimulation can be explained on the basis of
muscular hypothesis. It has been theorized that the lateral
pterygoid muscle has a special role in condylar growth
regulation.

According to lateral pterygoid hypothesis.
1. The activity of the lateral pterygoid muscle is essential for
normal condylar growth.
2. Increased lateral pterygoid muscle activity is a prerequisite to
stimulation of increased condylar growth.
3. Increased activity of the superior head of lateral pterygoid
muscle is associated with functional appliance wear .

pad causes bone deposition in posterosuperior aspect of
condyle by stimulating condylar cartilage growth. This
produces sagittal advancement of mandible.
4. Coordination of electromyographic activity in the superior
head of the lateral pterygoid with measurements of condylar
growth indicates skeletal adaptation proceeds until muscle
activity is restored to normal levels.
This in turn stimulates the retrodiscal pad. Increased activity of the
retrodiscal

• Parts of lateral pterygoid muscle and retrodiscal pad. Functional
appliances wear causes stimulation of both.

AND THEIR MODUS OPERANDI/ COMMON MECHANISMS BY WHICH FUNCTIONAL APPLIANCES WORK
The mandibular condyle is normally subjected to pressure,
which is one component of the local homeostatic mechanism
controlling its growth. When a functional appliance is worn, it
distracts the condyle from the fossa thereby removal of the
physical restraint occurs, which facilitates increased rate of
growth .
Unloading of condyle. Arrow
indicates posterosuperior
elongation of mandibular
condyle and adaptation to
new position.
Unloading of the Mandibular Condyle

Growth Stimulation and Growth Acceleration
Growth stimulation2,12 can be defined in two ways:
1. As the attainment of a final size larger than would have
occurred without treatment or
2. As the occurrence of more growth during a given period
than would have been expected without treatment.
Pre-treatment (extra-oral and intra-oral) and
post-treatment (extra-oral and intra-oral) photograph of the patient
following successful treatment outcome concurrent with Twin Block
appliance
Skeletal and
Dentoalveolar changes
concurrent
to use of Twin Block
appliance in Class II
division I cases with a
deficient mandible:
A cephalometric study

This is a hypothetical plot of the
response to functional appliance
treatment, illustrating the difference
between (1) absolute stimulation (larger
as an adult) and (2) temporal
stimulation (acceleration of growth). As
the figure suggests, an acceleration of
growth often occurs when a functional
appliance is used to treat mandibular
deficiency but the final size of the
mandible is little, if any larger than it
would have been without the treatment.
Collett stated that it cannot be
concluded that functional appliances
are effective in stimulating and
increasing mandibular growth.

The difference between growth acceleration in response to a
functional appliance and true growth stimulation. If growth
occurs at a faster-than-expected rate while a functional
appliance is being worn, and then continues at the expected
rate thereafter so that the ultimate size of the jaw is larger,
true stimulation has occurred. If faster growth occurs while
the appliance is being worn, but slower growth thereafter
ultimately brings the patient back to the line of expected
growth, there has been acceleration, not a true stimulation.

Arch Expansion
Albert Owenfound that lateral expansion was evident in many of the patients
treated with functional regulator. However, the time taken for lateral expansion is
more than for sagittal correction. Hence, longer treatment duration is
recommended, if lateral expansion is part of the treatment objective.
FR III appliance.
American Journal of Orthodontics and
Dentofacial Orthopedics
Volume 125, Number
Treatment effects of Fra¨nkel functional
regulator III in children with Class III
malocclusions

Remodeling Changes in TMJ
Decreased Biochemical Feedback
Stutzmann and Petrovic found that the zone of functional
chondroblasts in condyle secretes a substance that retards
mitotic activity of stems cells—a sort of negative feedback.
Stimulation of lateral pterygoid subsequent to functional
appliance wear causes quick maturation of chondroblasts,
consequently secreting less ‘negative feedback’ material.
Removal of this biochemical brake causes acceleration of
condylar growth.
Fränkel appliance type III (FR-III)

Glenoid Fossa Remodeling
Remodeling of glenoid fossa has been attributed to
anterior mandibular positioning and correction of jaw
relationship. Large volume of new bone was found to be
formed in the glenoid fossa, especially along the anterior
border of the postglenoid spine.

Soft-tissue Changes
Re-education of the Musculature
Andresen hypothesized that by continually holding the mandible
forward in Class II cases, the muscles would be obliged to learn a new
functional pattern. Gradually both the jaws and teeth would adapt to
the new jaw relationship prescribed by the appliance.
Management of Severe Class II
Malocclusion with Fixed
Functional Appliance: Forsus
The Journal of Contemporary Dental
Practice, May-June 2011;12(3):216-220

Changes in Neuromuscular Anatomy and Function
Neural excitation is produced by all functional appliances. Functional appliances
register a new sensory engram for mandibular position. Correct neural
stimulation of temporomandibular joints, muscles, periodontium and mucosa
produces good stomatognathic equilibrium.
Management of Skeletal Class II Malocclusion with Functional Regulator II Volume 1 • Issue 3 • 1000118Pediatr Dent Care, an open access journal
FR II appliance therapy.
Post Functional Extra oral photographs.

Muscular Changes During Functional Appliances
Elongation of muscle fibers and migration of muscle attachment along bony surfaces
are evident during functional appliance therapy. Changes in muscle dimension are
observed.
Pterygoid Response
It is the rapid adaptive clinical response seen shortly after wearing the appliance
probably for a few weeks.
Treatment of the Mouth Breather with
Changes on the Occlusion and
Body Posture Problems through the Human
Body Total Care Method -
Aragão Function Regulator (HBTC-RFA): A
Case Report

It is characterized by pain when retracting the
mandible due to altered activity of the medial head of
the lateral pterygoid muscle in response to the
mandibular protrusion. This may be due to the
formation of ‘tension zone’ distal to the condyle.

• It should be comfortable and acceptable for the patients.
• It should promote better compliance.
• It should offer good range of mandibular movements.
• It should be simple and inexpensive.
• It should be easy to fit.
The ideal requirements of a functional appliance are

Fränkel appliance type I (FR-I))
• It should be adaptable to both Class II and Class III
malocclusions.
• When used with fixed appliances, it should not cause
breakage of fixed appliance components.
• It should be usable in both mixed and permanent dentitions.
• It should provide good results with minimal patient
cooperation.

ADVANTAGES AND LIMITATIONS
OF FUNCTIONAL APPLIANCES
Advantages
• Functional appliances are effective in cases where dysfunction is the
cause for malocclusion.
• They are the most effective in the correction of Class II malocclusion in
children in the mixed dentition period.
• They can be used to correct open bite and deep bite cases.
• Maintenance of oral hygiene is easier with functional appliances.
• They require less chairside time.
• They restore muscular balance.
Treatment of skeletal class II division 1
malocclusion with mandibular deficiency using
myofunctional appliances in growing individuals
JOURNAL OF INDIAN SOCIETY OF PEDODONTICS AND
PREVENTIVE DENTISTRY | Jan - Mar 2012 | Issue 1 | Vol 30 |

• Since treatment is initiated in mixed dentition stage, the
possibility of psychological trauma to the child because of
malocclusion is reduced.
• Functional appliances try to correct the skeletal problems.
Activator in place

Limitations
• Most of the functional appliances are bulky and, therefore,
inconvenient for the patients.
• Patient cooperation is not good.
• A good degree of expertise is required in the management
of functional appliance.
• They are not suitable for adults with skeletal problems.
Balters bionator type I

Limitations
• Individual tooth problems cannot be corrected.
• They are not suitable for high-angle cases.
• They cannot be used in cases with crowding. Minor crowding, if
present, has to be corrected prior to functional appliance treatment.
• Second phase of treatment with fixed appliance is usually required
to obtain detailed finishing of occlusion.
• They are not suitable for non-growing patients.
Activator with lower incisal capping and labial bow
APOS Trends in Orthodontics | July 2013 | Vol 3 | Issue 4
Early Intervention in Skeletal Class II and dental
Class II division I malocclusion

INDICATIONS AND CRITERIA FOR FUNCTIONAL
APPLIANCE THERAPY
In general, functional appliances are used in the treatment of Class II division
1 malocclusion. Functional appliances are used to correct deficiency states
only, namely, correction of mandibular and maxillary deficiencies. A case with
functional retrusion responds well with functional appliance therapy.
Functional appliances are used in the management of Class III due to
retrognathic maxilla in a growing child. Other indications are prevention and
correction of deleterious oral habits that include digit sucking, lip sucking,
mouth breathing and other functional aberrations.
Class II division 1 malocclusion. Class III

APPLIANCE THERAPY
The criteria for case selection are as follows:
1. Skeletal criteria:
a. A decreased lower facial height based on profile
assessment (low angle case).
b. Proportionate facial balance between upper and middle
face.
c. Mild to moderate Class II facial pattern.
d. Positive visualized treatment objective.

d. No labial tipping or flaring of mandibular incisors.
e. Moderate deep overbite.
f. Anteroposterior molar Class II relationship.
g. Preferably no midline asymmetry.
2. Dental criteria:
a. No crowding in the maxillary or mandibular dental arches.
b. A good mandibular arch with no rotations or displacement of teeth.
c. Relatively flat mandibular occlusal plane.

APPLIANCE THERAPY
3. Soft-tissue criteria:
a. Competent or potentially competent lips where the lower lips
will be able to stabilize the upper teeth after correction.
b. Muscular pattern that does not exhibit undue tightness.
Volume 2 • Issue 1
Pediatr Dent Care, an open access journalPromising Effect of Treatment at Early
Adolescent Age: A Case Report

APPLIANCE THERAPY
4. Emotional criteria:
a. Keen patient interest and desire
from both parent and patient.
b. Patient’s potential cooperation is
highly essential.

APPLIANCE THERAPY
5. Respiratory criteria: No nasal obstructions or chronic
respiratory disorders.
6. Age/growth criteria:
a. Functional jaw orthopedics is primarily indicated in patients
who have still growth left in them.
b. The ideal age for commencement for appliance is late mixed
dentition stage, i.e. by 9 years of age.

APPLIANCE THERAPY
7. Functional criteria:
a. The assessment of the relationship between rest position
and occlusion, to differentiate a functionally true and a forced
bite malocclusion, is crucial. The clinician also must
distinguish whether the malocclusion is a functionally true
one, with a normal path of closure from postural rest of
habitual occlusion or a functional retrusion, with the condyle
moving up and back from postural rest to habitual occlusion.
Frontal intraoral view showing an anterior
crossbite - intercuspal position (A). Frontal intraoral view
showing the edge-to-edge contact of the incisors - centric
relation (B)

APPLIANCE THERAPY
Normally, condylar action in the lower joint cavity is primarily rotary from the rest of occlusion. Translatory
condylar movement not only jeopardizes the normal condyle-disk eminence relationship but also produces a
retruded spatial mandibular malposition on full occlusion.
Rotation and translation of the mandibular
condyle during opening. (arrow through the condyle)
Direction of condylar translation during opening; (1)
moderate jaw opening; (2) near wide opening.

INDICATIONS AND CRITERIA FOR FUNCTIONAL APPLIANCE THERAPY
A primary treatment objective must be to eliminate the retruded condylar
position, harmonizing it with the more anterior postural rest position. This can
be done quite successfully using functional orthopedic procedures. If the path
of closure is normal, with only rotary condylar function from postural rest
position to occlusion, and the malocclusion is a true sagittal skeletal
discrepancy, the treatment challenge is different.
Opening movement of the mandible. (a) In centric occlusion, the teeth are in uniform contact on all sides with the an-
tagonists; the mandible is at its closest to the maxilla, and the condyle lies deep in the articular fossa. (b) From centric occlusion,
an opening movement of approximately 10 mm can be made as a pure hinge movement. For wider jaw opening, a gliding move-
ment downward and forward is added to the pure hinge movement. (c) For maximum opening movement, the condyle now slides
downward and forward as far as the horizontal surface of the articular tuberosity. This movement is enforced by the lateral pterygoid
muscle

APPLIANCE THERAPY
Not only the occlusal position must be changed, but also a neuromuscular
adaptation to the new postural position of the mandible must occur, as the condyle
grows up and backward to its correct relationship with the fossa structures.
Achieving a permanent neuromuscular adaptation to the appliance-oriented
mandibular postural position can be difficult. If the original postural resting position
persists a functional disturbance ‘Sunday bite’ or dual bite is the consequence.
Border movements
of the mandible in the sagittal
plane

INDICATIONS AND CRITERIA FOR FUNCTIONAL APPLIANCE THERAPY
b. The examination of the relationships between overjet and the
function of the lips is another important procedure. If the lower lip
postures and functions in the incisal gap created by the excessive
overjet and if hyperactive, adaptive, and exacerbative mentalis muscle
function is present, these deforming activities should be eliminated
during the day, if the functional appliance of choice is worn only at night.

APPLIANCE THERAPY
c. The posture and function of the tongue should
be assessed. In some malocclusions, abnormal
tongue function needs to be controlled with
accessory elements or appliances.

C L INI C A L S IGNI F I C ANC E
Clinical VTO
Clinical visualized treatment objective was advocated by Creekmore
as an aid to decide about the type of appliance in skeletal Class II
malocclusion. The procedure consists of asking the patient to bring
the mandible to an edge-to-edge bite relationship. Change in the
appearance of the patient is noted at two levels: (1) one at the edge-
to-edge position and (2) the other at a position midway between the
existing occlusion and edge-to-edge position.
• If the profile worsens at the edge-to-edge position, it means the fault
lies in maxilla. It is a case of maxillary prognathism and appliances,
like the maxillary intrusion splint or headgears, are advised.
• If the profile improves at the edge-to-edge position, it means the
fault lies in the mandible. It is a case of mandibular retrognathism.
Functional appliances to stimulate mandibular growth are indicated.
• If the profile improves midway, it is a case of combination of
maxillary prognathism and mandibular retrognathism. Appliances,
like activator headgear, twin block with headgears, are indicated.

DESCRIPTION OF APPLIANCES
Upper Anterior Flat Bite Plane
This consists of an acrylic platform made parallel to the occlusal
plane, which is present behind the upper incisor teeth on which the
lower incisor bite . Anterior bite planes are most successful, if they
are used
in patients who have large interocclusal clearance. Bite opening by
anterior bite plane should not interfere with normal freeway space.
The posterior teeth should be maintained at 2–3 mm separation.).
(A) Upper anterior flat bite plane. Lower incisor
occludes with the flat anterior bite plane.
Leveling and alignment and Placement of fixed
upper anterior flat bite plate.

Mechanism of Action
Bite planes cause differential eruption of posterior teeth. When
the appliance is worn, the posterior teeth are freed from
mastication and occlusion. The posterior teeth supraerupts and
cause reduction of deep overbite. This effect is known as
‘opening the bite’. Bite planes also cause relative intrusion.
Upper Anterior Flat Bite Plane
a flat anterior bite-plane should be trimmed during
overjet reduction to give space for retraction of the
upper incisors and their associated gingivae. The
bite-plane should be maintained to prevent re-
eruption of the lower incisors and only removed
towards the end of overjet reduction.

Bite Plane with Labial Bow
The important side effect of anterior bite plane is the labial proclination of the upper anterior
teeth. This can be minimized by placing a labial bow. The idea of placing a labial bow in upper
anterior bite plane is to prevent labial proclination of upper incisors.
The labial bows should not be activated for retraction with bite planes. After the
overbite has been reduced, the bite plane is trimmed and then the upper incisors are
retracted.
(B) Labial thrust of bite plate appliance (A) and labial
bow counteracts the labial thrust (B).

Sved Bite Plane
Another method to prevent labial proclination of upper incisor with bite
plane is by using Sved bite plane. Sved in the year 1944 modified the
bite plane by extending the acrylic plate to cover the incisal edges of
the upper anterior teeth. This eliminates the forward component of
force, which causes proclination.
Sved bite plane is a highly satisfactory method of supporting the bite
while allowing the posterior teeth to erupt. Sved bite planes should be
worn while eating. Sved bite planes are a form of reinforced anchorage.
C) Sved bite plane. The labial or forward thrust of the bite plate appliance is
counteracted by the acrylic plate that covers the incisal edges.

Uses of Anterior Bite Planes
• Used to reduce the overbite.
• Used to correct TMJ problems.
• Correction of bruxism.
• Correction of occlusal prematurities.
• Used as a periodontal splint.
• Eliminates functional retrusion effects.
• Promotes increase in mandibular intercanine width since the
restricting influence of the maxillary arch is removed.
• Used as a dental crutch.

Upper Anterior Inclined Plane
The appliance looks like a flat anterior bite plane . The
difference is the incorporation of an anterior inclined
plane to engage the lower incisors and
Upper anterior inclined plane.
cause the mandible to slide anteriorly.

Normally, the guide plane has angulations of approximately 45°
with a seating groove for the lower incisors to reduce the labial
tipping of lower anteriors. The upper anterior inclined plane is
also used as retention appliance after functional appliance
therapy, like twin block.
The maxillary anterior inclined plane favors the forward
movement of the mandibular teeth or the mandible advancement
from a distal bite into a neutral occlusion.

Lower Inclined Planes/Catalan’s Appliance
Lower inclined plane is an appliance used for the correction of
anterior crossbite when one or more upper teeth are in lingual
relation to lower incisors . This appliance was introduced by Catalan
150 years ago. Appliance is usually recommended to
be worn only for a maximum of 3 weeks. Inclined planes are
contraindicated in cases without sufficient overbite.
(A) Cemented incline plane; (B) Removable inclined
plane.

Indications
• The lower inclined plane is indicated during the eruptive stages of incisors when
there is a good degree of overbite.
• All inclined planes cause opening of the bite by allowing posterior teeth to erupt.
• The advantages of inclined plane include:
• Ease of fabrication.
• Correction of crossbite is very fast because functional forces are used.
• Trauma to tooth is minimal.
• Minimal or no relapse.

• If the appliance is worn for a long time,
it leads to anterior open bite due to
overeruption of posterior teeth.
• Appliance has to be removed to check
the correction achieved.
• Precise alignment of the teeth is not
achieved.
Disadvantages of inclined plane:
• Difficulty in eating with the appliance.
• Speech problems.

Fabrication
In the working models, draw the design of an inclined plane. The
inclined plane should include a tooth and half on both sides of the
crossbite area. The inclined plane is waxed up at an angle of
approximately 45° to the occlusal plane. Posteriorly extend
sufficiently to prevent the patient from biting into retruded
position. Waxed up inclined plane is acrylized.
During insertion, the bite should not be opened more than 4 or 5
mm as extreme opening causes muscle fatigue. The finished
appliance is cemented with thin mix of luting cement (zinc
oxyphosphate). Recall appointment after week. Correction is
achieved in 2 or 3 weeks’ time.

Vestibular Screens/Oral Screens
Oral screen is a sheet of acrylic resin that is worn inside
the lips and outside the teeth. Oral screen/vestibular
screen is a functional appliance because it has no active
elements designed to produce force. It produces its effect
by redirecting the pressure of the muscles and soft
tissues, like lips and cheek. Vestibular screens16 were
introduced by Newel in the year 1912. The terms oral
screens and vestibular screens are used as synonyms by
many of the authors. Krauss differentiates between oral
screen and vestibular screen .

Oral Screen
• Used to control abnormal habits, namely, mouth breathing and tongue
dysfunction.
• Teeth contact is present with acrylic.
Vestibular Screen
• Extended into the vestibule, in contact with the alveolar process.
• No teeth contact.
• Vestibular screens are also called lip molder.

Mechanism of Action
• The oral screen prevents the pressures from cheeks from
acting on the dentition . Because of this, the tongue is free to
exert its force. This causes passive expansion of the arches.

Mechanism of action of oral screen. (A) The screen prevents forces of
buccinator mechanism from acting on the dentition. (B) Other effects of oral
screen. 1, Produces mandibular advancement; 2, Improves the tonicity of
upper and lower lip; 3, Pressure from lip is transmitted to incisors, which
causes retraction of maxillary incisors; 4, Might cause intrusion of maxillary
incisors; 5, Screen prevents muscle force from acting on dentition. This
causes passive expansion of apical base; 6, Differential eruption of molars
and opening of bite.

• The pressure from the lips is directed to the incisors. This causes
lingual movement of the labially proclined teeth. Retroclination of
maxillary incisors results.
• Lower jaw is moved forward, if the appliance is fabricated in
protrusive bite.
• Hypotonic lips are activated. Tonicity of the lips is improved.
• Possible intrusion of maxillary incisors and differential eruption of
molars.
• Passive expansion of apical base.

Other Actions
• Stimulation of proper nasal breathing.
• Cessation of habits, like finger and thumb
sucking, lip biting.

Construction of the Appliance
Appliances are preferably made in clear acrylic . Working models placed in
normal occlusion
or protrusive bite is taken for Class II division1 malocclusion.
Wax up of the appliance is done. Anterior segment is influenced directly by the
appliance. So, incisal third of anterior teeth is not covered with wax. Posterior segment
is not influenced by the appliance directly. It acts by keeping away the appliance from
the tissues. To effect this change, the buccal surface of teeth and alveolar process are
covered with two layers of wax up to the distal aspect of first permanent molar in
permanent dentition. It extends to the vestibular depth.
Wax up for oral screen.

Extension
In deciduous dentition, it extends up to distal of second
deciduous molar. Correct curve is provided between the
upper and lower incisors and lower labial sulcus to
accept the lower lip. Edges are made less thick than the
buccal vestibular sulcus depth. Allowances are made
for labial and buccal frena.
Appliance is processed with either heat-cure or self-
cure acrylic and trimmed and polished.

Adjustment of the Appliance
• Appliance should be worn by the patient every night and also during
daytime when possible.
• Lip seal exercises should be done for about 30–45 min/day.
• Breathing holes should be gradually reduced in size.
• Padding with quick setting self-cure acrylic is done in areas where
tooth contact is present. Padding is done with pink acrylic.
Oral screen training. (Left) The oral screen is inserted predentally, behind closed lips. (Right)
The patient must press the lips firmly together, then strongly pull the handle straight
forward, away from the mouth, and maintain pressure for 5-10 s

Uses of Oral Screen
• Used as both active and passive appliance.
• Used for the correction of tongue thrusting, thumb sucking and lip
biting habits.
• Correction of mouth breathing when the airway is patent.
• Correction of mild distoclusion.
• Correction of flaccid hypotonic orofacial musculature.
• Counteract deficiencies in lip posture and function.
• Correction of mild proclination of incisors.

Advantages
• Simple and versatile appliance in early interceptive treatment.
• Oral screen establishes a better muscle balance between the tongue
on the inside and buccinator mechanism on the outside.
• Corrects the faulty relationships of upper and lower lips to each other
and near-normal lip seal becomes possible.
• They contribute to the development of a proper functioning occlusion.
• Effective mechanism for reducing or eliminating hyperactive mentalis
activity.
• Best suited to work with abnormal lip and tongue activity.

Disadvantages
• It is not a complete mechanotherapy.
• It is only an initial assault or phase 1 correction
of orthodontic problem .
The Use of Oral Screen in Children Patients with
Mouth Breathing Habit: A Case Report
International Journal of Science and Research (IJSR)
ISSN: 2319-7064

MO D I F I C AT I ONS O F O R A L S C R E EN
1. Hotz modification.
2. Screen with breathing holes.
3. Double oral screen.
4. Oral screen used in open bite cases.
5. Rehak’s modification
Kraus placed holes in the
front part of oral screen to
assist mouth breathing
patients initially during
adjustment period
Hotz introduced a ring or
lip loop to assist in lip
exercises to increase the
length of short upper lip

Modifications
Hotz Modification
This modification involves addition of wire loop to the anterior part
of the screen . Patient holds the loop and pulls the appliance
forward while simultaneously resisting the displacement of the oral
screen with tightly held lips.
Hotz modification of oral screen.

Oral Screen with Breathing Holes.
The breathing holes are placed in the labial part of the oral
screen. A button with its string attached is placed on its
lingual aspect. The patient is advised to exercise
by pulling the string through the breathing hole. Holes may
be gradually reduced in size as nasal breathing takes over.

Double Oral Screen by Krauss
This is useful in patients with abnormal tongue posture, tongue
thrust . A lingual screen is attached to the vestibular screen by two
0.9 mm wires that run through the bite in the area of lateral incisors.
Oral screen used in open bite cases . The tongue is kept away from
the dentition by an acrylic projection.
(A) Double oral screen. (B) Oral screen for open bite.

Modification of Rehak
In this, a nipple is combined with the screen that projects
out . The nipple has to be retained by the lips. Therefore, the
natural sucking movements are used to increase the effects
of the oral screen.
(C) Rehak modification.

Lip Bumper
The lip bumper (or lip plumper) is a functional component that is used
along with a lower or upper fixed appliance. It is a combined fixed
removable appliance or component of fixed appliance.
Lip bumper in maxilla and mandible. Molar needs to
be corrected in the second figure.

Types of Lip Bumper
1. Lip bumper based on the ability to be removed.
a. Combined fixed removable—in this, the lip bumper portion can
be removed from the fixed part, which is a molar tube.
b. Component of fixed appliance—lip bumper is also soldered to
the molar band where it cannot be removed separately.
c. Removable lip bumper—the whole appliance can be removed.

.
2. Lip bumper based on the arch used .
a. Maxillary lip bumper (Denholtz
appliance).
b. Mandibular lip bumper.
Types of Lip Bumper

Design of Lip Bumper
Typically, it is a vestibular arch carrying an acrylic pad engaged
to lower molar bands . The pad stands 2–3 mm away from the
teeth and gingiva. It lies about 4 mm below the cervical margins
of the lower incisors. The lower lip is thus held forward. The
diameter of the wire used is about 0.93 mm. The wire can be
either soldered or inserted into the molar tube with a U bend or
coil springs.

Mechanism of Action
Lip bumpers are used when there is problem in the upper or lower lip . Appliance
prevents the hyperactivity of the mentalis muscles in the same way as lip shields
or vestibular screen. Lip bumper prevents the abnormal force from acting on the
incisors. The other effect of lip bumper is that it causes proclination of the incisors
and distalization of molars.
Arrows denote proclination of incisors and
distalization of molars.
Mechanism of action of lip bumper.

Uses of Lip Bumper
• Used in the correction or elimination of lip trap.
• Eliminates hyperactive mentalis activity.
• Lip bumpers are used to upright molars.
• They can be used as space regainers when there is mesial
drift of first molar.
• Lip bumpers are used as anchorage saver.
• Molar distalization can be achieved. It is the only appliance that
is used for distalization of lower molars.
• Reduction of overjet by proclination of lower incisors.

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