1. 1
Dr. Mohammed Alruby
Orthodontics for G.P
Functional appliances
For general practitioners
Prepared by
Dr. M Alruby

2. 2
Dr. Mohammed Alruby
Orthodontics for G.P
Functional appliances are large category of orthodontic appliances that used primarily
to reposition of the mandible in order to alter the muscular forces against the teeth and
craniofacial skeleton.
Functional appliances are used for growth modification procedures that are aimed at
intercepting and treating jaw discrepancies. They can bring about the following changes:
1- Change the relationship of the jaws.
2- Change the direction of the growth of the jaws.
3- Acceleration of desirable growth.
4- Provide more favorable environments foe developments of dentition through:
a- Modify the muscle function.
b- Relive abnormal muscle function.
c- Selectively alter the eruptive path o the teeth.
5- Selectively inhibit the skeletal growth.
Classification of functional appliances:
1- Myotonic appliances: they are functional appliances that depend on the muscle mass for
their action.
2- Myodynamic appliances: they are functional appliances that depend on the muscle activity
for their action.
3- Removable functional appliances: they are functional appliances that can remove and
inserted into the mouth by the patient for example: activator and bionator.
Uses and indications of functional appliances:
1- When the muscle dysfunction play a role in etiology of malocclusion.
2- Where alteration of muscle function may provides an optimum condition for normal
dentofacial development.
Functional appliances may be indicated in the following:
1- Anteroposterior discrepancies on mild disproportional bases as Class II, Class III.
2- Vertical discrepancies on mild disproportional skeletal bases (open bite or deep bite).
Timing of treatment:
All the functional appliances are probably most effective in the growing children to gain
maximum benefits from pubertal growth spurt.
Treatment principle:
Functional appliances work on two broad principles:
1- Force application: comprehensive stress and strain act on the structures involved and
result in a primary alteration in form with a secondary adaptation in function. Most of the
fixed and removable appliances work on this principle.
2- Force elimination: this principle involves the elimination of abnormal and restrictive
environmental influences on the dentition thereby allowing optimal development. Thus
function is rehabilitated with secondary changes in form. All functional appliances are
assemblies of a few simple components. Each component has a desired function and is
generally incorporated for a specific purpose. The currently used appliances are made of
combination from three basic functional components. They are bite planes, shields or
screens and construction of working bites. These components produce skeletal and
dentoalveolar changes by acting on the following:

3. 3
Dr. Mohammed Alruby
Orthodontics for G.P
1- Eruption (bite plane).
2- Linguofacial muscle balance (shields or screens).
3- Mandibular repositioning (construction of working bite).
Advantages of functional appliances:
1- It enables elimination of abnormal muscle function thereby aiding in normal development.
2- Treatment can be initiated at an early age, so psychological disturbances associated with
malocclusion can be avoided.
3- They did not interfere with oral hygiene maintenance.
4- These appliances are mostly fabricated at the dental laboratory, thus less chair side time
is spent which enables more patients to be treated.
Limitations of the functional appliances:
1- They cannot be used in adult patients in whom growth has ceased.
2- They cannot be used to bring about individual tooth movement.
3- Most functional appliances are dependent on the patient for timely wear. Thus the patient
cooperation is essential for the success of the treatment.
4- They may require pre-functional orthodontic tooth movement for correction of minor local
irregularities that may interfere with functional thereby.
5- Fixed appliance therapy may be required at the termination of treatment for final
detailing of the occlusion.
Action of functional appliances:
Functional appliances are capable of producing the following changes:
1- Orthopedic changes:
a- Myounctional appliances are capable o accelerating the growth in condylar region.
b- They can bring about remolding of the glenoid fossa.
c- They can change the direction of growth of the jaws.
2- Dento-alveolar changes:
They can bring about deto-alveolar changes in the sagittal, transverse and vertical directions.
Most functional appliances allow the upper anterior to tip palatally and lower anterior to tip
labially.
In transverse direction, they can bring about expansion of the dental arches by incorporating
screws in them or by shielding the buccal muscles away from the dental arch.
In the vertical plane, they can be designed to allow selective eruption of the teeth.
3- Muscular changes:
Functional appliances can improve the tonicity of the oro-facial musculature.
Visual treatment objective (VTO):
This is an important diagnostic test undertaken before making a decision to use a functional
appliance. This test enables us to visualize how the patient' profile would be after functional
appliance therapy. It is performed by asking the patient to bring the mandible forward. An
improvement in profile is considered a positive indication for the use of functional appliance. In
case of the profile worsens, and then other treatment modalities have been considered.
Photographs of the patient taken with forward mandibular posture are a valuable aid in
motivating the patients and parents.

4. 4
Dr. Mohammed Alruby
Orthodontics for G.P
Vestibular screen
The vestibular screen is a simple functional appliance that takes the form of curved shield of
acrylic placed in the labial vestibule.
Principle:
The vestibular screen can be used either to apply the forces of the circum-oral musculature to
certain teeth or to relieve those forces from the teeth thereby allowing them to move due to forces
exerted by the tongue. So the vestibular screen works on the principles of both force application
as well as force elimination.
Indications:
The following are the indication for the use of the vestibular screen:
1- This appliance can used to intercept the habits such as thumb sucking, mouth breathing,
tongue thrust, lip biting and cheek biting.
2- Can used to perform muscle exercise to help in correction of the hypotonic lip and cheek
muscles.
3- Can used to correct anterior proclination.
Fabrication:
1- Upper and lower impressions are made and the working models poured. The casts should
reproduce the depth of the vestibular sulcus.
2- The upper and lower casts are occlude in normal intercuspation and the model sealed
together using plaster.
3- The vestibular screen should extend into the sulcus to the point where the mucosal tissue
reflects outwards. Care should be taken not to impinge on the frenum and the muscle
attachments.
4- Posteriorly the appliance should extend up to the distal margin of the last erupted molar.
5- The models are covered with 2-3mm of wax over the labial surface of the teeth and the
alveolar process.
6- The appliance is fabricated using either self cure or heat cure acrylic resin.
7- The appliance is smoothened using sand paper and polish.
The patient is instructed to maintain lip seal during wear the appliance. During the
first few days the patient may show certain areas of irritation in the sulcular and frenal areas,
such areas of the appliance should be carefully trimmed to avoid tissue irritation.

5. 5
Dr. Mohammed Alruby
Orthodontics for G.P
Activator
Removable appliance used to advance the mandible and generated a biomechanical force
as the muscle 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 described as
an exercise appliance. Although the original activator was made of rubber, the appliance
currently is made of acrylic.
Uses:
1- Most frequently used in correction of Class II division 1 malocclusion.
2- Cases of Class II division 2 malocclusion.
3- Cases of Class I with deep bite.
Contraindication of activator:
1- The appliance not used in correction of Class I problems of crowded teeth caused by
disharmony between the teeth size and jaw size.
2- The appliance is contraindicated in children with excess of lower facial height and
extreme vertical mandibular growth.
3- The appliance in not used in children with lower incisors prominent.
4- The appliance not used in children with nasal stenosis caused by structural problems
within the nose or chronic untreated allergy.
Advantage of activator therapy:
1- It uses existing growth of the jaws.
2- During treatment the patient experiences minimal oral hygiene problems.
3- The intervals between appointments are long.
4- The appointments are usually short due to need for minimal adjustments.
5- More economic.
Disadvantage of activator therapy:
1- Require very good patient cooperation.
2- The activator cannot produce a precise detailing and finishing of the occlusion. Thus post-
treatment fixed appliance therapy may be needed for perfecting the occlusion.
3- It may produce moderate mandibular rotation (anteriorly downward). Thus activators are
not used in case of excessive lower face height.
Mode of action:
The appliance is made to fit in the upper arch, and the mandible fit in the appliance on a forward
direction, so when it is worn the muscles of mastication are stretched beyond their resting
posture which has two effects:
1- The muscle of mastication exert a force on the mandible in an attempt to return to their
resting position, this force is transmitted into the maxilla via the appliance , thus a form of
inter-maxillary force is created to move the maxillary teeth backward and the mandibular
teeth forward.
2- The forward posture of the mandible influences the growth at the mandibular condyle and
TMJ fossa and thus modifies the basal bone relationship.
N: B:
1- Activator generally not recommended for treatment of patient with bimaxillary
protrusion, hence the protrusion of the lower incisors prevent satisfactory correction of
the over-jet.

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Dr. Mohammed Alruby
Orthodontics for G.P
2- Patient with flaccid inactive lips are particularly suited to the appliance which tend to
initiate the reflex contraction of the lips to increase their tone.
3- Activators are more suitable for correction of arch mal-relationship in patient with well
aligned teeth, crowding often require correction by fixed appliances before placement of
activator.
4- Any loose deciduous teeth should be removed prior to placement of appliance as they
likely to produce patient discomfort under the appliance.
Fabrication of activator:
Construction of the wax bite:
The wax bite is an inter-maxillary wax record used to relate the mandible to the maxilla in the
three dimension of space. They are used to reposition the mandible in order to improve the
skeletal inter-jaw relationship. The bite registration involves repositioning the mandible in a
forward direction as well as opening the bite vertically. In most cases, the mandible is advanced
by 3-4mm and the bite opened to the extent of 2-3mm beyond the free way space. The general
considerations for construction bite are:
1- In case of over-jet is too large, the forward positioning is done step wise in 2-3 phases.
2- If the forward positioning is not more than 3-5mm, then the vertical opening can be 4-
6mm.*
Bite registration:
1- The amount of sagittal and vertical advancement of the mandible is planned.
2- A horse shoe shaped wax block is prepared for insertion between the upper and lower
teeth. It should be 2-3mm thicker than the planned vertical opening.
3- The patient is made to sit in an upright relaxed unstrained position.
4- The mandible is guided to the desired sagittal position. The operator should merely guide
the mandible using the thumb and forefinger. He should not use the pressure or force.
5- The patient is asked to practice placement of the mandible at the desired sagittal position
a few times before the registration of the bite.
6- The horseshow shaped wax block is placed over the occlusal surface of the lower cast and
is gently pressed so as to form the indentation of the lower buccal teeth.
7- The wax block is placed in the lower jaw and the patient is asked to bite at the desired
sagittal position, then removed and placed on the models and check.
8- The excess wax is trimmed off and the hardened wax block is again tried in the patient's
mouth.

7. 7
Dr. Mohammed Alruby
Orthodontics for G.P
Preparation of wire elements:
The usual design requires an upper labial bow. The labial bow is made of wire 0.09 or 0.08 mm.
and consists of horizontal section with 2 vertical loops, the ends of the vertical loops enter the
acrylic body between the canine and the deciduous 1st
molars or the 1st
premolar, the labial bow
can be active or passive.
Fabrication of acrylic portion:
The appliance consists of three parts:
1- Maxillary part.
2- Mandibular part.
3- Interocclusal part.
N: B= the patients taught how to use, place and remove the appliance by himself.
= usually the patient is asked to wear the appliance for 2 to 3 hours daily for the first week,
during the second week the patient is asked to wear it for 3 hours during the day as well as while
sleeping.
= in case of the patients has difficulty in using the appliance during night, more day time use
is prescribed until the patient can use it the entire night.
Trimming of the activator:
After fabrication of the activator it is usually found to fit tightly as acrylic is interposed between
the upper and lower occlusal surfaces. Selective trimming of the acrylic is done in the direction
of tooth movement.
The teeth in the buccal segment can be moved mesially and distally to help in treating Class II
malocclusion as the maxillary molars are allowed to move distally while the mandibular molars
are allowed to move mesially by loading the maxillary mesio-lingual surface and mandibular
disto-lingual surface

8. 8
Dr. Mohammed Alruby
Orthodontics for G.P
Functional regulators
Functional regulator 2 of Frankel (FR2):
They are used for treatment of Class II division 1 or division 2 malocclusion and was consists of
acrylic and wire components:
Acrylic components:
1- Buccal shield.
2- Lip pads.
3- Lower lingual pads.
Wire components:
1- Palatal bow.
2- Labial bow.
3- Canine extension.
4- Upper lingual wire.
5- Lingual cross over wire.
6- Support wire for lip pads.
Lip pads:
The lower lip pads are also called pellots. The lip pads help in elimination of abnormal perioral
muscle activity. It helps in eliminating lower lip trap, which cause or accentuates the
proclination of upper incisors.
Buccal shields:
The buccal shields are also called vestibular shields. The buccal shields are made to extend as
deeply into the vestibule as possible within the confines of patient comfort and tissue attachment.
These shields stand away from the dentition and basal alveolar bone. This helps in unrestricted
dento alveolar bone.

9. 9
Dr. Mohammed Alruby
Orthodontics for G.P
Functional regulator 3 of Frankel (FR3):
Is indicated in Class III malocclusion characterized by maxillary skeletal retrusion and not
mandibular prognathism. The appliance should be used during mixed dentition and early
permanent dentition.
FR3 haws two upper lip pads. The lip pads are larger and more extended than the lower pads of
FR2, the purpose of lip pads are:
1- To eliminate the restrictive pressure of the upper lip on the underdeveloped maxilla.
2- To exert tension on the tissues and periosteal attachment in the depth of the maxillary
sulcus to stimulate the bone growth.
The buccal shields stand away from the maxillary posterior dento alveolar structures by about
3mm. the buccal shield are in contact with the mandibular apical bone. They serve to eliminate
the buccinators muscle force and also cause a periosteal pull leading to bone growth.
Labial support wires connect the lip pads together and to the buccal shields.
Some effects of the functional appliances:
1- effect on the masticatory function:
Some authors reported that the activator therapy helps in normalization of the masticatory
functions, so others recommended the use of the activator until adaptation to the normal chewing
pattern.
2- Effects on swallowing pattern:
The original appliance activator is made4 loose, so that constantly falling down. This caused a
reflex elevation of the tongue and contraction of the mandibular elevators, which also the same
neuromuscular pattern occurs during normal swallowing.
3- Dento- alveolar effects:
Vertical: functional appliances have the ability to control differentially the vertical height of the
teeth, stopping some teeth while permitting others to develop vertically through the selective
relief built in the appliance. Thus aids in leveling the occlusal plane, correcting deep bites and
open bite cases.

10. 10
Dr. Mohammed Alruby
Orthodontics for G.P
Antro-posterior: the functional appliances move the maxillary dentition against the mandibular
dentition utilizing reciprocal inter-maxillary anchorage, and thus brought about dento alveolar
remodeling an antro-posterior direction, which is very helpful in the correction of Class II and
Class III providing excellent results when the skeletal bases permit.
4- Skeletal effects:
Effect in maxilla: with FR2 appliance several patients showed a backward rotation of the
maxilla, so that the maxilla was more retrognathic at the end of treatment period.
Effect on the mandible: with FR2 appliances there is a redirection of the mandibular growth