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7/29/2019 Functional ApplianceHGHDFG

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Functional Appliance

- Dr. Adelegan O.A.


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Outline

Introduction Brief History of Removable Appliances

Definition of Functional Appliances

Classification Components

Clinical management Impression

Bite Registration

Timing of growth modification Advantages

Disadvantages


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History of Removable Appliance

In USA, Victor Hugo Jackson was the chiefproponent of removable appliance among the pioneerorthodontist in the early 20th century.

At that time neither the modern plastic for baseplatematerial nor stainless steel wire were available. Whathe used was vulcanite bases and precious metals ornickel silver wires

In early 1900s, George Crozat developed aremovable appliance which consisted of effectiveclaps on molars. Heavy gold wires as framework and alight gold wire to produce desired tooth movement.


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For a variety of reasons, development of removableappliance continued in Europe but neglected in USAbecause Angle dogmatic approach to occlusion with emphasis on

precise tooth positioning has less impact in Europe social welfare system developed more rapidly in Europe than

USA with emphases on a limited orthodontic treatment for alarge number of people which is carried out by generalpractitioners rather than orthodontists

precious metals for fixed appliances were not readily

available in Europe because of their social welfare and alsobecause its use was banned in dentistry


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A major part of European removable

orthodontic appliance of this period was

Functional Appliance.

In the European approach of the mid

20th century. Removable appliance was

differentiated into

Active plates for tooth movement

Functional appliance for growth modification


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Definition of Functional Appilance

A functional appliance is an orthodonticsappliance that is used to alter the position of themandible either by holding it open or by holdingit open and forward.

Pressure created by the stretch of the musclesand soft tissues are transmitted to the dental andskeletal structures, moving teeth and modifying

growth.

A functional appliance could perhaps be calledmandibular displacing device.


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Definition of Functional Appliance(Contd)

The term functional appliance is anabbreviation of myofunctional appliance whichis what such devices were called in Britainduring the 1950s and 1960s.

The prefix myo was later dropped in USA todistinguish this term from treatment from the

then popular myofunctional therapy which wasdirected at muscles or restraining to altersome so called oral habits


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Definition of Functional Appliance(Contd)

The monoblock designed by Pierre Robin

which was used in neonates with

micromandible and cleft lip and palate (Pierre

Robin Syndrome) was the forerunner offunctional appliance,

but the activator developed in Norway by

Andresen in the 1920s was the 1st functional

appliance to be widely accepted.


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Classification of Functional

Appliances

Passive tooth borne Andresen

Havold

Bionator Twin block

Active tooth borne Orthopaedic Correction

Tueschers Appliance

Van Beek headgear activator Stockil headgear activator

Tissue Borne Frankel Appliance


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Appliances contd

Removable

All functional appliance except Herbst

Fixed

Herbst being the only fixed appliance


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Appliances contd

Graber and Neumann Classification

Those that displace the mandible to a

moderate degree and are intended to

stimulate muscle activity i.e. myodynamicBionator and Andresen

Those that induce more extreme

displacement and rely on the elasticproperties of the muscles and facia for their

action (myotonic) e.g. Havold


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Appliancescontd

Isaac et al

Rigid

Andresen

Havold

Bionator

More Flexible Frankel appliance


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Activators

The original functional appliance design was a block of plasticcovering the teeth of both arches and the palate, made to fitloosely, advance the mandible several mm for class II correctionand open the bite 3 -4 mm.

The appliance (Andresen) has the following features

Lingual flange extension stimulate the forward position of themandible

A labial bow for control of maxillary anterior teeth

An acrylic cap over the lower incisors to control both eruption andmesial movement

A facets or flutes in the acrylic to direct the eruption of the posteriorteeth mesially in lower arch and distally and buccally in the upper

arch.

In the current design, i.e. Wood side activator, the facets isreplaced by a plastic (acrylic) shelf which impede the eruption ofthe upper posterior teeth. It also has the other features as above


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Mechanism of action of Andresen

It is fitted in the mouth with the mandiblepostured forward.

As a result, tension is generated in the muscle(temporalis muscle) and the transmitted forceof the muscles help to retract the mandible,tends to move the upper buccal teeth distallyand upper anterior teeth lingually through the

pressure by the labia bow (but this can beprevented by not activating the labial bow)while the reciprocal force will tend to bring thelower teeth forward.


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Mechanism of action of Andresen

Forward postures of the mandible also stimulatethe growth centres of the mandibular condylesso there is increase in growth of the mandibleand thus helps to reduce or eliminate thediscrepancy in jaw relationship

The Andresen appliance is worn 10 12 hrs aday.

Because it is monoblock, patient cant speakwith it

It is better worn after school and at night tillmorning


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BIONATOR (Balters type)

Similar to Andresen, but the bulk of palatalcoverage is eliminated.

Also has three variants

Standard appliance for class II correction

A screening appliance for elimination of abnormal tongue

activity

Reverse appliance for treatment of class III


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Herbst Appliance

It is the only fixed functional appliance

It consists of mandibular and maxillary arches splintedwith frameworks that are usually cemented or bonded(but can be removable) and connected with a pin-end-tube device that holds the mandible forward.

The jaw position is controlled by the pin and tube device.

Pressure the teeth can produce significant tooth

movement in addition to an effects.

Despite the fact that it is fixed the dental versus skeletaleffect depend on patients compliance.


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Advantages of Herbst appliance

It works 24 hrs a day

Patient co-operation not required

Treatment time is short (6 8 mths)


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TWIN BLOCK (Clark appliance)

It can also be used as removable or fixed.

The twin block appliance consists of individualmaxillary and mandibular plates with ramps that

guide the mandible forward as the patient closesdown.

The maxillary and mandibular portions areconfigured so that interaction of the 2 parts controlshow much the mandible is postured forward andhow much the jaws are separated vertically.

It is similar to the Herbst in that pressure against theteeth rather than the mucosa is employed to bringthe jaw forward


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TWIN BLOCK (Clark appliance)

Advantages

It allows nearly a full range of mandibularmovement

Easy acclimatization Reasonable speech

Disadvantage

Displacement of the mandible can occurfreely despite the absence of active springsor screws


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Havold appliance

It is a modification of the Andresen appliance.

It has an occlusal shelves which contact with

the upper but not the lower posterior teeth,

thus allowing the lower posterior teeth to erupt

and move mesially and correct the molarrelationship from class II to class I


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Active Tooth borne appliance

They are modification of activators and bionators designs thatinclude expansion screws or springs to move the teeth.

In the correction of a class II malocclusion as the patient movesthe lower jaw forward in a class I position, a crossbite tendency isusually apparent, therefore transverse expansion of the upperarch is nearly always needed,

so the springs or screws in active functional appliances wereadded to the basic design to provide this expansion.

But in many cases, an additional goal may be further expansionof the upper and lower arches to correct crowding.


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Tissue borne appliances

Frankel appliance or function regulator is the only tissue borneappliance.

It consists of acrylic shields which lie in the vestibule of the mouth,both labiallly and buccally.

It also consist of small lingual pad which lie against the lingualmucosa beneath the lower incisors, which stimulate mandibularrepositioning.

Much of the appliances is located in the vestibule however and it alter

both mandibular posture and the contour of facial soft tissues.

It serves as an arch expansion appliance in addition to its effect onjaw growth because the arches tend to expand when lip and cheekpressure is removed.


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Mechanism of Action of Functional

Appliance

The exact mode of action is not known

but there are different postulations

Eruption guidance this is a mechanism

whereby the vertical development of a groupof teeth can be enhanced, inhibited or

redirected and thus assist alteration of

occlusal relationship. Basically, there is a

belief that if vertical eruption of teeth is

prevented, the forward and upward

movement of the teeth is prevented


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Mandibular reposturing the appliances are

constructed in such a way that the mandible is held

in a postured position and with the teeth out of

occlusion, the overall effect of this is altered-bony

development.

The mandibular repositioning has been known to

have the following

Redirection or retardation of the horizontal growth of the

maxillar, the basal area of the maxillar is restrained in theirnormal forward growth.

The anterior downward rotation of the maxillar is

enhanced


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Tipping movement this movement occurs

in both labial and buccal teeth. This can

occur as a result of contact between the

appliance and the teeth


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Components of functional appliance

Each functional appliance, no matter what name itcarries is simply a melding of wires and plasticcomponents.

The appliance consists of Functional component which generate forces by altering posture

of the mandible, changing soft tissue pressure against the teethor both

A tooth controlling components.

Although the functional components are the heart of theappliance, they only constitute a small portion of the totalappliance, the bulk of which is devoted to controlling theposition of the teeth


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Functional component

Lingual flanges (which rests against the alveolarmucosa below the mandibular molars). It provides thestimulus to posture the mandible forward

The lingual pads (which contacts the mucosa belowthe lower incisors). It also provide stimulus to posturethe mandible forward. Contact of the pad or flange with soft tissue (alveolar mucosa)

not the teeth is the key to mandibular repositioning. If they

contact the mandibular incisor, they can produce a labiallydirected force against these teeth as the mandible attempt toreturn to normal resting posture. For this reason, activatorsand bionators are usually relieved behind the lower incisors.


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Functional component (Contd)

Ramps supported by the teeth are another mechanismfor posturing the mandible forward.

the sliding pin and tube device also force the

mandible to be positioned forward by holding the teeth

lip pads (which is positioned low in the vestibulelabially) force the lip musculature to stretch during

function.It is considered as an adjunct to mandibularrepositioning rather than a primary functionalcomponent.


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Tooth controlling component

Arch expansion components

Buccal shields and wires to hold the soft tissue

away from the teeth. The effect is to distrupt the

tongue and cheek equilibrium and this inturn lead to

facial movement of the teeth and arch expansion

Expansion screws and screens can be use to

actively increase the transverse diameter of the

arches or to modify the anterior-posterior dimension

of the appliance.


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vertical control component

acrylic or wires when placed in contact with a tooth andthe vertical dimension is opened past the normal posturalposition, the stretch of the soft tissues will exact andintrinsic force on the teeth. Intrusion does not usually occur

probably the because the force is not constant, but if thepatient wears the appliance often, eruption is impeded.

Thus the presence or absence of incisal or occlusal stopsincluding bite blocks provide a way of controlling thevertical position of anterior and posterior teeth allowing

teeth to erupt where this is desirable and preventing itwhere it is not.

Lingual shields remove the resting tongue from betweenthe teeth. This has the effect of enhancing tooth eruption.


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Stabilizing components. Claps this help to retain the functional appliance in position in the

mouth. Though it was thought in early days of functional applianceand a loose fit was important and therefore claps werecontraindicated, it is clear now that growth effect with or withoutclasps is remarkably similar. Clasps help the first time wearer toadapt to the appliancel. They can be used initially and then removedor deactivated if desired when the patient has learned to wear theappliance

Labial bow across the maxillary incisors in many functionalappliances should be considered as a stabilizing component. Itspurpose is to help guide the appliance into proper position, not to tipthe upper incisors lingually. For this reason, labial bow is adjustednot to touch the teeth when the appliance is seated in position.

Torquing springs which contact the incisors in the cervical 1/3 areaimed at counteracting the tipping movement often produced by alabial bow.

Cli i l t f f ti l


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Clinical management of functional

appliance :Impression

The impression for functional appliance differ fromthose of other ortho diagnostic records in twoimportant ways Areas where appliance component will contact soft tissue

must be clearly delineated. Most appliances use contact

with the lingual mucosa to stimulate forward posturing ofthe mandible, so this is a critical area. The impression mustinclude the alveolar process below the lower molars if longlingual flanges are to be employed.

The impression must not stretch and excessively displacesoft tissues in an area of contact with the appliance. This is

critical when lip pads and buccal shields are planned. Toomuch extension of the impression will result in pads andshields that are too long and will cause soft tissue irritationand ulceration when the appliance is worn

Cli i l t f f ti l


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Clinical management of functional

appliance: Bite Registration

The construction of bite for the functional appliance for class IIpatients advances the mandible so that the condyles are out ofthe fossae and separate the jaw by predetermined amount. Inclinical practice, the mandible is advanced to 7 to 8 mm. Greateradvancement may lead to patients discomfort which can reducecompliance. For most patients, initial advancement is limited to 4

to 6mm. The vertical opening depends on the appliance design and

purpose

With franckel appliance, the minimum opening is 3 to 4mm. Thisamount of space is necessary for connectors between the facialand the lingual components of the appliance

With interocclusal stop or facet to guide the eruption, about 4-5mm vertical opening is needed.

If bite blocks to limit posterior eruption are planned, 5 6mm ofseparation are needed.


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Timing of growth modification

Whatever the kind of appliance that is used or growtheffect desired, if growth is to be modified, the patienthas to be growing.

Growth modification has to be done before theadolescent growth spurt ends. In theory, it could be done at any time up to that time.

Because of the rapid growth exhibited by childrenduring the primary dentition years, it would seem thattreatment of jaw discrepancies by growth modificationshould be successful at a very early age


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Timing of growth modification contd

The rationale for treatment at ages 4 6 would be that the causeof the rapid rate of growth, significant amount of skeletaldiscrepancies would be overcome in short time.

This implies that once discrepancies in jaw relationships arecorrected, proper function would harmonious growth thereafterwithout further treatment.

Unfortunately, although most antero-posterior and verticalproblems can be treated during he primary dentition years,relapse occurs because of continued growth in the originaldisproportionate pattern.

If children are treated very early, they usually need furthertreatment during the mixed dentition and again in the earlypermanent dentition to maintain the correction


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Timing of growth modification contd

The opposite point of view will be that since treatment in permanentdentition will be required anyway, there is no point in starting treatmentuntil then.

But delaying treatment that long has two potential problems

By the time the canines, premolar and second molars erupt, there maynot be enough growth remaining for effective modification, especially ingirls

The child will be denied the psychosocial and functional benefit oftreatment during an important period of development.

A child can benefit from treatment during the pre-adolescent years ifaesthetic and resultant social problems are substantial or if he or she istrauma-prone.


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Advantages of functional appliances

It utilises the growth potential of dental arches to the maximumand can achieve a better facial profile than conventionalappliances

treatment can be commenced in the mixed dentition and can beeffective during pubertal growth spurt

minimal chair side time is required

less frequent adjustment

it is economical

it is the only appliance that brings about true skeletal changes

Di d t f F ti l


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Disadvantages of Functional

Appliances

Precise control of tooth position is not possible

variable response in post-pubertal patients and it isineffective in adults

not suitable for cases where crowding is present

with the exception of fixed functional appliance, it is

totally dependent on patients cooperation.

it is bulky and often unpleasant to wear


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Thank You

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