Myofunctional Appliances

Dr. Vincy Antony

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DEFINITION

A functional appliance is an appliance that changes the posture of the mandible, holding it open or open and forward.(PROFFIT)

Functional appliances are loose removable appliance designed to alter the neuromuscular environment of the orofacial region to improve occlusal development and/or craniofacial skeletal growth.(MOYERS)

Definition -

Myofunctional appliances are passive appliances which harness the natural forces of the oral musculature that are transmitted to the teeth and alveolar bone through the medium of the appliance

These appliances either transmit, eliminate or guide the natural forces of the musculature

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Functional Appliances bring about the following changes

1) An increase or decrease in jaw size.

2)A change in spatial relationship of the jaws.

3)Change in direction of growth of the jaws.

4)Acceleration of desirable growth.

History

He, in the year 1880, first introduced the term and concept of “jumping the bite” in patients with mandibular retrusion.

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He designed an appliance that basically was a vulcanite maxillary plate with an anterior inclined plane that guided the mandible to a forward position

Norman Kingsley

He, in the year 1902, created an appliance called the ‘monobloc’.

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It was called so because it was made from a single block of vulcanite.

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It was used to position the mandible forward in patients with glossoptosis and severe mandibular retrognathism who risked occluding their airways with their tongue.

Pierre Robin

Impressed by Kingsley’s concepts, he, in 1908 create a passive loose fitting appliance that he called ‘biomechanic working retainer’.

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Andresen, became associated with Karl Haupl, a periodontist, at the University of Oslo.

They teamed up to write about the appliance, which they termed as the ‘Activator’ ; because of its ability to activate muscle forces

Viggo Andresen

In the year 1918, he, for the first time presented the concept of ‘Myofunctional Therapy’ to the American Society of Orthodontists.

Alfred Paul Rogers

Emil Herbst, in the year 1909, invented the first fixed functional appliance.

He called it the ‘hinge’.

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It was a ‘bite jumping’ kind of appliance that subjected the mandible to a constant forced protrusion.

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It was not very well accepted, and was soon forgotten.

In the year, 1949, he proposed his appliance, which was basically an elastic bimaxillary appliance with wire elements.

Hans Peter Bimler

Taking into consideration the bulkiness of the Activator, Balters, in the year 1950, proposed his own appliance – the Bionator, which was much less bulky than the Activator.

Wilhelm Balters

Balters’ Bionator

In the year 1960, he presented his own appliance called the ‘Function Regulator’ which was based on a completely different philosophy.

Rolf Frankel

• In the year 1977, Hans Pancherz, reintroduced the ‘Herbst Appliance’ originally proposed by Emil Herbst in 1909

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• In the same year i.e. 1977, William Clark introduced the ‘ Twin Block Appliance ’.

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• In the year 1980, J.J.Jasper, introduced the ‘Jasper Jumper ‘ appliance.

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• GRABER AND VARDIMON(1989)

Magnetic functional appliance therapy

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Classification

A ) According to the support –Profitt’s Classification

1. Tooth borne passive

(e.g. activator, bionator)

2. Tooth borne active (e.g. modifications of activator with active components like an expansion screw, spring etc.)

3. Tissue borne (e.g. Functional Regulator of

Frankel )

Classification

B) According to their Mode of Action (Houston et Al’s Classification) –

1) Myotonic appliance

- they depend on the muscle mass for their

action (e.g. activator,bionator)

2) Myodynamic appliance

- they depend on the muscle activity for their

action. Eg.elastic open activator (EOA), Bimler's appliance, modified bionator etc

• MYOTONIC APPLIANCE

They are appliances that depend on muscle mass for the action.

Night time wear.

Eg:Activator

Bionator

• MYODYNAMIC APPLIANCE

They are appliances which depend on muscle activity for their function.

More elastic,full time wear

Eg:elastic open activators

Bimler’s appliance

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Classification

C) According to the appliance type-

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1) Removable functional appliance

(e.g. Activator, Bionator)

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2) Fixed Functional Appliance

(e.g. Jasper Jumper, Herbst appliance)

Classification

D) According to Graber – Neumann -

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Group I : They transmit muscle force directly to the teeth (e.g. inclined plane)

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Group II : They reposition the mandible activating the associated musculature, thus creating a force that is transmitted not only to the teeth but also to the other structures (e.g. activator, bionator)

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Group III : They too reposition the mandible, but their operating area is in the buccal vestibule, outside the dental arch. Supporting bone and teeth are influenced by changing the muscle balance through use of shields and screens (e.g. Frankel FR)

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E) Classification based on application of force

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1. Force Application-

eg. Andresen/ Haupl activator, Balter's bionator etc.

2. Force Elimination-

eg. Frankel appliances

Advantages of Functional Appliances

1. Treatment can be initiated at early age.
2. Try to correct the skeletal problems
3. Enables elimination of abnormal muscle function.
4. Psychological disturbance associated with malocclusion can be avoided.
5. Since the appliances are mostly fabricated in the laboratory, less chair side time is required.
6. They do not interfere with oral hygiene maintenance.

Disadvantages

1) They cannot be used in adult patients.

2) They cannot bring about individual tooth movement.

3) Patient cooperation is essential.

4) Crowding needs to be corrected prior to treatment.

5) Fixed appliance treatment may be required later for final detailing of occlusion

How it works ?

• Induces a new pattern of mandibular closure (Protruded)

How it works ?

New mandibular closing pattern - protruded

Myotactic Reflex.

Condylar Adaptation.

Viscoelastic Property

Equilibrium theory

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The teeth are subjected to various forces from the tongue within and the buccal and labial musculature outside. Yet their position remains the same, implying that the forces exerted by the associated musculature are well balanced or in equilibrium.

Equilibrium theory

This theory states that an object subjected to unequal forces will be accelerated and thereby will move to a different position in space.

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It means that if any object is subjected to a set of forces, but remains in the same position, those forces must be balanced.

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Equilibrium theory

Although these forces are extremely light in magnitude, they act for a much longer duration of time.

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The duration threshold has been found to be approximately 6 hours per day.

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Since these light pressures maintain tooth position, any disturbance in their balance would expect these pressures to affect tooth position.

Consequence of change in Equilibrium

Large portion of the cheek has been surgically removed because of infection.

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The teeth in the associated area clearly show buccal flaring due to loss of the restraining forces exerted by the cheek musculature.

PRINCIPLES OF FUNCTIONAL APPLIANCE THERAPY

• Important principle-the adaptation between form and function
• Functional appliance either induce change in form or function.
• Neuromuscular adaptation allows the form and function to get adjusted.
• Works by 2 principles:

(a) force application

(b) force elimination

Mode of Action

Depending on the type of myofunctional appliance used, the mode of action can be divided into 2 major treatment principles :

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1)Force application

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2) Force elimination

Force Application

Compressive Stress & Strain

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Primary alteration in form.

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Secondary adaptation in function.

(Activator acts by the principle of force application)

Force Elimination

Elimination of abnormal & restrictive environmental factors.

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Rehabilitation of function.

Secondary change in form.

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(FR, Lip bumper, Oral screen)

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�Factors essential for the success of functional appliance:�

• Proper diagnosis
• Growth pattern
• Appliance selection
• Patient compliance

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CASE SELECTION

Age

– between 10yrs & pubertal growth phase.

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Dental Considerations-

- No gross individual tooth irregularities.

- if there ,treat it prior to / after functional therapy.

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Skeletal Considerations-

- ideal - moderate to severe class II.

- low mandibular angle.

- deep bite.

- Mild class III with reverse overjet & average overbite.

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Compliance –

- high degree of motivation.

- minimum supervision.

Visualized Treatment Objective (VTO) –Holdaway 1971

Important diagnostic test

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Enables us to visualize the patient’s profile after functional appliance therapy.

Visualized Treatment Objective ( VTO )

The patient is instructed to close the teeth in habitual occlusion with the lips relaxed.

The patient is then asked to posture the mandible into a correct sagittal relationship, reducing the overjet.

If this clinical exercise makes the facial balance look better, the myofunctional appliance will probably be beneficial to the patient.

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Change in appearance of pt. is noted at 2 levels: 1. edge to edge position�2. at a position midway between edge to edge and the existing occlusion

• If the profile improves at edge to edge position, it means fault lies in the mandible- case of mandibular retrognathism- functional appliances
• If the profile worsens at edge to edge position, it means fault lies in the maxilla- case of maxillary prognathism- maxillary splint with headgear
• If the profile improves midway, it is a combination of maxillary prognathism and mandibular retrognathism- twin block with headgear

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VTO FOR CLASS III�

• In cases of patients with Class III,roll of cotton is kept in the upper labial vestibule.

In cases with maxillary retrusion, the profile improves with cotton roll.

In Class III due to prognathic mandible, profile worsens.

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CLINICAL VTO

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Mechanism of Action of Functional Appliances

1. Re-education of musculature
2. Lateral pterygoid muscle stimulation
3. Decreased biochemical feedback
4. Unloading of mandibular condyle
5. Transduction of viscoelastic forces
6. Differential eruption of teeth

RE-EDUCATION OF MUSCULATURE�

*Continously holding the mandible forward in Class II cases,muscles will be obliged to learn a new functional pattern.

*Muscular adaptation takes place subsequent to functional appliance therapy.

Lateral pterygoid muscle stimulation�

• Functional appliance

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• Stimulation of lateral pterygoid muscle

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• Increased activity of the retrodiscal pad

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• Growth of condylar cartilage

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• Posterior superior deposition of bone in condyle

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• Sagittal growth of mandible

Decreased biochemical feedback�

Functional appliance wear

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Stimulation of lateral pterygoid

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Zone of functional chondroblasts in condyle secretes a substance that retards mitotic activity of stem cells.

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Causes acceleration of condylar growth

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Unloading of mandibular condyle�

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Functional appliance is used

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Condyle is distracted from fossa

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Causing increased condylar growth

Transduction of viscoelastic forces�

Functional appliances harness the passive tension arising from the inherent elasticity in muscle, skin and tendinous tissue

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And transmit to the dentition

Differential eruption of teeth�

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• Eruption pattern modified by

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• Placing molar stops

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• Providing acrylic guide planes

CRANIOFACIAL RESPONSE TO FUNCTIONAL APPLIANCES

EFFECTS PRODUCED BY FUNCTIONAL APPLIANCES

1)DENTO ALVEOLAR CHANGES

2)SKELETAL CHANGES

3)MUSCULAR CHANGES

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1)DENTO ALVEOLAR CHANGES

The reduction of overjet and overbite occurs rapidly with functional appliances in class II malocclusion.

• Proclination of lower anteriors.
• Retraction of upper anteriors.
• Differential eruption of teeth.
• Relative intrusion where the lower incisors are prevented from supra-erupting and molars are allowed to erupt.This causes opening of the bite or deepbite correction.

2)SKELETAL CHANGES

Seen in both maxilla and mandible.

• In Class II

1.Midface restriction

a. Restriction of forward maxillary growth is observed.

2.Mandibular growth induction

a. Growth acceleration of mandible takes place.

b. change in condylar position.

c. Glenoid fossa remodeling

d. Redirection of condylar growth.

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• IN CLASS III
• Stimulation of maxillary growth.
• Restriction of mandibular growth.

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3.MUSCULAR CHANGES DURING FUNCTIONAL APPLIANCES

• Elongation of muscle fibres.
• Migration of muscle attachment along bony surfaces.
• Changes in muscle dimension are observed.

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Construction Bite

The construction bite is an intermaxillary wax record used to relate the mandible to the maxilla in all the planes of space (vertical, horizontal and transverse).

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It is the most important step for proper fabrication of a myofunctional appliance and ultimately the correct treatment of the skeletal discrepancy of the patient.

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Also known as the ‘ Working Bite ‘

General rules for Construction Bite

1) If the overjet is too large, the anterior positioning of the mandible is done stepwise, to be accomplished in two or three phases. In such cases, however, the bite should not exceed 7 to 8mm, or roughly 75% of the mesio-distal width of the first permanent molar.

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2) If there is severe labial tipping of the maxillary incisors, they should be uprighted first, if possible by a pre-functional appliance.

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General rules for Construction Bite

3) If the forward positioning of the mandible is 7 to 8 mm, the vertical opening must be slight to moderate, about 2 to 4mm.

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4) If the forward positioning is no more than 3 to 5mm, the vertical opening should be 4 to 6mm.

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5) Lower midline shifts or deviations can be corrected only if there is actual lateral translation of the mandible itself.

Myofunctional Appliances

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Removable

Lip Bumper

Vestibular Screen

Inclined Plane

Activator

Bionator

Frankel appliance

Twin Block

Fixed

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Rigid Fixed

Flexible fixed

Hybrid appliances

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How it works ?

• FUNCTIONAL MATRIX THEORY

Melvin Moss

Increased Periosteal Matrix Function

( Muscle Stretch)

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Secondary & Compensatory Transformation of Skeletal Units

Change in position of mandible

(Change in volume of functional space/ Capsular Matrix)

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Secondary & Compensatory translation in spatial arrangement

of

maxilla & mandible.

SERVO SYSTEM THEORY

Functional Appliance

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Increased Contractive activity of LPM

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Intensification of the repetitive activity of

the retrodiscal pad (bilaminar zone)

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Increase in growth—stimulating factors

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SUPPLEMENTARY LENGTHENING OF MANDIBLE

IDEAL REQUIREMENTS

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1.Should be comfortable and acceptable for the patients.

2.Should promote better compliance.

3.Should offer good range of mandibular movements.

4.Should be simple and inexpensive

5.Should be easy to fit

6.Should be adaptable to both class II and class III malocclusion.

7.When used with fixed appliances, should not cause breakage of fixed appliance components.

8.Should be usable in both mixed and permanent dentition.

9.They should provide good results with minimal patient co-operation.

Inclined Plane

Introduced by Catlan more than 150 years ago.

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Types : Removable

Fixed

Indication :

This appliance is limited to the simplest of cases, involving one or two teeth in crossbite.

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LOWER ANTERIOR INCLINED BITE PLANE- CATLAN'S APPLIANCE

• Correction of crossbite where permanent molars are not erupted and deciduous molars are lost
• Cemented type
• Incisal capping with Adams clasp
• Incisal capping with lingual plate
• Incisal capping with Adams clasp and labial bow

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• It is made by adding an inclined plane to the removable mandibular Hawley type of retaining appliance.
• The appliance includes a labial bow that is used for retraction of labially malposed incisors back into alignment.
• Interproximal stripping of the incisors helps in this process.

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Inclined Plane

The resultant correction is a by-product of a combined depressing and anterior vector.

The steeper the plane, the greater the forward pressure on the maxillary incisor, and hence the faster will be the correction of the malocclusion.

• All inclined planes have the characteristic of opening the bite by allowing the posterior teeth to erupt. Hence the inclined plane is contra-indicated unless there is an appreciable amount of overbite.
• Also contraindicated in correction of crossbite due to mandibular prognathism

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If used properly, the correction does not take more than 6 weeks.

Vestibular Screen

It is a simple functional appliance that takes the form of a curved shield of acrylic, placed in the labial vestibule.

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Patient is asked to wear the

appliance at night and 2-3

hours during the day time.

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Introduced by Newell in the year 1912.

Vestibular Screen

Principle :

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The appliance works on the principle of both,

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Force Application as well as Force Elimination.

Working principle

relieve abnormal forces from teeth so thereby allowing them to move due to forces exerted by tongue. (force elimination)

or

apply forces of circumoral musculature to certain teeth (force application)

Vestibular Screen

Indication :

1. Correction of thumb sucking, lip biting, and tongue thrust.
2. Correction of mouth breathing, when the airways are open.
3. Mild distoclusions, with premaxillary protrusion
4. Open bite in the deciduous and mixed dentition.
5. Flaccid, hypotonic orofacial musculature.

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Vestibular Screen

Modifications of the Appliance –

1. 1)Hotz Modification : Screen is fabricated with a metal ring projecting between upper and lower lips. It is used to carry out various muscle exercises.

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2)In case of mouth breathers, the screen is fabricated with a number of holes, which are gradually closed in a phased manner.

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3) Modification of Rehak : The screen is combined with a nipple which protrudes but is retained by the lips. The natural sucking movements are used to enhance the effect of the screen.

• 4) Kraus’ Double Screen – A smaller lingual screen is attached to the vestibular screen with two 0.036 inch wires that run through the bite in the lateral incisor area (combined oral and vestibular screen). This is useful in correction of abnormal tongue posture and also in tongue-thrust and open-bite cases.

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• It helps in correcting mild class II div I malocclusion cases. It can bring about slight forward repositioning of the lower jaw if the oral screen is fabricated on casts with construction bite take in slight anteriorly repositoned mandible.
• It increases the tonicity of muscles by providing exercise to the muscles.

FABRICATION OF ORAL SCREEN

1. Upper and lower impressions up to the depth of the vestibular sulcus are made and the working models are poured.
2. Working casts are sealed in occlusion using modelling wax.
3. The upper and lower casts are seated in normal intercuspation and models are sealed together using POP.In case if the appliance is intended for correction of mild class II molar relation,a constuction bite is taken to advance the mandible

4) A single sheet of modelling wax to be used as a spacer is adapted on to the labial and buccal surfaces of the teeth extending well into the functional depth of the sulcus. Care should be taken not to impinge on the frenum and the muscle attachments. These should be relieved while waxing and subsequently while constructing the oral screen. Posteriorly spacer should extend up to the mesial half of the buccal surface of the last erupted teeth.

5) Entire labial surface of the teeth and the alveolar process are covered with a wax layer of 2-3 mm thickness of wax.

6) In case of proclined teeth which need to be retracted, a window is cut and the wax relief is removed to expose the incisal one-third of the teeth. This makes the acrylic screen come in direct contact with the most proclined anterior teeth.

7) The appliance can be fabricated with self-cure or heat-cure acrylic resin.

8) Any areas of irritation in the sulcular and the frenal areas should be relieved to avoid tissue irritation. Appliance is polished with sand paper before delivery.

MANAGEMENT OF THE APPLIANCE

The patient is instructed to wear the appliance fulltime at night and a minimum of 3-4 hours during the day time.

The patient is asked to close tightly when wearing the appliance to maintain a proper lipseal.

Any areas of irritation in the sulcular and frenal areas should be relieved to avoid tissue irritation.

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LIP BUMPER

Combined removable & fixed appliance

Used to shield lips away from the teeth

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Lip Bumper

Indications

• To eliminate lip sucking habit
• To eliminate the force from hyperactive mentalis & to relieve flattening or crowding of lower anteriors.
• Anchorage augmentation
• Distalization of molars
• As space regainers

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Lip Bumper

The appliance works by the principle of force elimination.

The unwanted force of the hyperactive mentalis is shielded. The tongue function then exerts pressure on the lingually tipped lower anterior teeth, thus bringing about their correction.

Modification of the appliance :

Denholtz Appliance – similar to the lower lip bumper but used in the maxillary arch to effect maxillary molar repositioning.

ACTIVATOR

Activator

Introduced by Andresen in 1908. He initially called it the ‘biomechanic working retainer’.

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Andresen later teamed up with Haupl, a periodontist, and named his appliance the ‘Activator’ ; because of its ability to activate muscle forces.

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Other Names – 1) Andresen’s appliance

2) Monobloc

3) Norwegian appliance

4) Biomechanic working retainer

Activator

Indications –

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1) Skeletal Class II malocclusion

2) Skeletal Class III malocclusions

3) Class I open bite malocclusion

4) Class I deep bite malocclusion

5) Children with lack of vertical development in the lower facial height

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Well aligned maxillary and mandibular dentition, with mandibular incisors upright over the basal bone - Essential criteria.

Activator

Contra Indications

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1) Patients with crowded teeth caused by disharmony between tooth size and jaw size.

2) Patients with increased lower facial height and extreme vertical mandibular growth.

3) Severely labially tipped lower incisors.

ADVANTAGES

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1. Utilizes the existing natural growth potential of the jaws.
2. Appliance is hygienic and easy to maintain by the patient.
3. The appointments are usually short due to minimal adjustments and the intervals between appointment is long.
4. More economical.

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DISADVANTAGES

1. Treatment requires good patient cooperation.

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• Precise detailing or finishing of the occlusion is not possible with any functional appliance. Thus post treatment fixed mechanical appliance therapy is needed for detailing of the occlusion.

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• Pretreatment fixed appliance is needed in case of lower anterior crowding.

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• Activator acts as a hinge and results in backward and downwards rotation of the mandible. Thus Activators are contraindicated in patients with already excessive lower facial height.

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• Bulkier comparatively.

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MODE OF ACTION OF ACTIVATOR�

• Andresen – Haupl concept

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• Harvold – Woodside – Herren concept

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• Transitional concept

According to Andresen and Haupl,

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• the activator induces musculoskeletal adaptation by introducing a new pattern of mandibular closure.
• patient has to move the mandible forward to engage the appliance.
• results in stretching of the elevator muscles of mastication which start contracting, thereby setting up a myotactic reflex.

This generates kinetic energy which causes:

1. Prevention of further forward growth of the maxillary dentoalveolar process.
2. Distal force for maxillary dentoalveolar process
3. Reciprocal forward force on the mandible

In addition to this myotactic reflex, a condylar adaptation by backward and upward growth occurs.

A third factor is the force generated while swallowing and during sleeping.

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Other concept to explain the mode of action of the Activator –

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The Harvold – Woodside – Herren concept :

According to Harvold, Woodside and Herren passive tension caused by stretching of muscles, soft tissue, tendinous tissue etc., is responsible for the action. They called it the ‘viscoelastic property’

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Hence the bite in the activator should be raised more than the normal freeway space, so that the stretching of the tissues can occur.

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• Herren, Harvold & Woodside – Viscoelastic property

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Bite opens the mandible beyond the postural rest vertical dimension,stretching the soft tissues like a splint ,induces no myotactic reflex activity but instead applies a rigid stretch & creates a build up of potential energy

Activator

Construction

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The appliance basically consists of a single mass of acrylic that seats both, the maxillary as well as mandibular dental arches.

The only wire component is an upper labial bow used for retraction of upper anterior teeth.

Incisal capping or lower labial bow is sometimes done to prevent the lower incisors from tipping labially.

Fabrication

1. Impression
2. Bite registration
3. Articulation of the model
4. Preparation of the wire elements
5. Fabrication of the acrylic portion

a. maxillary part

b. mandibular part

c. inter-occlusal part

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Fabrication of Activator

• Working model

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• Construction Bite

- three dimensional positioning mandible

• Horse shoe shaped wax block ( 2-3mm thicker than planned vertical opening).
• Relaxed patient positioning.
• Position of mandible practised.
• Indentation of lower cast.
• Bite taking
• Try it on model
• Chill & articulate the models in reverse direction.

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TAKING A WORKING BITE

• Wire Component

- Labial bows are made of 0.8 mm or 0.9 mm wire with crossover between canines & first deciduous molars

(or first premolars). - can be active / passive.

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• Acrylic portion

Activator

Construction Bite –

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There are basically 4 types of construction bites :

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1) Low construction bite with markedly forward mandibular positioning

2) High construction bite with slightly anterior mandibular positioning

3) Construction bite without forward mandibular positioning

4) Construction bite with opening and posterior positioning of the mandible

Activator

1) Low construction bite with markedly forward mandibular positioning :

The mandible is placed forward to considerable extent (7 – 8mm), with minimal vertical opening (2-3mm).

The mandible should be atleast 3mm posterior to the most protrusive position possible.

Vertically it should remain within the limits of interocclusal clearance.

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The Activator constructed with such a bite is called as the horizontal ‘H’ activator. e.g. Class II div 1 cases with horizontal growth pattern.

Activator

2) High construction bite with slightly anterior mandibular positioning :

• The mandible is positioned less anteriorly (3-5mm).
• The vertical opening is high (4-6mm), depending on the existing interocclusal space.
• The vertical is opened a maximum of 4mm beyond the postural rest position.

The activator constructed with such a bite is called as the vertical ‘V’ activator. e.g. Class II div 2 cases with vertical growth pattern.

Activator

3) Construction bite without forward mandibular positioning –

(a) Deep-bite malocclusions:

• Activators are designed and trimmed to permit extrusion of molars in deepbite cases caused by infraocclusion of molars.
• In deepbite cases caused by extrusion of anteriors, treatment through intrusion of incisors is possible to only a limited extent.

(b) Open-bite malocclusions :

The bite is opened 4 – 5mm to develop sufficient depressing force on the molars that are in premature contact.

Activator

4) Construction bite with opening and posterior positioning of the mandible :

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• This is the bite usually taken in Class III skeletal malocclusion.
• The bite is opened vertically by about 5mm.
• The posterior placement is by about 2mm.

The activator constructed for such Class III case is called as the ‘reversed’ Activator.

Trimming of Activator

A) For correction of vertical discrepancy –

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1. For intrusion of teeth –

• The incisal edges in case of anteriors and the cusps tips in case of posteriors are the only portions that are allowed to remain in contact with acrylic.
• If labial bows are used, they should be placed below the area of greatest convexity to help in intrusion.

Trimming of Activator

2. For extrusion of teeth –

• For extrusion of both, the anteriors as well as the posteriors, the lingual surface is loaded above the area of greatest convexity in the maxilla, and below the area of greatest convexity in the mandible.
• Placing a labial bow in the gingival one-third of the labial surface also helps in extrusion.

Trimming of Activator

B) For correction of sagittal discrepancy –

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1. Protrusion of incisors –

• The lingual surface of tooth is loaded with acrylic and a passive labial bow is given that is kept away from teeth to prevent perioral soft tissues contacting the teeth.

2. Retrusion of incisors –

• The acrylic is trimmed away from the lingual surface and an active labial bow is used to bring about retrusion.

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3. Movement of posteriors –

• Depending on the existing malocclusion, the molars are allowed to move mesially or distally, by loading the disto-lingual surface or the mesio-lingual surface respectively.

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Trimming of activator

• Honeycomb appearance

C) For correction of transverse discrepancy –

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• The buccal movements of teeth can be brought about by allowing contact of the acrylic on the lingual surface of the teeth to be moved transversely.

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PROBLEMS ENCOUNTERED WITH ACTIVATOR

1. Difficulty in tolerating the appliance. Causes may be:
1. Feeling of foreign body sensation to the appliance.
2. Bulkiness of the appliance.
3. Excessive bite opening or forward advancement of the mandible in construction bite.

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2.Discomfort and pain due to:

• Poor fit of the appliance
• Roughened tissue surface
• Sharp edges and unrelieved undercuts
• Over extension,sharp margins or soft tissue impingement
• Distortion of labial bow when used as handle to remove the appliance.

Modifications of Activator

1) Wunderer’s modification :

• Used in skeletal Class III cases.
• The activator is split horizontally, with the upper and lower portions connected by a screw called the Weise screw.
• As the screw is opened, the maxillary portion moves anteriorly, with a reciprocal thrust acting on the mandibular teeth.

Modifications of Activator

2) Herren – Shaye Activator :

• Construction bite is taken in a strong mandibular propulsion, sometimes reaching the maximum.
• According to Herren, with every mm increase of forward position of mandible, the sagittal force increases by about 100gm.
• The Herren activator is fixed by clasps to the maxillary dentition.
• Consistent and reliable wear of 9 hrs/ day is considered sufficient by Herren.

Modifications of Activator

3) Bow activator of A.M.Schwarz:

• The upper and lower halves are connected by an elastic bow.
• Independent maxillary or mandibular expansion can be brought about by incorporating a screw in that particular half.
• Activating the bow only on one side is possible in case of unilateral disto-occlusion.

Modifications of Activator

4) Reduced activator or the Cybernator of Schmuth :

• The acrylic part of the appliance is reduced.
• A coffin spring made of 1.1 or 1.2mm wire is incorporated in the design.
• The slender lower anterior part is split in the middle, thus avoiding its breakage.

Modifications of Activator

5) Karwetzky modification :

• The appliance consists of maxillary and mandibular active plates joined in the first molar area by a ‘U’ bow.
• The plates also extend over the occlusal surface of all teeth.
• The wire for the U bow is 1.1mm.

Types –

Type I : for correction of Class II

Type II : for correction of Class III

Type III: for bringing about asymmetric advancement of the mandible

MANAGEMENT OF THE APPLIANCE

The patient is demonstrated to place and remove the appliance in mouth.

• The appliance is to be worn 2 to 3hours during the day for the first week.
• During the second week the patient sleeps with the appliance in mouth and wears it for 1-3 hours each day.
• The appliance is checked during the third week to evaluate the trimming. If the patient is wearing the appliance without any difficulty and following the instructions, checkup appointments are scheduled every 6 weeks.

Assessment of progress is done by the presence of any wear facets- will indicate that the patient is using the appliance.

Presence of pterygoid response should be checked. In the presence of pterygoid response patient will close the mandible in forward position even when the appliance is removed from the mouth. This shows patient is wearing the appliance regularly.

FINAL FINISHING OF THE CASE

After reaching the desired results with the activator, the case is put under retention by gradually reducing the duration of wearing the activator. Final finishing and detailing can be done with fixed appliance if necessary.

Bionator

The bulkiness of the activator and its limitations to night-time wear led Balters to develop this appliance in the year 1950.

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Types of Bionators :

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1. Standard bionator (for correction of Class II )

2. Reversed bionator ( for correction of Class III )

3. Open-bite bionator

Bionator

Balters’ Philosophy :

• Balters believed that the equilibrium between the tongue and the circumoral muscles is responsible for the shape of the dental arches.
• The functional space for the tongue is essential for normal development of the orofacial system.
• A discoordination of the tongue functions could lead to abnormal growth and actual deformation.
• Hence, the purpose of the Bionator was to establish good functional co-ordination and eliminate these deforming, growth-restricting aberrations.

Bionator

Indications :

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1) In Class II div 1 malocclusions having :

a. well aligned dental arches

b. retruded mandible

c. not severe skeletal discrepancy

d. labial tipping of upper incisors

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2) Class III malocclusions

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3) Open – bite malocclusions

Bionator

Construction of the Standard Bionator:

• The acrylic portion is greatly reduced as compared to the Activator .
• Consists of lower horse-shoe shaped lingual plate extending upto the distal of the first permanent molars.
• For the upper arch, the appliance has only palatal extensions that cover the premolar and the molar.

The wire components

• Consist of a labial bow with buccal extensions ( buccinator shields ), and a palatal bar formed with a 1.2mm wire.
• The palatal wire is kept 1mm away from the mucosa directed distally.

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Bionator

Construction of the Reversed Bionator :

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The acrylic component is the same as that of the standard appliance.

The labial bow runs in front of the lower incisors instead of the upper incisors.

The palatal bar is directed anteriorly, unlike the posterior direction seen in the standard appliance.

Bionator

Construction of the open-bite appliance –

The construction bite is kept as low as possible.

To inhibit tongue movement, the lower lingual acrylic portion extends into the upper incisor region as a lingual shield, closing the anterior space.

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The labial bow runs between the incisal edges of the upper and lower anterior teeth, thus stimulating the lips to achieve correct lip seal, and encourage extrusive movement of the incisors.

Frankel Function Regulator

Introduced by Rolf Frankel in the year 1960

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The distinguishing characteristic of this appliance was its vestibular area of operation.

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Types of appliances :

1) FR I ( includes FR Ia, Ib, Ic )

2) FR II

3) FR III

4) FR IV

5) FR V

Frankel Function Regulator

The Frankel Philosophy :

• According to Frankel, the buccinator mechanism and the orbicularis oris complex has a potential restraining influence on the outward development of the dental arches, particularly in the transitional period.
• If these buccinator mechanism pressures are screened from the dentition, significant expansion may occur in the critical inter-canine area.
• For the success of this appliance, however, daily functional exercise ( oral gymnastics ) is vitally important.

Frankel Function Regulator

Working Principle of the Frankel appliance :

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The appliance works on the principle of force elimination.

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The buccal shields and the lip pads, shield the dentition away from the restrictive influence of the buccinator orbicularis-oris complex. The functional activity of the tongue then causes the outward development of the dental arches.

The shields and the pads also exert an outward periosteal pull on the dental arches that leads to bone formation and lateral movement of the dento-alveolar complex.

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• Working Principles

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• Vestibular arena of operation.

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• Sagittal correction via tooth borne maxillary anchorage.

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• Differential eruption guidance.

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• Minimal maxillary basal effect

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• Periosteal pull by buccal shield & lip pads.

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MODE OF ACTION OF FR�

1. Increase in transverse sagittal direction

- by use of buccal shields and lip pads

2. Increase in vertical direction

- by allowing the lower molar to erupt freely because appliance is fixed to the upper arch

3. Muscle adaptation

- The form and extension of the buccal shields

and lip pads along with the prescribed exercises corrects the abnormal peri-oral muscle activity.

Frankel Function Regulator

Indications of the Frankel appliance :

1) FR Ia – used in Class I deep-bite cases with protruded maxillary and retruded mandibular incisors.

2) FR Ib – used in Class II div 1 cases with deep-bite and overjet not exceeding 7mm.

3) FR Ic – used in more severe Class II div 1 malocclusion with overjet more than 7mm

4) FR II – used in Class II div1 and div 2 cases

5) FR III – used in Class III malocclusions

6) FR IV – used in open-bite malocclusions

7) FR V – used with headgear in long face patients

COMPONENTS OF THE APPLIANCE�

Acrylic components

• Buccal shields/ vestibular shields
• Lower Lip pads
• Upper labial or lip pads
• Lingual shields

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Wire components

• Palatal bow
• Labial bow-Upper, lower
• Canine extensions
• Lower lingual springs
• Canine clasp/canine loop
• Occlusal rest
• Lingual cross over wire

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Frankel Function Regulator

Construction of FR Ia :

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Acrylic components –

• Buccal shields – to shield the restraining effect of the buccinator mechanism.
• Lower Lip pads ( Frankel called them ‘pelots’ ) – to shield the restraining effect of the orbicularis oris complex.

b) Wire components –

• Palatal bow (0.040 inch) – to strengthen the appliance. The recurved ends act as occlusal rests, preventing the appliance from being dislodged superiorly and also prevent supra-eruption of first molars.
• Lower lingual bow (0.028 inch) – to provide proprioceptive signal to the mandible so that it remains in the forward position.
• Maxillary labial bow (0.036 inch) – to prevent any labial tipping of the upper incisors.
• Canine loops (0.036 inch) – assist in anchoring the appliance and help in guiding the eruption of canine.
• Lower labial support wire (0.036 inch) – serve as a skeleton for the lip pads.
• Lower cross-over wire (0.040 inch) – they connect the lower lingual apparatus to the buccal shields.

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Frankel Function Regulator

Construction of FR Ib :

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All the components are the same as that of FR Ia except that, the FR Ib has lower lingual acrylic pad instead of the lower lingual bow.

Frankel Function Regulator

Construction of FR Ic :

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The wire and the acrylic components are same as that of FR Ib except for the following :

The buccal shield are split vertically and horizontally.

The antero-inferior portion contains the wires for the lower lingual acrylic pad and the lip pads. The cross-over wire permits advancement of the mandibular apparatus. The vertical split is then filled with cold cure acrylic and polished.

• Fabrication of FR 2

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• a – labial bow.
• b – canine loop.
• c – buccal shield.
• d – lip pads.

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• Fabrication of FR 2
• a – cross palatal stabilizing wire.
• b – maxillary lingual bow / protrusion bow.
• c – lower lingual spring.
• d – buccal shield.
• e – lip pads.
• f – lower lingual pad / plate.

• Construction bite for FR

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• Done in same way as for activator.
• Edge to edge incisor positioning ( not more than 2.5 – 3mm advancement)
• 2.5 – 3.5 mm opening of buccal segment.
• Maintain the midline.

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Frankel Function Regulator

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Construction of FR II :

It is the same as that of FR Ib except the following :

Upper lingual bow (0.032 inch) – it is added behind the maxillary incisors. Serves to maintain the pre-functional alignment achieved. Frankel originally called it a protrusion bow.

Modified canine loops – they contact the canines only on the buccal surface. They are placed 2-3mm away from the canine so shield the canine from restrictive muscle influences.

Frankel Function Regulator

Construction of FR III :

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a) Acrylic components :

• Buccal shields
• Upper lip pads – to eliminate the restrictive influences of the upper lip on the under-developed maxilla and also to exert periosteal pull in the sulcus area.

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b) Wire components -

• Lower labial bow
• Upper lingual protrusion bow – to stimulate forward movement of the upper teeth.
• Upper palatal bow
• Mandibular first molar occlusal rests
• Upper labial support wires.

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The FR III should be used in the deciduous or early permanent dentition in Class III malocclusions characterized by maxillary retrognathism and not mandibular prognathism.

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Frankel Function Regulator

Construction of FR IV :

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It’s the same as that of FR II except for the following:

• Absence of canine loops and protrusion bow
• 4 occlusal rests on maxillary permanent first molars and deciduous first molars – to prevent tipping of the appliance and discourage eruption of teeth.

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Frankel Function Regulator

Construction Bite :

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• For minor sagittal problems, an edge-to-edge bite is preferred. The vertical opening should be only large enough to allow the cross-over wires through the interocclusal space without contacting the teeth

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• In Class III cases, the construction bite procedure involves retruding the mandible as much as possible, with the condyle in the most posterior position in the fossa. The bite opening is kept to a minimum to allow lip closure with minimum strain.

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Frankel Function Regulator

Other relevant important points –

• Separators – they are placed between the deciduous canine – deciduous first molar and deciduous second molar – permanent molar embrasures to create space for seating of the wires
• Seating grooves – if the separators don’t create enough space, grooves are cut taking care to not to injure the first permanent molars.
• Wax relief – this is done during fabrication so that the buccal shields stand away from the teeth and tissues. The thickness of the wax must not exceed 4 – 5mm in the tooth area and 2.5 – 3mm in the alveolar area.

Frankel Function Regulator

Wear time :

• First 2 weeks – 2 to 4 hours per day
• 3 weeks to 6 weeks – 4 to 6 hours per day
• 6 weeks onwards – full time wear

Patient is asked to perform oral gymnastics.

Oral Gymnastics :

These are oral exercises recommended by Frankel. They are absolutely essential for the success of the Frankel appliance therapy. They include :

• Keeping the lips closed at all times
• Talking
• Reading aloud
• Swallowing

Activator

• Tooth-borne appliance
• Loose fitting appliance
• Does not act as an exercise device
• Harnesses muscle forces

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• Bulk of appliance placed within the teeth
• Only 1wire component
• 1 single acrylic block
• Mandibular advancement by 6-7mm
• Vertical opening is more
• Worn during night
• Speech is not possible

Frankel

• Tissue-borne appliance
• Firm maxillary anchorage
• Acts as an exercise device
• Prevents abnormal muscle forces
• Bulk of appliance placed in the vestibule
• Many wire components
• 3 acrylic parts
• Mandibular advancement by 2.5-3mm
• Minimum vertical opening
• Worn during day and night
• Speech is possible

Twin Block Appliance

The appliance was developed by William Clark in 1977.

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The unique and distinct advantage that this appliance has over other appliances is that this is the only myofunctional appliance that is divided into a separate upper and lower plates.

TWIN BLOCK

• Effectively combines the techniques of inclined planes with inter maxillary & extra oral traction.
• Lower & upper inclined plates causes functional mandibular advancement.

Twin Block Appliance

Construction of the appliance –

• The appliance consists of upper and lower plates having occlusally inclined bite planes. The upper bite block is placed such that the leading edge of the inclined plane is positioned mesial to the lower first molar and not obstruct its eruption.
• The inclined planes are angled at 70 degrees to the occlusal plane, and this angulation is usually effective in guiding the mandible into occlusion in a forward position.

• The flat occlusal bite block, is reduced bucco-lingually in the lower canine region, providing sufficient space for tongue movement.
• The lower lingual flange is kept thick to provide strength.
• The upper plate is anchored to the maxillary dentition by means of ‘Delta’ clasps (designed by Clark in 1985). These clasps are preferred over Adam’s clasp because of their distinct advantage of very low breakage ( 1% in Delta clasp as compared to 10% in Adam’s clasp )
• The appliance also incorporates an upper labial bow for the sole purpose of retention.

Twin Block Appliance

Types of Twin Block Appliances :

1. Standard Twin Block ( for correction of Class II )

2. Reverse Twin Block ( for correction of Class III)

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Treatment stages in Twin Block Therapy –

a) Active Phase – the appliance is worn for 6 to 9 months to achieve correction of the malocclusion.

b) Support Phase – the twin block appliance is removed and an upper anterior inclined plane is worn to retain correct incisor relationship until buccal segment occlusion is fully established ( 4 to 6 months ).

Twin Block Appliance

Advantages of Twin Block over other Functional Appliances :

1. It is designed such that it can be worn full time.
2. Full time wear allows the patient to adapt completely and provides continuous application of light physiologic force.
3. Causes less interference with normal function.
4. Appearance is considerably improved on fitting the appliance, thus motivating the patient.
5. Allows independent control of upper and lower arch width.
6. Rapid correction of malocclusion.
7. Integration with fixed appliances is simpler.

The Pterygoid Response�

• Within a few days of the fitting of twin block appliances, the position of muscle balance is altered so greatly that the patient experiences pain when retracting the mandible
• Due to the formation of a “tension zone” distal to the condyle

FUNCTIONAL ORTHOPEDIC MAGNETIC APPLIANCES (FOMA).�

FIXED FUNCTIONAL� APPLIANCES

Rigid Fixed functionals

• Herbst and its modifications
• The Universal Bite Jumper
• The Mandibular anterior repositioning appliance (MARA)

FLEXIBLE FIXED FUNCTIONAL

APPLIANCES (FFFA’s)

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• Jasper Jumper
• Adjustable Bite Corrector (ABC)
• Klapper spring
• Churro Jumper

HYBRID FIXED FUNCTIONAL APPLIANCES

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Push force - a) Eureka spring

b) Twin force bite corrector

c) Forsus spring

d) Sabbagh Universal spring (SUS)

Pull Force - a) Saif spring

b) Calibrated force module

c) Alpern Class II correctors

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Miscellaneous - a) Rick-a-Nator

b) Fixed Twin block etc.

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Fixed Functional Appliances

Their advantage over removable functional appliances :

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• The operator can make use of the residual growth spurt which otherwise is difficult when removable appliance is used.
• The appliance does not depend on patient compliance.

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Herbst Appliance

Initially introduced by Emil Herbst in the year 1909.

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The appliance did not get immediate acceptance and was slowly forgotten.

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It was then reintroduced by Hans Pancherz in 1977.

Herbst Appliance

The appliance is used for correction of Class II malocclusions due to retrognathic mandible in the following cases :

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• Patients at the end of their growth spurts.
• Mouth breathers
• Unco-operative patient

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Herbst Appliance

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The appliance acts by way of a bilateral telescopic mechanism that mechanically keeps the mandible in a constant protruded position.

The device consists of a tube into which a plunger fits

The tube is fixed to the distal end of the maxillary molars while the rod is fixed to the lower first premolars.

Herbst Appliance

Types of appliances :

1. Banded Herbst appliance

2. Bonded Herbst appliance

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Banded Herbst : the upper first molars and lower first premolars are banded. The tubes are fixed to the upper first molars while the plunger to the lower first premolar by means of pivots.

Bonded Herbst : it consists of a wire reinforced acrylic splint that covers the occlusal, buccal and lingual surface of all teeth except the anteriors. Pivots are fixed to these wire frameworks. The tube is fixed to the pivots of the maxillary molar while the plunger to pivots of the mandibular premolar.

Jasper Jumper

Introduced by J.J.Jasper in the year 1980.

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It is also used in the skeletal correction of Class II malocclusions with maxillary excess and mandibular deficiency.

Jasper jumper /modified Herbst

• More flexible

Jasper Jumper

Appliance design :

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• The appliance basically consists of a modular system.
• The module can be attached to the fixed appliance.
• The jumper is constructed of stainless steel coil attached at both ends to stainless steel end caps

Jasper Jumper

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The end caps are attached to the fixed appliance in the maxillary posterior and mandibular anterior region

• The force module is attached to the maxillary arch by a ball pin that passes through face bow tube.
• Anteriorly the module is attached to the lower arch wire, distal to canine by way of small bayonet bend and a lexan bead

Jasper Jumper

Mode of Action –

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• The modules are available in 7 sizes, ranging from 26mm to 38mm in length.
• The distance between the mesial aspect of the upper face bow tube and the distal aspect of the lexan ball distal to canine is measured.
• To this distance, 12mm is added.
• When the teeth occlude, the module being longer tends to curve thereby producing a mesial force on mandibular arch and distal force on the maxillary arch.

The Forsus spring

- 3 M Unitek