ACTIVATOR AND ITS MODIFICATIONS

1.0 : Introduction :

In the past 20 years there has been increasing awareness of growth

modifications produced by functional appliances among orthodontists.

Major reasons for their popularity includes

Increasing recognition of FORM & FUNCTION

Realization that NEUROMUSCULAR INVOLVEMENT is vital in

treatment.

Recognizing the IMPORTANCE OF AIRWAY in therapeutic

considerations

Growing understanding of HEAD POSTURE AND ITS ROLE

GROWTH MODIFICATION as far as possible is the IDEAL

APPROACH. The "envelope of discrepancy" graphically illustrates the current

concepts of how much change can be brought about by orthodontic tooth

movement that is camouflage alone (Inner Circle). Orthodontic tooth

movement combined with growth modification (Middle Circle) and surgical

correction (outer circle).

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ENVELOPE OF DISCREPANCY

The "envelope of discrepancy” for maxillary and mandibular

arches. The middle circle for the lower arch indicates that the mandible and

mandibular teeth can be brought forward 10mm by a combination of growth

changes and tooth movement but can be brought back (restrained) by only

5mm. Growth modification is more effective in treating MANDIBULAR

DEFICIENCY.

Functional appliance may be

1. Tooth Borne - Passive (MYOTONIC) eg. Andreson's Activator

(Depends on Muscle Mass for their Action) Balter's Bionator

2. Tooth Borne - Active (MYODYNAMIC) eg. Elastic Open Activator

(Depends of Muscle activity for their function) Klammpt's activator

3. Tissue Borne – Passive eg. Oral Screen, Lip Bumper

4. Tissue Borne – Active eg. Frankel

2.0 : History and Evolution of Activator:

KINGSLEY introduced "Jumping of the bite": in 1879 to correct sagittal

relationship between Upper and lower jaws.

HOTZ modified the kingsley's plate into a vorbissplate (used it for deep

bite and retrognathism).

From Kingsley's concept, VIGGO ANDRESEN 1908 developed a loose

fitting appliance on his daughter as a retainer during summer vacations

which gave remarkable results. He called it BIOMECHANICAL

RETAINER.

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Some yrs before this, PIERRE ROBIN created monobloc to position the

mandible forward to prevent occluding the airway in patients of

GLOSSOPTOSIS.

Andresen moved to Oslo University, Norway where he met KARL

HAUPL (a periodontist and histologist) who became convinced that

appliance induced growth changes in a physiological manner. Then the

name ACTIVATOR or Norwegian system was coined.

This paved way for a series of modifications and an array of functional

appliances and opened a new area in the field of orthodontics-functional jaw

orthopedics.

3.0 : Indications of Activator:

Actively growing individual with favorable (horizontal) growth pattern.

Well aligned maxillary and mandibular teeth

Mandibular incisors should be upright over the basal bone.

Used In

1. Class II Div 1

2. Class II Div 2 after aligning the incisors

3. Class III

4. Class I open bite

5. Class I deep bite

6. For cross bite correction (Trimming done in such a way that maxillary

molars are moved laterally and mandibular molars lingually).

7. Preliminary before Fixed appliance to improve skeletal jaw relationship.

8. For post- treatment retention

9. Used for opening the space for 5 5 or even 4 4 by using jack screws 5 5 4 4

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10. Simultaneously serves as a space maintainer in mixed dentition, the

acrylic is extended into the space of missing tooth.

11. Treatment of snoring. Found to be more effective than soft palate lifter

mouth shield (Swedish dental journal - 1996 -20 (5))

3.1 : Contra Indications

1. Class I crowding, due to tooth size jaw discrepancy

2. Increased lower facial height.

3. Extreme vertical mandibular growth

4. Severely procumbent lower incisors

5. Nasal stenosis.

6. Non growing individuals

Efficacy of Activator:

According to Andresen & Haupl,

Activator is effective in exploiting the interrelationship between

FUNCTION and changes in INTERNAL BONE STRUCTURE.

During GROWTH, there is also interrelationship between FUNCTION

and EXTERNAL BONE FORM.

The CONDYLAR ADAPTATION to the anterior positioning of the

mandible consists of growth in an upward and backward direction to

maintain the integrity of TMJ. This adaptational process in induced by

the loose fitting appliance.

4.0: Classification of views : Views of various authors are classified into 3

groups

1. PETROVIC (1984): McNAMARA (1973) substantiate the Andresen

Haupl's Concept that MYOTATIC reflex activity and ISOMETRIC

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CONTRACTION induce musculoskeletal adaptation by introducing a

new mandibular closing pattern.

Superior head of lateral pterygoid plays an important role in assisting the

skeletal adaptations.

Pertovics research on condylar cartilage growth stimulation is by

activating the lateral pterygoid.

2. SELMER - OLSEN, HERREN 1953, HARVOLD 1974 & WOODSIDE

1973 do not agree with the myotactic reflex.

According to their views,

VISCOELASTIC PROPERTIES OF MUSCLE AND STRETCHING OF

SOFT TISSUES are decisive for activator action.

Each application of force induces secondary forces in tissues which

inturn introduces a bio-elastic process and that is important in stimulating

skeletal adaptation.

Stages of Visco-Elastic Reaction (Depends on magnitude and duration of

applied force)

Empting of vessels

Pressing out of interstitial fluid

Stretching of fibres

Elastic deformation of bone

Bioplastic adaptation

Woodside recommends opening the mandible upto 10-15mm with the

construction bite.

SCHMUTH, WITT AND KOMPOSCH feel displacing mandible 4 - 6 mm

below intercuspal position to be ideal. Observed long periods of continuous

pressure from mandibular teeth against the activator.

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ESCHLER 1952 refers to opening the vertical dimension beyond 4mm in

construction bite as the "muscle stretching method" which works alternatively

with isotonic and isometric contractions.

Other than these, some authors state 4-6mm bite opening is the ultimate

decision as to whether the force delivered is KINETIC ENERGY (Isometric

contraction) or POTENTIAL ENERGY (Viscoelastic properties) or

combination.

5.0: Force analysis in activator therapy:

When functional appliance activates the muscles, various types of forces

are created - STATIC , DYNAMIC and RHYTHMIC forces.

Static forces are permanent (eg. force of gravity, posture, elasticity of

soft tissues and muscles)

Dynamic forces are interrupted (eg. movements of head and body,

swallowing)

Rhythmic forces are associated with respiration and circulation.

Mandible transmits rhythmic vibrations to the maxilla.

5.1 : Effectiveness of activators during sleep :

Serves as a "Night Guard" preventing deleterious nocturnal

parafunctional activity and stimulating normal muscle activity.

(Mandibular protraction enhances metabolic pump activity of the

retrodiscal pad thereby increases blood flow. Catabolic byproducts

were forced out on mandibular retraction.

Protracted, unloaded condyle enhances condylar growth increments

and favourable upward and backward growth direction.

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HOTZ, PETROVIC, OUDET, STUZMANN stated that growth

increments were greater at night due to increased growth hormone

secretion.

SELMER-OLSEN said that the muscles could not be stimulated during

sleep as nature has designed them to be at rest. Swallowing occurred

only 4-8 times in an hour during night.

Electromyographic study of temporalis and masseter with and without

activators (AJO - Aug 1998)

It is observed that there was 1. Similar postural activity for both muscles

with or without activator. 2. During swallowing of saliva, muscle activity was

higher with the activator. 3. During maximal clenching similar activity in

anterior temporalis with or without activator. Higher activity in masseter

muscle with the activator.

Increased interrupted electromyographic (IEMG) activity with activators

during swallowing of saliva supports a recommendation for DIURNAL WEAR

OF ACTIVATOR because the frequency of saliva swallowing during sleep is

very low.

The higher activity during saliva swallowing with the activators is

particularly important because it is a functional activity repeated between 600

and 2400 times each day.

5.2 : Head posture during sleep

When the patient is upright-muscle tension, muscle tonus and

atmospheric pressure equals the weight of the mandible, associated tissues and

the activator. They act in opposite directions so the forces get balanced.

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During sleep - activator, gravity, muscle tension, muscle tonus all act in

the same direction. However during sleep, lips drop open, mouth breathing

ensues and function is minimal.

HARVOLD & WOODSIDE wanted to exceed the free - way space

limits to keep the appliance in place at night during sleep so as to

maintain the corrective stimulus.

Two principles employed in modern activator

1. FORCE APPLICATION - the source is usually muscular

2. FORCE ELIMINATION - dentition is shielded from normal and

abnormal functional tissue pressures by pads, shields and wires.

5.3 : Types of forces employed in activator therapy

Growth potential includes eruption and migration of teeth which

produces natural forces and those can be guided, promoted and inhibited

by the activator.

Muscle contraction and stretching of soft tissues produces artificial

forces effective in all three planes. Sagittal plane - mandible propelled

down and forward so that force is delivered to the condyle. Vertical

plane - teeth and alveolar process either loaded or relieved of normal

forces. Transverse plane - forces can be created with midline reactions.

According to WITT,

Approximate sagittal force 315 - 395 gms.

Optimal vertical force 70 - 175 gms.

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In a study by NORO et al (AJO - 94 Feb) magnitude of forces

generated by passive tension of soft tissues increased from 80 - 160 gms

in class II patients and 130 - 200 gms in class III patients when the

construction bite heights changed from 2 to 8mm.

Direction of forces changed from vertical to posterior and from vertical

to anterior in class II and class III respectively.

Forces exerted by passive tension remained significantly longer than that

exerted by active contractions irrespective of construction bite heights.

Study concluded that forces produced by PASSIVE STRETCH

REFLEX plays an important role inducing changes.

6.0: DIAGNOSTIC PREPARATION:

Patient compliance is very necessary. Motivation of the patient is also to be

analyzed.

6.1: Treatment Timing: - should be coincident with periods of active

growth. Mostly initiated during MIDDLE to LATE MIXED DENTITION.

6.2: Study Model Analysis:

1. The first permanent molar relationship in habitual occlusion.

2. Nature of midline discrepancy - if present, functional analysis done to

determine the path of closure from postural rest to occlusion. If midline

changes, functional problem is likely which can be corrected by the

functional appliance. If the dentoalveolar midlines are not coinciding

functional appliance cannot be used.

3. Symmetry of dental arches evaluated.

4. If curve of spee - leveling needed is severe - activator cannot perform it.

5. Crowding and any dental discrepancies are noted.

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6.3 : FUNCTIONAL ANALYSIS

1. Precise registration of postural rest position.

2. Path of closure determined.

3. Prematurities noted.

4. Clicking or crepitus in the TMJ palpated.

5. Interocclusal clearence or free way space measured.

6. Respiration (if disturbed nasal respiration present - choice will be an

open activator)

7. Size of tonsil and adenoids recorded.

6.4: CEPHALOMETRIC ANALYSIS

Helps to identify the craniofacial morphogenetic pattern to be treated.

1. Direction of growth determined (average, horizontal or vertical)

2. Differentiation between position and size of jaw bases.

3. Morphological peculiarities

4. Axial inclination and position of maxillary and mandibular incisors.

VTO - VISUAL TREATMENT OBJECTIVES - Is the method of

predicting what the end result of treatment would be.

1. Clinical VTO

2. Cephalometric VTO

Clinical VTO:

Patient is asked to close the mouth in habitual occlusion and relax the

lips - PROFILE is carefully studied. It can be photographed.

Next the patient is asked to posture the mandible forward into a correct

sagittal relationship, reducing the overjet. A photograph can be taken

again.

According to one of the methods, if profile improves with

1/2 protrusion FRANKEL recommended

Full protrusion ACTIVATOR or BIONATOR

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If the profile still does not Improve ACTIVATOR with HEAD GEAR.

Cephalometric VTO Considerable controversy exists over the cephalometric growth

forecasting technique.

Rickets short term prediction is widely used because it is easily

employed in software. But it makes no attempt to predict post

growth positions of major land marks such as sella.

Hold away growth prediction has 12 stages of VTO. It provides a

dynamic assessment of facial morphology.

Treatment Planning

Next step after collection of diagnostic information is to plan the

construction bite.

Extent of anterior positioning for class II malocclusion.

Extent of posterior positioning for class III malocclusion are

determined.

ANTERIOR POSTIONING OF MANDIBLE

The usual intermaxillary relationship for average class II problems is

END TO END INCISAL. It should not exceed 7 to 8mm or 3/4 of mesiodistal

dimension of first permanent molar.

Construction bite in edge to edge Anterior positioning of the mandible Relationship with slight opening. from the rest position.

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End to end incisal positioning is contra indicated in

1. If overjet is too large

2. Labial tipping of maxillary incisors is severe (corrected with a

Pre- functional appliance).

3. An incisor erupted markedly on to the lingual side (Anterior positioning

of mandible with the malposed incisors is termed pathological cross-

bite (ESCHLER 1952). Prefunctional appliance will eliminate the need

for this pathological construction bite.)

OPENING THE BITE

To determine the height of the bite

1. Mandible should be dislocated from its postural rest position in atleast

one direction - SAGITTAL or VERTICAL

2. If the forward positioning is great, vertical opening should be minimum

(for example - when the forward positioning is 7 to 8mm vertical

opening should be 2 to 4 mm. If the forward positioning is reduced to 3

to 5 mm vertical opening is increased to 4 to 6 mm ).

7.0 Construction bite for various types of activators.

7.1 ANDRESON APPLIANCE

Vertical opening is within the limits of free way space ( 2 to 4 mm).

Mandibular advancement being 3 to 5 mm.

Used for less severe class II MO with deep bite and upright or lingually

inclined lower incisor.

MODUS OPERANDI

The appliance induces activation of MYOTACTIC REFLEX &

ISOMETRIC CONTRACTIONS. These muscle forces are transmitted by

the appliance to move the teeth. Thus the appliance uses KINETIC

ENERGY.

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REFLEX CONTROL OF SKELETAL MUSCLE CONTRACTION

MECHANISM OF STRETCH OR MYOTACTIC REFLEX

Stretch reflex when elicited causes contraction of the stretched muscle.

Muscle stretch receptors are proprioceptive nerve endings called muscle

spindles situated within the muscle.

MUSCLE SPINDLES

Contain

2-15 THIN INTRAFUSAL MUSCLE FIBERS NUCLEAR BAG

MUSCLE FIBRE REGION

(Striated & contractile) (non contractile)

Impulses arise

Conducted

Group I A sensory fibre

Synapse with

'' efferents

supply the extra fusal muscle fibre

responsible

CONTRACTION OF STRETCHED MUSCLE.

Therefore called "monosynaptic reflex arc"

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Functional significance of stretch reflex serves as a mechanism for

upright posture or standing.

Similarly stretch reflex acts in the mandibular musculature to maintain

postural rest position in relation to maxilla.

1. HARVOLD WOOD-SIDE ACTIVATOR

The mandible is placed approximately 3mm distal to the most

protrusive position sagitally and vertically an extreme separation of 10

to 15mm beyond the free way space.

MODUS OPERANDI

Here the mandible is opened beyond 4mm so it does not work in the

same manner as Anderson's activator but by stretching of soft tissue - THE

VISCO ELASTIC EFFECT. In such cases CLASP - KNIFE REFLEX

plays a role.

MECHANISM OF CLASP KNIFE REFLEX OR AUTOGENIC

INHIBITION

Example: Spastic limb Resistance encountered

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Due to

Hyperactive reflex contraction

If carried out forcibly

Limb collapses readily

This phenomena is called CLASP KNIFE RIGIDITY (i.e. muscle first resists

and then relaxes)

Stimulus is EXCESS STRETCH when elicited leads to muscle

relaxation. Receptors are Golgi tendon organs situated in the muscle. Impulses

conducted by group I B sensory nerve fibre act on motor neuron or '' efferent

supplying the stretched muscle . It is a DISYNAPTIC REFLEX ARC because

an INTER NEURON is interposed between sensory and motor neuron.

Functional significance :- is to protect overload by preventing damaging

contractions against strong stretching force.

7.2 H - ACTIVATOR

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Activator constructed with LOW VERTICAL OPENING and a

markedly forward mandibular positioning is designated as horizontal or

'H' activator.

Indications:

Class II Div 1 with sufficient overjet

Class II Div 1 MO where there is mandibular overclosure that results in a

functional retrusion of the mandible. In such cases activator can act in the

sense of "Jumping the bite"

Class II Div 1 MO with posteriorly positioned mandible due to growth

deficiency with horizontal growth pattern.

As a mandible moves mesially to engage the appliance, elevator

muscle of mastication get activated.

When teeth engage the appliance MYOTACTIC REFLEX is

activated.

In addition muscle force arising during biting and swallowing

causes stimulation of muscle spindles which elicits reflex muscle

activity.

Effects of H - activator

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1. Mandible can be postured forward without tipping the lower incisors

labially.

2. LIP TRAP got eliminated

3. Maxillary incisors can be positioned upright or lingualy

4. Anterior growth vector of maxilla is slightly inhibited.

Class II Div 1 MO with vertical growth pattern when treated with H activator

results in DUAL BITE.

7:4 V-ACTIVATORS

Activator with large vertical opening and minimal anterior positioning is

designated as V activator. Mandible is positioned anteriorily only 3-5mm ahead

of habitual occlusion. Vertical opening 4 to 6mm beyond the postural rest

position.

Indicated in vertical growth pattern.

MODUS OPERANDI

Induces myotactic reflex activity. The greater vertical opening thus

allows the myotactic reflex to remain operative even when the musculature is

more relaxed ( that is when the patient is sleeping).

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Stretching of muscles and soft tissue elicits an additional force - the

viscoelastic force. This stretch reflex influences inclination of maxillary base.

7:5 Technique for construction bite in VERTICAL DIMENSION PROBLEMS (deep over bite and open bite)

Forward positioning of the mandible is not indicated if sagittal correction is

unnecessary (example - in deep bite and open bite and in selected cases of

crowding) .

7:5:1 Deep bite MO.

May be dentoalveolar or skeletal .

In dentoalveolar problems, the deep overbite may be due to infra-

occlusion of buccal segments or supra - occlusion of anterior segments.

Construction bite may be moderate or high depending on the free way space. If

it is due to supra - occlusion of anterior segments, interocclusal space is usually

small and should resort to high construction bite. Intrusion of incisors is possible

to only a limited extent when an activator in being used.

Skeletal deep bite MO's have a horizontal growth pattern, for which forward

inclination of maxillary base can compensate. Loading the incisors can achieve

a slight forward inclination of the maxillary base as well as frees the molars to

erupt. Here the construction bite is high (5 to 6mm beyond the free way space ).

A dento alveolar compensation is possible by extrusion of lower molars and

distal driving of upper molars with stabilizing wires.

7:5:2 Open bite MO:-

Anterior positioning of mandible is necessary if the skeletal relationship is

orthognathic. Bite is opened 4 to 5mm to develop a sufficient elastic depressing

force and load the molars that are in premature contact.

7:5:3 Arch length deficiency problems:-

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MO with crowding can sometimes be treated with the activator and can

accomplish the desired expansion because it is anchored intermaxillarly. The

appliance works in a manner similar to that of two active plates with

jackscrews in upper and lower parts. Construction bite should be low.

6. Construction bite for CLASS III MO

Goal is posterior positioning of mandible or maxillary protraction. The

construction bite taken by retruding the lower jaw. Extent of vertical opening

depends on the retrusion possible.

In PSEUDO CLASS III, functional deviation is present where the forced bite

is easily achieved. The mandibular incisors hit prematurely in an end to end

contact and mandible slides anteriorly to complete the occlusal relationship.

In these cases vertical opening is for enough to clear the incisal guidance for

construction bite. Here it is possible to achieve edge to edge bite relationship

with posterior teeth still out of contact.

In SKELETAL CLASS III MO with normal path of closure from postural rest

to habitual occlusion, treatment not possible with functional appliance.

8:0 Fabrication of the activator

After mounting the casts, wire elements are made. Primary wire elements are

the UPPER OR LOWER LABIAL BOW. Upper (U) loop starts in lateral

incisors canine embrasure area. Lower canine loops starts more distally is

mesial third of the canines. Labial bows can be active or passive. If active

made out of 0.9mm if passive made out of 0.8mm.

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Additional elements consist of springs, expansion screws, spurs.

(Jackscrews fixed on the casts.)

Fabrication of the acrylic parts consist of UPPER , LOWER AND INTER

OCCLUSAL PARTS. Upper and lower parts consist of DENTAL AND

GINGIVAL PORTIONS. Flanges of upper part extends 8 to 12 mm high in

gingival area and covers the alveolar crest. Flanges of lower part extends 5 to

12mm in gingival area. Flange extention is greater in V activators as the

patients of this category have open mouth postures.

Can be prepared with cold acrylic directly on models or wax pattern done and

invested in a flask to be prepared in heat cure.

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9:0 Trimming of the activator

In order to stimulate the functional activity of the perioral musculature with

the loose appliances so that the movement and eruption of selected teeth can be

guided, certain areas of the acrylic which contact the teeth should be ground

away.

9:1 VERTICAL PLANE

Intrusion:- Only limited intrusion is possible. Relative intrusion is one

of the objectives.

Incisor intrusion: brought about by

1. Loading the incisal edge.

2. Labial bow placed in the incisal third.

Molar intrusion brought about by

1. Acrylic plate touching only the cusps.

2. Acrylic plate ground away from fissures and grooves.

If larger occlusal surfaces are loaded, reflex opening occurs frequently

resulting in less depressing action by the appliance.

Extrusion: indicated in OPEN BITE problems.

Incisor extrusion

1. Labial bow is placed in the gingival 1/3

2. Loading the gingival 1/3 on the lingual surface.

Molar extrusion

1. Enhancing eruption by grinding the acrylic plate from the occlusal

surface.

2. Acrylic contacting the gingival 1/3 on the lingual surface.

9:2 SAGITTAL PLANE :

Protrusion :

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1. Loading the lingual surface with acrylic contacts.

2. Screening away lip strains with passive labial bow or lip pards.

Auxiliaries used are

3. Protrusion springs (0.8mm)

4. Wooden pegs

5. Guttapercha may be added to the lingual acrylic.

Retrusion:

Acrylic trimmed away from behind the incisors.

Active labial bow.

FOR DISTAL MOVEMENT OF THE POSTERIORS

1. Guide planes should be on the mesio lingual surfaces.

2. Stabilizing wires or spurs can be used

3. Active open springs.

In class II div 1 MO with deep bite, acrylic contacts the mesio gingival

surfaces of upper posterior and distogingival surface of lower posteriors. The

upper teeth are hence guided in downward and backward directions and lower

teeth in an upward and forward directions to establish the proper sagittal and

vertical relations. Acrylic on the lingual surface of the upper incisors is ground

away and labial bow made active if they are to be retracted .

9:3 TRANSVERSE PLANE

To achieve transverse movement lingual acrylic surface opposite the

posterior should be in contact with the teeth. Higher level of force can be

obtained by adding a thin layer of self cure soft acrylic. More effective

expansion can be achieved with use of jack screws.

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SELECTIVE TRIMMING OF THE ACTIVATOR

During selective trimming only the upper or lower molars are extruded.

After erupting, eruption of antagonist can be controlled. Thus both sagittal and

vertical relationship can be influenced.

Eruption pathway of the molars should be considered. "CONTROLLED

DIFFERENTIAL ERUPTION GUIDANCE" must be employed for the best

interdental and occlusal plane relationship, particularly in case of flush terminal

plane relationships, proper selective grinding can convert an impending class II

or class III MO into class I interdigitation.

10:0 Effects of Activator Therapy on Dento Facial Structures.

10:1 EFFECTS ON THE MANDIBLE, (AJO 1989 March - functional review - Bishara and Ziaji)

Birkebaek, Melsen, and Terp, in an implant study that featured

laminographs of the temporomandibular joint, concluded that the major effects

of activator treatment were an increased amount of condylar growth and a

remodeling of the articular fossa. The combination of these effects resulted in

the PERMANENT ANTERIOR DISPLACEMENT OF THE MANDIBLE.

Using the implants for cephalometric superimpositions, they determined that

the appliance did not inhibit the growth of the maxilla, but that it did cause the

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maxilla and mandible to rotate in a downward and backward direction.

Condylar growth during the 10-month period of activator treatment increased

1.1 mm and was redirected 12o in a more posterior direction compared with

untreated control. They also found that treatment resulted in a slightly forward

displacement of the glenoid fossa as compared with the slightly backward

displacement in the controls. In addition, the anterior facial height increased by

1.1mm and the mandibular plane angle was increased by 2.5o. The mandibular

plane angle slightly decreased in the controls.

Other investigators also found 1.0 to 2.0 mm incremental increases in the

growth of the mandible after the use of activators.

Pancherz evaluated 30 Class II, div 1 children in the mixed dentition who

were treated successfully with activators. The controls were persons of the

same sex and similar ages with excellent occlusion. The activator was worn at

night for an average of 32 months. He found that mandibular growth increased

by 0.3 mm per year, but this was not statistically significant. He concluded that

the magnitude of mandibular growth was not affected by activator treatment.

Other investigators found similar changes.

EFFECTIVE CONDYLAR GROWTH CHANGES AND CHIN POSITION

CHANGES IN ACTIVATOR TREATMENT (AO 2001: 71: 4 - 11) (SABINE

RUF, SANDRA BALTROMEJUS, HANS PANCHERZ)

According to this study, activator patients exhibited.

1. Increase in the amount of vertical effective condylar growth.

2. Decrease in the amount of sagittal effective condylar growth.

3. Increase in the amount of vertical development of the chin

4. Anterior rotation of the mandible.

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It was concluded that effective condylar growth can be increased and

chin position can be changed by activator treatment. Thus it induces skeletal

changes although not always in desired (SAGITAL) therapeutic directions.

10:2 EFFECTS ON THE MAXILLA Several investigators have shown that

it possible to clinically alter the growth direction of the maxilla.

Williams and Melsen demonstrated that an increased posterior

maxillary vertical heights resulted in a backward rotation of the

mandible and pogonion. Forshberg and Odenrick noted a significant

decrease of the SNA angle. Vargervik and Harvold found that the

activator inhibited the horizontal growth of the maxilla by 2 mm;

Pancherz found it was restricted by 1.7 mm.

10:3 Effects on the dentition. Bjork, Calvert, Pancherz and wieslandser

and lagerstom, observed significant dentoalveolar change. A class I

occlusion was achieved through distal tipping of the maxillary teeth and

a mesial, vertical movement of the mandibular dentition.

Harvold and vargervik observed that the appliance also caused

1.4mm of maxillary incisor lingual tipping and 0.5mm of mandibular

incisor labial tipping, they concluded that the appliance achieved a class

I occlusion by inhibiting maxillary dentoalveolar mesial and vertical

development, while encouraging mandibular dentoalveolar mesial and

vertical development. Pancherz founds that more than 70 % of the

overjet was corrected by incisor tipping. Approximately 50% (2.5mm)

of the overjet was reduced by lingual movement of the maxillary incisor,

while 22 % (1.1mm) was reduced mandibular incisor flaring.

10:4 Effects on soft tissue. Forsberg and Odenrick observed that upper lip

retrusion was significantly more prevalent in the treated class II group

than the control group. The nose showed equal forward growth in both

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groups, but the soft-tissue pogonion was significantly further anteriorly

in the treated group. Furthermore in the treated group lip balance was

not achieved in patients with relatively retrognathic profiles or those

with steep mandibular planes.

Effect of early activator treatment in patients with class II MO

Evaluated by thin plate spline analysis - (AO 2001: 71; 120-126)

Christopher J. Lux ; Jan Rubel, Komposch .

Thin plate spline analysis turned out to be a useful morphometric

supplement to conventional cephalometrics because the complex patterns of

shape could be suggestively visualized by means of grid deformations.

In the age group of 9.5 – 11.5 male class II patients treated with activator the

grid deformations of total spline analysis pointed a STRONG ACTIVATOR

INDUCED REDUCTION OF THE OVER JET caused mainly by tipping of

the incisors and to a minor degree by a moderation of sagittal discrepancy,

particularly by slight advancement of the mandible.

There are several possible structural mechanisms through which activator

obtains the class II correction.

Optimizing mandibular growth (as a secondary response to its anterior

dislocation from the articular fossa).

Redirection of mesial and vertical growth of maxilla

Lingual tipping of maxillary incisors

Labial tipping of mandibular incisors

Mesial and vertical eruption of mandibular molars

Inhibition of mesial movement of the maxillary molars.

Remodeling changes in TMJ

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A combination of orthodontic (60% to 70%) and orthopedic (30% to 40%)

movements provides the correction necessary for successful treatment.

Muscle activity during activator treatment : (AJO 1991 April) Ingervall

and Thuer.

Treatment of class II Div1 with activator treatment brings about a

gradual decrease of postural activity of the posterior portion of temporalis

muscle and anterior portion of the digastric muscle.

Changes in the anterior portion of temporalis and masseter were not

discernible.

McNamara, besides the above findings also noted increased activity of the

lateral pterygoid muscle. This so called "PTERYGOID RESPONSE" was

thought to lead to a forward repositioning of the mandible. (Pterygoid response

is the rapid adaptive clinical response seen shortly after wearing the appliance

probably for few weeks. It is characterized by pain when retracting the

mandible due to altered activity of medial head of lateral pterygoid muscle in

response to the mandibular protrusion. This may be due to the formation of

"TENSION ZONE" distal to the condyle).

Existence of such an effect has been questioned by AUF DER MAUR.

Recent studies also have not given any evidence of the pterygoid response with

activator. It is observed only in functional appliances that are worn full time.

(eg Twin block)

11:0 Pit falls of treatment with activator:

1. DUAL BITE (JCO 1983 May – Robert Shaye) is commonly seen in cases

treated with activator. Initially, positional adaptation indeed takes place during

class II treatment. This Robert Shaye calls it as PHANTOM ACTIVATOR

PHENOMENA. However the tendency to function in a forward mandibular

27

position does not guarantee that STRUCTURAL ADAPTATION will follow

spontaneously.

Severe centric relation – habitual occlusion discrepancies may be observed in

the form of dual bite succinctly termed as "SUNDAY BITE".

It seen mostly in 1. POST PUBERTAL FEMALES treated with activators. 2.

VERTICALLY GROWING PATIENTS treated with 'H' activator.

If dual bite is present at the termination of treatment – it cannot be considered

successful. DUAL BITE CASES ARE FAILURES.

11:2 Activator produces LABIAL TIPPING OF LOWER INCISORS.

In correcting class II MO, appliance contacts the lingual of the lower incisors,

then as the muscles pull the mandible back toward CR position, incisor flaring

easily occurs.

This can be overcome by ACTIVATOR / HEAD GEAR combination (AJO

1996 July)

11:2 Activator cannot produce detailed PRECISE FINISHING OF

OCCLUSION. It should be followed by short phase of fixed appliance therapy

(or) require refinement of occlusion through tooth positioners.

12:0 Auxiliaries for efficient functioning of the activator

Muscular force developed by the forward displacement of the mandible

with the activator (as any Bimaxillary appliance) can be highly efficient if it is

well directed and applied. This is an isometric contraction, which can be

enhanced by the addition of an isotonic contraction produced when the

mandible meets a resistance that prevents further movement.

MAS – MOLAR ABUTMENT SYSTEM (JCO 1984 April (Dahan)) is a

device for enhancing anchorage of the activator (any removable appliances) by

28

transmitting muscular force to the upper molars, if necessary to entire upper

arch – through precise placement of a controlled amount of force.

Aim is to magnify the force generated by the isometric contraction of

muscles antogonistic to the forward displacement of mandible and to use that

force to displace the appliance and upper molars backward

System is composed of 3 elements :

1. MOLAR BANDS with buccal tube and a split tube to accept

intermediate organ.

2. INTERMEDIATE ORGAN – made of 1mm SS wire

3. ARTICULATING ELEMENT – consists of 2 to 3 tubes anchored in the

orthopedic appliance.

THEY SHORTEN THE ORTHOPEDIC PHASE OF TREATMENT.

13:0 Modifications of the activator

Broadly categorized into 2 types

I. Appliances with ONE RIGID ACRYLIC MASS for maxillary and

mandible arches but with reduced volume or bulk.

a. Reduced volume in anterior palatal region to restore contact between

tongue and palate eg. ELASTIC OPEN ACTIVATOR

Disadvantages : construction bite cannot be opened too much vertically

b. Reduction in alveolar region and with a cross-palatal wire instead of full

acrylic plate. Eg. BIONATOR

II. Appliance consisting of 2 parts joined by wire bows. Muscle impulse are

reinforced by wire elements in the design. Eg. SCHWARZ DOUBLE

PLATE.

Following are the modifications :

1. Eschler's modification

2. Herren's activator (1953)

29

3. Herren's shage activator – LSU activator

4. The bow activator of Schwarz

5. Reduced activator of Cybernator of Schmuth

6. The Karwetsky appliance

7. The propulsor

8. The cutout (or) palate free activator

9. Elastic open activator of Klammt

10. Stockfish's Kinetor

11. Hamilton expansion activator system. (or) Bonded activator

12. Bionator

13. Combined activator /HG Orthopaedics.

14. MAD – Magnetic Activator Device.

1. ESCHLER'S MODIFICATION of labial bow the improved the

intermaxillary effectiveness. One part was active moving the teeth, other

passive, holding soft tissues of lower lip away and this enhancing the tooth

movement desired.

2. HERREN ACTIVATOR 1953 : Herren's concept was in complete

opposition to be Kinetic concept of Andersen Haupl.

30

Since observations on sleeping patients have revealed that there are

relatively few movements of the mastigatory apparatus and therefore of the

appliance itself. A slight unconscious lowering of the mandible will detach the

activator.

Hence he advocated

Triangular clasps to maxillary dentition.

A maximum forward positioning in essential with the construction bite

around 8-10mm.

Garber referred this appliance as a SPLINT and a "MYOTNIC"

appliance and claimed to exert 500gms of continuous force due to

stretched muscle.

3. (LOUISIANA STATE UNIVERSITY) L.S.U. or Activator of Shaye is

essentially a modification of Herren activation.

In this appliance the lower incisor bite on a plane formed by the acrylic.

Hence growth in occlusal direction is impeded. The eruption of premolars and

molars are achieved by selective grinding and the occlusal plane is leveled.

Ace to AUF DE MAUR (1978) & HERREN (1953) wearing of this

appliance does not bring about any increased activity of LPM.

Herren and L.S.U. activator exert their actions mainly through sagittal

repositioning of the mandible. These appliances have 2 step effects.

During wear the more forward positioning of the mandible is the cause of

reduced growth of LPM (Simultaneously) a new sensory engram is formed

for the new positioning of the lower jaw.

When not worn the mandible functions in a more forward position in such a

way, the retro-discal pad is much more stimulated as a result of which

earlier beginning of condylar chondroblast hypertrophy – and consequently

an increased growth rate of condylar cartilage takes place.

31

Thus LPM mediates the action of activator but the stimulating effect as

condylar growth appears to be produced almost exclusively during the time

which appliance is not worn.

4. WUNDERER'S MODIFICATIONS:-

Wunderer's modifications is used for class III MO. Consists of an activator

which was split horizontally, the upper and lower halves are connected with a

screw which is situated in a extension of the mandibular portion behind the

maxillary incisors. By opening the screw, maxillary portion is moved anteriorly

with a reciprocal backward thrust on the mandibular portion.

To enhance the appliance retention, occlusal surface of buccal teeth are

covered with acrylic. The construction of such an appliance is facilitated by

a screw designed by WEISE.

5. THE BOW ACTIVATOR OF SCHWARZ this was developed by A.M.

Schwarz in 1956. He was influenced by the elastic properties of Bimler's

appliance and some contributions from the Wunderer's appliance.

32

It consisted of an activator split into half horizontally and connected by an

elastic metal bow with a safety pin curve – to absorb the shock of jaws

during closing. There is a possibility of activating only the bow on the side

of a unilateral distoclusion.

Construction bite is minimal forward positioning of the mandible.

Appliance gets easily distorted and so results achieved are minimal.

6. THE REDUCED ACTIVATOR (OR) CYBERNATOR OF SCHMUTH

(Schmuth type of activator or cybernator with two labial bows)

This was designed by Professor G.P. Schmuth of Bonn.

Acrylic part is reduced for a manner similar to that of bionator.

Consists of labial wire and coffin spring (1.1mm)

Slender acrylic part is split in the midline. This avoids frequent

breakages.

Construction bite similar to that of an activator was preferred. Head-

gear tubes may be incorporated into the appliance.

7. THE KARWETSKY APPLIANCE : quite similar to Schwarz bow activator

33

Constructed with an improved technique and an apparently increased

efficiency

Consists of maxillary and mandibular active plates joined by a 'U' bow

in region of 1st permanent molars. The plates are extended over the

occlusal surfaces.

The height of construction bite is equal to inter occlusal clearance.

Depending on the placement of the ends of the 'U' Bow 3 types have been

created.

Type–I for Class II MO

Type–II for class III

Type–III to influence the mandible in a transverse direction. Used in facial

asymmetry (or) lateral cross-bite cases.

The appliance exerts a delicate influence on the dentition and on the

TMJ.

Can be combined simultaneously with fixed appliance particularly when

there are severe rotations.

With patient co-operation correction can be achieved rather quickly

5 – 8 months in favourable cases.

Duration of wear : atleast 3 hours during the day and during sleeping

hours.

8. CUTOUT OF PALATE FREE ACTIVATOR :

34

Developed by Metzelder. He combines bionator with original Anderson

Haupl activator. Mandibular part is the same as activator. In maxillary portion

acrylic covers only palatal or lingual aspect of buccal teeth. There is no palatal

coverage and coffin springs to lend strength and stability. It can be worn both

during day and night. Bite taken in edge to edge incisal relationship. Different

types of possibilities of treatment are made according to the principles

established by Balter.

9. ELASTIC OPEN ACTIVATORS (EOA): This another daytime

activators designed by G. Klammt of Gorlitz The appliance

consists of bilateral acrylic parts (an upper and lower labial wire,

a palatal arch and guide wires for the upper and lower anteriors).

35

EOA can be used for various MO including extraction cases. Flat acrylic

surface permits closure of spaces created by extraction since there is no

interference in the interproximal area.

ELASTIC ACTIVATOR FOR TREATMENT OF OPEN BITE (BJO 1999 –

Stellzig, Steegmayer)

The rigid intermaxillary acrylic of lateral occlusal zones is replaced by

elastic rubber tubes.

By stimulating the orofacial muscular system by ORTHOPEDIC

GYMNASTICS (chewing gum effect). Activators intrudes upper and lower

posterior teeth.

Possibility of eliminating habits by supplementary incorporation of a CRIB.

Fabrication is simple.

Treatment started in the mixed dentition.

Worn for 14 hours per day, closure of the open bite occurred within 8

months of treatment.

Can be used alone or with HG or FA or as a retention appliance.

A noticeable counter clock-wise rotation of the mandible was accomplished

by a decrease of gonial angle.

10. THE KINETOR : It is also an elastic activator developed by Dr.

HUGO STOCKFISH in 1951. It was combination of functional

principles with active operation of various screws and spring

added to the appliance. It has the capacity to expand the arches in

all 3 directions.

36

11. THE PROPULSOR : this was conceived by MUHLEMAN and

refined by HOTZ. It is described as a HYBRID APPLIANCE

with features of both monobloc and simpler oral screen or mask.

Advantage of the propulsor over activator like appliances :Is wide coverage

and ability to effect changes in the alveolar process.

Useful in MAXILLARY DENTOALVEOLAR PROTRUSION.

Eliminating any functional retrusive tendencies and offsets any functional

dominance of posterior temporalis fibers seen in class II div 1 MO.

Construction bite : Similar to an activator but taken in a more forward position

No wire configuration are used with the propulsor.

As intermaxillary relation improves, the appliance is reactivated (or)

modified by adding acrylic to the area that contacts the upper anterior

segment.

37

Acrylic between the occlusal surface of the first molars serves to stabilize

the appliance.

As treatment progresses, acrylic is removed progressively to allow for

unhindered eruption of molar, thereby reducing in the overbite.

HYPER PROPULSOR ACTIVATOR : (JCO 1985 Feb – George Gaumond)

The splint hyperpropulsor activator combined with extra oral force is

useful in young children with severe overjet and overbite who suffer from

fractured maxillary incisors at an early age (between 6 to 9).

Appliance is simple, sturdy, well tolerated, acts quickly (6 to 10 months),

inhibits thumb sucking, minimizes tipping of incisors and occlusal plane

and achieve stable results.

Consists of a BIMAXILLARY BLOCK OF ACRYLIC

One must register in wax the relationship of mandible with maxilla in

maximum hyper propulsion and mouth wide open (the only limit the

discomfort of the patient) incisal edges of upper and lower incisors should

be separated by 12 – 15 mm.

By virtue of the thickness of acrylic (12-15mm) and a high – pull E.O.

force, this appliance works efficiently at night and does not require day time

wear.

An anterior opening is built into the appliance to facilitate breathing.

Favours mandibular growth, it also inhibits maxillary growth. Mandible is

displaced anteriorly by the appliance and exerts a posterior force on the

mandible.

Upper and lower incisor axes were not altered; occlusal plane was not

tipped due to the addition of E.O. force.

38

Vertical dimension remained unchanged because acrylic prevents molar

eruption.

Petrovic et al (1981) showed that HP is effective if retrognathism is

associated with anterior growth rotation.

Role of LPM and meniscotemporo mandibular frenum (retrodiscal pad) in

spontaneous growth of mandible and in growth stimulated by postural hyper

propulsor (AJO 1990 May – Stutzmann and Petrovic)

The following conclusions were made.

1. HP induces supplementary lengthening of mandible

2. Opening of Stutzmann's angle induced by the appliance – was only a

transient phenomena.

In long run, lengthening of mandible elicited by postural hyper

propulsor occurs exclusively through supplementary growth.

For Postural hyperpropulsor 1. High tissue level growth potential and

responsiveness as detected biologically by the mandibular subperiosteal

ossification rate and alveolar bone turn over occurred.

12. COMBINATION OF TPA AND LINGUAL ARCH WITH THE

ACTIVATOR

Often a Mesiolingual rotation of upper first molar is found in class II

cases. For this Goshgarian transpalatal bar is efficient when combine with

activator. Lingual arch is used a space maintainer.

13. BONDED ACTIVATOR : Designed by HAMILTON who termed it as an

expansion activation approach. This achieves dramatic and rapid correction. It

is bonded to the maxillary arch and the forward guidance of the mandible is

achieved by proprioceptive guidance from the lingual flanges of the appliances.

39

There is no actual joining of maxillary and mandibular arches. It is also useful

in mixed dentition phase.

14.COMBINED ACTIVATOR / HG ORTHOPEDICS :

Prime target of treatment concept employing activator and HG

combination is to restrict developmental contributions that tend towards a

Skeletal class II and to enhance developmental contributions that tend to

harmonize the AP relations of maxillo mandibular structures

Hasmond introduced this concept in 1969.

Pfeiffer Grobety (1975) attached facebow directly to the activator and

applied occipital traction (to prevent the undesirable Kloehn effect of molar

eruption and downward pull of anterior end of palatal plane when cervical

traction is used) to achieve better vertical and rotational control during

orthopedic class II treatment.

40

Thurow incorporated removable acrylic splint in the upper arch to obtain

enmasse control. Face bow was directly incorporated and occipital pull

applied to restrain downward and forward displacement of maxillary

complex

Janson combines bionator with HG.

41

Indications :

Correction of SK Class II discrepancy in growing patients is the operational

field of A/HG appliance.

Reduction of anterior growth vector of maxillary complex can be produced

relatively well. HG treatment to upper arch with heavy forces up to 1000gm

per side for 16 hours can elicit a maximal maxillary contribution.

Indicated in SK Class II in which anterior movement of chin prominence in

desirable and atleast some posteriorly directed maxillo dentoalveolar

reaction is acceptable.

Used for class II correction in deciduous, mixed and permanent dentition

High angle cases are particularly domain of this combination.

A/HG – well suited for RETENTION of a corrected class II. Stability of the

result will depend on the balance between growth components of maxilla,

dento alveolar process and growth contribution of the condyles and glenoid

fossa. RELAPSE occurs if discordination persists after treatment.

Contraindications :

Dental class II situation with a SK. Class I profile should not treated

with this setup.

Excessive vertical growth due to structural, muscular or functional

disturbance cannot be totally regulated with this appliance.

Best treatment timing – will be the EARLY MIXED DENTITION stage.

E.O. force levels

1. Full mixed dentition 300 to 400mg

2. Mixed dentition during exfoliation 150 to 250mg

in the upper buccal segments

3. Full permanent dentition 400 to 600mg

4. Retention 150 – 400mg

42

Two commonly used A/HG combination are

1. Pfeiffer Grobetty combination therapy.

2. Stockli Teuscher activator therapy.

A sequence (or) a combination of sequences may be required.

1. Preparatory intra-maxillary treatment (W-appliance, rapid expansion (RME),

utility arches).

2. Sk. Class II correction with A/HG.

3. Intra maxillary detailing and inter-maxillary co-ordination (Full FA).

4. Retention of corrected class II with A/HG.

Frequent combinations 1 & 2 or 3 & 4. In severe cases-1,2, 3 & 4.

According to CLAUDE and CHABRE'S (1990) reports on the effects

of ACT/HG combinations. The following results were observed.

Clockwise rotation of palatal plane with no movement of PNS and

downward movement of ANS.

Downward tipping of occlusal plane with eruption of upper molars.

Eruption and retroclincation of upper incisors resulting in the correction

of overjet and anterior open bite.

Closing of facial axis and anterior mandibular rotation with forward

displacement of pognion.

Inhibition of forward maxillary growth combined with forward

mandibular growth results in correction of class II.

Improvement of class II profile

YOZTUIK and TANKUTER in their study on evaluation of skeletal and

dental effects of activator and A/HG combinations in growing children reported

that.

Horizontal growth of maxilla was restrained in both but was more

apparent in A/HG combination.

43

Activator stimulated mandibular growth by changes in the condyle

while A/HG merely restricted maxilla and allowed the mandible to

grow.

Both reduced the inclination of upper incisors.

Distalisation of upper molar in A/HG and mesialisation of lower molar

in activator are seen.

The control of axial inclination of lower incisor appears to be more

effective with A/HG combinations.

H.J. REMMELICK and B.G. TAN 1991.

During A/HG therapy, sagittal jaw relationship improved in class II Div

1 patient without occurrence of vertical skeletal change.

Considerable maxillary retroclination and mandibular incisior

proclination occurred with A/HG combination.

Growth and treatment changes in patients treated with a A/HG appliance

(AJO 2002 ; 121: 376-38). Margareta Bendeus, Urabn Hagg.

On average, there was small, favourable, skeletal growth changes in

subjects with class II div 1 MO.

The skeletal effect of A/HG appliance was primarily limited to restraint

of forward maxillary growth.

There was modest enhanced of mandibular growth during initial phase

of treatment only.

Vertical dental effect of A/HG appliance was to restrain the eruption of

maxillary molars and incisors. Overall sagittal dental charges were

favourable

15. MAD – MAGNETIC ACTIVATOR DEVICE.

Magnetic activator device can be used for correction of

1. Mandibular lateral deviation (MAD I)

44

2. Class II MO (MAD II)

3. Class III MO (MAD III)

4.Open bite cases (MAD IV)

Magnetic force ranges from 150 – 600gms preside and skeletal vs. dental

response depends on the intensity of magnetic force used.

Optimum force for 7 to 12 yrs – 300 gms per side.

MAD II – (AJO 1993 : 103 : Ali Darendeliler and Jean Pierre Joho)

Samarium Cobalt (Sm2 Co17) magnets of 4 x 4 x 6x 1 mm dimensions

were used.

30o inclination of occlusal surface of magnet to the basal surface

produces an OBLIQUE FORCE VECTOR to correct class II MO.

4mm – buccolingual thickness is only 1mm larger than a std edgewise br

of the magnet – so size and shape are compatible with vestibular shape.

In class II cases with normal vertical proportions, magnets are placed

distal to upper canine and distal to lower first premolars

In class II deep bite situations, inclination of the magnets and

subsequent magnetic force orientation is such that to produce dental

45

extrusion in premolar – molar area located more posteriorly and produce

an ATTRACTING FORCE between them.

In class II open bite situation, 2 pairs of lateral magnets is a repelling

configuration can be used posteriorly – to produce molar and premolar

intrusion, some distal movements in upper arch, pushes the mandible

downward and forward.

46

A pair of attracting magnets located at the retroincisal area - help to

achieve symmetry, align the upper and lower midlines, stabilise the appliace

against rippling forces.

MAD IV for skeletal open bite (JCO 1995-Sep Darendeliler & Semayuksel)

Consists of removable upper and lower plates.

Uses NEODYMIUM (Nd2Fe17B) magnets coated with stainless steel.

Consists of 4 posterior repelling magnets which generates a force of

300 gms each for introducing the molars.

2 anterior attracting midline magnets also generates 300 gms force.

It guides the mandible into centered midline position.

Exerts an anterior closing effect.

Enhances ANTERIOR ROTATION OF THE MANDIBLE.

MAD IVa – used where anterior segment of maxilla is vertically correct.

(or) overdeveloped gummy smile. Anterior magnets in contact.

MAD IVb – used when additional extrusive effect is needed in the

maxillary anterior region. Anterior magnets placed 2mm apart, posterior

magnets in contact

MAD IVc – used when only anterior extrusion is needed posterior magnets

are omitted. Anterior magnets 1-2mm open

SKELETAL OPEN BITE cases with high mandible plane angles and

overbite of –5mm to –1.5mm got reasonably well corrected after wearing MAD

IV on full-time basis (except during meals).

16. BIONATOR : Balter's bionator is referred as the "skeleton of an activator"

which is LESS BULKY and ELASTIC and permits day and night wear (Except

during meals).

47

Philosophy : According to Balter, the equilibrium between tongue and

circumoral muscles is responsible for the shape of the dental arches and

intercuspation and he considers the tongue (as the centre of reflex activity in

oral cavity) as the most important factor in treatment. A discordination of its

functions could lead to abnormal growth and actual deformation.

Main objective of the appliance : Is to establish a muscular equilibrium

between the forces of the tongue and outer neuro-muscular envelop.

Principle of treatment bionator does not activate the muscle but modulates

muscle activity thereby enhancing normal development of inherent growth

pattern and eliminates abnormal and potentially deforming environmental

factors.

Construction Bite : Bite is positioned EDGE TO EDGE relationship. Bionator

cannot make allowances for facial pattern and growth direction.

Balter reasoned that high construction bite drops the mandible open, tongue

instinctly moves forward to maintain an open airway leading to TONGUE

THRUST. Since the bite is not opened, myotactic reflex activity is stimulated

and loose appliance works with KINETIC ENERGY.

Indications of Bionator :

I. Used in the treatment of class II div1 MO in mixed dentition

48

Case selection should be such that

The dental arches are well aligned originally

The mandible is in a posterior position (ie. Functional retrusion)

Skeletal discrepancy is not too severe.

A labial tipping of upper incisor is evident.

II. Used in Open bite cases

III. Used in Class III MO

IV. Used in TMJ problems in adults.

Not Indicated :

1. In Class II relationship if it is caused by maxillary prognathism

2. In vertically growing patients

3. Labial tipping of lower incisors.

Bionator types

1. The standard appliance

2. Open bite bionator

3. Reversed bionator for class III.

Standard appliance : Consists of a lower horse shoe shaped acrylic. Upper arch

has only posterior lingual extension. Upper anterior portion is open from canine

to canine. Tongue function is controlled by edge to edge incisal relationship

49

50

leaving no space for tongue thrust activity. Function and posture of lips and

cheeks are guided by 2 wires.

* CROSS PALATAL BAR (1.2mm) * LABIAL BOW WITH EXTENSIONS

(0.9mm) with buccinator loops. Cross palatal bar stabilizes the appliance and

orients the tongue and mandible anteriorly to achieve class I relationship.

Labial bow – aid in lip closure.

Buccinator loops – screens the muscular forces in the vestibule.

Open bite bionator : used to inhibit abnormal posture and function of the

tongue with a goal of moving it into a more posterior or caudal position.

Labial bow runs between the incisal edge of upper and lower incisors.

Trimming of the appliance : When treatment begins, trimming all the guiding

acrylic planes simultaneously is not possible due to lack of bulk. Some acrylic

surfaces are used to stabilize others can be ground to bring about tooth

movement. In the next phase the loaded areas are trimmed and vice versa.

Thus periodic loading (prevention of eruption) and unloading

(stimulation of eruption) of the same area are necessary. The same tooth

functions as an anchor and later allowed to erupt.

51

Bionator in TMJ problems :

Specially indicated in TMJ patients who have bruxism, clenching,

clicking or crepitus.

Standard bionator is used.

Construction bite – need not move the mandible as far forward

Main purpose of bionator is to prevent the riding of the condyle over the

posterior edge of the disk to cause clicking.

Bionator therapy with local heat applications and muscle relaxants –

give dramatic results.

Changes in soft tissue profile following treatment with bionator. (AO 1995 Vol

65 Nov William Lange, Varun Kalra)

Age group treated 9 – 12 years.Duration – 18 months.

Following changes were observed

1. Decreased skeletal convexity.

2. Decreased facial convexity.

3. Increased anterior and posterior facial heights.

4. Decreased overjet and overbite.

5. Uncurling and increase in length of the lower lip minimal effect on the upper

lip.

6. Minimal effect on the upper lip.

Modifications of Bionator :

1. Biomodulator of Fleischer :

Acrylic body reduced in size.

Labial bow with buccinator loops replaced by a maxillary buccolabial

arch wire and a separate mandibular labial arch wire.

Cross palatal bar opens in a distal direction (as in class II bionator).

52

Saggital anchorage is reinforced with wire spurs, located mesial to

maxillary molars or canine (depending on MO)

2. Bio – M-S. appliance :

Consists of labial wire like the biomodulator which screens off the lip

trap.

Additional METAL OCCLUSAL BITE PLANE (0.5mm) thick which

provides a functional occlusal plane to normalize the vertical position of

teeth by leveling the curve of spee through eruption of posterior teeth,

thereby aids in correction of deep bite.

Metal occlusal bite plate allows proprioceptive contact of selected teeth

that do not need to erupt which stimulating the teeth that are in infra-

occlusion and not touching the metal plate. Thus selective trimming of

the acrylic for GUIDED ERUPTION is not required.

53

3. Bionator combined with orthopedic force.

Janson combined bionator with extra oral force.

Witzig introduced Orthopedic corrector – I and II

Orthopedic corrector I : Contains lateral and anterior expansion screws in the

lower arch. Decreased treatment time, more stable results were achieved.

Added several modifications for specific tooth movements like rotations,

tongue training, space closure was also obtained.

Orthopedic corrector II: also contains lateral and anterior expansion screws in

the lower arch. Used to correct open bite in mixed dentition. Enlarges dental

arches without tipping. Used in TMJ patients for repositioning of the mandible.

Finest stable results in shortest period of time is obtained.

Comparative study of bionator and headgear. AP skeletal changes

after early class II treatment with binators and HG (AJO 1998; 113 : 40-

50) (Stephen. D. Keeling, Timothy T. Wheeler).

Age group treated 9 – 10 years.

Both bionator and Head gear revealed

54

Skeletal changes largely attributed to enhanced mandibular anterior

growth.

Did not affect maxillary growth.

Corrected class II molar relationship

Reduced overjet.

After 1 year of treatment skeletal changes observed with both B/HG were

stable , dental movements relapsed.

Comparative study of Functional Regulator2 (FR2) and bionator in

treatment of class II MO. AJO 2002 ; 121 : 458 – 66 Marao Rodrigue de

Smedra, Jose Fernandez.

Following results were interpreted.

1. No significant change in maxillary growth

2. Significant increase in mandibular growth observed (greater increase in

patients treated with bionator).

3. No change in growth direction.

4. Bionator growth had greater increase in posterior facial height.

5. Both caused labial tipping of lower incisors lingual inclinations of upper

incisors.

6. Significant increase in mandibular posterior dento alveolar height.

Treatment effects of both were dentoalveolar with the small significant

skeletal change.

14:0 Conclusion :

The individualization of the basic concept of Andersen night time

application has given a number of clinicians the opportunities to express their

own biomechanical ability and personal preferences for tooth moving

appurtenances. It is believed that experience will dictate subsequent

modifications of functional appliances in achieving facial balance and harmony

during formative years of facial and dental development.

55

References

1. Dentofacial orthopedics with functional appliances ( Thomas -

M.Graber, Thomas Rakosi, Alexander petrovic)

2. Removable Orthodontic appliances (T.M.Grater Bedrich Neumann)

3. Current orthodontic concepts and Techniques (T.M.Graber,

Brainerd .F.Swain)

4. Orthodontics - Current Principles and Techniques (T.M.Graber,

Robert L.Vanarsdall)

5. The Clinical management of Basic maxillofacial Orthopedic Appliances

(Terrance J.Spahl, John W.Witzig)

6. Orthodontic and Orthopedic Treatment in the mixed dentition (James -

A. Mc.Namara, William L.Brudon).

7. Activator's mode of action (AJO July 1959 Volume 45. Paul Herren)

8. Activator and Electromyographic study - (AJO - Aug 1988)

9. Magnitude of forces generated by passive tension of soft tissues (AJO -

94-Feb)

10. Effects of Activator therapy on Dentofacial structures (AJO 1989 -

March. Final review - Bishara & Ziaji)

11. Muscle activity during activator treatment (AJO - 1991 - April)

(Ingervall & Thuer)

12. Dual bite - Phantum Activator phenomenon (JCO - 1983 May - Robert

Shaye)

13. Effect of Early Activator treatment in patients with class II MO.

(Evaluated by thin plate Spline Analysis) (Christopher.J.Lux, Jan

Rubel, Komposch - AO - 2001:71:120 - 126)

56

14. Effective condylar growth and chin position changes in Activator

treatment (AO - 2001 : 71: 4 - 11) (Sabine Ruf, Pancherz)

15. MAS - Molar abutment system (JCO - 1984 April Dahan)

16. Elastic Activator for treatment of open bite (BJO - 1999 - Stellzig,

Steegmayer)

17. Hyper propulsor Activator (JCO - 1985 - Feb - Georges Gaumond)

18. Role of CPM & meniscotemporal mandibular frenum (AJO - 1990 -

May - Stutzmann & Petrovic)

19. Growth and treatment changes in patients treated with a HG - Activator

appliances (AJO - 2002; 121 : 376 - 38) (Margareta Bendeus, Urban

Hagg).

20. Anterioposterior skeletal & dental changes after early class II treatment

with bionators & headgear (AJO - 1998;113:40 - 50) (Stephen

D.Keeling, Timothy Wheeler)

21. Magnetic activator device II (MADII) for correction of class II, Div 1

MO (M.Ali Darendeliler, Jean - Pierre John AJO 1993; vol.103)

22. Open bite correction with the magnetic Activator Device IV (M.Ali

Darendeliler, Sema Yuksel) JCO - 1995 - Sep (569 - 576)

23. Changes in Soft tissue profile following treatment with the bionator

(AO 1995 volume 65 No.6 William Lange, Varun kalra)

24. Comparitive study of the Frankel (FR-2) and bionator appliances in the

treatment of class II MO (AJO 2002;121:458 - 66 Marcio Rod rigues)

25. Cephalmetric changes during treatment with the open-bite bionator -

(AJO - 1992 April Weingbach & Smith).

57