Activator Functional Appliance

ACTIVATOR FUNCTIONAL APPLIANCE
Dr.Taher Manasawala
Orthodontics and Dentofacial Orthopedics

CONTENTS
 INTRODUCTION
 HISTORY AND DEVELOPMENT
 PHILOSOPHIES OF ACTION
 MODE OF ACTION
 FORCE ANALYSIS
 SKELETAL AND DENTOALVEOLAR EFFECTS OF
ACTIVATOR
 INDICATIONS

 SELECTION OF CASES
 DIAGNOSTIC PREPARATION
 CONSTRUCTION BITE
 FABRICATION
 TRIMMING OF ACTIVATOR
 MANAGEMENT
 MODIFICATIONS
 ADVANTAGES AND DISDVANTAGES
 CONCLUSION
 REFERENCES

INTRODUCTION
 The term functional appliance refers to a variety of removable
appliances designed to alter the arrangement of various muscle
groups that influence the function and position of mandible in
order to transmit forces to dentition and basal bone.
 These muscular forces are generated by altering mandibular
position sagittaly and vertically resulting in orthodontic and
orthopedic changes.
TEXTBOOK OF DENTOFACIAL ORTHOPEDICS WITH FUNCTIONAL APPLIANCES BY
THOMAS GRABER,THOMAS RAKOSI,ALEXANDRE G. PETROVIC.

 For many years, the exclusive province of dentofacial
orthopedics was Europe, while North America was firmly
rooted in Angle’s fixed appliance philosophy, yet it was
Norman W. Kingsley who first (1879) used forward
positioning of the mandible in orthodontic treatment

 Kingsley’s removable plate with molar clasps might be
considered the prototype of functional appliances, having a
continuous labial wire and a bite plane extending posteriorly
 As he described it, “The object was not to protrude the lower
teeth, but to change or jump the bite in the case of an
excessively retreating lower jaw.”

 As a result of studies on a dolphin’s tail fin, Wilhelm Roux is
credited as the first to study the influences of natural forces
and functional stimulation on form (1883)
 Later, Karl Häupl saw the potential of Roux’s hypothesis and
explained how functional appliances work through the
activity of the orofacial muscles

The road to discovery :Milestones in
history
THE 20TH CENTURY – BEFORE AND DURING WORLD
WAR I
1. PIERRE ROBIN(Charolles 1867-Paris 1950)
 The first practitioner to use functional jaw orthopedics to treat a
malocclusion was Pierre Robin (1902).
 His appliance influenced muscular activity by changing the
spatial relationship of the jaws. Robin’s monobloc was actually
an adaptation of Ottolengui’s removable plate, which, in turn,
had been a modification of Kingsley’s maxillary plate.

 Extended all along the lingual surfaces of the mandibular teeth,
but it had sharp lingual imprints of the crown surfaces of both
maxillary and mandibular teeth.
 It incorporated an expansion screw in the palate to expand the
dental arches.

 Hotz used VORBISSPLATE,which was a modification of
Kingsleys plate,in treatment of deep bite retrognathism in which
there was a likelihood of a functional retrusion that is caused by
overbite and when the lower incisors were lingually inclined that
is caused by hyperactivity of mentalis muscle and lower lip.

 Robin designed his monobloc specifically for children with the
glossoptosis syndrome (ectomorphic constitution, adenoid facies,
mouth breathing, high palate, and other problems).
 It has since been named the Pierre Robin syndrome

2.VIGGO ANDREASEN(Copenhagen 1870-1950)
 In 1909, Viggo Andresen (1870-1950) (Fig 2) removed his
daughter’s fixed appliances before she left for her summer
vacation, as was customary at the time, and placed a Hawley-
type maxillary retainer.
 On the mandibular teeth, he placed a lingual horseshoe flange
that guided the mandible forward about 3 to 4 mm in
occlusion

 On his daughter’s return, he was surprised to see that nighttime
wearing of the appliances had eliminated her Class II
malocclusion, and it was stable.
 Applying this technique to other patients resulted in significant
sagittal corrections that he could not produce with conventional
fixed appliances

 The original Andresen activator was a tooth-borne, loosely fitting
passive appliance consisting of a block of plastic covering the
palate and the teeth of both arches, designed to advance the
mandible several millimeters for Class II correction and open the
bite 3 to 4 mm.
 The original design had facets incorporated into the body of the
appliance to direct erupting posterior teeth mesially or distally,
so, despite the simple design, dental relationships in all 3 planes
of space could be changed

BETWEEN THE TWO WORLD WARS-
 In 1925, Andresen, then director of the orthodontic department
at the University of Oslo, began developing for the
government a simple method of treating Norwegian children.
 He modified his retainer into an orthodontic appliance, using
a wax bite to register the mandible in an advanced position

 Activator use became so widespread among European
practitioners that there was concern that proper diagnosis was
being neglected. Unfortunately, reminiscent of Angle’s
following, “functional jaw orthopedics became a profession of
faith, a religion, beside which no other opinion was tolerated

 A variety of different functional appliances are available.
The appliance selected for treatment is based on type of
anomaly, growth direction, growth prediction and
presence or absence of functional disturbances.
 Each proponent of different functional appliance, has
conceived his own concept and working hypothesis

HISTORY AND DEVELOPMENT OF
ACTIVATOR
 In the year 1880 Dr. N.W. Kingsley wrote, in his treatise on
oral deformity, that he had developed a maxillary plate with an
inclined plane for the purpose of “Jumping the bite” forward in
cases of extreme mandibular retrusion
 The idea was further evolved by French dentist Dr. Pierre
Robin, who published a paper in 1902 describing his
“monobloc” appliance to be used for bimaxillary expansion

 Impressed by Kingsley’s concepts and appliances,
Andreasen developed a mobile , loose fitting appliance
modification that transferred functioning muscle stimuli to
the jaws , the teeth and supporting structures .
 The progenitor was a modified Kingsley plate

 Andreasen used this appliance as a retainer over summer
vacation for his daughter after he removed fixed appliances
used to correct a distocclusion
 He called this as a “biomechanical working retainer”

 He believed in the theories, expounded by Roux and
Wolfe in the 1890s that changes in biomechanical function
bring about corresponding changes in both internal
structures of bone as well as external shape
 By the time Andreasen and Haupl teamed up to write about
their appliance , they termed it an activator as it could
activate the muscle forces

 The appliance consisted of an upper maxillary plate with an
anterior flange extending into the lingual area of the mandibular
arch that on closing held the lower jaw in a forward position
relative to the maxilla with a bite opening of approximately 5mm
between the posterior teeth
 The appliance also had a labial bow or labial archwire across the
maxillary anterior teeth for the purposes of stabilizing the
appliance and retracting overly protruded maxillary anterior
teeth.

PHILOSOPHIES OF MODE OF ACTION
 According to the original Andresen Haupl concept the
forces generated in activator therapy are due to muscle
contractions and myotatic reflex activity.
 There is stimulation of the muscles by a loose appliance,
and the moving appliance moves the teeth. The muscles
function with kinetic energy, and intermittent forces are of
clinical significance

 According to the second working hypothesis the appliance is
squeezed between the jaws in a splinting action. The appliance
exerts forces that move the teeth to this rigid position.
 The stretch reflex is activated, inherent tissue elasticity is
operative, and there is strain without functional movement
 The appliance uses potential energy.

 For this mode of action an overcompensation of the
construction bite in the sagittal or vertical plane is necessary
 An efficient stretch action is achieved by the
overcompensation and the viscoelastic properties of the
contiguous soft tissues

 The third approach enlists the modes of action of the preceding
two. It can be called a transitional type of activator action,
which alternately uses muscle contraction and viscoelastic
properties of soft tissue
 The ultimate decision as to whether the force delivered is
kinetic energy or potential energy or a combination of both
depends on factors such as nature of the malocclusion , the
interocclusal clearance etc

 All the modes of action are dependent on the direction and
degree of opening of the construction bite.
 By taking into account the individual characteristics of the
facial skeleton, the individualized growth processes, and the
goal of treatment, the clinician can fabricate the appliance to
work according to the desired mode of action

MODE OF ACTION
 Andresen stated that this appliance has a stimulating effect on
jaw development.
 In class II cases when the mandible is brought forward into
Class I relationship, there is stimulation of protractors and
elevators with stretching of retractors resulting in the change
in functional pattern of muscle and the bone structures as
they adopt to the new functional environment

 For stimulating these muscles, the appliance should be loosely
fitting and as the patient every time tries to occlude, or
swallow, upper and lower teeth contact resulting in jolts to the
periodontal membrane. This acts as a stimuli for tissue
rebuilding.
 They were of the opinion that myotatic reflex activity and
isometric muscle contraction induce musculo-skeletal
adaptation by inducing new mandibular closing pattern.

CLASP KNIFE REFLEX
 The basis for such severe increase in the displacement of
mandible is the clasp knife reflex or autogenic inhibition or
lengthening reaction
 When a spastic limb is flexed forcibly resistance is
encountered.
 If the flexion forcibly carried further, the resistance to the
flexion was found to disappear and previously rigid limb
collapses readily.

 The excessive stretch of the muscle brings into play some new
influence which inhibits the stretch reflex and allows the
muscle to be lengthened with little or no resistance
 The receptors for clasp knife reflex are Golgi tendon organs
located in the tendon of the muscle and the stimulus for the
reflex is excessive stretch, impulses conducted from the
sensory nerve fibres of Golgi tendon organ act on the motor
neuron supplying the stretched muscle.
TEXTBOOK OF REMOVABLE ORTHODONTIC APPLIANCES ,T.M.GRABER,BEDRICH
NEUMANN,SECOND EDITION.

 The output of motor neuron depend on the balance between 2
antagonistic inputs. One from Golgi tendon organ inhibiting the
muscle contraction, other from the nuclear bag of the muscle
facilitating muscle contraction.
 The functional significance of the clasp knife reflex, is to protect
the overload by preventing damaging contraction against
stretching forces

 The viscoelastic properties of muscle and the stretching of the
soft tissues are decisive for activator action.
 During each force application, secondary forces arise in the
tissues, introducing a bioelastic process.
 Thus not only the muscle contractions but also the viscoelastic
properties of the soft tissue are important in stimulating the
skeletal adaptation.

 Depending on the magnitude and duration of the applied force,
the viscoelastic reaction can be divided into the following
stages:
1. Emptying of vessels
2. Pressing out interstitial fluid
3. Stretching of fibres
4. Elastic deformation of bone
5. Bioplastic adaption

 Stretching of muscles give rise to stretch reflex
contractions.
 Stretch reflex by activator displacing mandible beyond
rest position is tonic type. The tonic activity of the muscles
varies with the level of wakefulness or sleep.

 When worn during day the activator elicits increased frequency
of swallowing movements. Also as the activator is squeezed
between the teeth, it elicits passive tension in the stretched
muscles thus it transfers continuous force from the muscle to
the teeth.
 During sleep when muscles are tonic, myoclonic twitches of
tongue push the activator against the teeth. These intermittent
forces are transmitted through the appliance to the teeth.

 Rationale behind Harvold and Wood side hypothesis is that
mandible normally drops open when the patient is asleep.
 If it is opened 3 to 4 mm by the appliance one of the two
things happen, either appliance may fall out or it may be
ineffective because the wider open sleep position

 Harvold and Woodside doubted the actual contractions taking
place when the patient is sleeping. They recommended wide
open construction bite so that appliance does not fall off
 Muscle tension arises as a consequence of stretching of tissues
and the over extended activator stretches the soft tissues like a
splint. The appliance induces no myotatic reflex activity but
instead a rigid stretch and builds up potential energy.

 Eschler supported Andersen Haupl’s concept based in muscle
physiology experiments. He found action currents in patients
wearing activator as compared to patients not wearing
 Eschler denies activators potential to activation of the muscle
directly. Its effect depends on the stretch reflex.

 On insertion of the appliance, the mandible is elevated by
isotonic muscle contractions succeeded by isometric
contractions which is tonic in nature.
 Mandible assumes static position in contact with the appliance
and is prevented from reaching the occlusion. The elevators and
retractors remain contracted, fatigue of the muscle occurs.
 Muscle relaxes and the mandible drops down. When the
muscles have recovered the cycle starts again

Force analysis in activator therapy
 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
 ACTIVE FORCES- forces produced by springs,
jackscrews, pads.

SKELETALAND DENTOALVEOLAR
EFFECTS OF THE ACTIVATOR
 The influence of activator on the condyle is very much
controversial.
 The possibility of influencing condylar growth with functional
orthodontic appliances is conditioned by psychogenetic and
ontogenetic peculiarities of the condylar cartilage

 Petrovic has shown, the lateral pterygoid muscle has a decisive
role in this growth.
 Forward posturing of the condyle activates the superior head
of the lateral pterygoid. In young individuals this induces a cell
proliferation in the condyle and a growth response.

The purpose of this study was to develop a standardized method
of laminagraphy and to apply this to the evaluation of the
changes in the temporomandibular region after activator therapy

 Normalization of the molar relationship occurred in the
activator group while little change in the control group
 The articular fossa and tuber were slightly displaced
anteriorly in the activator group while backward in the
control group
 The centre of condyle showed a growth direction of 120
degrees in the control group while 132 degrees in the
activator group
Birkebæk L, Melsen B, Terp S. A laminagraphic study of the alterations in the
temporo-mandibular joint following activator treatment. The European Journal of
Orthodontics. 1984 Jan 1;6(1):257-66.

The aim of the present investigation was to analyze and compare
the effect of the Andreasen appliance and the Herbst appliance
during class II treatment in terms of effective growth changes and
their influence on the chin position considering the mandibular
rotation

 The comparison between the activator and the Herbst group
revealed larger effective TMJ and chin changes during
Activator therapy
 The treatment effects showed marked group differences for both
the amount and direction of effective TMJ changes.
 The changes were vertical and slightly anterior in the Activator
group, and predominantly posterior in the Herbst group.
Baltromejus S, Ruf S, Pancherz H. Effective temporomandibular joint growth and chin position
changes: Activator versus Herbst treatment. A cephalometric roentgenographic study. The
European Journal of Orthodontics. 2002 Dec 1;24(6):627-37.

 The chin changes, the treatment effects for the Herbst group
exceeded those for the Activator group in both directions,
caudally and anteriorly.
 The Activator group showed anterior rotation and the Herbst
group a slight posterior rotation of the mandible
Baltromejus S, Ruf S, Pancherz H. Effective temporomandibular joint growth and chin position
changes: Activator versus Herbst treatment. A cephalometric roentgenographic study. The
European Journal of Orthodontics. 2002 Dec 1;24(6):627-37.

Since it remains unclear whether the activator is able to alter the
mandibular growth pattern or causes only dentoalveolar changes,
the present study is aimed at clarifying whether the activator has a
skeletal treatment effect on the mandible.

• The treatment effects showed that effective condylar
growth was increased and the chin position changed by
activator therapy
• However, neither the condylar nor the chin changes were
in the desired (sagittal) therapeutic direction.
• Thus, as a class I molar relationship was achieved in all
activator patients despite the missing sagittal skeletal
therapeutic growth component, the correction of the class
II malocclusion was most probably the result of
dentoalveolar changes
Ruf S, Baltromejus S, Pancherz H. Effective condylar growth and chin position changes in
activator treatment: a cephalometric roentgenographic study. The Angle Orthodontist.
2001 Feb;71(1):4-11.

The purpose of this investigation was to evaluate
cephalometrically the mechanism of antero-posterior occlusal
changes in activator treatment.

 The following results were found
1. The improvement in occlusal relationships in the molar and
incisor segments was about equally a result of skeletal and
dental changes.
2. Overjet correction averaging a 2.4 mm more mandibular
growth than maxillary growth, a 2.5 mm distal movement of the
maxillary incisors, and a 0.1 mm mesial movement of the
mandibular incisors
Pancherz H. A cephalometric analysis of skeletal and dental changes contributing to
Class II correction in activator treatment. American Journal of Orthodontics. 1984 Feb
1;85(2):125-34.

 Class II molar correction averaging 5.1 mm was a result of 2.4
mm more mandibular growth than maxillary growth, a 0.4 mm
distal movement of the maxillary molars, and a 2.3 mm mesial
movement of the mandibular molars.
 When the findings were compared with longitudinal records of
persons with normal occlusion (Bolton Standards), activator
treatment seemed to inhibit maxillary growth, move the
maxillary incisors and molars distally, and move the
mandibular incisors and molars mesially.
Pancherz H. A cephalometric analysis of skeletal and dental changes contributing to
Class II correction in activator treatment. American Journal of Orthodontics. 1984 Feb
1;85(2):125-34.

In the present study of dental, skeletal and soft tissue changes following
activator treatment the effects of treatment were separated from growth
changes by comparing the results of treatment in the activator group with
facial development in a group of untreated Class II Division 1 patients, and
with the growth curves of individuals with ideal occlusion.

• Forsberg and Odenrick 1981 observed that upper lip retrusion
was significantly more prevalent in treated Class II group
than in control group.
• Nose showed equal forward growth in both the groups.
• Soft tissue pogonion is further anterior in treated group.
• Further more it was found that in the treated group lip
balance was not achieved in patients with relatively
retrognathic profiles or those with steep mandibular planes.
Forsberg CM, Odenrick L. Skeletal and soft tissue response to activator treatment. The European
Journal of Orthodontics. 1981 Jan 1;3(4):247-53.

• TREATMENT TIMING
 Reey, Eastwood, says that mixed dentition period was best
for activator treatment.
 Experience clinicians like Bjork concluded that activator
was most effective in deciduous dentition
 Less effective in mixed dentition and Limited effect in
permanent dentition

INDICATIONS
 Partial or total correction of Cl II Div 1 cases
 Partial or total correction of Cl II Div 2 cases
 Correction of Cl I open bite (Dental not skeletal).
 Correction of Cl I deep bite case
 As a preliminary treatment before major fixed appliance therapy
 As post treatment retention in children with deep bite caused by
overclosure.
 Children with lack of vertical development in lower facial
height.

SELECTION OF CASES
1. Skeletal criteria-
 A mild skeletal Cl II facial pattern.
 A decreased lower face height which is based on a profile
assessment from the nostril to chin point.
 Proportionate balance between upper and midface heights

2. Dentoalveolar criteria
 No crowding in the upper and lower arches.
 A good integral mandible with no rotations and no
displacement of the teeth.
 A relatively flat mandibular occlusal plane.
 No labial tipping of the mandibular incisors relative to the
mandibular plane.
 A moderate deep anterior over bite, either closed or slightly
open, with a 50% to 70 vertical anterior overlap.
 A maxillary labial segment that is proclined with or without
spacing
 no mid line asymmetry.

 Soft tissue -Competent or potentially competent lips in
which the lip is capable of stabilizing the upper anterior
teeth after correction has taken place.
 Preferably a muscular pattern that does not exhibit undue
tightness of lips and cheeks.
 Respiratory - No nasal obstruction or chronic respiratory
disorder
 Emotional - Keen patient interest and desire and potential
co-operation from both patient and parent

Diagnostic preparations
 Patient compliance - It is very essential. It is very important
to assess clinically patients somatic, psychological aspect
and motivation potential.
 Motivation potential can be enhanced by visual treatment.

 Visual treatment objective is creating an “instant correction”
in a Cl II malocclusion by moving the mandible forward into
an anterior more normal sagittal relationship so that the
patients sees the potential and objective of correction and is
more likely to work towards the goal.
 It also helps the clinician to diagnose and anticipate whether
therapeutic goal is an improvement

 Study model Analysis
Following information can be derived form the study model.
1. 1st molar relationship in habitual occlusion.
2. Nature of midline discrepancy, if any (dentoalveolar non
coincidental midlines cannot be corrected by activator).
3. Symmetry of dental arches
4. Curve of Spee is checked to diagnose whether it can be
leveled.
5. Degree of crowding and dental discrepancies are checked.

 Functional Analysis –
1. Precise registration of postural rest position is done as
vertical opening of construction bite depends on this.
2. Path of closure from postural rest to habitual occlusion is
checked and sagittal / transverse deviations are recorded.
3. TMJ is palpated. It is also auscultated for clicking and
crepitus.
4. Interocclusal clearance and freeway space is checked.
5. Mode of respiration is checked (oral, nasal, oronasal).

 Cephalometric Analysis –
1. It is done to establish the nature of craniofacial morphogenetic
pattern to be treated.
2. It also provides most important information for planning the
construction bite.
3. The direction of growth whether average, horizontal or vertical
can be predicted.
4. Differentiation between position and size of jaw bases is
observed.
5. Morphologic characteristics are also observed.
6. The axial inclinations and positions of maxillary and mandibular
incisors are recorded.
7. Hand wrist x-rays are taken to assess growth status

Construction bite
 The construction bite is an intermaxillary wax record used
to relate mandible to the maxilla in three dimensions of
space.
 They are used to reposition the mandible in order to
improve skeletal inter-jaw relationship.

According to glossary of orthodontic terms -:
 construction bite -
It is a bite registration at the desired occlusal relationship , to permit
articular mounting of the casts for fabrication of an (most commonly
functional) appliance .
 Bite registration -
A wax record of an occlusal relationship between the maxilla and
mandible , used in the trimming of orthodontic casts or in mounting
of casts on an articulator

General considerations for construction bite
1. In case the overjet is too large, the forward positioning is
done step wise in 2-3 phases.
2. In cases of forward positioning of the mandible by 7-8
mm, the vertical opening should be slight to moderate i.e
2-4 mm.
3. If the forward positioning is not more than 3-5 mm, then
the vertical opening can be 4-6

Sagittal or anterior positioning of mandible should not exceed
7-8 mm or ¾ mesiodistal dimension of 1st permanent molar.
 For example in class II cases anterior positioning to this
magnitude is contraindicated when:
1. The overjet is too large.
2. There is severe labial tipping of maxillary incisors
3. When there are lingually erupted incisors

 Vertical or Opening the bite:- The vertical and sagittal
relationship are intimately linked.
 Guiding Principles
1. Mandible must be dislocated in atleast one direction from
postural rest position. This is essential to activate
musculature and induce a strain in the tissues.
2. If magnitude of forward positioning is great 7-8 mm then
vertical opening should be minimal, so that muscles are not
overstreched.
3. If extensive vertical opening is required the mandible must
not be positioned anteriorly

 Frontal or Midline establishment - midlines of the maxilla
and mandible should coincide when the construction bite is
taken regardless of shifting of teeth in one or both the jaws

Execution of construction bite technique
• The patient is seated in an upright position. Posture should be
relaxed or not strained
• Mandible gently guided into predetermined position
• Operator should guide but do not force the mandible into the
desired sagittal jaw relation

• The exercise is to be repeated by the patient & then hold the
forward position of the mandible for awhile
• A horseshoe shaped wax bite rim is prepared on the cast for
insertion
• Should be of proper arch form & size & wide enough
• 2-3mm thicker than planned construction bite.

• After the operator is sure that the patient can replicate the
exercise, soften wax placed in the mouth
• Operator should control edge to edge relation & midline
registration.
• Wax carefully removed from the mouth without distorting
it.

• Check in upper & lower model. Place it in chilled water.
• Again put it on the cast. Trim with the help of scissor so that
operator can be sure that the wax is in close approximation
to all cusp of the teeth.
• Harden wax again check in the mouth.
• Construction bite must be taken on the patient, not on the
articulated models.

Alternative method
• Use either a thick or thin 'bite
fork'. The thick (yellow) ones are
for when an overbite needs
reducing and thin (blue) for
normal or reduced overbites.
• Explain to the patient what is
required, that they posture
forward to the required
occlusion.

Variations in the construction bite
1. Low construction bite with marked mandibular
forward positioning:
• This kind of construction bite is characterized by marked
forward positioning of the mandible but minimal vertical
opening.
• Vertically the opening is minimal and is within limits of the
interocclusal clearance. This kind of activator constructed
with marked sagittal advancement but minimal vertical
opening is called an “H activator”.

2. High construction bite with slight mandibular forward
positioning:
• The mandible is positioned anteriorly by 3-5 mm only and bite is
opened vertically by 4-6 mm or a maximum of 4 mm beyond the
resting position.
• This kind of activator constructed with minimal sagittal
advancement but marked vertical opening is called a “V
activator”.

 The V type of activator is indicated in Class II div 1
malocclusion having a vertical growth pattern

Disadvantages of wide open construction bite
1. if the construction bite is wide open it will be difficult
to wear the appliance & adapt to the new relationship.
2. muscle spasm often occur & the appliance tends to
fall out of mouth.
3. makes lip seal difficult.

3. Construction bite without mandibular forward
positioning
 Indications
1. Deep overbite
2. Infraocclusion of buccal segment
3. Supraocclusion of incisors
4. Openbite

4. Construction bite with
opening and posterior
positioning of the mandible
• In Class III malocclusion, the
bite is taken after retruding the
mandible to a most posterior
position.
• The bite is opened sufficiently
to clear the bite. In general a
vertical opening of 5mm and a
posterior positioning of about 2
mm is required.

Fabrication of activator
 After the construction bite is taken and checked on the patient
and rechecked on stone working models, the working models
are mounted on the fixator.
 The fixator allows upper and lower parts to be made
separately and both parts are united in the correct construction
bite on the fixator

 The extensions of acrylic body and flanges are drawn on the
upper and lower working models. The wire elements can also
be drawn
 The bow is active or passive and influences soft tissue without
touching teeth. The wire usually used is 0.8 mm round
stainless steel.

• The appliance consists of upper, lower and interocclusal
parts.
• In the upper and lower, the dental and gingival portions
can be differentiated.
• In the lower cast, the gingival portion can be extended
posteriorly.
• Flanges for upper cast are usually 8-12 mm high in
gingival area covering the alveolar crest. Lower acrylic
plate is 5-10 mm high but in molar region it is as great as
10-15 mm

ACTIVATOR
DR TAHER MANASAWALA
1ST PG STUDENT
DEPT OF ORTHODONTICS AND DENTOFACIAL ORTHOPEDICS

Mechanism of action of the activator
MYOTACTIC REFLEX

• The impulses arising from the muscle spindles are conducted by
group1A sensory nerve fibres.
• The sensory fibres synapse with the motor neuron called alpha
efferrents that supply the extrafusal muscle fibres.
• The myotactic reflex is therefore a monosynaptic reflex because
there is no interneuron associated with it.
• The stretch reflex acts in mandibular musculature to maintain the
postural rest position of mandible in relation to the maxilla

Trimming of the activator
 Planned trimming of the appliance in tooth contact area is
carried out to bring about dentoalveolar changes so as to
guide the teeth into good relation in all the 3 planes of
space.
 Approximate trimming can be done on plaster casts,
however, the final grinding must be done in the mouth.

 A few contacts are left to stabilize the appliance until the
patient adjusts. Then the remainder of planned trimming is
done, on the second or third visit
 Single movements are analyzed as to where each tooth should
ultimately be with respect to contiguous teeth.
 The total planned grinding procedure is written up and
checked off as each trimming procedure is performed.

 All guiding planes that have been ground and all areas in
contact with the teeth should be checked for shiny surfaces
to see whether the appliance is being correctly worn and is
working properly.
 Reshaping of acrylic guide areas may be needed after initial
trimming and they should be evaluated for the same.

Management of appliance
 Motivation of patient
 Duration – minimum 14 hours.
 Gradual increase in duration of wear after appliance delivery
over a period of 1-2 weeks.
 Patient should be seen after 2 weeks to ensure that the
appliance is comfortable and to encourage adequate wear.

 Review appliance during active treatment 6 to 8 weeks.
Progress assessed by measuring the overjet and observing
correction of buccal segment relationship (ensuring that the
mandible is fully retruded and that the patient is not
posturing forwards).
 Treatment of appliance must be checked and adjusted.

 Important to check that the appliance is not causing unwanted
interference with eruption of permanent teeth, and trimmed as
appropriate.
 Recording of standing height as slow progress of appliance may
be because the patient is not in a rapid growth phase.
 Encouragement and motivation of patient at review
appointments.

 When overjet is reduced fully, or preferably overcorrected
slightly, amount of appliance wear – reduced progressively.
 Reduction should be gradual, over about a year and the overjet
and buccal segment correction must be monitored to ensure that
they remain stable.
 Appliance to be worn till the end of pubertal growth spurt.

MODIFICATIONS
 Harvold’s modification
 Herrens shage activator – LSU activator.
 The bow activator of Schwarz.
 Reduced activator of Cybernator of Schmuth.
 The Karwetsky appliance.

 The propulsor
 The cutout (or) palate free activator.
 Elastic open activator of Klammt.
 Stockfishs Kinetor.
 Hamilton expansion activator system. (or) Bonded activator
 Combined activator /HG Orthopedics.

 Harvold’s modification :-
• Differs from Andresen’s activator in
following respects
• Degree of opening is greater –5 mm
beyond freeway space
• Increase effect of myotatic reflex
• Introduce viscoelastic property of
stretched muscle and soft tissues.

 Herrens activator
• He proposed that the posture of mandible during the night,
changes and alternates with its normal posture in conjunction with
orofacial function during the day.
• A slight unconscious lowering of the mandible will occur and
detach the activator from the maxillary parts and lessen its
effectiveness

 The Herrens activator was thus
fixed with clasps to the maxillary
dentition , screws and springs are
employed along with the active
plates
 Jacksons clasps , Duyzings clasps
and triangular clasps can be used
as well

 The construction bite for the Herrens activator is taken with an
advanced position of the mandible and overcompensation of the
post normal occlusion
 In a case of complete class II relationship , the mandible is
moved forward the width of the premolar plus an additional
3mm and the vertical opening being 2-4 mm

Herrens concept of overcompensation
 The following rules must be observed during
construction bite:
 1)Positioning the mandible in an anteroposterior
direction dominates over vertical direction.
 2)Anterior positioning: From the postnormal
disto occlusion the mandible is carried forward-
not only to a neutral molar relationship but also
an additional 3-4 mm beyond.

 In open bite cases interocclusal
distance between upper and
lower molars is decisive to take
the construction bite(4-6mm).
 Thus the wax bite keeps the
mandible constantly open
beyond the rest position.

 Wunderers modification
• Indicated Class III malocclusion
Design
• Activator split horizontally into an
upper half and lower half which are
connected with a screw situated in
an extension of mandibular portion
behind the maxillary incisors.

• Opening of the screw causes
maxillary portion to move
anteriorly and a reciprocal back
thrust on mandible is effected.
• Retention is from occlusal
surface of buccal segment. The
screw was designed by Weise

 Van Beek Activator
• Introduced by van Beek (1982, 1984)
• Full acrylic coverage of labial surface of maxillary
anterior teeth. No labial bow. Thus upper anteriors held
in position and not allowing any retroclination.
• Relieving of lingual surface in lower incisor and alveolar
process area. Also covered by acrylic.

• Bows present bilaterally for attachment of high pull
headgear.
• Bows short and incorporated in anterior part of acrylic.
• Point of force application – maxillary canines
• Outer part of bow – inclined upwards.
• Results in intrusion of maxillary anterior teeth

 BOW ACTIVATOR OF A.M. SCHWARZ Designed
by A.M. Schwarz
 Consists of an upper half and lower half connected with
an elastic bow.
 Advantages
 Step by step forward positioning can be done
 Transverse mobility can be brought
 The bow can be activated only on one side for correction
as unilateral disto-occlusion
 Independent maxillary or mandibular expansions can be
effected by incorporation of a screw.

 Disadvantages
 Easily distorted
 Difficulty in adapting loops
 Breakage of bow portion

 With the treatment of class II div 1 malocclusion a beginning can
be made by forward positioning , increasing this gradually by
periodic adjustments as recommended by Frankel .
 The transverse mobility was thought by Schwarz to have an
additional stimulus. There is a possibility of also activating the
bow unilaterally on the side of disto-occlusion

 Reduced activator or cybernator of Schmuth
• Designed by Prof. Schmuth
• Resembles a bionator with acrylic portion of the activator reduced
from the maxillary anterior area leaving a small flange of acrylic
on the palatal slopes.
• Two halves connected by an omega shaped palatal wire (1.1 – 1.2
mm).Full time wear

Advantages –
1. Saves time and labor
2. Easy patient acceptance
3. Can be used along with fixed appliance
4. Headgear tubes can be incorporated for Extraoral force
application

The propulsor
• Designed by Muhlemann &
Refined by Hotz
• It is a hybrid appliance with
features of both the monobloc and
the simple oral screen.

 A definite advantage of the propulsor over the other functional
orthopedic activator like appliance is in its coverage of and the
ability to effect changes in the alveolar process ,in addition to
the teeth of the maxillary anterior segment ,this makes the
appliance to be used readily in case of maxillary protrusion

o Design
 Has no wire components and made
completely with acrylic. The acrylic
between occlusal surface of the 1st
molar stabilizes appliance, with
improvement in intermaxillary
relations.
 The appliance is reactivated by
adding acrylic in the upper anterior
segment.

 Advantage
1. Light weight – minimum
bulk of appliance
2. It effects changes in
alveolar process and teeth
in maxillary anterior
segment

 Cut out or palate free activator
• Modification made by Metzelder in an attempt to combine the
advantages of bionator with Andresen’s activator.
• Mandibular portion – similar to activator
• Maxillary portion – acrylic covering only the palatal aspect of
buccal teeth and a small part of adjoining gingival.

 The narrow anterior portion of the
appliance is reinforced with a
jackscrew if expansion is contemplated
and if expansion not required wires
should be used .
 The labial wire is same as the one used
for a conventional activator of 0.9mm
diameter .there is coffin spring in the
palate

• Advantages
• Convenience of use for prolonged periods.
• Excellent in mandibular posturing in TMJ dysfunction
cases.
• Easy to make
• Active components can be added

 Elastic open activator :-
• Type of daytime activator designed by
G. Klammt.
• Modified activator consisting of some
of elements of Bimler’s appliance.
• EOA seems to resemble a bionator, but
there is no acrylic anteriorly and hence
no vertical stabilization as in bionator.

 Bilateral acrylic parts – stabilization
of acrylic portion accomplished by
means of contact with lingual
surfaces of maxillary & mandibular
canines.
 Upper and lower labial wires
[(similar to bionator) but are a
separate components]

 There are 2 types of EOA-
1. One type lacks any acrylic
projection for the interproximal
spaces , and it has a flat surface
contacting the lingual surface of the
buccal teeth
2. The other type has acrylic
projections contiguous to the entire
lingual aspect of the teeth in the
buccal segments

 The upper and the lower wire emerges
from the acrylic between the canine and
the 1st premolar
 The wire touches the labial surface and
proceeds on the other side in an identical
manner
 Small tubings to prevent breakage
 Palatal spring to facilitate expansion

The Karwetzky modification
 Consists of maxillary and mandibular active plates, joined by
a upper bow in region of first permanent molars.
 Maxillary and mandibular plates not only cover the lingual
tissues and lingual aspects of teeth, it also extends over
occlusal aspect of all teeth.
 Allows for stepwise advancement of mandible by adjustment
of upper loop.

 Acrylic between upper and lower parts are made flat and joined
by a bow made of 1.1 mm round stainless steel wire.
 Depending upon the placement of ends of the U bow,three
types of Karwetzky activator are created.
1. Type I - for Cl II Div 1 malocclusion
2. Type II - for Cl III malocclusion
3. Type III - used in facial asymmetry and lateral crossbite

TYPE 1

TYPE 2

TYPE 3

Reverse activator
 Construction bite - Bite is taken by
retruding the jaw. The extent of vertical
opening depends on the retrusion
possible
 In Functional protrusion class III
malocclusion the mandibular incisor
hit prematurely in an end-to-end
contact, and the mandible then slides
anteriorly to complete the full occlusal
relationship

 The vertical dimension of construction bite is opened far
enough to clear the incisal guidance, which eliminates the
protrusive relationship with mandible in centric relation.
 The prognosis for pseudo class III malocclusion is good,
especially if therapy is started in early mixed dentition.
 In early mixed dentition period, skeletal manifestation are
not usually severe, since the malocclusion develops
progressively
In Functional protrusion class III malocclusion

 Mandibular labial bow is used
to guide the mandible distally,
as the teeth occlude.
 The maxillary labial bow If
needed kept away from labial
surfaces to relieve any lip
pressure

 The acrylic was relieved on lingual
surface of mandibular incisors and
maxillary incisors supported with
close contact.
 Maxillary incisors are tipped labially
with small screws, wooden pegs (or)
lingual springs (or) by application of
gutta percha lingual to incisors.

 Changes
1. Articular angle increased because of posterior
positioning mandible
2. Mandibular plane angle slightly opened.
3. SNA increased
4. ANB increased
5. Maxillary incisor tipped labially
6. Mandibular incisors tipped lingually

 Activator Headgear Appliance
 Pfeiffer and Groberty in 1972 studied the simultaneous
use of cervical appliance and activator.
 Stockli and Teuscher also conducted studies on the effects
of activator headgear therapy.
 With activator headgear treatment the dentoalveolar
reactions in the upper jaw and skeletal reactions in the
lower jaw contribute about equally to the correction of
Class II malocclusions

• Cervical appliance slows down and interrupts growth of
maxilla
• It initiates a distal movement of the anchor molars and to
some extent adjacent teeth.
• Tips anchor teeth if desired
• Extrudes the molars and opens the bite
• Tips anterior part of the palate down

Indications :-
1. Skeletal Class II deviation in which an anterior movement of
chin is desirable and at least some posteriorly directed
maxillary Dentoalveolar reaction is acceptable.
2. High angle cases
Contraindications :-
1. Dental Class II situations with a skeletal Class I profile – can
lead to unpleasant concave profile.

The aims of this study were to determine whether the activator and
activator headgear encourage mandibular growth, and whether there is
any superiority of one appliance over the other or if the resultant
changes are due to normal growth.

• Both the activator and activator headgear combination
encouraged significant mandibular growth but had little
restraining effect on maxillary growth
• Retroclination of the maxillary incisors and proclination of
the mandibular incisors were inevitable results of using both
appliances.
• The resultant skeletal, dentoalveolar and soft tissue changes
significantly differed from those of normal growth.
Türkkahraman H, Sayın MÖ. Effects of activator and activator headgear treatment:
comparison with untreated Class II subjects. The European Journal of Orthodontics. 2005 Aug
10;28(1):27-34.

 THE KINETOR
 Designed by Hugo Stockfish (1951)
 It was an elastic activator which is easier for patient to wear
during the day.
 It was a night time wear appliance and required a treatment
time of 2 to 4 years.
 Active operation of various screws and springs added to the
appliance

 Disadvantages –
1. it is a complicated system and
subject to breakage, difficulty of
construction, and adjustments.
2. It does have the capabilities of
expanding the arches in all three
directions, sagittaly, vertically and
horizontally with jackscrews, but
does violate the principle of
simplicity.

MAGNETIC ACTIVATOR DEVICE (MAD)
• Designed by Dr. Ali Darendilier in 1993
• The conventional activator is constructed as a two piece,
upper and lower activator.
• Samarium Cobalt magnets are used in attractive or
repelling mode to achieve orthodontic and orthopaedic
correction.

 Modifications –
1. Magnetic Activator Device : MAD I - For Mandibular
deviations
2. Magnetic Activator Device : MAD II - For Class II
malocclusion
3. Magnetic Activator Device : MAD III - For Class III
malocclusion
4. Magnetic Activator Device : MAD IV - For open bite
malocclusion

ADVANTAGES
1. Treatment may be started during late deciduous or mixed
dentition period.
2. Disturbances or suppression of normal stomatognathic
functions, which occur usually with conventional fixed
appliances is avoided with activators.
3. Finger sucking, abnormal tongue posture and function,
mouth breathing can be easily corrected.
4. Activators maintain the beneficial therapeutic effect for
long periods of time without requiring the usual office
visits which is needed in fixed appliances

5. Repairs are seldom needed, and they are simple to
perform and the cost factor is low, chair side time is
minimal.
6. For the post treatment retention the same appliance can
be used.
7. Activators make possible the combination of
prosthodontic and orthodontic treatment at the same time
with built in space control.
8. No impairment of esthetics during the day since the
appliance is used most during nighttime

9. The forces employed are physiological and produce no
damage either to teeth or supporting tissue and also injury to
the soft tissue is negligible.
10. The teeth are not banded there is no risk of decalcification
from cement less conducive to carious incidence and good
hygiene

DISADVANTAGES
1. Cannot be used in patient who are un co- operative.
2. Greater selectivity of cases is necessary than with fixed
appliance.
3. Age is a factor in some types of treatment which will
prevent the use of activator.
4. If crowding is of marked degree the use of the activator
is limited.
5. No detailed precise finishing of occlusion.

CONCLUSION
 Activator is one of the first myofunctional appliance being
used.
 There is considerable controversy that exists regarding the
mechanism of action of activator.
 Hence, no uniform agreement exists regarding the optimal
way to construct or use this appliance

 It is less effective in its influence on maxillary prognathism or
vertical growth pattern.
Patients must be selected with care and attention and also
must be paid to every detail in its manipulation.

References
 TEXTBOOK OF DENTOFACIAL ORTHOPEDICS WITH FUNCTIONAL
APPLIANCES BY THOMAS GRABER,THOMAS RAKOSI,ALEXANDRE G.
PETROVIC.
 TEXTBOOK OF REMOVABLE ORTHODONTIC APPLIANCES
,T.M.GRABER,BEDRICH NEUMANN,SECOND EDITION.
 BIRKEBÆK L, MELSEN B, TERP S. A LAMINAGRAPHIC STUDY OF THE
ALTERATIONS IN THE TEMPORO-MANDIBULAR JOINT FOLLOWING
ACTIVATOR TREATMENT. THE EUROPEAN JOURNAL OF
ORTHODONTICS. 1984 JAN 1;6(1):257-66.

 BALTROMEJUS S, RUF S, PANCHERZ H. EFFECTIVE
TEMPOROMANDIBULAR JOINT GROWTH AND CHIN POSITION
CHANGES: ACTIVATOR VERSUS HERBST TREATMENT. A
CEPHALOMETRIC ROENTGENOGRAPHIC STUDY. THE EUROPEAN
JOURNAL OF ORTHODONTICS. 2002 DEC 1;24(6):627-37.
 RUF S, BALTROMEJUS S, PANCHERZ H. EFFECTIVE CONDYLAR
GROWTH AND CHIN POSITION CHANGES IN ACTIVATOR
TREATMENT: A CEPHALOMETRIC ROENTGENOGRAPHIC STUDY.
THE ANGLE ORTHODONTIST. 2001 FEB;71(1):4-11.

 PANCHERZ H. A CEPHALOMETRIC ANALYSIS OF SKELETALAND
DENTAL CHANGES CONTRIBUTING TO CLASS II CORRECTION IN
ACTIVATOR TREATMENT. AMERICAN JOURNAL OF
ORTHODONTICS. 1984 FEB 1;85(2):125-34.
 FORSBERG CM, ODENRICK L. SKELETAL AND SOFT TISSUE
RESPONSE TO ACTIVATOR TREATMENT. THE EUROPEAN
JOURNAL OF ORTHODONTICS. 1981 JAN 1;3(4):247-53.
 TÜRKKAHRAMAN H, SAYIN MÖ. EFFECTS OF ACTIVATOR AND
ACTIVATOR HEADGEAR TREATMENT: COMPARISON WITH
UNTREATED CLASS II SUBJECTS. THE EUROPEAN JOURNAL OF
ORTHODONTICS. 2005 AUG 10;28(1):27-34.

History and development of activator
 Norman William Kingsley (1829-
1913) has been called by some as the
‘FATHER OF ORTHODONTICS’.
 A dentistry professor in New York ,in
1866 he published a ‘Treatise on oral
deformities of mechanical surgery’
The masters of functional orthodontics , Aurelio Levrini and Lorenzo Favero.

 He designed an appliance (1880) aimed at ‘jumping the bite’ in
cases of accentuated mandibular retrusion
 It consisted of a maxillary plate with a mandibular anterior
inclined plane or advancement vallum
 The vulcanite plate was fastened to the maxillary arch with silk
bindings to the palatal plane to move the anterior teeth backward

 The purpose of the device was not
only to push the mandibular
incisors forward but also modify
the entire articulation
 Although it was a functional
appliance , the bite jumper had the
disadvantage of still being
anchored to the maxillary arch

 In case of class II malocclusion caused by protrusive maxilla and
retrusive mandible , he used a silver maxillary plate with a
mandibular inclined plane from canine to canine to achieve the
jump bite
 Extraoral occipital traction which he introduced around 1860
was then applied to his plate

 The purpose was to shift the mandible forward to have it assume a
normal sagittal relationship with the maxilla and maintain that
position
 Kingsley should also be credited with having intuited the
physiologic bases of orthodontic movement , when he stated that
‘the rich vascularization of the alveoli provides such elasticity that
the teeth can move outwards taking the bone wall with them’’

The monobloc and the masticator
 In an article appearing on October
26,1902 and read to the French
Stomatology Society even prior to Viggo
Andresen , Pierre Robin described a
functional appliance for jaw bone
expansion and glossoptosis therapy
 He introduced the monobloc appliance to
treat this syndrome and the term was
coined by Sauvez

 To his way of thinking the fall back of the tongue connected with
the syndrome with effects not only on respiration but also on the
cephalic thoracic vascularization and innervation causing
psychological illness
 Robin’s aims were first medical oriented towards general
pathoses and only secondarily orthodontic

 Robin’s thinking about the work mechanism of his famous
appliance had 2 main therapeutic aims and one of them was to
expand the jaw bones
 The space destined for the tongue was enlarged by means of the
muscular forces transmitted to the teeth and the alveolar processes
through vulcanized rubber of the monobloc helped by the forces
of the jackscrews

 The dilating monobloc simultaneously makes it possible to create
the space the teeth need to regulate the dental arches and ensure
immediate retention of the results
 In correspondence to the palatal vault, the appliance had one or
more double guided transversal screws , while a spur adapted to
the vestibular surface of the maxillary incisor as a stabilizer

 Therefore this appliance had 2 working
mechanisms, one in A-P direction and one
in the transverse direction.
 It consisted of a block of rubber
occupying the whole surface of the
palate, the lingual surface of the
dentoalveolar arches and extending 5-
6mm below the gingival edges of the
teeth in the mandibular arch

 One of the two components of the monobloc was the spur which
was an auxiliary element used to stabilize the appliance and act
as a reminder for the patient to close his /her lips.
 He suggested that the device had to be worn during the day as
long as possible and had to only be removed during meals and
when the patient reads aloud

 He also advocated the masticator appliance which was a vulcanite
chewing plate that could also be equipped with a central screw
and retention elements
 The mastication surface of the plate had imprints of the opposite
occlusal surface taken from the same construction bite used to
articulate the plaster casts in preparing the monobloc

 Viggo Andresen a general dentist in
Copenhagen , knew that June 14,1908 should
have been a doubly special day for a special
patient of his, his daughter who was
undergoing treatment for a class II
malocclusion
 Summer vacation had began that day and he
would be removing her fixed appliance

 For sometime Andresen had been thinking of how to make a
device that would prevent relapse he noted in his patients on their
return from their vacation
 Therefore he made a vulcanite bimaxillary plate which forced the
mandible to maintain a position forward of and inferior to the
repose position

 At the end of the summer break Andresen noted unexpected
improvements in his daughters occlusion meaning that in addition
to being a means of retention it could also be used as an active
appliance
 In August 1909 Andresen presented his “retention platte’’ at the 5th
International Dentistry Congress in Berlin after having it used for
several years

 He modified the Kingsley’s retention plate with an anterior
advancement wall , adding inferior lateral extensions “in the
shape of a wing diverging back ’’and shortening the anterior zone
at the level of the mandibular incisors

 In its initial version the plate was made of rubber and had
inclined plane not only in the anterior region but also in the
lateral region reaching the dental collars.
 It had two metal clasps on the central incisors arranged not to
occlude with the opposing teeth .

 In 1912 the plate was made from aluminum and lacked the
inclined plane in the anterior region
 The other new additions was a vestibular arch , replacing the
clasps on the incisors
 In Nov 1930, Andresen had gone back to rubber for his
retention plate using a Wipla wire for the vestibular arch and a
coffin spring in cases where expansion was needed

 Andresen acknowledged that compared with rubber , Paladon has
a number of excellent advantages
 One of the many advantages was the ability to make
modifications by relining parts directly or indirectly or by adding
new ones

 Definition :-
• The appliances used in functional orthopedics are mobile , not
tooth fixed. They are passive , not acting through their own
forces but serving solely as a means of transmitting the
muscular stimuli coming from the mastication muscles ,
tongue, cheeks and the lips .
• Through the appliance these stimuli reach the paradental
tissues , the maxillary bones , and at the same time also acting
on the TMJ in which they cause a tissue transformation

 The labial arch is usually made of 0.8mm Wipla wire and rests on
the vestibular surface of the central incisors , slightly lower than
its maximum curvature
 To fold the labial arch 4 pincers are recommended , including a
particular one designed by Andresen himself

 Pins , wires and guide loops are
auxiliary components made with
Wipla wire between 7.7mm –
0.8mm .
 Their task is to induce localized
dental movements such as mesio-
distalizations , to recoup space in
the case of loss of anchorage or
create intrusions

 These pins , wires and guide loops do not act by means of their
elasticity ‘but by beating teeth intermittently’ during the activators
movements.
 When these auxiliary means enter into a particular tension under a
masticatory load the functional orthopedic appliance takes on the
characteristics of an active mobile appliance

 Coffin spring is another auxiliary component made from Wipla
wire 1.2mm used for jawbone expansion
 For its modelling the author also used a preformer of his own
invention consisting of 2 iron spikes fastened to a wooden block

 By slightly widening the spring , when the patient clenches his
or her teeth on the activator , the appliance tautens and works on
the teeth and the osseous portion involved
 The action of the spring must not be continuous or excessive but
should simply correspond to muscle activity , otherwise the
activator would become an active device

 Screws can also be used to shift the guide planes close to the teeth
that have been already shifted
 Little portions of still hot, softened gutta percha are placed in
special housing prepared in the vulcanite body of the activator
 Orange sticks fit into special little holes made in the rubber with a
cone shaped fissure bur on the level of certain guide planes

The purpose of this study was to assess and compare the soft tissue proﬁle
changes produced by the TB and activator appliances, both with each other and
with the changes resulting from natural growth alone.

 Growing Class II division 1 patients revealed significant profile
changes after TB and activator treatment.
 The effects of activator and TB treatment on the soft tissue profile
were similar; they both significantly changed the soft tissue profile
 The most pronounced effects of both appliances were forward
movement of mandibular soft and hard tissue landmarks.
 Longitudinal studies are required to evaluate the stability of the
observed soft tissue changes

1. Horizontal and angular changes in the position of the
mandible
2. Horizontal changes in the position of the maxilla
3. Horizontal changes in the position of the incisors, lips, and
chin
4. Changes in total anterior-face height
5. Relationships between soft- and hard-tissue changes during
treatment

 Relative to sella, translation of the mandibular symphysis was
the same in the three groups
 However, more posterior rotation of the mandible occurred with
fixed- appliance treatment than with activator therapy.
 The fixed appliance with extraoral force restricted anterior
movement of the maxilla more than the activator

 There was a greater tendency for the maxillary incisors to tip
lingually during treatment with the functional appliances, the
fixed appliances caused a more bodily movement.
 Aside from the upper lip, the changes in soft tissue profile showed
little difference among the three treatment groups
 There was no difference in the increase in total anterior-face
height, regardless of whether functional or fixed appliances were
used.

The aim of this systematic review of the literature was to assess the scientific
evidence on the efficiency of functional appliances in enhancing mandibular
growth in Class II subjects.

 Two-thirds of the samples in the 22 studies reported clinically
significant supplementary elongation in total mandibular length as
a result of overall active treatment with functional appliances.
 The short-term amount of supplementary mandibular growth
appears to be significantly larger when the functional treatment is
performed at the adolescent growth spurt.
 Both the bionator and the activator had intermediate scores of
efficiency (0.17 and 0.12 mm per month, respectively). The Frankel
appliance had the least efficiency (0.09 mm per month)

 The Herbst appliance showed the highest coefficient of
efficiency (0.28 mm per month) followed by the Twin-block
(0.23 mm per month)

The aim of this study was to compare the efficiencies of three
functional appliance systems-- Activator, Activator-Headgear
Combination, and Bass appliances -- in the correction of
skeletal Class II malocclusion.

 Greater improvement in the sagittal skeletal relationship (ANB
angle) was obtained in both the Bass and ACHG groups than in
the Activator group.
 The Bass appliance was found to be more effective in the control
of the unwanted side effects (proclination of the lower incisors,
retroclination of the upper incisors).
 Unfavorable labial tipping of the lower incisors was prevented
also with the ACHG appliance.

Trimming the activator for vertical control
Intrusion - Limited movement possible
Extrusion -Selective extrusion in mixed dentition is
a major and valid treatment objective, affecting both
vertical and horizontal tooth relationships.

 Intrusion of teeth :-
 Incisors :-
Achieved by loading incisal edges
of teeth.
Only surface contacting acrylic are
incisal edges.

 If active labial bow is used, it
should touch the incisors
below the area of greatest
convexity (or on incisal third).
 Indicated in deep overbite
cases.

 Molars :-
1. Achieved by loading only
the cusps of teeth.
2. Indicated in openbite
cases, when there is
minimal or non-existent
inter-occlusal clearance

• Extrusion of teeth :-
• INCISORS
 Requires loading their lingual surfaces
in the maxilla above and in the mandible
below the areas of greatest convexity.
 Labial bow placed above the area of
greatest convexity.
 Indicated for open bite problems,
particularly chronic finger-sucking in
which the incisors are relatively
intruded.

 Molars :-
1. Can be facilitated by loading the
lingual surfaces of these teeth
above the area of greatest
convexity in maxilla or below the
greatest convexity in mandible.
2. Indicated in deepbite problems.

Trimming the activator for sagittal control
1. Protrusion of incisors
 Loading can be achieved by loading
entire lingual surface
1. Tipping of incisors labially by low
magnitude of force since applied
2. force is spread over a large surface.
 Loading of incisal third of lingual
surface
1. Tipping of incisors with a higher
magnitude of force
.

 Protrusion can also be achieved
by means of auxiliary elements
1. Protrusion springs (0.8mm wire)
2. Wooden peg
3. Gutta percha
4. Self curing acrylic

 Retrusion of incisors :-
Trimming of acrylic from behind the
incisors to be retruded and an active
labial bow.

 Transverse movements-
• Lingual acrylic surfaces
opposite the posterior teeth
must be in contact with the
teeth.
• Expansion type jackscrews
also can be used.

Molars (Posterior teeth) :-
Distalizing movements –
 Guide planes load the molars on mesiolingual surfaces. Extend
only up to the greatest convexity in the mesiodistal plane.
 Mesial movements can be prevented by using stabilizing wires
or spurs (0.9 mm) can be also activated to provide distalizing
eruption guidance.
 Distalizing guidance – possible with active open springs.

 Mesial movements :-
 Guide planes contact teeth on
distolingual surfaces. Extend up
only to the greatest lingual
circumference in the mesiodistal
plane.
 Indicated in upper dental arch in
Class III malocclusion without
crowding.

 Summary of activator trimming
 Class II malocclusions
 Incisors –
1. Retrusion of upper incisors – labial bow activated
2. Acrylic capping to prevent extrusion
3. Protrusion of lower incisors – labial bow passive
 Posterior teeth –
1. Upper teeth – moved posteriorly or withheld from mesial
movement by guide planes and stabilizing wires.
2. Lower teeth – mesial movement as they erupt

 Class III malocclusions
 Incisors
1. Upper incisors – loaded for protrusion, labial bow passive (lip
pads can be used)
2. Lower incisors – need to be retruded labial acrylic cap, lingual
acrylic, ground away
 Posterior teeth –
Guide planes in upper posterior teeth trimmed for mesial
movement.
Eruption of upper teeth downward and forward direction

 Lower teeth –
1. guide planes trimmed to contact mesiolingual cuspal
surfaces for all possible posterior vector stimulus as these
teeth erupt.
2. Minimum eruption of lower posterior teeth.

 Selective trimming of the activator –
• During selective trimming procedures , only the upper and
the lower molars are extruded
• After these teeth have erupted sufficiently the eruption of
the antagonist can be controlled
• If selective grinding is being planned then the eruption
pathway should be considered

 Lower molars upward and slightly forward
Upper molars  downward and forward
For correction of Class II malocclusion
 Upper molars – restricted
 Lower molars – move upward and mesially
 Therefore Class II converted to Class I, but this results in
mandibular vertical rotation, accentuating mandibular
retrognathism.

 Such reaction favourable in cases with horizontal growth direction
and deepbite.
 In cases with vertical growth pattern and tendency to open bite,
the distal portion of molars can be altered before their final
eruption.
 After eruption of lower molars, the distal surface of upper second
deciduous molars may be sliced.

 Design of the upper incisors
• Deep overbite incisal edges are loaded with acrylic
• Open bite grounding of acrylic from incisal edges
Retrusion of the upper incisor requires relief on the lingual
surface and active labial bow
A special design consideration is generally required for
construction bite and retrusive movements in the fabrication of
V activator

 Extrusion of the incisors would not be desirable in deep bite
cases , thus a guide plane at the labio-incisal area to guide the
incisors without extrusion
 The acrylic from the lingual surface is grounded and an active
labial bow is given
 The incisors will move along the path described by the guide
plane

 In cases where more bodily movement is desirable , the labial
acrylic cap is extended to the area of greatest convexity at the
junction of the incisal and middle thirds of the labial surface.
 The labial bow is kept at the gingival third
 This design has a two fold objective:
1. Influence the axial inclination of the teeth
2. Affect the inclination of the maxillary base in vertical growth
pattern

Design of the lower incisor area
• Conventionally made appliance – loads the lingual surfaces of
lower incisors which tips the teeth labially because of the
reciprocal intermaxillary reaction built into the construction
bite and design of nighttime wear appliance.
• Desirable if lower incisors are lingually inclined because of
hyperactive mentalis function and lip trap.

 If lower incisors labially tipped, classical activator in Class II
division 1 cases is contraindicated because
• Protruded lower incisors contact the lingual of maxillary incisors,
eliminating the overjet before the buccal segment sagittal mal-
relationship is completely corrected.
• If mandible continues to grow anteriorly after appliance therapy
this will lead to crowding of lower anteriors.

 Depending on the axial inclination and position of incisors,
there are 3 possibilities –
1. Labial tipping of lower incisors (loading acrylic on lingual
surface)
2. Holding the incisors in their initial position.
3. Uprighting the lower incisors while the mandible is being
anteriorly positioned.

References
 Varlik SK, Gultan A, Tumer N. Comparison of the effects of Twin
Block and activator treatment on the soft tissue profile. The
European Journal of Orthodontics. 2008 Feb 14;30(2):128-34.
 Remmer KR, Mamandras AH, Hunter WS, Way DC. Cephalometric
changes associated with treatment using the activator, the Frankel
appliance, and the fixed appliance. American Journal of
Orthodontics. 1985 Nov 1;88(5):363-72.
 Cozza P, Baccetti T, Franchi L, De Toffol L, McNamara JA.
Mandibular changes produced by functional appliances in Class II
malocclusion: a systematic review. American Journal of
Orthodontics and Dentofacial Orthopedics. 2006 May 1;129(5):599.

 The masters of functional orthodontics , Aurelio Levrini and
Lorenzo Favero.
 Cura N, Saraç M, Öztürk Y, Sürmeli N. Orthodontic and
orthopedic effects of activator, activator-HG combination, and
Bass appliances: a comparative study. American Journal of
Orthodontics and Dentofacial Orthopedics. 1996 Jul
1;110(1):36-45.

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