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ACTIVATOR
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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 sagitally and
vertically resulting in orthodontic and orthopedic
changes.

 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. Incidentally, he also advocated the use of
this appliance for the treatment of “glossoptosis”. But
his concept of moving the mandible and the tongue
forward to correct mandibular retrusion and free up the
esophageal and tracheal passages survives down to this
day.

 But then an individual arrived on the scene who took all the various
ideas and theories about using the functional appliances to treat
dental malocclusions, coordinated the appropriate information, and
after some initial trial and error, devised an appliance that reflected
the true genius that he was.
 His name was VIGGO ANDRESEN, and his appliance was the
Activator.
 Andresen was originally Dane, But he eventually become Director of
the orthodontic department in the Dental School at Oslo, Norway.
 He developed an appliance similar to monobloc, except that in
monobloc expansion screw was incorporated. Andresen was not
aware of the monobloc appliance and its influence on the bone
shape, size, and position leading to correction of sagittal malrelation
in the growing child. He used the appliance to prevent relapse of
the fixed appliance treated case. The appliance he developed was
a modified Hawely type retainer on the maxillary arch and
horseshoe shaped flange in the lower arch. After the period of 3
months he was surprised to see the complete sagittal correction and
improved profile.

 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

 Andersen believed that many malocclusions were functional in origin
and that if form followed function”, it followed that correct function
would eventually lead to correct from.
 The activator he constructed transmit the tissue-forming functional
stimuli of the perioral and masticatory muscles, tongue, and teeth to
the periodontal tissues, alveolar bone, and temporomandibular joint
bringing about the eventual resolution of the structural Class II
deformity.
 Its use was confined to Class II, Division 1; Class II, Division2; and
pseudo-Class III malocclusions.
 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.
The appliance was meant to be worn by the patient only at
night, and its projected treatment time consisted of 18 to 24 months.
The life of appliance was about 9 months. They were initially made
of Vulcanite. Therefore, several appliances were required to be
fabricated in order to complete a case.

ANDRESEN APPLIANCE

 He was appointed as a professor at the Dental
School at Oslo, Norway. Here he had the good
fortune to strike up an alliance with a fellow staff
member at the same institution, the Austrian-
born periodontist and pathologist Karl Haupl.
 A Physician by training, Haupl was a superb
scientist of considerable international reputation.
Haupl was extremely excited, for Andersen‟s
findings coincide exactly with results he had
already seen independently relative to tooth
migration and tissue and bone reaction.

 To understand the working hypothesis of activator, Haupl
tried to apply the functional adaptation hypothesis of
“William Roux” to the clinical application of activator.
 This become a foundation for the theoretical basis of
functional jaw orthopedics.
 His main focus was on the reaction of alveolar bone on
normal and abnormal masticatory muscle function and
it‟s influence in periodontium.
 He explained that Andresen Activator causes muscle
stimuli of adequate influence creating adaptational
changes in the periodontal tissue and the alveolar bone.
 At the same time there was a discussion regarding the
growth stimulation, but Haupl was under the strong belief
that growth is guided primarily by hereditary factors and
only the extent of the growth changes can be influenced
by functional stimuli this statement of opinion has lead to
controversy between orthodontists and basic scientists.

 Together they further developed the appliance-induced
mandibular advancement techniques, refined it, and
unlike previous individuals, were able to support their
clinical observations with sound research data.
 Haupl was offered the prestigious position of Director of
the Dental Clinic at the University of Prague. From such
an eminent position, he had great leverage in convincing
other European orthodontists that Andersen‟s method as
an effective therapeutic method of “functional jaw
orthopedics”, a term they coined together
 Timely supportive data from men like A.M.
Schwarz, whose active plates could move individual
teeth and whose methods complimented and enhanced
Activator therapy, coupled with the proof of men like A.H.
Ketcham from America, that heavy force of fixed
appliances caused pathologic root resorption, brought
the European orthodontic community to applause for the
new biologically superior method of removable appliance
therapy.

 Everyone in Europe disagreed to its effectiveness.
 .One of the controversies raised was the inability of some clinicians
to obtain permanent mandibular repositioning.
 This was due to the incorrect nature of construction bites used at
that time and the lack of understanding of this important step in the
beginning.
 The bites were generally, at first, not taken with the mandible in an
inferior or protruded enough position. By not gaining enough
interocclusal space between the posterior teeth or without enough
tension on the muscles of the jaws from proper protrusion of the
mandible, the Activator‟s action and efficiency is greatly diminished.
 The construction bites were initially taken with the mandible opened
just beyond, the physiologic rest position. Generally, this was not
enough. Gradually, as more clinicians experimented with the
technique, they realized that the construction bite had to be taken
with the mandible in a more open and protruded position. But
despite these initial difficulties, the Activator was used in many
thousands of cases throughout Europe with outstanding results.

 Moreover, one of the problems with wearing the
Activator was its size.
 It was a bulky appliance at first; and by virtue of the full
palatal covering, it made speech very difficult. This was
not considered an important drawback as the activator
was to be worn only at night.
 Another difficulty with this appliance, and with all
appliances of that time, was that they had to be made
out of vulcanite. When minor tooth movements were
desired, gutta-percha melted with chloroform was used
and “layered on” in order to make the appliance a little
thicker behind the tooth that was to be moved. Another
method of individual advocated the drilling of holes in
various places in the vulcanite and gluing in small
wooden pegs that would put pressure upon the teeth to
be moved when the appliance was inserted.

 With the advent of modern acrylic, a new world of
feasibility was created for the orthodontist using
functional appliances. Its lightweight strength, low
porosity, and ease of manipulation made this “wonder”
material used for creating intraoral orthodontic devices.
 The late-model Activators were made out of acrylic,
rather than vulcanite, once this material become
available. But they were still made in the traditional
black color as were the original models in order to
facilitate grinding high spots and various other
adjustments. Thus, any excessive contact by the teeth
on the appliance would cause a shiny spot to appear
denoting the place where an adjustment was needed
and where acrylic should be reduced.
 The other eminent Orthodontists who worked on
activator are Wooside, Petrik, Eschler, Herren, Harvold
and Ahlgren.

PHILOSOPHIES OF MODE OF
ACTION
 According to the mode of action, there are two main
principles. A third approach combines the two
rationales.
 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. A successful treatment depends on muscle
stimulation, the frequency of movements of the
mandible, and the duration of the effective forces.
Activators with a low vertical dimension construction bite
function this way.

 According to the second working hypothesis
the appliance is squeezed 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
works using potential energy. For this mode of
action in 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 appliances in this group have a greater bite
opening than recommended by Andersen and Haupl,
but they do not over compensates as do Harvold and
Woodside. The stretch reflex resulting from activators
in this group is seen as a longlasting contraction. The
intermittent forces induced by the contractions are not
as pronounced as in the original construction. Eschler
observed the occurrence of both isometric and isotonic
contractions when this appliance construction was
used.
 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. www.indiandentalacademy.com

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.www.indiandentalacademy.com

 Opposing to Andresen, Herren based his mode of action
of the activator on the basis of spatial relation between
position of mandible and postural rest position. He
observed in sleeping patients that the activator showed
no significant influence on the general behaviour of the
wearer. Frequency of movements of mandible remained
same with and without activator, neither there was
increase in secretion of saliva, nor increase in
swallowing movements. The muscles were in relaxed
and tension less condition. Thus concluding that
activator does not work in the way stated by Andresen.
 As the activator does not have any anchorage except
maxillary and lingual extension of acrylic, he was under
the impression that at night appliance will not retain its
position. A slight unconscious lowering of mandible will
detach activator from maxilla. Therefore Herren
activator is fixed by clasps to maxillary dentition and he
also recommended a high vertical and sagittal
displacement of mandible to prevent detachment of
appliance.

 The Herren type or L.S.U. type activator and extraoral forward
traction exert their action mainly through the sagittal
repositioning of the mandible.
 This kind of functional appliance seems to have a two step
effect: during the time of wearing the appliance, the more
forward positioning of the mandible is the cause of reduced
growth of the lateral pterygoid muscle; simultaneously a new
sensory engram is formed for the new positioning of the lower
jaw.
 During the time that the activator is not worn, the mandible is
functioning in the more forward position in such a way that the
retrodiscal pad will be much more stimulated than in the
controls. The increased repetitive activity of the retrodiscal pad
produces an earlier beginning of the condylar chondroblast
hypertrophy and an increased growth rate of condylar cartilage.
In other wards, the lateral pterygoid muscle does mediate the
action of the activator but the stimulating effect on condylar
growth appears to be produced during the time when the
appliance is not worn www.indiandentalacademy.com

 According to Herren, mandible hyoid bone, tongues are
considered to be the components of masticatory organ.
 The movements of mandible can be active or passive.
The active movements results from contraction of
musculature. The passive movement resulting indirectly
due to active influence of neighbouring structures.
 Rest position of mandible can be active resulting from
the active muscular contraction or passive where in the
mandible is placed in rest position responding to
equilibrium of acting forces.
 As the activator is inserted, mandible is prevented from
moving in all directions of space except caudally. Thus it
is unable to assume most of the rest position that occur
during nighttime wear. Forces which pull the mandible
towards these rest positions are absorbed by the
appliance and transmitted to the teeth and alveolar
process.

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. This phenomenon is
called clasp knife reaction that is, muscle first resists, then relaxes.
 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.
 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

 Rational behind Harvold Wood side hypothesis is that
mandible normally drops open when the patient is sleep.
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. They open the mandible with
construction bite as much as 15mm beyond postural rest
position. 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.

 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:
 Emptying of vessels
 Pressing out interstitial fluid
 Stretching of fibres
 Elastic deformation of bone
 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. In
waking state, tonic activity is increased. In sleeping
state, tonic activity is depressed and in deep sleep it is
completely abolished.
 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

 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.
Without stretching of muscles, there will be no effect of
the appliance and the effect is proportional to the degree
of mandibular displacement. He recommends an inter
occlusal clearance 4-6mm. He agrees with Andresen
that increased frequency of mandibular movements
occur when an activator is worn.
 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 relax and the mandible drops down.
When the muscles have recovered the cycle starts againwww.indiandentalacademy.com

Effects on Condyle
 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. In contrast to
primary cartilages (epiphyses, sphenoccipital synchrondroses)
growth is regulated to a high degree by local exogenous factors.
 According to Moss and Petrovic condylar growth is an expression of
a locally based homeostasis for the establishment and maintenance
of a functionally coordinated stomatognathic system.
 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.
 Bireback and Melsen in 1984 laminographic study observed
increased amount of condylar growth and remodellingof glaenoid
fossa EJO-1984 EFFECT OF ACTIVATOR ON CONDYLAR
GROWTH
 Luder in 1981-82 observed two types of results with the activator
treatment which may be sex related. In boys there was marked
increase of mandibular relocation due to stimulated condylar growth.
and it is possible to alter amount and direction of condylar growth to
a clinically relevant extent by activator treatment .EJO 1981www.indiandentalacademy.com

 The activator can, to a limited degree,
control the upper growth vector, supplied
by the sphenoccipital synchondrosis,
which moves the maxillary base in a
forward direction. If the mandible cannot
be positioned anteriorly, then maxillary
growth can be inhibited and redirected.
The growth and translation of the
nasomaxillary complex can be influenced,
particularly by activators of a special
construction.

Condylar development and mandibular
rotation and displacement during activator
treatment (AJO 1982 Apr)
 An analysis of the effects of activator
treatment on the spatial development of the
mandible over 11 months was performed via the
metal implant method for a group of nineteen
patients. A posteriorly directed condylar
development, in conjunction with an anterior
rotational pattern, was found to be optimal if a
basal class II malocclusion is to be treated by
means of a forward developmental displacement
of the mandible

Effective temporomandibular joint growth
and chin position changes: Activator versus
Herbst treatment. A cephalometric
roentgenographic study.EJO -2002
 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.
 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.

changes in activator treatment: A
cephalometric roentgenoraphic study
 The present investigation revealed that
effective condylar growth can be increased
and the chin position can be changed by
activator treatment. Thus activator
treatment induces skeletal
changes, although not always in the
desired (sagittal) therapeutic direction.
(Angle Ortod 2001: 71: 4 – 11).

Effects on maxilla
 Regarding activator effect on maxilla
authors like Harvold and Vargervik,
Jacobson have observed anterior
downward rotation of maxilla.
 Studies by Harvold and Vargervik (1971)
indicated that forward development of
maxilla was retarded.
 Vargeroik and Harvold (1985) found that
activator inhibited the horizontal growth of
maxilla by 2mm.AJO 1985 NOV

A cephalometric analysis of skeletal and dental changes
contributing to Class II correction in activator treatment (AJO
1984 Feb)]
 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 (3) 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. (4) 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.

EFFECTS ON MANDIBLE
 The effect of the activator on the mandible can be indirect as a result
of growth of the condyle plus the rotation of the mandible anteriorly
leading to increase in the mandibular length
 studies by Williams and Melson showed that the improvement of
skeletal class II was because of posterior superior direction of
condylar growth combined with an anterior rotation of the
mandible, and also they concluded that the forward positioning of
the mandible aided the correction of the skeletal discrepancy, it was
found to be positively correlated to the vertical development of the
posterior part of the mandible.
 Dr. Remmer in his study on the cephalometric changes associated
with treatment using the activator, Frankerl appliance, and fixed
appliance observed that the activator was found to be more effective
in correcting the sagittal discrepancy than Frankel appliance.
 Studies by Freunthaller on cephalometric observation in Class II
division I malocclusion treated with the activator, there was
significant movement of the entire mandible anteriorly leading to
correction of Class II malocclusion.
 Studies by Dr. Luder has also supported that activator treatment has
a positive influence on the mandible.

Mandibular changes during functional appliance
treatment AJO 1993 Aug.
 The purpose of this prospective trial was to
determine the changes in position and size of the
mandible in children treated with either the Frankel
function regular or Harvold activator.
 The main effects of both appliances were to allow
vertical development of the mandibular molars and
increase the height of the face. The Harvold appliance
proclined the lower incisors and increased mandibular
arch length. We could find no evidence to support the
view that either appliance was capable of altering the
size of the mandible.

Response to activator treatment in Class II
malocclusions
 A clinical study was designed to disclose the effects of
activator treatment in the correction of Class II
malocclusions.
 Treatment results shows (1) inhibition of forward growth
of the maxilla, (2) inhibition of mesial migration of
maxillary teeth, (3) inhibition of maxillary alveolar height
increase and extrusion of mandibular molars, (4)
increased growth of the mandible, (5) anterior relocation
of the glenoid fossa, (6) mesial movement of mandibular
teeth

Effects on Soft Tissues
 Very little study was carried out on effects of
activator on the soft tissues, but however studies
by 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.

TIMING OF TREATMENT
 Reey, Eastwood, says that mixed dentition
period was best for activator treatment.
 Experience clinicians like Bjork concluded that
activator was
Most effective in decidous dentition
Less effective in mixed dentition and
Limited effect in permanent dentition
 It is also effective in neonatal and Juvenile
period. As prechondroblastic and condroblastic
activity is increased in condyle according to
Carlson et al.

INDICATIONS
 Partial or total correction of Cl II Div 1 cases
 Partial or total correction of Cl II Div 2 cases
 Partial or total correction of Cl II 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.

Advantages
 Treatment may be started during late deciduous or mixed dentition
period.
 Disturbances or suppression of normal stomatognathic functions,
which occur usually with conventional fixed appliances is avoided
with activators.
 finger sucking, abnormal tongue posture and function, mouth
breathing can be easily corrected.
 Activators maintain the beneficial therapeutic effect for long periods
of time without requiring the usual office visits which is needed in
fixed appliances.
 Repairs are seldom needed, and they are simple to perform and the
cost factor is low, chair side time is minimal.
 For the post treatment retention the same appliance can be used.
 Activators make possible the combination of prosthodontic and
orthodontic treatment at the same time with built in space control.
 No impairment of esthetics during the day since the appliance is
used most during nighttime.
 The forces employed are physiological and produce no damage
either to teeth or supporting tissue and also injury to the soft tissue
is negligible.
 The teeth are not banded there is no risk of decalcification from
cement less conducive to carious incidence and good hygienewww.indiandentalacademy.com

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

SELECTION OF CASES
 Following are the empirical criteria for
case selection.
A. Skeletal
 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

B. Dental
 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.

C. Soft tissue
 Competent or potentially competent lips in which
the lip well as 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.
 D. Respiratory
 No nasal obstruction or chronic respiratory
disorder
 C. Emotional
 1. Keen patient interest and desire and potential
co-operation form both patient and parent

TREATMENT PLANNING
PRETREATMENT CONSIDERATIONS
 Before activator treatment is started –
forward movement of mandible is checked
to see that it is not blocked by occlusal
interferences that makes the correction of
disto occlusion impossible.
 For example buccal crossbite of upper
1st premolar impedes the forward
movement of the mandible

DIAGNOSTIC PREPARATIONS
 A. Patient compliance: It is very essential. It is
very important to assess clinically patient‟s
somatic, psychological aspect and motivation
potential.
Objective
 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 sagital 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.
 First molar relationship in habitual occlusion.
 Nature of midline discrepancy, if any
(dentoalveolar non coincidental midlines
cannot be corrected by activator).
 Symmetry of dental arches
 Curve of spee is checked to diagnose
whether it can be leveled.
 Degree of crowding and dental discrepancies
are checked.

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

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

CONSTRUCTION BITE
 The construction bite is an intermaxillary wax record
used to relate the mandible to the maxilla in the three
dimensions of space. They are used to reposition the
mandible in order to improve the skeletal inter-jaw
relationship. The bite registration involves repositioning
the mandible in a forward direction as well as opening
the bite vertically.
GENERAL CONSIDERATIONS FOR CONSTRUCTION
BITE
 In case the overjet is too large, the forward positioning is
done step wise in 2-3 phases.
 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.
 If the forward positioning is not more than 3-5 mm, then
the vertical opening can be 4-6 mm.www.indiandentalacademy.com

 In taking a construction bite one should
look at the bite in three different planes of
space
 Sagital
 Vertical
 Frontal

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

B. Vertical or Opening the bite:
 The vertical and sagittal relationship are
intimately linked.
Guiding Principles
 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.
 If magnitude of forward positioning is great 7-8
mm then vertical opening should be
minimal, so that muscles are not overstreched.
 If extensive vertical opening is required the
mandible must not be positioned anteriorly

 C. 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

Sequential steps for construction bite
 Amount of horizontal and vertical displacement of the mandible is
determined. Mark the amount of horizontal shift on the buccal
surfaces of first molars.
 Show the patients on the cast and a mirror the direction in which
the mandible should move. Now practice the movement by
guiding the mandible in the desired direction. Advise the patient
to move according to verbal direction and stop when asked to do
so.
 Soften a sheet of wax and make a roll 1 cm in diameter. The
shape of the roll should be conformed to the lower dental cast.
Now press the roll so that only buccal teeth are covered, in front
the wax lies lingual to the incisors. Make grooves to indicate
midline.
 Remove excess wax on the distal ½ of the last molar and
retromolar region

 Transfer the wax to the patients mouth fitting it on the lower arch,
in the same manner.
 Ask the patient to move the mandible forward as practiced and
bite till the proper amount of vertical opening is achieved.
 Remove wax from the mouth and chill it. Remove excess wax till
the occlusal surface of the molars are visible. All excess wax
contacting the soft tissues, interproximal papilla and palate are
removed.
 Place the wax bite between the casts. Check whether the
mandible has moved in the desired amount in the three planes of
space. If incorrect, wax is added on the superior surface and
repeated.
 Replace hard wax bite in the patient‟s mouth to check for a proper
fit.
 Construction bite should be taken on the patient and not on
articulated models. Construction bite prepared on casts have the
following disadvantages:
 Appliance does not fit and these are frequent disturbances during
sleep
 Asymetrical biting on the appliance
 Greater stress on lower incisors which can cause unwanted
procumbancy

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.
 As a rule of thumb the anterior advancement should
not exceed more than 3 mm posterior to the most
protrusive position. Vertically the opening is minimal
and is within the limits of the inter-occlusal clearance.
This kind of activator constructed with marked sagittal
advancement but minimal vertical opening is called an
“H activator”. The H activator is indicated in a patient
with class II, division 1 malocclusion having a
horizontal growth pattern

High construction bite with slight anterior
mandibular positioning:
 The mandible is positioned anteriorly by 3-5 mm
only and the 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
a Class II, Division 1 malocclusion having a vertical
growth pattern.

Construction bite without forward positioning
of the mandible:
 Sometimes a construction bite without
forward positioning of the mandible is
made in cases such as deep bite and
open bite

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

FABRICATION
 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
 Each labial bow consist of a horizontal middle section, two vertical
loops, and wire extensions through the canine or deciduous first
molars and they are embedded din the acrylic body.
 The horizontal portions crosses above convexity in deep bite and
below convexity in open bite.
 The bow is active or passive and influences soft tissue without
touching teeth.
 The wire usually used is 0.8 mm round stainless steel..

Fabrication of the Acrylic portion
 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.

STEPWISE PROCESS FOR ACRYLISATION
 Before acrylic portion are made the casts are put
in a water bath for 20 min.
Then isolated and dried.
 Fixation of wire elements and acrylic free areas
are covered with wax.
 Upper and lower portions are moulded from self
curing acrylic.
 The upper and lower parts are joined with acrylic
in interdental areas.
 After polymerization of the appliance it is ground
and polished. However it is not ground for
specific tooth guidance. This is done with the
patients on the chair.

TRIMMING OF THE ACTIVATOR
 After fabrication of the activator it is usually found to
fit tightly as acrylic is interposed between the upper and
lower occlusal surfaces. Planned trimming of the
appliance in tooth contact area is carried out to bring
about dento-alveolar changes so as to guide the teeth
into good relation in all the 3 planes of space.
 Selective trimming of acrylic is done in the direction
of tooth movement
 The acrylic surfaces that transmits the desired force by
contact with the teeth are called guiding planes. The
areas of acrylic that contact the teeth become polished.
 Approximate trimming can be done on the plaster casts.
However, final trimming should be done at the chair side.

TRIMMING OF ACTIVATOR FOR VERTICAL
CONTROL
 Selective trimming of the activator can be
done to intrude or extrude the teeth.
 Intrusion of teeth:
 Intrusion of the incisors are achieved by loading
the incisal edge of these teeth with acrylic. In
case labial bows are used, they should be
placed below the area of greatest convexity i.e
incisally, to aid in the intrusion.

 . In case intrusion
posteriors is needed
then only the cusp
tips are loaded with
acrylic. The fossae
and fissures are free
of acrylic. This
applies a vertical
intrusive force on the
molars.

 Extrusion of the
incisors, the lingual
surface is loaded above
the area of greatest
convexity in the maxilla
and below the area of
greatest convexity in the
mandible. The extrusive
movement can be
enhanced by placing a
labial bow above the area
of greatest convexity i.e
in the gingival 1/3 of the
labial surface

 In case of molars,
extrusion is brought
about by loading the
lingual surface above
the area of greatest
convexity in maxilla
and below the area of
greatest convexity in
mandible

TRIMMING OF THE
ACTIVATOR FOR
SAGITTAL CONTROL
 Protrusion of incisors: In
case the incisors be
protruded, lingual surface
of the teeth is loaded with
acrylic and a passive
labial bow is given that is
kept away from teeth to
prevent perioral soft
tissues contacting the
teeth

 Retrusion of incisors:
The acrylic is trimmed
away form the lingual
surface and an active
labial bow is used to
bring about retrusion
of the incisors

 Movement of posterior teeth in sagittal
plane: The teeth in the buccal segment
can be moved mesially and distally to help
in treating Class II and Class III
malocclusion. In Class II
malocclusion, the maxillary molars are
allowed to move distally while the
mandibular molars are allowed to move
mesially by loading the maxillary
mesioligual surface and mandibular
distolingual surfacewww.indiandentalacademy.com

MESIAL MOVEMENT OFMOLARS
DISTAL MOVEMENT OF MOLARS

Movement Of Teeth In
Transverse Plane
 It is possible to trim
the activator to stimulate
expansion of buccal
segment This is done by
contact of acrylic on the
lingual surfaces of the
teeth to be moved
transversely. But better
expansion is possible by
placing a jack screw in
the activator

MODIFICATIONS OF ACTIVATOR
 The original Andresen appliance made of
vulcanite or acrylic fabrication consisted of
maxillary and mandibular components joined
together. Since appliance is worn at night
during sleep due to the slackening of the
mandible the appliance is rendered ineffective
and there is frequent loss of appliance during
sleep. Hence to overcome the above drive
backs, modifications were made.

PROPULSOR
 Designed by Muhlemann
 Refined by Hotz
 It is a hybrid appliance with features of both he monobloc
and the simple oral screen. Construction bite is smaller
compared to activator with the mode of action same as
that of activator.
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.
Indication
 In cases of maxillary dentoalveolar protrusion
Advantage
 Light weight – minimum bulk of appliance
 It effects changes in alveolar process and teeth in
maxillary anterior segment.www.indiandentalacademy.com

PROPULSAR

ELASTIC OPEN ACTIVATOR (EOA)
 Designed by G. Klammt of Gorlitz of GERMANY (1955)
Design
 acrylic is reduced from anterior palatal region to
restore exteroceptive contact between tongue and
palate.
Advantages
 No obstruction to oral cavity
 Reduced size comfortable to the patient
 Can be used during day also.
Disadvantages
 Construction bite cannot be opened too much because
vertically the tongue function is not under control and
may thrust into interincisal gap.
 Lack of support in cutaway area is disadvantageous.

ELASTIC OPEN
ACTIVATOR

WUNDERER‟S MODIFICATION
 Designed by Wunderer
 Indicated C1 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

WUNDERERS MODIFICATION

BOW ACTIVATOR OF A.M. SCHWARZ
 Designed by A.M. Schwarz
Design
 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 distoocclusion
 Independent maxillary or mandibular expansions can be effected by
incorporation of a screw.
Disadvantages
 Easily distorted
 Difficulty in adapting loops
 Breakage of bow portion
Indications
 Treatment of CI II div I malocclusion in deciduous
dentition

BOW ACTIVATOR

THE KARWETZKY MODIFICATION
 Design by Karwetzky
Design : Similar to Bow activator of Schwarz but with improved
technique
 Consists of maxillary and mandibular active plates joined by a‟U‟
bow in 1st permanent molar region. Acrylic covers lingual tissue,
gingivae, teeth and also occlusal aspects of all teeth.
 Construction bite is done with mandible in postural rest position
 Forward position of mandible is done in stages
 The Labial bow is made from 0.9 mm round stainless steel wire, for
retention
 Various other elements could be incorporated
 Acrylic between upper and lower parts are made flat and joined by a
„U‟ 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.
 Type I - for CI II Div 1 malocclusion
 Type II - for CI III malocclusion
 Type III - used in facial asymmetry and lateral
crossbite

KARWETZKY MODIFICATION

Advantages
 Exerts a delicate force on dentition and tempero
mandibular joint
 Mobility of parts allows various mandibular
movements making it more comfortable and
reinforces various functional stimuli.
 Supplements treatment of certain jaw fractures
 Used with certain types of orthognathic surgeries, in
adults
 Correction may be achieved quickly within 5-8
months making it a versatile appliance
 Screws, labial bows, springs can be used to
enhance appliance action.

REDUCED ACTIVATOR OR CYBERNATOR OF
SCHMUTH
 Design by Prof. G.P.F. Schmuth
 Design : Major portion of acrylic is trimmed
off
 Advantage
 Easier to construct customary labial bows are
used auxillaries also can be used. According to
Schmuth “It is not a new method or a new appliance
but an adaptation of the activator to use principles of
myofunctional appliance in the simplest manner

REDUCED ACTIVATOR

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

KINETOR

HERREN’S ACTIVATOR
 Designed by Paul Herren
 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.
 So, Herren modified that activator by
 Overcompensating the vertical position in construction bite
registration
 Seating firmly the appliance against maxillary dental arch with
arrowhead clasps. Jackson clasp also can be used.
Construction bite:
 Differs from Andreson activator in the sagital
positioning which is greater than the vertical opening.
 Anterior positioning is 3-4 mm beyond neurtroocclusion
 Vertical positioning is 2-4 mm apart incisal edge.
Uses
 To correct CI II malacclusion
 To retard forward growth of maxilla
 To reposition the mandible
 Successful results achieved during transitional as well as early
permanent dentition
 High rate of stablity and success

LSU ACTIVATOR
 Robert Shaye follows the same principle and
design as Herren Activator. Lower incisors bite
on a plane formed by acrylic so that growth in
occlusal direction is restricted.
 Acrylic freed from occlusal aspects of posterior
teeth enhances eruption of premolars and
molars and decreases the curve of spee

BIONATOR
Designed by Balters
Design
 Less bulky than activator
 Takes tongue as an essential factor in development of dentition
 The Bionator maintains the forward position, preventing the
deleterious parafunctional effects at night.
 The construction bite is opened slightly with mandible in a forward
position and the lower incisors can then be capped. No grinding is
done thus when the acrylic is worn, it grasps or leads both uypper
and lower buccal segments, guiding the mandible forward during the
clenching or bruxing activity.
 The Bionator is an effective appliance for treating functional or mild
skeletal Class II malocclusions in the mixed and transitional
dentitions.
 patient compliance is excellent for both day time and night time wear
 . A special indication is in the treatment of TMJ patients who have
bruxism and clenching, clicking and crepitus.

BIONATOR

HARVOLD-WOODSIDE ACTIVATOR
 Designed by Dr. Egie Harvold
 Differs from the classical activator in the following aspects.
 Degree of opening is greater
 Labial arch wire is formed very differently from the conventional
activator
 The degree of opening is atleast 5 mm more – beyond the freeway
space so that an increased effect of myotatic reflex is effected. It
also has an added effect of visco elastic properties of connective
tissue and muscles of face. The acrylic design is brought about by
trimming out in the buccal segments.
 In the upper: only the cusp-tips are seen through the wax spacer
thus putting a restraining effect on the maxillary buccal segments.
 Lower activator acts directly on the mandibular
mucopesitosteum and via this to the basal bone.
 In contrast to Andersen appliance where untrimmed facets
cause forward movement of teeth. This Activator has generous
lingual flanges which provide good retention.
 Labial arch extends from premolar to premolar, usually passive
and rests at the junction of gingival and middle 1/3 of the anteriors –
1.5 to 1 mm away from the canines. 0.8 or 0.9 mm round stainless
steel wire are used. www.indiandentalacademy.com

ACTIVATOR HEADGEAR APPLIANCES
 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.www.indiandentalacademy.com

INITIAL EFFECTS OF TREATMENT OF CLASS II
MALOCCLUSION WITH THE HERREN ACTIVATOR-
HEADGEAR COMBINATION, AND JASPER JUMPER
AJO 1997 JULY.
 The initial effects of treatment of Class
II, Division 1 malocclusion with an
activator, according to Herren (27 patients), with
an activator – deadgear combination (20
patients), or with the jasper jumper appliance
(25 patients) were studied on lateral
cephalograms from before and after 6 to 8
months of treatment.
 Skeletal changes accounted for 42%, 35%, and
48% of the overjet correction by the Herren-type
activator, the headgear-activator, and the jasper
jumper, respectively.
 The correction of the molar relationship
occurred to 55%, 46%, and 38% by skeletal
changes in the respective groups.

DENTAL AND SKELETAL CONTRIBUTIONS TO
OCCLUSAL CORRECTION IN PATIENTS
TREATED WITH THE HIGH-PULL HEADGEAR –
ACTIVATOR COMBINATION AJO – 1990 JUNE.
 The purpose of this study was to examine dental and
skeletal changes in patients treated with the high-pull headgear –
activator combination. The results showed that class II correction
often was achieved by distal repositioning of the maxillary teeth
(mean, 0.07mm) and mesial repositioning of the mandibular teeth
(mean, 3.3 mm) with a wide range of variation.

MAGNETIC ACTIVATOR DEVICE (MAD) AJO 1993 MARCH
Designed by Dr. Ali Darendilier in 1993
Design
 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
 Magnetic Activator Device : MAD I - For Mandibular
deviations
 Magnetic Activator Device : MAD II - For Class II
malocclusion
 Magnetic Activator Device : MAD III - For Class III
malocclusion
 Magnetic Activator Device : MAD IV - For open bite
malocclusion
Advantages:
 Continuous force
 Freedom of movement for the mandible

MAGNETIC ACTIVATOR DEVICE

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