Activator and its modifications

ACTIVATORACTIVATOR
www.indiandentalacademy.comwww.indiandentalacademy.com

INTRODUCTIONINTRODUCTION
 The term functional appliance refers to a varietyThe term functional appliance refers to a variety
of removable appliances designed to alter theof removable appliances designed to alter the
arrangement of various muscle groups thatarrangement of various muscle groups that
influence the function and position of mandibleinfluence the function and position of mandible
in order to transmit forces to dentition and basalin order to transmit forces to dentition and basal
bone.bone.
 These muscular forces are generated byThese muscular forces are generated by
altering mandibular position sagitally andaltering mandibular position sagitally and
vertically resulting in orthodontic and orthopedicvertically resulting in orthodontic and orthopedic
changes.changes.

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

HISTORY AND DEVELOPMENTHISTORY AND DEVELOPMENT
OF ACTIVATOROF ACTIVATOR
 In the year 1880 Dr. N.W. Kingsley wrote, in his treatiseIn the year 1880 Dr. N.W. Kingsley wrote, in his treatise
on oral deformity, that he had developed a maxillaryon oral deformity, that he had developed a maxillary
plate with an inclined plane for the purpose of “Jumpingplate with an inclined plane for the purpose of “Jumping
the bite” forward in cases of extreme mandibularthe bite” forward in cases of extreme mandibular
retrusion.retrusion.
 . The idea was further evolved by French dentist Dr.. The idea was further evolved by French dentist Dr.
Pierre Robin, who published a paper in 1902 describingPierre Robin, who published a paper in 1902 describing
his “monobloc” appliance to be used for bimaxillaryhis “monobloc” appliance to be used for bimaxillary
expansion. Incidentally, he also advocated the use ofexpansion. Incidentally, he also advocated the use of
this appliance for the treatment of “glossoptosis”. Butthis appliance for the treatment of “glossoptosis”. But
his concept of moving the mandible and the tonguehis concept of moving the mandible and the tongue
forward to correct mandibular retrusion and free up theforward to correct mandibular retrusion and free up the
esophageal and tracheal passages survives down to thisesophageal and tracheal passages survives down to this
day.day.

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

 He believed in the theories, expounded byHe believed in the theories, expounded by
Roux and Wolfe in the 1890s that changesRoux and Wolfe in the 1890s that changes
in biomechanical function bring aboutin biomechanical function bring about
corresponding changes in both internalcorresponding changes in both internal
structures of bone as well as externalstructures of bone as well as external
shapeshape

 Andersen believed that many malocclusions were functional inAndersen believed that many malocclusions were functional in
origin and that if form followed function”, it followed that correctorigin and that if form followed function”, it followed that correct
function would eventually lead to correct from.function would eventually lead to correct from.
 The activator he constructed transmit the tissue-forming functionalThe activator he constructed transmit the tissue-forming functional
stimuli of the perioral and masticatory muscles, tongue, and teeth tostimuli of the perioral and masticatory muscles, tongue, and teeth to
the periodontal tissues, alveolar bone, and temporomandibular jointthe periodontal tissues, alveolar bone, and temporomandibular joint
bringing about the eventual resolution of the structural Class IIbringing about the eventual resolution of the structural Class II
deformity.deformity.
 Its use was confined to Class II, Division 1; Class II, Division2; andIts use was confined to Class II, Division 1; Class II, Division2; and
pseudo-Class III malocclusions.pseudo-Class III malocclusions.
 The appliance consisted of an upper maxillary plate with an anteriorThe appliance consisted of an upper maxillary plate with an anterior
flange extending into the lingual area of the mandibular arch that onflange extending into the lingual area of the mandibular arch that on
closing held the lower jaw in a forward position relative to the maxillaclosing held the lower jaw in a forward position relative to the maxilla
with a bite opening of approximately 5mm between the posteriorwith a bite opening of approximately 5mm between the posterior
teeth. The appliance also had a labial bow or labial archwire acrossteeth. The appliance also had a labial bow or labial archwire across
the maxillary anterior teeth for the purposes of stabilizing thethe maxillary anterior teeth for the purposes of stabilizing the
appliance and retracting overly protruded maxillary anterior teeth.appliance and retracting overly protruded maxillary anterior teeth.
The appliance was meant to be worn by the patient only at night,The appliance was meant to be worn by the patient only at night,
and its projected treatment time consisted of 18 to 24 months. Theand its projected treatment time consisted of 18 to 24 months. The
life of appliance was about 9 months. They were initially made oflife of appliance was about 9 months. They were initially made of
Vulcanite. Therefore, several appliances were required to beVulcanite. Therefore, several appliances were required to be
fabricated in order to complete a case.fabricated in order to complete a case.

ANDRESEN APPLIANCE

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

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

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

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

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

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

PHILOSOPHIES OF MODE OFPHILOSOPHIES OF MODE OF
ACTIONACTION
 According to the mode of action, there are two mainAccording to the mode of action, there are two main
principles. A third approach combines the twoprinciples. A third approach combines the two
rationales.rationales.
 According to the originalAccording to the original
Andresen Haupl concept the forces generated inAndresen Haupl concept the forces generated in
activator therapy are due to muscle contractions andactivator therapy are due to muscle contractions and
myotatic reflex activity. There is stimulation of themyotatic reflex activity. There is stimulation of the
muscles by a loose appliance, and the moving appliancemuscles by a loose appliance, and the moving appliance
moves the teeth. The muscles function with kineticmoves the teeth. The muscles function with kinetic
energy, and intermittent forces are of clinicalenergy, and intermittent forces are of clinical
significance. A successful treatment depends on musclesignificance. A successful treatment depends on muscle
stimulation, the frequency of movements of thestimulation, the frequency of movements of the
mandible, and the duration of the effective forces.mandible, and the duration of the effective forces.
Activators with a low vertical dimension construction biteActivators with a low vertical dimension construction bite
function this way.function this way.

 According to the second working hypothesisAccording to the second working hypothesis
the appliance is squeezed the jaws in athe appliance is squeezed the jaws in a
splinting action. The appliance exerts forcessplinting action. The appliance exerts forces
that move the teeth to this rigid position. Thethat move the teeth to this rigid position. The
stretch reflex is activated, inherent tissuestretch reflex is activated, inherent tissue
elasticity is operative, and there is strainelasticity is operative, and there is strain
without functional movement. The appliancewithout functional movement. The appliance
works using potential energy. For this mode ofworks using potential energy. For this mode of
action in overcompensation of the constructionaction in overcompensation of the construction
bite in the sagittal or vertical plane isbite in the sagittal or vertical plane is
necessary. An efficient stretch action isnecessary. An efficient stretch action is
achieved by the overcompensation and theachieved by the overcompensation and the
viscoelastic properties of the contiguous softviscoelastic properties of the contiguous soft
tissues.tissues.

 The third approach enlists the modes of action of theThe third approach enlists the modes of action of the
preceding two. It can be called a transitional type ofpreceding two. It can be called a transitional type of
activator action, which alternately uses muscleactivator action, which alternately uses muscle
contraction and viscoelastic properties of soft tissue.contraction and viscoelastic properties of soft tissue.
The appliances in this group have a greater biteThe appliances in this group have a greater bite
opening than recommended by Andersen and Haupl,opening than recommended by Andersen and Haupl,
but they do not over compensates as do Harvold andbut they do not over compensates as do Harvold and
Woodside. The stretch reflex resulting from activatorsWoodside. The stretch reflex resulting from activators
in this group is seen as a longlasting contraction. Thein this group is seen as a longlasting contraction. The
intermittent forces induced by the contractions are notintermittent forces induced by the contractions are not
as pronounced as in the original construction. Eschleras pronounced as in the original construction. Eschler
observed the occurrence of both isometric and isotonicobserved the occurrence of both isometric and isotonic
contractions when this appliance construction wascontractions when this appliance construction was
used.used.
 All the modes of action are dependent on the directionAll the modes of action are dependent on the direction
and degree of opening of the construction bite. Byand degree of opening of the construction bite. By
taking into account the individual characteristics of thetaking into account the individual characteristics of the
facial skeleton, the individualized growth processes,facial skeleton, the individualized growth processes,
and the goal of treatment, the clinician can fabricateand the goal of treatment, the clinician can fabricate
the appliance to work according to the desired mode ofthe appliance to work according to the desired mode of
action.action.

MODE OF ACTIONMODE OF ACTION
 Andresen stated that this appliance has a stimulatingAndresen stated that this appliance has a stimulating
effect on jaw development. In class II cases when theeffect on jaw development. In class II cases when the
mandible is brought forward into Class I relationship,mandible is brought forward into Class I relationship,
there is stimulation of protractors and elevators withthere is stimulation of protractors and elevators with
stretching of retractors resulting in the change instretching of retractors resulting in the change in
functional pattern of muscle and the bone structures asfunctional pattern of muscle and the bone structures as
they adopt to the new functional environment,they adopt to the new functional environment,
 For stimulating these muscles, the appliance should beFor stimulating these muscles, the appliance should be
loosely fitting and as the patient every time tries toloosely fitting and as the patient every time tries to
occlude, or swallow, upper and lower teeth contactocclude, or swallow, upper and lower teeth contact
resulting in jolts to the periodontal membrane. This actsresulting in jolts to the periodontal membrane. This acts
as a stimuli for tissue rebuilding.as a stimuli for tissue rebuilding.
 They were of the opinion that myotatic reflex activity andThey were of the opinion that myotatic reflex activity and
isometric muscle contraction induce musculo skeletalisometric muscle contraction induce musculo skeletal
adaptation by inducing new mandibular closing pattern.adaptation by inducing new mandibular closing pattern.

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

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

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

CLASP KNIFE REFLEXCLASP KNIFE REFLEX
 The basis for such severe increase in the displacement of mandible is theThe basis for such severe increase in the displacement of mandible is the
clasp knife reflex or autogenic inhibition or lengthening reaction.clasp knife reflex or autogenic inhibition or lengthening reaction.
 When a spastic limb is flexed forcibly resistance is encountered. If theWhen a spastic limb is flexed forcibly resistance is encountered. If the
flexion forcibly carried further, the resistance to the flexion was found toflexion forcibly carried further, the resistance to the flexion was found to
disappear and previously rigid limb collapses readily. This phenomenon isdisappear and previously rigid limb collapses readily. This phenomenon is
called clasp knife reaction that is, muscle first resists, then relaxes.called clasp knife reaction that is, muscle first resists, then relaxes.
 The excessive stretch of the muscle brings into play some new influenceThe excessive stretch of the muscle brings into play some new influence
which inhibits the stretch reflex and allows the muscle to be lengthened withwhich inhibits the stretch reflex and allows the muscle to be lengthened with
little or no resistancelittle or no resistance
 The receptors for clasp knife reflex are golgi tendon organs located in theThe 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,tendon of the muscle and the stimulus for the reflex is excessive stretch,
impulses conducted from the sensory nerve fibres of golgi tendon organ actimpulses conducted from the sensory nerve fibres of golgi tendon organ act
on the motor neuron supplying the stretched muscle.on the motor neuron supplying the stretched muscle.
 The output of motor neuron depend on the balance between 2 antagonisticThe output of motor neuron depend on the balance between 2 antagonistic
inputs. One from golgi tendon organ inhibiting the muscle contraction, otherinputs. One from golgi tendon organ inhibiting the muscle contraction, other
from the nuclear bag of the muscle facilitating muscle contraction. Thefrom the nuclear bag of the muscle facilitating muscle contraction. The
functional significance of the clasp knife reflex, is to protect the overload byfunctional significance of the clasp knife reflex, is to protect the overload by
preventing damaging contraction against stretching forcespreventing damaging contraction against stretching forces

 Rational behind Harvold Wood side hypothesis is thatRational behind Harvold Wood side hypothesis is that
mandible normally drops open when the patient is sleep.mandible normally drops open when the patient is sleep.
If it is opened 3 to 4 mm by the appliance one of the twoIf it is opened 3 to 4 mm by the appliance one of the two
things happen, either appliance may fall out or it may bethings happen, either appliance may fall out or it may be
ineffective because the wider open sleep positionineffective because the wider open sleep position
 Harvold and Woodside doubted the actual contractionsHarvold and Woodside doubted the actual contractions
taking place when the patient is sleeping. Theytaking place when the patient is sleeping. They
recommended wide open construction bite so thatrecommended wide open construction bite so that
appliance does not fall off. They open the mandible withappliance does not fall off. They open the mandible with
construction bite as much as 15mm beyond postural restconstruction bite as much as 15mm beyond postural rest
position. Muscle tension arises as a consequence ofposition. Muscle tension arises as a consequence of
stretching of tissues and the over extended activatorstretching of tissues and the over extended activator
stretches the soft tissues like a splint. The appliancestretches the soft tissues like a splint. The appliance
induces no myotatic reflex activity but instead a rigidinduces no myotatic reflex activity but instead a rigid
stretch and builds up potential energy.stretch and builds up potential energy.

 The viscoelastic properties of muscle and theThe viscoelastic properties of muscle and the
stretching of the soft tissues are decisive forstretching of the soft tissues are decisive for
activator action. During each force application,activator action. During each force application,
secondary forces arise in the tissues,secondary forces arise in the tissues,
introducing a bioelastic process. Thus not onlyintroducing a bioelastic process. Thus not only
the muscle contractions but also the viscoelasticthe muscle contractions but also the viscoelastic
properties of the soft tissue are important inproperties of the soft tissue are important in
stimulating the skeletal adaptation. Dependingstimulating the skeletal adaptation. Depending
on the magnitude and duration of the appliedon the magnitude and duration of the applied
force, the viscoelastic reaction can be dividedforce, the viscoelastic reaction can be divided
into the following stages:into the following stages:
 Emptying of vesselsEmptying of vessels
 Pressing out interstitial fluidPressing out interstitial fluid
 Stretching of fibresStretching of fibres
 Elastic deformation of boneElastic deformation of bone
 Bioplastic adaptionBioplastic adaption

 Stretching of muscles give rise to stretch reflexStretching of muscles give rise to stretch reflex
contractions.contractions.
 Stretch reflex by activator displacing mandible beyondStretch reflex by activator displacing mandible beyond
rest position is tonic type. The tonic activity of therest position is tonic type. The tonic activity of the
muscles varies with the level of wakefulness or sleep. Inmuscles varies with the level of wakefulness or sleep. In
waking state, tonic activity is increased. In sleepingwaking state, tonic activity is increased. In sleeping
state, tonic activity is depressed and in deep sleep it isstate, tonic activity is depressed and in deep sleep it is
completely abolished.completely abolished.
 When worn during day the activator elicits increasedWhen worn during day the activator elicits increased
frequency of swallowing movements. Also as thefrequency of swallowing movements. Also as the
activator is squeezed between the teeth, it elicits passiveactivator is squeezed between the teeth, it elicits passive
tension in the stretched muscles thus it transferstension in the stretched muscles thus it transfers
continuous force from the muscle to the teeth. Duringcontinuous force from the muscle to the teeth. During
sleep when muscles are tonic, myoclonic twitches ofsleep when muscles are tonic, myoclonic twitches of
tongue push the activator against the teeth. Thesetongue push the activator against the teeth. These
intermittent forces are transmitted through the applianceintermittent forces are transmitted through the appliance
to the teethto the teeth

 Eschler supported Andersen Haupl’s concept based inEschler supported Andersen Haupl’s concept based in
muscle physiology experiments. He found actionmuscle physiology experiments. He found action
currents in patients wearing activator as compared tocurrents in patients wearing activator as compared to
patients not wearing.patients not wearing.
 Eschler denies activators potential to activation of theEschler denies activators potential to activation of the
muscle directly. Its effect depends on the stretch reflex.muscle directly. Its effect depends on the stretch reflex.
Without stretching of muscles, there will be no effect ofWithout stretching of muscles, there will be no effect of
the appliance and the effect is proportional to the degreethe appliance and the effect is proportional to the degree
of mandibular displacement. He recommends an interof mandibular displacement. He recommends an inter
occlusal clearance 4-6mm. He agrees with Andresenocclusal clearance 4-6mm. He agrees with Andresen
that increased frequency of mandibular movementsthat increased frequency of mandibular movements
occur when an activator is worn.occur when an activator is worn.
 On insertion of the appliance, the mandible is elevatedOn insertion of the appliance, the mandible is elevated
by isotonic muscle contractions succeeded by isometricby isotonic muscle contractions succeeded by isometric
contractions which is tonic in nature. Mandible assumescontractions which is tonic in nature. Mandible assumes
static position in contact with the appliance and isstatic position in contact with the appliance and is
prevented from reaching the occlusion. The elevatorsprevented from reaching the occlusion. The elevators
and retractors remain contracted, fatigue of the muscleand retractors remain contracted, fatigue of the muscle
occurs. Muscle relax and the mandible drops down.occurs. Muscle relax and the mandible drops down.
When the muscles have recovered the cycle starts againWhen the muscles have recovered the cycle starts again

Effects on CondyleEffects on Condyle
 The influence of activator on the condyle is very much controversial.The influence of activator on the condyle is very much controversial.
 The possibility of influencing condylar growth with functionalThe possibility of influencing condylar growth with functional
orthodontic appliances is conditioned by psychogenetic andorthodontic appliances is conditioned by psychogenetic and
ontogenetic peculiarities of the condylar cartilage. In contrast toontogenetic peculiarities of the condylar cartilage. In contrast to
primary cartilages (epiphyses, sphenoccipital synchrondroses)primary cartilages (epiphyses, sphenoccipital synchrondroses)
growth is regulated to a high degree by local exogenous factors.growth is regulated to a high degree by local exogenous factors.
 According to Moss and Petrovic condylar growth is an expression ofAccording to Moss and Petrovic condylar growth is an expression of
a locally based homeostasis for the establishment and maintenancea locally based homeostasis for the establishment and maintenance
of a functionally coordinated stomatognathic system.of a functionally coordinated stomatognathic system.
 Petrovic has shown, the lateral pterygoid muscle has a decisive rolePetrovic has shown, the lateral pterygoid muscle has a decisive role
in this growth. Forward posturing of the condyle activates thein this growth. Forward posturing of the condyle activates the
superior head of the lateral pterygoid. In young individuals thissuperior head of the lateral pterygoid. In young individuals this
induces a cell proliferation in the condyle and a growth response.induces a cell proliferation in the condyle and a growth response.
 Bireback and Melsen in 1984 laminographic study observedBireback and Melsen in 1984 laminographic study observed
increased amount of condylar growth and remodellingof glaenoidincreased amount of condylar growth and remodellingof glaenoid
fossa EJO-1984 EFFECT OF ACTIVATOR ON CONDYLARfossa EJO-1984 EFFECT OF ACTIVATOR ON CONDYLAR
GROWTHGROWTH
 Luder in 1981-82 observed two types of results with the activatorLuder in 1981-82 observed two types of results with the activator
treatment which may be sex related. In boys there was markedtreatment which may be sex related. In boys there was marked
increase of mandibular relocation due to stimulated condylar growth.increase of mandibular relocation due to stimulated condylar growth.
and it is possible to alter amount and direction of condylar growth toand it is possible to alter amount and direction of condylar growth to
a clinically relevant extent by activator treatment .EJO 1981a clinically relevant extent by activator treatment .EJO 1981www.indiandentalacademy.comwww.indiandentalacademy.com

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

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

Effective temporomandibular joint growthEffective temporomandibular joint growth
and chin position changes: Activator versusand chin position changes: Activator versus
Herbst treatment. A cephalometricHerbst treatment. A cephalometric
roentgenographic study.EJO -2002roentgenographic study.EJO -2002
 The comparison between the activator and theThe comparison between the activator and the
Herbst group revealed larger effective TMJ andHerbst group revealed larger effective TMJ and
chin changes during Activator therapychin changes during Activator therapy
 The treatment effects showed marked groupThe treatment effects showed marked group
differences for both the amount and direction ofdifferences for both the amount and direction of
effective TMJ changes. The changes wereeffective TMJ changes. The changes were
vertical and slightly anterior in the Activatorvertical and slightly anterior in the Activator
group, and predominantly posterior in the Herbstgroup, and predominantly posterior in the Herbst
group.group.
 The chin changes, the treatment effects for theThe chin changes, the treatment effects for the
Herbst group exceeded those for the ActivatorHerbst group exceeded those for the Activator
group in both directions, caudally and anteriorly.group in both directions, caudally and anteriorly.
The Activator group showed anterior rotationThe Activator group showed anterior rotation
and the Herbst group a slight posterior rotationand the Herbst group a slight posterior rotation
of the mandible.of the mandible. www.indiandentalacademy.comwww.indiandentalacademy.com

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

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

A cephalometric analysis of skeletal and dental changesA cephalometric analysis of skeletal and dental changes
contributing to Class II correction in activator treatment (AJOcontributing to Class II correction in activator treatment (AJO
1984 Feb)]1984 Feb)]
 The purpose of this investigation was to evaluate cephalometricallyThe purpose of this investigation was to evaluate cephalometrically
the mechanism of antero-posterior occlusal changes in activatorthe mechanism of antero-posterior occlusal changes in activator
treatment.treatment.
 The following results were found (1) The improvement in occlusalThe following results were found (1) The improvement in occlusal
relationships in the molar and incisor segments was about equally arelationships in the molar and incisor segments was about equally a
result of skeletal and dental changes. (2) Overjet correctionresult of skeletal and dental changes. (2) Overjet correction
averaging a 2.4 mm more mandibular growth than maxillary growth,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 mma 2.5 mm distal movement of the maxillary incisors, and a 0.1 mm
mesial movement of the mandibular incisors (3) Class II molarmesial movement of the mandibular incisors (3) Class II molar
correction averaging 5.1 mm was a result of 2.4 mm morecorrection averaging 5.1 mm was a result of 2.4 mm more
mandibular growth than maxillary growth, a 0.4 mm distal movementmandibular growth than maxillary growth, a 0.4 mm distal movement
of the maxillary molars, and a 2.3 mm mesial movement of theof the maxillary molars, and a 2.3 mm mesial movement of the
mandibular molars. (4) When the findings were compared withmandibular molars. (4) When the findings were compared with
longitudinal records of persons with normal occlusion (Boltonlongitudinal records of persons with normal occlusion (Bolton
Standards), activator treatment seemed to inhibit maxillary growth,Standards), activator treatment seemed to inhibit maxillary growth,
move the maxillary incisors and molars distally, and move themove the maxillary incisors and molars distally, and move the
mandibular incisors and molars mesially.mandibular incisors and molars mesially.

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

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

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

Effects on Soft TissuesEffects on Soft Tissues
 Very little study was carried out on effects ofVery little study was carried out on effects of
activator on the soft tissues, but however studiesactivator on the soft tissues, but however studies
by Forsberg and Odenrick 1981 observed thatby Forsberg and Odenrick 1981 observed that
upper lip retrusion was significantly moreupper lip retrusion was significantly more
prevalent in treated Class II group than in controlprevalent in treated Class II group than in control
group. Nose showed equal forward growth ingroup. Nose showed equal forward growth in
both the groups. Soft tissue pogonion is furtherboth the groups. Soft tissue pogonion is further
anterior in treated group. Further more it wasanterior in treated group. Further more it was
found that in the treated group lip balance wasfound that in the treated group lip balance was
not achieved in patients with relativelynot achieved in patients with relatively
retrognathic profiles or those with steepretrognathic profiles or those with steep
mandibular planes.mandibular planes.

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

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

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

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

SELECTION OF CASESSELECTION OF CASES
 Following are the empirical criteria forFollowing are the empirical criteria for
case selection.case selection.
A. SkeletalA. Skeletal
 A mild skeletal Cl II facial pattern.A mild skeletal Cl II facial pattern.
 A decreased lower face height which isA decreased lower face height which is
based on a profile assessment from thebased on a profile assessment from the
nostril to chin point.nostril to chin point.
 Proportionate balance between upper andProportionate balance between upper and
midface heightsmidface heights

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

C. Soft tissueC. Soft tissue
 Competent or potentially competent lips in whichCompetent or potentially competent lips in which
the lip well as capable of stabilizing the upperthe lip well as capable of stabilizing the upper
anterior teeth after correction has taken place.anterior teeth after correction has taken place.
 Preferably a muscular pattern that does notPreferably a muscular pattern that does not
exhibit undue tightness of lips and cheeks.exhibit undue tightness of lips and cheeks.
 D. RespiratoryD. Respiratory
 No nasal obstruction or chronic respiratoryNo nasal obstruction or chronic respiratory
disorderdisorder
 C. EmotionalC. Emotional
 1. Keen patient interest and desire and potential1. Keen patient interest and desire and potential
co-operation form both patient and parentco-operation form both patient and parent

TREATMENT PLANNINGTREATMENT PLANNING
PRETREATMENT CONSIDERATIONSPRETREATMENT CONSIDERATIONS
 Before activator treatment is started –Before activator treatment is started –
forward movement of mandible is checkedforward movement of mandible is checked
to see that it is not blocked by occlusalto see that it is not blocked by occlusal
interferences that makes the correction ofinterferences that makes the correction of
disto occlusion impossible.disto occlusion impossible.
 For example buccal crossbite of upperFor example buccal crossbite of upper
1st premolar impedes the forward1st premolar impedes the forward
movement of the mandiblemovement of the mandible

DIAGNOSTIC PREPARATIONSDIAGNOSTIC PREPARATIONS
 A. Patient complianceA. Patient compliance: It is very essential. It is: It is very essential. It is
very important to assess clinically patient’svery important to assess clinically patient’s
somatic, psychological aspect and motivationsomatic, psychological aspect and motivation
potential.potential.
ObjectiveObjective
 Motivation potential can be enhanced by visualMotivation potential can be enhanced by visual
treatment. Visual treatment objective is creatingtreatment. Visual treatment objective is creating
an “instant correction” in a Cl II malocclusion byan “instant correction” in a Cl II malocclusion by
moving the mandible forward into an anteriormoving the mandible forward into an anterior
more normal sagital relationship so that themore normal sagital relationship so that the
patients sees the potential and objective ofpatients sees the potential and objective of
correction and is more likely to work towards thecorrection and is more likely to work towards the
goal. It also helps the clinician to diagnose andgoal. It also helps the clinician to diagnose and
anticipate whether therapeutic goal is ananticipate whether therapeutic goal is an
improvement.improvement.

Study model AnalysisStudy model Analysis
 Following information can be derived formFollowing information can be derived form
the study model.the study model.
First molar relationship in habitual occlusion.First molar relationship in habitual occlusion.
Nature of midline discrepancy, if anyNature of midline discrepancy, if any
(dentoalveolar non coincidental midlines(dentoalveolar non coincidental midlines
cannot be corrected by activator).cannot be corrected by activator).
Symmetry of dental archesSymmetry of dental arches
Curve of spee is checked to diagnoseCurve of spee is checked to diagnose
whether it can be leveled.whether it can be leveled.
Degree of crowding and dental discrepanciesDegree of crowding and dental discrepancies
are checked.are checked.

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

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

CONSTRUCTION BITECONSTRUCTION BITE
 The construction bite is an intermaxillary wax recordThe construction bite is an intermaxillary wax record
used to relate the mandible to the maxilla in the threeused to relate the mandible to the maxilla in the three
dimensions of space. They are used to reposition thedimensions of space. They are used to reposition the
mandible in order to improve the skeletal inter-jawmandible in order to improve the skeletal inter-jaw
relationship. The bite registration involves repositioningrelationship. The bite registration involves repositioning
the mandible in a forward direction as well as openingthe mandible in a forward direction as well as opening
the bite vertically.the bite vertically.
GENERAL CONSIDERATIONS FORGENERAL CONSIDERATIONS FOR
CONSTRUCTION BITECONSTRUCTION BITE
 In case the overjet is too large, the forward positioning isIn case the overjet is too large, the forward positioning is
done step wise in 2-3 phases.done step wise in 2-3 phases.
 In cases of forward positioning of the mandible by 7-8In cases of forward positioning of the mandible by 7-8
mm, the vertical opening should be slight to moderate i.emm, the vertical opening should be slight to moderate i.e
2-4 mm.2-4 mm.
 If the forward positioning is not more than 3-5 mm, thenIf the forward positioning is not more than 3-5 mm, then
the vertical opening can be 4-6 mm.the vertical opening can be 4-6 mm.

 In taking a construction bite one shouldIn taking a construction bite one should
look at the bite in three different planes oflook at the bite in three different planes of
spacespace
SagitalSagital
VerticalVertical
FrontalFrontal

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

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

 C. Frontal or Midline establishmentC. Frontal or Midline establishment
 midlines of the maxilla and mandiblemidlines of the maxilla and mandible
should coincide when the construction biteshould coincide when the construction bite
is taken regardless of shifting of teeth inis taken regardless of shifting of teeth in
one or both the jawsone or both the jaws

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

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

LOW CONSTRUCTION BITE WITH MARKEDLOW CONSTRUCTION BITE WITH MARKED
MANDIBULAR FORWARD POSITIONINGMANDIBULAR FORWARD POSITIONING::
 This kind of construction bite is characterized byThis kind of construction bite is characterized by
marked forward positioning of the mandible butmarked forward positioning of the mandible but
minimal vertical opening.minimal vertical opening.
 As a rule of thumb the anterior advancement shouldAs a rule of thumb the anterior advancement should
not exceed more than 3 mm posterior to the mostnot exceed more than 3 mm posterior to the most
protrusive position. Vertically the opening is minimalprotrusive position. Vertically the opening is minimal
and is within the limits of the inter-occlusal clearance.and is within the limits of the inter-occlusal clearance.
This kind of activator constructed with marked sagittalThis kind of activator constructed with marked sagittal
advancement but minimal vertical opening is called anadvancement but minimal vertical opening is called an
“H activator”. The H activator is indicated in a patient“H activator”. The H activator is indicated in a patient
with class II, division 1 malocclusion having awith class II, division 1 malocclusion having a
horizontal growth patternhorizontal growth pattern

High construction bite with slight anteriorHigh construction bite with slight anterior
mandibular positioning:mandibular positioning:
 The mandible is positioned anteriorly by 3-5 mmThe mandible is positioned anteriorly by 3-5 mm
only and the bite is opened vertically by 4-6 mm or aonly and the bite is opened vertically by 4-6 mm or a
maximum of 4 mm beyond the resting position. Thismaximum of 4 mm beyond the resting position. This
kind of activator constructed with minimal sagittalkind of activator constructed with minimal sagittal
advancement but marked vertical opening is called aadvancement but marked vertical opening is called a
“V activator”. The V type of activator is indicated in“V activator”. The V type of activator is indicated in
a Class II, Division 1 malocclusion having a verticala Class II, Division 1 malocclusion having a vertical
growth pattern.growth pattern.

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

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

FABRICATIONFABRICATION
 After the construction bite is taken and checked on the patient andAfter the construction bite is taken and checked on the patient and
rechecked on stone working models, the working models arerechecked on stone working models, the working models are
mounted on the fixator.mounted on the fixator.
 The FIXATOR allows upper and lower parts to be made separatelyThe FIXATOR allows upper and lower parts to be made separately
and both parts are united in the correct construction bite on theand both parts are united in the correct construction bite on the
fixator.fixator.
 The extensions of acrylic body and flanges are drawn on the upperThe extensions of acrylic body and flanges are drawn on the upper
and lower working models. The wire elements can also be drawnand lower working models. The wire elements can also be drawn
 Each labial bow consist of a horizontal middle section, two verticalEach labial bow consist of a horizontal middle section, two vertical
loops, and wire extensions through the canine or deciduous firstloops, and wire extensions through the canine or deciduous first
molars and they are embedded din the acrylic body.molars and they are embedded din the acrylic body.
 The horizontal portions crosses above convexity in deep bite andThe horizontal portions crosses above convexity in deep bite and
below convexity in open bite.below convexity in open bite.
 The bow is active or passive and influences soft tissue withoutThe bow is active or passive and influences soft tissue without
touching teeth.touching teeth.
 The wire usually used is 0.8 mm round stainless steel..The wire usually used is 0.8 mm round stainless steel..

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

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

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

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

 . In case. In case intrusionintrusion
posteriors is neededposteriors is needed
then only the cuspthen only the cusp
tips are loaded withtips are loaded with
acrylic. The fossaeacrylic. The fossae
and fissures are freeand fissures are free
of acrylic. Thisof acrylic. This
applies a verticalapplies a vertical
intrusive force on theintrusive force on the
molars.molars.

 Extrusion of the incisorsExtrusion of the incisors,,
the lingual surface isthe lingual surface is
loaded above the area ofloaded above the area of
greatest convexity in thegreatest convexity in the
maxilla and below themaxilla and below the
area of greatest convexityarea of greatest convexity
in the mandible. Thein the mandible. The
extrusive movement canextrusive movement can
be enhanced by placing abe enhanced by placing a
labial bow above the arealabial bow above the area
of greatest convexity i.eof greatest convexity i.e
in the gingival 1/3 of thein the gingival 1/3 of the
labial surfacelabial surface

 In case of molars,In case of molars,
extrusionextrusion is broughtis brought
about by loading theabout by loading the
lingual surface abovelingual surface above
the area of greatestthe area of greatest
convexity in maxillaconvexity in maxilla
and below the area ofand below the area of
greatest convexity ingreatest convexity in
mandiblemandible

TRIMMING OF THETRIMMING OF THE
ACTIVATOR FORACTIVATOR FOR
SAGITTAL CONTROLSAGITTAL CONTROL
 Protrusion of incisorsProtrusion of incisors: In: In
case the incisors becase the incisors be
protruded, lingual surfaceprotruded, lingual surface
of the teeth is loaded withof the teeth is loaded with
acrylic and a passiveacrylic and a passive
labial bow is given that islabial bow is given that is
kept away from teeth tokept away from teeth to
prevent perioral softprevent perioral soft
tissues contacting thetissues contacting the
teethteeth

 Retrusion of incisorsRetrusion of incisors::
The acrylic is trimmedThe acrylic is trimmed
away form the lingualaway form the lingual
surface and an activesurface and an active
labial bow is used tolabial bow is used to
bring about retrusionbring about retrusion
of the incisorsof the incisors

 Movement of posterior teeth in sagittalMovement of posterior teeth in sagittal
plane:plane: The teeth in the buccal segmentThe teeth in the buccal segment
can be moved mesially and distally to helpcan be moved mesially and distally to help
in treating Class II and Class IIIin treating Class II and Class III
malocclusion. In Class II malocclusion,malocclusion. In Class II malocclusion,
the maxillary molars are allowed to movethe maxillary molars are allowed to move
distally while the mandibular molars aredistally while the mandibular molars are
allowed to move mesially by loading theallowed to move mesially by loading the
maxillary mesioligual surface andmaxillary mesioligual surface and
mandibular distolingual surfacemandibular distolingual surface

MESIAL MOVEMENT
OFMOLARS
DISTAL MOVEMENT OF MOLARS

Movement Of Teeth InMovement Of Teeth In
Transverse PlaneTransverse Plane
 It is possible to trimIt is possible to trim
the activator to stimulatethe activator to stimulate
expansion of buccalexpansion of buccal
segment This is done bysegment This is done by
contact of acrylic on thecontact of acrylic on the
lingual surfaces of thelingual surfaces of the
teeth to be movedteeth to be moved
transversely. But bettertransversely. But better
expansion is possible byexpansion is possible by
placing a jack screw inplacing a jack screw in
the activatorthe activator

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

PROPULSORPROPULSOR
 Designed byDesigned by MuhlemannMuhlemann
 Refined byRefined by HotzHotz
 It is a hybrid appliance with features of both he monoblocIt is a hybrid appliance with features of both he monobloc
and the simple oral screen. Construction bite is smallerand the simple oral screen. Construction bite is smaller
compared to activator with the mode of action same ascompared to activator with the mode of action same as
that of activator.that of activator.
DesignDesign
 Has no wire components and made completely withHas no wire components and made completely with
acrylic. The acrylic between occlusal surface of the 1stacrylic. The acrylic between occlusal surface of the 1st
molar stabilizes appliance, with improvement inmolar stabilizes appliance, with improvement in
intermaxillary relations. The appliance is reactivated byintermaxillary relations. The appliance is reactivated by
adding acrylic in the upper anterior segment.adding acrylic in the upper anterior segment.
IndicationIndication
 In cases of maxillary dentoalveolar protrusionIn cases of maxillary dentoalveolar protrusion
AdvantageAdvantage
 Light weight – minimum bulk of applianceLight weight – minimum bulk of appliance
 It effects changes in alveolar process and teeth inIt effects changes in alveolar process and teeth in
maxillary anterior segment.maxillary anterior segment.

PROPULSARPROPULSAR

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

ELASTIC OPENELASTIC OPEN
ACTIVATORACTIVATOR

WUNDERER’S MODIFICATIONWUNDERER’S MODIFICATION
 Designed byDesigned by WundererWunderer
 IndicatedIndicated C1 III malocclusionC1 III malocclusion
DesignDesign
 Activator split horizontally into an upper halfActivator split horizontally into an upper half
and lower half which are connected with aand lower half which are connected with a
screw situated in an extension of mandibularscrew situated in an extension of mandibular
portion behind the maxillary incisors. Openingportion behind the maxillary incisors. Opening
of the screw causes maxillary portion to moveof the screw causes maxillary portion to move
anteriorly and a reciprocal back thrust onanteriorly and a reciprocal back thrust on
mandible is effected. Retention is frommandible is effected. Retention is from
occlusal surface of buccal segment. Theocclusal surface of buccal segment. The
screw was designed by Weisescrew was designed by Weise

WUNDERERS MODIFICATIONWUNDERERS MODIFICATION

BOW ACTIVATOR OF A.M. SCHWARZBOW ACTIVATOR OF A.M. SCHWARZ
 Designed byDesigned by A.M. SchwarzA.M. Schwarz
DesignDesign
 Consists of an upper half and lower half connected with anConsists of an upper half and lower half connected with an
elastic bow.elastic bow.
 Step by step forward positioning can be doneStep by step forward positioning can be done
 Transverse mobility can be broughtTransverse mobility can be brought
 The bow can be activated only on one side for correction asThe bow can be activated only on one side for correction as
unilateral distoocclusionunilateral distoocclusion
 Independent maxillary or mandibular expansions can be effected byIndependent maxillary or mandibular expansions can be effected by
incorporation of a screw.incorporation of a screw.
DisadvantagesDisadvantages
 Easily distortedEasily distorted
 Difficulty in adapting loopsDifficulty in adapting loops
 Breakage of bow portionBreakage of bow portion
IndicationsIndications
 Treatment of CI II div I malocclusion in deciduousTreatment of CI II div I malocclusion in deciduous
dentitiondentition

BOW ACTIVATORBOW ACTIVATOR
www.indiandentalacademy.com

THE KARWETZKY MODIFICATIONTHE KARWETZKY MODIFICATION
 Design byDesign by KarwetzkyKarwetzky
DesignDesign : Similar to Bow activator of Schwarz but with improved: Similar to Bow activator of Schwarz but with improved
techniquetechnique
 Consists of maxillary and mandibular active plates joined by a’U’Consists of maxillary and mandibular active plates joined by a’U’
bow in 1st permanent molar region. Acrylic covers lingual tissue,bow in 1st permanent molar region. Acrylic covers lingual tissue,
gingivae, teeth and also occlusal aspects of all teeth.gingivae, teeth and also occlusal aspects of all teeth.
 Construction bite is done with mandible in postural rest positionConstruction bite is done with mandible in postural rest position
 Forward position of mandible is done in stagesForward position of mandible is done in stages
 The Labial bow is made from 0.9 mm round stainless steel wire, forThe Labial bow is made from 0.9 mm round stainless steel wire, for
retentionretention
 Various other elements could be incorporatedVarious other elements could be incorporated
 Acrylic between upper and lower parts are made flat and joined by aAcrylic between upper and lower parts are made flat and joined by a
‘U’ bow made of 1.1 mm round stainless steel wire.‘U’ bow made of 1.1 mm round stainless steel wire.
 Depending upon the placement of ends of the ‘U’ bow – three typesDepending upon the placement of ends of the ‘U’ bow – three types
of Karwetzky activator are created.of Karwetzky activator are created.
 Type IType I -- for CI II Div 1 malocclusionfor CI II Div 1 malocclusion
 Type IIType II -- for CI III malocclusionfor CI III malocclusion
 Type IIIType III -- used in facial asymmetry and lateralused in facial asymmetry and lateral
crossbitecrossbite

KARWETZKY MODIFICATIONKARWETZKY MODIFICATION

Activator and its modifications

Activator and its modifications

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (18)

Similar to Activator and its modifications

Similar to Activator and its modifications (20)

More from Indian dental academy

More from Indian dental academy (20)

Recently uploaded

Recently uploaded (20)

Activator and its modifications