Activator and its modifications /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


Kingsley(1879) –
“ jumping the bite ”
Robin 1902- Monobloc.
Viggow Andresen (1908)
Andresen and Haupl (1955)
- Activator.


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MECHANISM OF THE STRETCH (OR) MYOTATIC
RELEX:
How does it work?
Monosynaptic?
Postural rest position?
Isometric contractions?





Harvold and Woodside ,Herren ,Selmer-Olsen
viscoelastic properties of soft tissue
Rationale?



Bite registered for 3mm to 4 mm distal to the most protruded
position is to avoid the possibility of initiating Golgi tendon organ
activity and thus eliminate any undesirable myotatic reflex



Witts supported a combination of isometric muscle contractions and
viscoelastic properties being responsible for the forces delivered by
the activator and used intermediate construction bite height.



Eschler attributed the muscle contraction to proprioceptive stretch
reflexes and observed the occurrence of both isometric and isotonic
contraction with use of the activator.




Forces employed in activator therapy are categorized as,



The growth potential, including the eruption and migration of
teeth, produces natural forces; these can be guided, promoted
and inhibited by the activator.



Muscle contractions and stretching of the soft tissues initiate
forces when the mandible is relocated from its postural rest
positions by the appliance. Whereas forces may be functional
in origin, the activation is artificial.


Artificially functioning forces can be effective in three planes
Sagittal plane:


Mandible is propelled down and forward.



muscle force is delivered to the condyle and a strain is
produced



Slight reciprocal force can be transmitted to the maxilla during
this maneuver.
Vertical Plane:






Teeth and alveolar processes are either loaded with or relieved
of normal forces.
if construction bite is high, a great strain is produced
if transmitted to the maxilla, these forces can inhibit growth
increment and direction and influence the inclination of the
maxillary base.

Transverse plane:


Forces can be created with midline corrections.



Various active elements like springs, screws can be built in to
the activator to produce an active biomechanical type of force
application.
The mode of force application, magnitude and direction depend
on the three dimensional dislocation of the mandible, which is
determined by the construction bite.




The original appliance
consists of a combined
upper and a lower plate at
the occlusal plane only onewire elements was used i.e.
A labial arch for upper
anterior teeth.


♫

♫

Edge-to-edge incisal
relationship to stimulate the
mandibular growth. The
construction bite for the
activators was taken with
the lower jaw in class I or
over corrected class I molar
relationships
Vertical opening not
beyond rest position of the
mandible




Skeletal ChangesClass II Div I)



The Skeletal effect of the activator depends on growth
potential.



Two divergent growth vectors propel the jaw bases in an
anterior direction.



The sphenoccipital synchordrosis moves the cranial base and
nasomaxillary complex up and forward



The condyle translates the mandible in a downward and
forward direction.



In contrast to primary cartilages (epiphyses, sphenoccipital
synchondroses) a condylar growth is regulated to a high degree
by local exogenous factors.



Petrovic - forward posturing of the condyle activates the
superior head of LPM and condylar growth.



The activator can, to a limited degree control the upper growth
vector supplied by the sphenoccipital synchondrosis, which
moves the maxillary base forward.



Total anterior facial height increases with lower facial height
increased by more than twice as much.




The Retrodiscal pad controls mandibular growth in two ways.



The vascular component controls the condylar cartilage growth
rate and endochondral ossification rate.



An increase in interactive activity of the retrodiscal pad
produces an increase in condylar cartilage growth and
endochondral ossification.






An increase in interactive
activity of the retrodiscal
pad -accentuation of the
ramus posterior concavity
and a local increase in bone
apposition and the number
of negative charges at the
ramus posterior concave
surface.
Accentuation of the ramus
anterior convexity and local
increase in bone resorption
and number of positive
charges at the ramus
posterior convex surface.www.indiandentalacademy.com

♫

The improvement in sagittal occlusal relationship was due
about equally to skeletal and dental charges.

♫

Overjet correction- mandibular growth exceeding maxillary
growth and distal movement of the maxillary incisors.

♫

Class II molar correction -mandibular growth exceeding
maxillary growth and mesial movement of the mandibular
molars.


♫

Inhibits maxillary growth, move the maxillary incisors and
molars distally and move the mandibular molars and incisors
mesially.

♫

Lingual tipping of maxillary incisors and labial proclination of
the mandibular incisors related to significant reductions in
overjet. Thus passive upper labial wire of activator intended to
avoid upper incisor tipping and acrylic cap on the incisal third
of the lower incisors can prevent proclination




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





Retraction of upper anterior teeth, followed by a similar
dropping back of the upper lip, improve a protrusive profile.
Stoner’s and associates found that,
Soft tissue improvements were produced by four principal
changes.
The gross movement of incisors
A reduction in the curl of the lower lip.
Vertical opening of the chin.
Forward positioning of the chin.
Reduction of overjet has the effect of uncurling both lips,
which enables the lips to hold together without undue effort.




Class II Div 2 malocclusions
The upper central incisors are tipped labially by springs at the
incisal margin.



The labial bow exerts lingual pressure at the labial gingival
margins to achieve lingual root movement.(Herren activator
preferred)



Open bite and Cross bite?


REVERSE ACTIVATOR




Construction bite
Bite is taken by
retruding the jaw. The
extent of vertical
opening depends on
the retrusion possible.








The mandibular incisor hit prematurely in an end-to-end
contact, and the mandible then slides anteriorly to complete the
full occlusal relationship.
The vertical dimension of construction bite is opened far
enough to clear the incisal guidance, which eliminates the
protrusive relationship with mandible in centric relation.
The prognosis for pseudo class III malocclusion is good,
especially if therapy is started in early mixed dentition. In early
mixed dentition period, skeletal manifestation are not usually
severe, since the malocclusion develops progressively.






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








The acrylic was relieved on
lingual surface of
mandibular incisors and
maxillary incisors
supported with close
contact.
Maxillary incisors are
tipped labially with small
screws, wooden pegs (or)
lingual springs (or) by
application of gutta percha
lingual to incisors.
Concurrently force was
eliminated in the upper
arch with maxillary lip pads
to allow the fullest extent
of growth potential



Changes



Articular angle increased because of posterior positioning
mandible



Mandibular plane angle slightly opened.



SNA increased



ANB increased



Maxillary incisor tipped labially



Mandibular incisors tipped lingually.




In a skeletal class III malocclusion with a normal path of
closure from postural rest to habitual occlusion, the treatment
with functional appliance is not always possible.



The true mandibular prognathism is undoubtedly one of the
most difficult conditions to treat orthodontically.









Harvold (1974) and Wood side (1973)
Wood side opens the mandible with the construction bite as
much as to 10 – 15 mm beyond postural rest vertical
dimension.
The forces generated by this extreme bite registration (10-15
mm) represent combination of forces generated by swallowing,
biting, activation of the myotatic reflex in the stretched muscles
of mastication and the power delivered through the viscoelastic
properties of stretched muscles, tendon tissue, Skin and
musculature.
This appliance works using potential energy.


Class II Div I with increased
LAFH (environmental factors)
 Actual adaptation of the maxilla to
the lower dental arch.
 Partially achieved by retroclination
of the maxillary base.
 Differential eruption of teeth
 good vertical control of both
dental arches and only minor
forward tipping of the lower
incisors.




Harvold has also emphasized the concept of the “Functional
occlusal place” and the role played by its manipulation in the
successful correction of class II malocclusions. This plane
represents the functional table of occlusion in the first
permanent molar, second molar and first premolar areas.



The level and inclination of the functional occlusal plane is the
result of the neuromuscular, growth and developmental forces
acting on the dentition.



The correct manipulation of the functional occlusal plane
involves the inhibition of maxillary buccal segment eruption,
which normally follows a downward and forward curvilinear
eruption path.



At the same time mandibular buccal segment are permitted to
erupt vertically in harmony with the vertical growth of the
lower face.



Because the mandibular molar erupt roughly at right angles to
the functional plane, change from class II malocclusion to class
I occlusion is facilitated.







The principle-complete
opposition to the kinetic
concept of Andersen –
Haupl appliance.
By overcompensating the
ventral position of the
mandible in the
construction wax bite.
By seating the appliance
firmly against the maxillary
dental arch by means of
arrowhead clasps similar to
those used in active plates.



Graber coined the term “myotonic appliance”.



The mandible is prevented from assuming the natural restposition – thus if the rest position prescribed by activator does
not coincide with natural rest position, the retractive
musculature is stretched.



In Class II malocclusion, the construction bite of the Herren
activator dislocates the mandible ventrally, parallel to occlusal
plane by a total of 8mm or more. The improvement of post
normal occlusion was directly related to the amount of
mandibular displacement, in taking the construction wax bite.



When the activator is inserted, the mandible is purposely
carried forward until it is possible to bite completely in to the
positioning splint.



The mandible is kept from being retracted because the
activator takes the load of these forces and transmits them in
an occipital direction, to the maxillary dental arch.



Since “action equals reaction” a force of equal magnitude but
opposite direction acts against the mandibular dental arch.




The force acts continuously only as long as the Herren or
L.S.U activator is in place i.e. 9 – 10 hrs during night.



The activator holds the retractive musculature of the mandible
passively stretched.



More over, the activator inserted between the teeth and
tongue act as a shield that keeps the tongue away from the free
way space, which enables the eruption of the teeth, provided
that the acrylic occlusal stops of posterior teeth are ground
away from the appliance.




According to rat studies reported by Petrovic et al, the action
of Herren type of activator comprises a two-stage effect.



During the time the activator is worn, the protrusive position
of the mandible (caused by construction bite) causes reduced
increase in length of the lateral pterygoid muscle and at the
same time forms a new sensory “engram” for positioning of
the mandible.



This causes the mandible to function in a more forward
position during the period when the activator is not worn.



The forward positioning of the mandible by the contraction of
the lateral pterygoid muscle, when the activator is not being
used causes an accelerated growth rate of condylar cartilage.


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Twin arrowhead clasp.
Expansion screws.
Lingual springs to correct moderate incisal irregularities.
Extension of the flanges towards the floor of the mouthmandibular anchorage(lower labial bow if needed)
Horizontal slot in maxillary incisors for comfort.
No pathologic changes in TMJ.
Asymmetrical Class II Div I- Expansion screws with
asymmetric cuts in the appliance




To correct the class II malocclusion in an expedient, reliable
and economic way.



To retard forward growth of the maxilla.



To reposition the mandible through mandibular growth, either
in a horizontal or in a vertical direction.



To achieve these performances in the transitional as well as in
the early permanent dentition, independent from the pubertal
growth peak in body height( by over compensating)



To provide a high rate of stability of the treatment results after
several years out of retention.



Herren activator holds the maxillary dental arch preventing the
maxillary forward growth, the mandibular dental arch carried
forward together with its basal arch.



The treatment results in,



Increase of SNB angle



Decrease of ANB angle



Mandible length increased (distance measured from middle of
the external ear opening & gnathion– from cephalometric head
films)



Change in position of the mandible, either a more forward or a
more downward direction.




Dentoalveolar compensation (distal movement of upper
molars, mesial movement of the lower molars) appeared to be
inversely related to skeletal adaptation.



The correction of molar relationship occurred to 55% by
skeletal changes.




Herren advocated
expansion
screws,lingual springs
for correction of
retruded incisors and
guiding spurs to relieve
minor crowding.




Retention period - (due to over compensation) 15 months after
normal (neutral) dental arch relationships is achieved and
overjet is corrected.



This normal dental arch relationship is maintained in taking the
construction wax bite for a retention activator. However the
mandible is carried forward by about 2 mm, beyond neutro
occlusion to compensate for the increase in overjet that occurs
as a result of rotation of the mandible around the condylar
hinge axis when a vertical inter occlusal clearance of 4 – 6 mm
is constructed.




If, treatment started too an early age, partial relapse occur after
retention. It is recommend to start treatment, when premolars
have erupted.



Corrections of Antero-posterior basal discrepancy, resulting
from this therapy, were shown to be stable even 5 years after
the end of retention.








The upper and lower halvesconnected-elastic bow.
It is thus possible to change
the relationship of the upper
and lower halves of the
appliance.
With the treatment of class II
division 1 malocclusion,
beginning can be made with a
small forward positioning,
increasing this gradually by a
periodic adjustment as
recommended by Frankel.




Taatz (1971) ,



appliances specially suited for treatment of class II division 1
malocclusion in the deciduous dentition.



Small children will have the appliance in place for longer
periods of time because they sleep more hours.



Young patients seem to adapt more easily to bringing the
mandible forward gradually than to a sudden forward
positioning.



Mixed dentition treatment is probably better from both a
growth response and a patient compliance standpoint.








Resembles bionator
customary labial wire of
the activator is used, as well
as most of other simple
appurtenances of this and
other myofunctional
appliances including the
coffin spring.
Construction bite?
Advantages?



Spurs added to prevent the mesial movement of molars during
the shedding of deciduous molars.



Can be combined with fixed appliance therapy.



Headgear tubes can be incorporated for extra oral force.






maxillary and mandibular
active plates, joined by a
U bow in the region of
the first permanent
molars.
In addition to acrylic
covering of the lingual
tissue aspects, gingiva and
teeth, plates also extend
over the occlusal aspects
of all teeth.




The height of the construction bite is that of interocclusal
space or clearance with the mandible in postural rest for the
karwetzky appliance.



Thus space varies with the malocclusions.




U-bow :1 long leg ; 1 short leg .The shorter leg is imbedded
in the upper appliance, whereas the longer leg is attached to
lower plate.



Combinations of different types of sagittal or transverse
screws, labial wires and springs enhance the basic appliance
action.



U-bow activator combined with fixed appliance when there are
severe rotations or there is need for selective extraction and
uprighting of teeth contiguous to extraction site.



Orthognathic surgery in adults like corticotomies and sub
apical resections, u bow activator has the potential for use.






hybrid appliance.
Advantage?
No wire configuration are used with propulsor, acrylic
connecting the upper buccal segment to the lower lingual
flange also serves as occlusal support to stabilize the appliance



As treatment progresses this acrylic is removed progressively to
allow for unhindered eruption of molars and resultant
reduction of the deep overbites, if exists.



Also if selective eruption is desired to reduce the class II buccal
segment relationship by upward and forward eruption of the
lower teeth while preventing forward eruption of upper teeth
by removing acrylic in the opposing lower molar area leaving
them free.



The compliance is usually good because of the lightweight
&minimum bulk of the appliance.






Advantage of the Bionator with some of those of the original
Andersen – Haupl appliance.
Parts?



Metzelder changes however do have some advantages.



Appliance is easier to make.



It may carry all the appurtenances described for the activator.



These include



The jackscrew for expansion



Petrik finger spring for moving individual teeth. (upper&lower
canine after extraction).



Springs for labial tipping of lower incisors.



Proclining springs for Class II Div 2 cases.


Open Bite

Class III








The elastic open activator
resemble the Bionator, with
acrylic anteriorly and with
more wires.
The Bionator though free
movable in the oral cavity,
is carefully stabilized on
posterior occlusal surfaces
or the lower incisors as the
occasion demands.
completely lacks such
stabilization and thus its
vertical mobility in the
mouth is unimpeded.



The appliance will react to most of the tongue
movements and so it must "come to terms" with the
tongue.



In this manner, a great number of impulses are
transmitted to the teeth, serving as the basis for
transformative changes.








bilateral acrylic parts, an
upper and lower labial wire,
a palatal arch and guiding
wires for upper and lower
incisors.
The acrylic parts extend
from the canine posteriorly
to the point just behind the
first or second permanent
molar if it is present.
The acrylic is quite thin in
order to leave the largest
possible space for the
tongue. Stabilization of
acrylic position is
accomplished by means of
contact with the lingual
surfaces of maxillary and
mandibular canines.



Relieve the crowding



To relieve the crowding of
maxillary central incisors,
half of maxillary labial wire
was omitted, with the other
half being used to engage
the incisor. On this side,
the guiding wire was used
only for the opposite side.




Space maintainer



For example, the second
deciduous molar has been lost
prematurely. Its space is
maintained by an extension of
contiguous acrylic; with the
flat acrylic surface .a double
wire is placed mesial to first
molar and distal to first
deciduous molars.



Class II division 1
malocclusion



Construction bite



With an overjet as large as
10mm, it is usually possible
to get the incisors in to an
edge-to-edge bite.



No TMJ problems, even
after such extensive
forward positioning of the
mandible.



Class II division 2 malocclusion or Deckbiss



Class III mal occlusion



Construction bite



Edge to edge bite of the
incisors or most retruded
mandibular position.



The maxillary labial wire
carries lip pads similar to
those of Frankel appliance.








Unilateral cross bite
Construction bite
Bite with slight over
correction of the midline is
advantageous.
The acrylic closely follows
the teeth, except in
mandibular part that
approximates the teeth in
cross bite.








Stockfish- Elastic activatorsemi double plate appliance
with latex tubing between
the upper and lower
components to stimulate
function.
Elastic appliance-isotonic
muscle contractions-less
force magnitude-less
effective.
Longer wearing timeefficient.



The appliance is split
horizontally with the upper
and lower portion
connected by a screw that is
embedded in an acrylic
extension of the
mandibular portion behind
the maxillary incisors.




As the screw is opened the maxillary portion moves anteriorly
with a reciprocal posterior thrust acting on the mandibular
dentition. Occlusal surfaces of the posterior teeth are covered
with acrylic to enhance retention.



The construction bite for class III case is taken in most
retruded or hinge axis position of the mandible with the incisal
edges 2mmor 3mm apart.



In addition to maxillary labial bow a mandibular labial bow
used to guide the mandible distally as they occlude.



A cervical headgear with a long
outer bow is used.



The inner bow is inserted into
buccal tubes attached to the
maxillary first molars and the
outer bow is adjusted to about 5°
below the inner bow.



This produces a predominantly
distal force through the center of
resistance of the molar teeth and
a lesser vertical extrusive force
component .



The neck strap produces a force of approximately 400 grams,
measured unilaterally.



The activator used is based on the design and application
described by Harvold and modified for use with a cervical
headgear applied to the maxillary first molars.



Brachyfacial and mesofacial types responded most favorably to
this combination.



This combination is contraindicated in dolichofacial type,
because it results in mandibular clockwise rotation



Duration of wear- 14 continuous hours a day.




Pfeiffer and Grobety supported combination activator —
cervical headgear therapy., for two reasons:




to extrude maxillary molars, and
to apply orthopedic traction to the maxilla and an activator to
induce orthopedic mandibular changes, restrain maxillary
growth, and cause selective eruption of teeth.



Drawbacks?






The inner face bow is
completely embedded in the
labial side of the maxillary
splint, and the short outer
arms are bent upward
depending on the desired angle
to the occlusal plane.
Torquing springs, jackscrews,
lip pads Can also be
incorporated.











Vertical control
the untrimmed interocclusal acrylic
acts as a bite block.
the inclination of the outer face
bow precise control over the
direction of force, according to the
following principles:
A force passing through the center
of resistance produces pure
translation in the direction of the
force.
A force passing at a distance from
the center of resistance generates a
moment, with a combined effect
of rotation (from the moment) and
translation (from the force).



Duration of wear



Active treatment usually takes about 10 months, with the
appliance worn at night and for a few hours during the day (1214 hours total per day).




Stockfish-Kinetor ( elastic activator ) with high pull headgear
attached to the buccal tubes in molar bands.



Hickam- Extraoral force applied to the hooks soldered to the
labial bow of the activator- control of the downward and
backward rotation of the maxilla and have a restrictive effect
on the horizontal and vertical maxillary basal and
dentoalveolar components.








Neville (1987)- maxillary
splint, with an anterior
expansion screw and an
incisor torquing spring .
Lingual pads for
mandibular growth
enhancement are slotted
into the splint, which also
carries detachable side and
labial screens.
The appliance system offers
considerable flexibility in
design, much as with an
edgewise approach.



The force is intermittent. This allows dynamic and rhythmic
muscle forces to act in such a manner that the appliance acts
by kinetic energy.



The direction of the desired force is determined by selective
grinding of the acrylic surfaces that contact the teeth.



The magnitude of force is determined by the amount of acrylic
that contact the teeth.



The acrylic surface that transmit the force and contact the
teeth are called guide planes



Evaluation?









INTRUSION OF
TEETH:
Incisors:
Can be achieved by loading
the incisal edges of teeth,
the labial bow should be
below the area of greatest
convexity or on incisal
third.
Molars:
Performed by loading only
the cusps. The pits and
fossas are cleared to
eliminate any possible
incline plane effect



Incisors:



Requires loading the acrylic
above the area of greatest
concavity in the maxilla and
below this area in the
mandible. Although not
effective can be enhanced
by placing the labial bow
convexity.



Indicated in Open bite
problems(finger sucking)



Molars:



Requires loading the acrylic
convexity in the maxilla and
below this area in the
mandible.



Indicated in deep bite cases.



Simultaneous extrusion of
both the upper and lower
buccal segments-no
adequate conttrol.








Incisors can be
protruded by loading
their lingual surface and
screening lip strain by
passive labial bow.
Entire lingual surface
loaded
Incisal third of lingual
surface is loaded.




Acrylic is trimmed from the back of incisor



Active Labial bow is incorporated






Distalization:
the Guide planes are
loaded in the mesio
lingual surfaces.
Indicated in class II
cases.




Mesial movement:



Can be achieved by loading the disto - lingual
surfaces.



Indicated for the upper arch in class III cases.




To achieve transverse
movement the lingual
acrylic surfaces opposite
to the posterior teeth
must be in contact with
teeth.



More effective expansion
can be achieved using
Jack screws.




If upper incisors are to be retruded and the labial bow is activeacrylic capping needed to prevent extrusion.



Lower incisor capping needed to prevent lower incisor
proclination.



Selective trimming of the acrylic that prevents mesial
movement of the upper buccal segments and enhances mesial
movement of the lower buccal segment- Class II correction.




The upper incisors are loaded for protrusion and labial bow
passive.



Lip pads used instead of labial bow to stimulate basal maxillary
development.



Lower incisors are retruded-acrylic ground lingually ,labial bow
active.



Upper posterior teeth guided mesially and lower posterior
teeth guided distally- Class III correction.




Deep bite cases: The incisors are guided for intrusion and
molars for extrusion .The labial bow active and contacts the
incisal third.



Open Bite cases: The incisor area trimmed for extrusion and
the molar area is intruded. The labial bow active and contacts
the gingival third.





appliance cannot be used by itself to correct crowding.
The appliance is not used in correction of Class I problems of
crowded teeth caused by disharmony between tooth size and
jaw size



Although the activator is effective in correction of overbite, it
does not routinely achieve such correction through the
intrusion of incisor teeth, but rather it permits the eruption
teeth in the buccal segments.



Because the teeth in the buccal segments are permitted to
follow their normal eruption paths and the incisor teeth are not
permitted to erupt; the effect of intrusion is achieved without
actually intruding the incisor teeth.



It is more likely that successful activator treatment coincides
with normal periods of active mandibular growth



Excessive LAFH and extreme vertical growth pattern.



Excessive procumbent lower incisors.



Nasal stenosis or chronic untreated allergy.



Non growing individuals.


Thought for the Day..!

Thank you
Leader in continuing dental education


Activator and its modifications /certified fixed orthodontic courses by Indian dental academy

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