Activator

Activator
Presented by : Ahmed Saeed Baattiah
Under supervision of:
Prof.Dr.Maher Fouda

 Definition
 History And Evolution Of Activator
 Indication
 Contra indication
 Advantage
 Disadvantage
 Components of the Activator
 Mode of Action of Activator
 Modifications of Activator
 Activator therapy
 Case Reports
 References
Van Beek Activator
Harvold-Woodside Activator
Teuscher Activator

Definition:
*Activator is a loose fitting appliance which was designed by
Andreasen and Haupl to correct retrognathic mandible.
*The appliance opens the bite, and the mandible is advanced for Class ll
correction .

History And Evolution Of Activator
 1879 -Norman Kingsley - introduced ( jumping of the bite) to correct
sagittal relationship between upper and lower jaws .
 1902- Pierre Robin– first practitioner to use functional jaw
orthopedics to treat a malocclusion -Monoblock-- in children with
glossoptosis Syndrome .

 1908 - Viggo Andresen (Denmark ) - developed a loose fitting
appliance on his daughter as a retainer during summer vacations
which gave remarkable results . He called it Biomechanical
Retainer
 Karl Haupl (Germany) – explained how functional appliances
work through the activity of the orofacial muscles
 Then the activator develop in Norway by Andresen in the 1920 ,
was the first functional appliance to be widely accepted .

NOW
WHAT ARE INDICATIONS OF ACTIVATOR ??

INDICATIONS
Various types of activators have been devised for the
treatment of various conditions like:
• Class II division I malocclusion
• Class II division II malocclusion after aligning the incisors
• Class III malocclusion – reverse activator is given
• Class I open bite malocclusion
• Class I deep bite malocclusion
• For post-treatment retention
• Children with decreased facial height
Van Beek activator
SKEL activator -Ruhland type II-2

CONTRAINDICATIONS
• Cannot be used in correction of Class I problems of crowded teeth where there
is disharmony between tooth size and jaw size
• Cannot be used in children with excess lower facial height
• Cannot be given in cases with lower proclination
• In case of nasal stenosis
• In non-growing individuals
Headgear-activator

ADVANTAGES
• Uses existing growth
• Minimal oral hygiene problems
• Appointments usually short
DISADVANTAGES
• Requires good patient co-operation
• Cannot produce precise detailing and finishing of occlusion.
Posterior view of Van Beek activator
SKEL activator -Ruhland type II-1

COMPONENTS OF THE ACTIVATOR
Basic activator
Labial bow : The wire used is spring hardened 0.9 mm stainless steel. It consist of
horizontal middle sections, two vertical loops and wire extensions through the
canine-deciduous first molar embrasure into the acrylic body.
Labial view of the Andresen appliance. Buccal view of the Andresen appliance.

Acrylic portion : This can be fabricated in cold cure acrylic directly on
the models or a wax matrix can be made first and then invested in the
flask
Andresen Appliance - lingual /
palatal view.
Andresen Appliance with
upper model removed.
Andresen Appliance with upper
model removed.

Mode of Action of Activator
When the activator is worn , mandible is held forward and the muscles of mastication are
stretched beyond their rest position of postural tonus.
It has been suggested that this has two effects :
1. The mastication exert a backward force on the mandible to return to their resting position .
This results in a forward force being exerted on the mandibular teeth and a backward force
on the maxillary teeth . It is an example for intermaxillary traction .
Elastic open activatorRigid open activator

2. This forward postural position induces growth at the mandibular condyles and
temporomandibular joint fossa , which effectively the length of the mandible and basal bone
relationship .
To summaries :
 We get skeletal and Dento alveolar changes as a result of the activator .
 Skeletal changes are explained as above and Dento alveolar changes are due to trimming of the
activator .
Harvold-Woodside activatorLip bumper activator Harvold-Woodside activator - class III

The Herren activator
Modifications of activator
Elements: Labial bow 0.8 mm spring hard.
Function: Modification of the muscular effect through an over dimensional opening of the occlusion.
Description: The over dimensional vertical opening of the occlusion, which is intended to alter the
muscular activity, is characteristic for this appliance.
The elements are bent as in the traditional activator
and a wax collar is fixed for the limitation of the
acrylic.

The vertical opening for the Herren activator is 8 to
10 mm, determined by the construction bite and
then set in the fixator.
The design of the appliance of the finished activator
does not differ from the classic activator.

The headgear activator according to van Beek
Elements: Headgear 1.2 mm spring hard
Function: Treatment of malocclusions class II-1
Description: This headgear activator achieves the mandibular position through the lingual wings of its lower
base.
Headgear-activator according to Herman van Beek. An orthopedic plate, modified into an activator . Effective in
Cass II-1 open and deep bite cases.

The models are set into the fixator by a construction bite with a
vertical opening of approximately 10 mm. Between the central and
lateral incisors the short and strong outer bows are set into the
acrylic of the activator. The lower incisors are grasped labially 2 mm
in acrylic in order to avoid their protrusion. The lingual surfaces
remain free. The upper incisors are also grasped in acrylic. The
position of the mandible is achieved through the long lingual wings
of the lower base.
The upper base plate is kept small. The palatal area of the upper
anterior teeth is blocked out with wax in order to allow a retrusion.
The lateral bite plane reaches to the center of the occlusal surfaces.
In the premolar region, the lower base is extended as far as possible
downwards.
In combination with a high pull headgear, this appliance
with bite block can be used to intrude the upper teeth.

The Teuscher activator
Elements: Headgear tubes, torque springs 0.5 mm spring hard, Coffin spring 1.2 mm spring hard
Function: Inhibition of the development of the upper jaw with simultaneous mandibular advancement
Description: This headgear activator hinders the development of the upper jaw with simultaneous
advancement of the mandible.
Base appliance with four torque springs. The torque
springs only contact the upper incisors in one point
shortly underneath the gingival margin. It is bent away
slightly to avoid contact with the rest of the clinical
crown. The retention is in the interocclusal area.

The headgear tubes lie between both tooth rows in the
area of the deciduous molars. The interocclusal area
should be high enough to allow a good anchorage of the
retentions of the headgear tubes in the acrylic. It should
also be checked from the occlusal point of view if they lie
parallel to be able to insert the inner bow without any
problems.
The acrylic base has to cover one third of the lower
incisors, and the upper incisors should be covered on the
palatal side up to one half and on the labial side, only to
the incisal edge.

Modifications of the Teuscher activator
a) Torque springs on the central incisors
The Teuscher activator allows the design of torque
springs on the central incisors in combination with
protrusion springs for labial movement on the lateral
incisors.
b) Sheet springs and labial bow
The same effect can be achieved with sheet springs and a
labial bow that should contact the most prominent teeth.

c) Labial pads
On the Teuscher activator, lip pads for the development
of the lower jaw can be attached as in the function
regulator according to Fränkel. Therefore the limit of the
vestibule has to be erased before making the appliance.
d) Lip bumper
Also, a lip bumper can be attached directly to the
appliance in order to support a protrusion of the lower
incisors. It has to be positioned in height of the gingival
margin in front of the lower incisors in a distance of
approximately 1 mm.

e) Expansion screw
Another variation for the expansion of both jaws: an
expansion screw between the upper and lower jaw.
f) Combination with fixed appliances
If the Teuscher activator is used in combination with a
transpalatal arch and upper molar bands, the activator
has to be liberated in the area of the molar tubes and the
palate.

The Harvold-Woodside activator for class II-1
Elements: Labial bow 0.9 mm spring hard, distalizing springs 0.9 mm spring hard
Function: Functional change of the occlusal plane in a malocclusion class II-1
Description: A vertical opening of up to 20 mm is necessary for this activator; the smooth lateral bite
plane maintains the upper incisors and the lower are grinded
In this class II-1 activator the labial bow is bent contacting
up to the canines, from there it is bent similar as the
buccinator loop to shield the cheek and is then bent through
a U-loop again towards the front; the retention finishes in
the area of the interocclusal opening. The distalizing springs
consist of a big loop in the molar region and have a distal
cantilever mesial of the first molars and its retention in the
incisal area.

The coverage with wax should be done carefully. The
characterizing feature of this appliance is the large vertical
opening in the buccal sections which is determined by a
construction bite. In order to guide the anterior movement in the
posterior region, a thin wax plane is added in the upper jaw and
a high wax plane, higher than half of the vertical opening, is
added in the lower jaw; the main purpose is to create plane
surfaces for the acrylic platforms.
If the fixator is closed the separation between both wax
planes in the buccal area should be of approximately one
millimeter, so that the lateral bite plane presents enough
stability.

On the models the extension of the acrylic shield over the
whole incisal area in the upper and lower jaw should be
limited with a wax frame. The retention of the labial bow
lies in the interocclusal acrylic right behind the upper
incisors. The models prepared this way can be covered
with acrylic and put into the pressure vessel for its
polymerization.
In the finished appliance, for their proper activation, only
the retention of the distalizing springs is covered with
acrylic. The labial bow only contacts the upper incisors.
The distal limitation of the appliance is the A-line.
The labial shield covers the incisors over one third of their
clinical crown. The lateral bite planes have no contact at
all with the posterior teeth in order to achieve the desired
vertical eruption.

The Harvold-Woodside activator for class III
Elements: Labial bow 0.9 mm spring hard, distalizing spring 0.9 mm spring hard
Function: Therapy of a class III malocclusion
Description: The class III activator should not hinder the buccal segments in their vertical eruption
In this class III activator, the labial bow in the lower jaw is
bent as an intermaxillary bow; its task in the upper jaw is to
shield off the lips through loops bent as labial pads. The
retention lies as in the class II appliance, in the anterior area of
the vertical opening. Also, the distalizing spring is bent with a
big loop in the molar region. Although in this appliance the
distal cantilevers are located behind the first molars, the
retention ends in the anterior palatal area.

As before, the wax coverage is very important. The big vertical
opening corresponds to the one in type-II. In this case, a wax
plane that reaches over the half of the vertical opening is added
onto the upper jaw. In the lower jaw, the posterior teeth are
slightly covered with wax and in the incisal area, from canine to
canine, the wax is concavely shaped; the loop and the distal
cantilever of the distalizing spring are also covered with wax.
For its proper stability, the acrylic in the interocclusal area should
show a thickness of one millimeter.
The acrylic shield of this appliance only covers the lower incisal
area and is correspondingly framed with a wax limitation.
Despite its location, a sufficient anchorage has to be guaranteed
for the retention of the labial bow. Before adding the acrylic both
models have to be hydrated.

In this class III appliance, the distal limitation is also marked by
the A-line. Once again, only the retention of the distalizing
springs is grasped in acrylic. In the upper jaw, the labial bow
does not contact but shields off the lip.
The upper teeth only contact the acrylic shield. The acrylic can be
trimmed and shaped individually by the orthodontist. The lateral
bite plane allows more vertical eruption for the upper posterior
teeth.

The activator according to Pfeiffer and Grobety
Elements: Modified labial bow with soldered triangular clasp 0.8 mm spring hard
Function: Retraction of the upper jaw with simultaneous distal movement of the upper teeth
Description: Retraction of the upper jaw, and under influence of the masticatory muscles, mesial
movement of the lower teeth with simultaneous distal movement of the upper teeth;
the headgear is only used combined with the fixator.
The impressions are filled with the bands in order to be able
to adapt the finished appliance better. In the original
appliance only a modified labial bow with a soldered
triangular clasp is bent.

The canine loops of the labial arch are placed as usual in the
canine area. Then the wire is bent distally and between the first
and second premolar it is bent into the retention. The screw is
fixed in the upper jaw and the base plate is limited with wax
stripes.
The activator additionally consists of lateral bite blocks and an
incisal cap in the lower anterior region.
The lower impression has to depict the lingual area very well in
order to extend the lower lingual wings as far as possible into
the sublingual area.

The lower wings of the activator should be very
pronounced on the lingual side favoring the activity of the
masticatory muscles.
This is a lateral view of the activator with its pronounced
lower wings.

The activator with spring bows according to Schwarz
Elements: Labial bow 0.8 mm spring hard, spring bow 1.2 mm spring hard
Function: Activation through muscle function
Description: Through the spring bows, which can be activated horizontally or vertically, the
muscle activity is stimulated
The base appliance only contains few elements, but can be
replenished in any way. A labial bow is bent for each
upper and lower jaw and the single plates are finished
with plane lateral bite blocks.

The polished and finished plates are set onto the models
which were articulated according to the construction bite.
Now the unifying spring bows can be bent and be added
into the acrylic of the single plates of the activator. These
spring bows are supposed to enhance muscle activity.
The spring bows reach distally over the base plate for a
proper activation. Different directions for their activation
are possible (horizontal, vertical).

The open bite activator with tongue crib
Elements: Labial bow 0.8 mm spring hard, Coffin spring 1.2 mm spring hard, tongue crib 1.0
mm spring hard, mandibular connection bow 1.0 mm spring hard.
Function: Intrusion of the posterior teeth, extrusion of the incisors and simultaneous protection
of the tongue.
Description: The tongue is kept from the teeth because of the tongue loop which follows
the curve of the dental arch.
The models are set into the fixator with the construction bite
and the vertical opening is determined. The labial bows are
bent as usual. The connecting bow in the lower jaw and the
Coffin spring in the upper jaw are fixed each 1 mm from the
gingival tissue. The divided tongue crib is fixed parallel to
the lingual or palatal area of the incisors.

The tongue crib consists of two divided loops. For the first half,
the wire is bent back 180° in the middle. The separation of the
parallel wires corresponds to half of the area to be closed off.
The loop is bent according to the curvature of the anterior
segment. Both wire ends are bent over for retention and are
anchored in the lateral part of the activator. The second half is
bent like a mirror image and is set on the other side.
The acrylic body of the open activator is designed quite
delicately. The anterior open base and the adapted tongue crib
make this a well accepted appliance by patients.

The Skel activator according to Ruhland type II-1
Elements: For class II-1 – II-2: Labial arch 0.9 mm spring hard, Coffin spring 0.9 mm spring hard,
occlusal molar rests 0.8 mm spring hard, occlusal rests canine 0.7 mm spring hard, protrusion
spring 0.7 mm spring hard For class III: Labial arch 0.9 mm spring hard, Coffin spring 1.1 mm
spring hard, lingual bow 0.9 mm spring hard, connection spring 0.9 mm spring hard
Function: A reduced elastic activator with different tasks for class II-1, II-2 and III
Description: A reduced elastic activator
Type II-1
In the upper as well as in the lower jaw, the labial bows are
set into the acrylic between the 1st and 2nd premolar. The
distally closed Coffin spring is located in the molar region.
The lower incisors area is shaped with protrusion springs.
The canines in the upper jaw are held with C-clasps.

The acrylic base is reduced in its anterior part and has no
interocclusal acrylic. The delicate design of the acrylic and
the relative thin wire elements make this appliance very
flexible.
Altogether the acrylic body is kept small.

The Skel activator according to Ruhland type II-2
Elements: For class II-1 – II-2: Labial arch 0.9 mm spring hard, Coffin spring 0.9 mm spring hard, occlusal
molar rests 0.8 mm spring hard, occlusal rests canine 0.7 mm spring hard, protrusion spring 0.7
mm spring hard For class III: Labial arch 0.9 mm spring hard, Coffin spring 1.1 mm spring hard,
lingual bow 0.9 mm spring hard, connection spring 0.9 mm spring hard
Type II-2
The upper and lower front region is developed using
protrusion springs. The labial arch passes between the 1st
and 2nd premolar into the acrylic. The first molars are
maintained by thorns. The Coffin spring is positioned in the
same way as in type II-1.

The acrylic base is the same as in type II-1. From the
mesial part of the canines to the distal end of the molars
both acrylic parts of the upper and lower jaw are
connected.
The making of this appliance corresponds mainly to the
one of type II-1, it differs only in the protrusion springs in
the upper jaw and the lacking of the occlusal rests for the
canines.

The Skel activator according to Ruhland type III-a
occlusal molar rests 0.8 mm spring hard, occlusal rests canine 0.7 mm spring hard,
protrusion spring 0.7 mm spring hard For class III: Labial arch 0.9 mm spring hard,
Coffin spring 1.1 mm spring hard, lingual bow 0.9 mm spring hard, connection spring 0.9
mm spring hard
Type III-a
The appliance for class III is horizontally divided. Two
distal spring bows connect the upper and lower part.

The elements in the lower jaw are two holding thorns and a
connecting bow. The upper jaw consists of protrusion springs, an
intermaxillary bow and a Coffin spring. First, both parts, upper
and lower, are finished separately. Interocclusal acrylic is not
necessary. With a construction bite, the upper and lower parts are
connected in the articulator through spring bows in the distal
part of the plates.
Through activation of the intermaxillary bow and both spring bows
the lower jaw is retruded.

The Skel activator according to Ruhland type III-b
occlusal molar rests 0.8 mm spring hard, occlusal rests canine 0.7 mm spring hard, protrusion
spring 0.7 mm spring hard For class III: Labial arch 0.9 mm spring hard, Coffin spring 1.1
mm spring hard, lingual bow 0.9 mm spring hard, connection spring 0.9 mm spring hard
Type III-b
In the lower part, the same type can be replenished with a
tongue crib which simultaneously serves as a connecting
bow. Support thorns can also be placed before the molars if
needed

The appliance is also divided horizontally and is activated
through the far distally fixed spring bows. The tongue crib
prevents a negative influence of the tongue. The
intermaxillary bow makes a distal movement of the mandible
possible.
View of the finished appliance type III b.

The Skel activator according to Ruhland type III-c
occlusal molar rests 0.8 mm spring hard, occlusal rests canine 0.7 mm spring hard,
protrusion spring 0.7 mm spring hard For class III: Labial arch 0.9 mm spring hard,
Coffin spring 1.1 mm spring hard, lingual bow 0.9 mm spring hard, connection spring
0.9 mm spring hard
Type III-c
Instead of the spring bows between the upper and lower
jaw, a prognathism screw (LS-Duobloc- Screw) was
installed. Through this screw a more uniform distal
activation of the lower part is possible.

The acrylic is added in one process by means of a dividing metal
plate. In order to install the prognathism screw parallel, a metal
pattern is needed for their installation.
The SKEL activator type III-c according to Ruhland works
through the bilateral activation of the lower screws which move
the base of the lower jaw distally against the base of the upper
jaw.

The elastic open activator according to Klammt (EOA)
Elements:
Function:
Description: Open activator with wide space for the tongue
Palatal bow 1.2 mm spring hard, labial bow 0.9 mm hard
Alignment of the anterior teeth
The labial bows lie parallel to each other and are bent buccaly
of the first molars into a loop. From there, they are guided
back mesially of the canines from where they are bent palatal
or lingual into the retention. The palatal bow is bent similar to
a Coffin spring and connects the acrylic parts.

For an ergonomic finish and material saving, the models
are blocked out with wax. Under the palatal bow, a wax
spacer is placed to ensure adequate clearance for tissue
comfort.
The acrylic shares lay orally from the canines to the last
molars forming a small band contacting teeth and gingiva.
The occlusal surfaces are not covered with acrylic and a
vertical support by the acrylic is left only in the canine
area.

The rigid open activator (SOA)
Elements: Connecting bow 1.5 mm hard, labial bow 0.9 mm hard, supporting thorns 0.8 mm spring
hard, protrusion spring 0.7 mm spring hard.
Function: Alignment of the anterior teeth
Description: Delicate activator with wide space for the tongue
For the SOA the elements are bent according to the
planned design and are fixed with wax. The rigid
connecting bow is under laid with tin foil before its
fixation in the area of the first molars of the upper jaw to
guarantee an even distance from the palatal gingival
tissue.

The acrylic base is designed as in the EOA, as delicate as
possible with interocclusal acrylic. The rigid connecting
bow gives the body of the appliance certain stability.
Because of the rigid connecting bow, with this appliance
expansion of the jaws is not possible.

The spring activator according to Sander
Elements: Labial bow 0.8 mm spring hard, protrusion loop 0.8 mm spring hard, triangular clasps 0.7 mm
spring hard, Adams clasps 0.7 mm hard, palatal bow 3.0 x 1.5 mm half round steel wire, a
special spring system according to Sander: 1.0-1.1 mm spring hard wire with simple or triple
loop
Function: Treatment of skeletal open bites and rehabilitation after TMJ injuries
Description: Special springs of 1.0-1.1 mm spring hard wire are located lateral in this appliance
and therefore do not hinder the tongue
For the making of the spring activator the models are set in the
fixator. As the acrylic base of the upper jaw is reduced, the
retentions have to be bent according to this situation being
anchored into this acrylic segment. The highest part of the palate
is covered with a tin foil which is 1 - 1.5 mm thick to guarantee
an even distance of the palatal bow and to avoid pressure areas.
The finished elements are fixed onto the model, acrylic is added
and the plate is finished.

The base of the upper plate should extend palatally as much as to
guarantee sufficient retention and stability for the special spring.
The upper plate is finished and polished completely in order to
allow an even adjustment of the upper and lower bite blocks.
Isolated with a thick wax layer, the upper bite block can be set
onto the polymerizing lower plate. Another option is to separate
both plates with a metal plate.
Special attention should be paid to the fact that the labial bow with
its occlusal parts does not lie over the occlusal plane. While
occluding firmly with the spring activator there should not be any
interfering contacts in the anterior area. The widths of the lateral
bite blocks have to be adapted orally so that the spring bow can
glide past the acrylic to connect the upper with the lower jaw.

The loops have to be bent in such a way that while closing the wire is
pushed into the loop, which means it is activated (safety pin principle).
The length of the spring can be calculated reaching from the last molar
approximately to the first premolar or canine.
After polishing both individually made plates and the bite blocks lay
even on each other, the height has to be checked in the fixator according
to the construction bite. The retentions of the springs have to be
anchored as far as possible into the distal area of the acrylic segments.
The springs should be incorporated into the plate without strain.
Instead of the palatal bow, the spring activator can also be fitted with a
transversal expansion screw or headgear tubes. If the headgear tubes
are incorporated in the area of the first premolars the triangular clasps
cease to apply.

The divided activator with screw for the upper jaw
Elements: Labial bow and retention thorns 0.8 mm spring hard
Function: Separate expansion of the maxilla
Description: The upper expansion screw is anchored in the lower jaw
The elements are bent following the design, in this case,
additionally with two protrusion springs. The extension
of the acrylic base is limited with wax. In this horizontally
divided appliance, after bending the elements, the lower
jaw is finished separately and polished.

In the interocclusal area, the upper and lower bite blocks
of the divided activator show a separation of almost one
millimeter. That is the reason why this area is covered
with wax to this height.
In the upper jaw, the screw is centered and fixed with wax
so that the retentions of the screw stick out into the lower
jaw. Therefore, in the anterior region, two notches have to
be grinded into the lower base plate. The fixator should be
able to open and close without interference. The area of
retention in the lower jaw is blocked out with wax.

Now acrylic is added on the upper jaw. While the acrylic is still
malleable the fixator is closed. The wax layer in the retention area of the
screw prevents the union of the upper and lower plate. This way the
upper plate can be sawed, finished and polished separately.
After this, both separately produced plates are unified to one appliance.
For this purpose, the division and the interocclusal area close to the
screw are covered with wax.
The upper part of this activator can be expanded without the lower jaw.

The U-bow activator according to Karwetzky
Elements: U-bow 1.2 mm spring hard, labial bow 0.8 mm spring hard
Function: Movement of the mandible in different directions, according to the specific type
(type I-III)
Description: Through the addition of different U-bows into the elastic activator, different directions
of mandibular movement are possible
For the U-bow activator separate upper and lower plates
with even grinded bite blocks and other elements
(depending on the planed design) are made. If screws are
added into the plates, they only have effect on that
specific jaw.

Type I distal activator Through both U-loops, which are anchored
into the acrylic in the region of the first molars. The long arm of
the U-bow is always fixed into the lower jaw, the short arm into
the upper jaw. In this type I distal activator the arms of the U-bow
point anteriorly.
Type II prognathism activator In type II both anchored arms of
the U-bow are directed posteriorly. The long arms are situated in
the lower plate as seen here.

Type III-a
Pan activator In this type III-a two different bows are built
in. On the right side, the upper short arm shows distally,
on the left side, the short upper arm shows mesially.
When activating the U-loops a panning movement to the
right is produced.
Type III-b Pan activator
In the type III-b the U-bows are incorporated opposite as
in type III-a. On the right side, the short upper arm shows
mesially, on the left side the short upper arm shows
distally. This way, when activating, a panning movement
to the left is the result.

Medium Opening Activator
Medium Opening Activator
with upper and lower model
removed.
The Medium Opening Activator (MOA), fabricated here
in clear heat cure material.
Design includes: -
* Lower incisal capping 3 / 3 .
* Anterior Palatal wire 3 / 3 in 1.0mm S.S wire.
* Labial Bow 3 / 3 - 0.9mm S.S wire.
* Adams clasps 64 / 46 - 0.7 mm S.S wire.
* Occlusal rests 64 / 46 - 0.8 mm S.S wire.
* Acrylic connecting 'struts' / vertical supports

Medium Opening Activator with upper
model removed
Medium Opening Activator with lower
removed

Another series of MOA pictures.
Medium Opening Activator with upper and lower models in situ.

Medium Opening Activator with upper
model removed.
Medium Opening Activator with lower
removed.

Wunderer activator
 Used for CI-III malocclusion
 Appliance is split horizontally
 Screw is embedded in the acrylic behind the
incisors
 Occlusal surface is covered with acrylic
 Weise screw

Palate – free activator - Metzelder

Bonded activator- Hamilton
 Mainly used in non compliant patients
 Used for expansion along with forward positioning of jaws

Activator therapy
 Diagnostic preparation
 Bite registration
 trimming of activator
 Management of the appliance

Diagnostic preparation
History
-growth status
-instant correction
-patient compliance
Study models
-Molar relationship
-Midlines
-Asymmetries
-curve of spee
-Dental discrepancies

Functional analysis
 Rest position of the mandible
 Path of closure from postural rest to habitual occlusion
 Premature contacts
 TMJ: a functional abnormal cases may need some modification of activator .
 Freeway space or interocclusal clearance
 Respiration :with allergies or disturbed nasal respiration
(Adenoid problem should be recorded ,patient will not be able to tolerate the
activator with adenoid problem).

Cephalometric Analysis ( will help in determining the following):
- Direction of growth : average ,horizontal or vertical
- Differentiation between Position & size of the jaws
- Dimensional variations
- Axial inclination and position of the maxillary and mandibular
incisors .
I. Facial skeleton analysis
A .The sadle angle:
The sadle angle is formed by joining the NS line and ArS line.
Its normal value is 123+5o The large sadle angle usually means
that there is a posterior condylar position ,and a mandible that
is posteriorly positioned with respect to the cranial base and
maxilla

b. Articular angle :
lies between the upper and lower parts of the posterior
contours of the facial skeleton. Normal value 143+6o Increased
Ar angle means retrognathic mandible, Decreased means
prognathic mandible.
c. The gonial angle:
acute or small Go angle means horizontal growth pattern and
favorable to activator therapy. In case of large angle (vertical
pattern), activator treatment is contraindicated.
d. The posterior facial height(S-Go) and anterior facial
height(N-M) ratio:
posterior facial height X 100/ anterior facial height
Less than 62% -Vertical growth
More than 65% -Horizontal growth.
Anterior facial height (nasion and menton) and
Posterior facial height (distance between S and Go)

II. Analysis of the jaw bases
a. SNA angle expresses the sagittal (antero-posteror)
relationship of the anterior limit of the maxillary apical
base. SNA angle is large in a prognathic maxilla and
decreased in retrognathic Maxilla.
b. SNB angle is large in prognathic mandible and
small in retrognathic mandible.
SNA angle (joining points S, N and A), SNB angle
(joining points S, N and B), and Basal angle Joining
palatal plane and base of the mandible .

c. Basal plane angle (maxillo-mandibular plane angle)
normal value is 25. It is smaller in horizontal growth
pattern and larger in vertical growth pattern.
d. Inclination angle is formed by the Pn line (a perpendicular
from soft tissue N) and the Palatal plane. Normal value 85
degree.
Anterior cranial base length (1), Maxillary base length(2),
Mandibular Base length (3), Ascending Ramus (4) and
Inclination angle (5)

III. Dentoalveolar analysis :
• Axial inclination of the incisors:
i. The upper incisors: SN angle is formed by joining the
long axis of the maxillary incisors and SN plane. The
posterior angle is measured. Normal value 102o Large
angle indicates labial crown tipping.
ii. The lower incisors: MP angle is formed by joining the
long axis of the lower incisors and mandibular plane.
The posterior angle is measured. Normal value is 90+3o
Large angle indicates labial crown tipping.
Upper incisor inclination (1)
Lower incisor Inclination (2)

iii. Position of the Incisors: the most common method is
to measure the distance of the incisal edges to the N-Pg
line (facial plane). The average position of the upper
incisors is 2mm to 4 mm anterior to the Facial plane
and lower incisors from 2 mm posterior to 2 mm
anterior to the facial plane.
Upper incisor position (1), Lower incisor position (2)

Rules for construction bite
• In a forward positioning of the mandible of 7-8mm,the
vertical opening should be slight to moderate (2-4mm)
• If the forward positioning is not more than3-5mm,the
vertical opening can be 4-6mm
• If the overjet is too large , forward positioning is done in 2-3
stages
Bite Registration

Bite Registration
Boxing wax Wooden spatula Hot water

Patient bites with incisors edge
to edge. ~ 6mm separation of
molars

Fold wax lengthwise twice to 1/3 size
Do not flatten

Turn folded wax lengthwise and fold once with spatula in between

Crimp lower edge against spatula
Do not flatten

Patient bites with incisor edge to edge

Trimming of the Activator
1. Sagittal Control
a. Class II correction:
Trimming is done so as to
encourage the mesial
movement of the lower molar
and distal movement of the
upper molar.
Trimming of the activator for Class
II correction. Note the lower
posterior segment is free to erupt
vertically and mesially.

Mesial movement of
molars
Distal movement of
molars

b. Protrusion of incisors
• In this case lingual surfaces of teeth are loaded with acrylic
and a passive labial bow is given
Activator design for protrusion of incisors. Note the
loading of the entire lingual surface and labial bow
away from the incisors to encourage labial
movement of the incisors

c. Retrusion of incisors
• Here the lingual surface is made totally free of acrylic
and an active labial bow is given
Activator design for retrusion of incisors. The labial
bow here is active and the lingual surfaces of the
incisors are relieved for lingual movement of the
teeth

2. Vertical Control
a. Intrusion of teeth
• Activator design for intrusion of teeth (for anterior
intrusion the labial bow is placed below the greatest
convexity in the upper and above the greatest convexity in
the lower)
• In case of intrusion of posteriors load the surfaces of the
teeth with acrylic

b. Extrusion of teeth
• Here the lingual surface is loaded above the
area of greatest convexity in the maxilla and
below the area of greatest convexity in the
mandible
• Also the labial bow can be placed at the
gingival 1/3 i.e. below the greatest convexity
• In case of posterior extrusion the lingual
surfaces below the greatest convexity are
loaded.
Activator design for extrusion of
teeth. (i)Anteriors.(ii)Posteriors

3. For Transverse Control
Jack screw is incorporated into
the activator for expansion
(trasnverse control) as and when
required.
Activator with jack screw, for transverse control

• The patient is demonstrated to place and remove the appliance in
mouth.
• The appliance is to be worn 2 to 3 hours during the day for the first
week.
• During the second week the patient sleeps with the appliance in
mouth and wears it for 1-3 hours each day.
• The appliance is checked during the third week to evaluate the
trimming.
• If the patient is wearing the appliance without any difficulty and
following the instructions, checkup appointments are scheduled
every 6 weeks.
MANAGEMENT OF THE APPLIANCE

Case Reports
Case 1
A 10-year-old male patient reported in good health with
chief complaint of protrusion of upper front teeth and
unpleasant looks.
The dental and medical history was unremarkable.
Extraoral examination showed convex facial profile with
posterior divergence of the face due to retrognathic
mandible. Lips were potentially competent and protrusive
with 6 mm of interlabial gap, everted lower lip, and
hypotonic upper lip.

Intraoral examination revealed late mixed dentition stage with erupting upper canine
and nearly exfoliating second deciduous molar on the left side. Dental arches were "U"
shaped and maxillary anteriors were proclined with spacing. The mandibular incisors
were impinging on palatal tissue on closure. In occlusion, there was a class II division 1
relationship with increased overjet of 11 mm and overbite of 8 mm. The molar
relationship was class II bilaterally.

The lateral cephalogram showed a severe skeletal ANB difference of 7°. The
maxilla was normal relative to the cranial base with an SNA at 80°. The
mandible was retrognathic with an SNB value of 73°. The maxillary incisors
were proclined.

Diagnosis: Skeletal class II jaw relationship with Angle′s class II division 1 malocclusion with
average growth pattern. Hand wrist radiograph was taken to confirm the growing status of
patient.
Treatment plan: Growth modification with myofunctional appliance therapy (activator)
followed by final detailing of occlusion with fixed pre-adjusted edgewise appliance.
The objectives of growth modification procedure (myofunctional appliance) were to reduce the
skeletal class II pattern, achieve a class I skeletal and dental relation, establish normal overjet
and overbite, reduce the convex profile, and improve the lip incompetency. Myofunctional
appliance (Activator) was planned for growth modification therapy. Patient was instructed to
wear the activator for 14 hours/day.

Results achieved: Patient′s soft tissue facial profile was improved, along with lip
incompetency, reduction of the severe overjet and deep impinging overbite, and achievement of
class I skeletal and dental relationships

The cephalometric analysis after myofunctional therapy demonstrates favorable forward growth of the
mandible. There was a reduction of the skeletal class II with a 5° decrease in the ANB angle through
forward growth of the mandible. The post-treatment value of SNB at 79° indicates the advancement of
mandible.

At the end of treatment, the patient had pleasing and well-settled dentition

Comparison of pre-treatment and post-treatment cephalometric values . Total
treatment time was 22 months.

Case 2
An 11½-year-old boy patient reported with the chief
complaints of forwardly placed upper front teeth and
unpleasant looks.
Extraoral examination revealed a convex profile mainly
due to retrognathic mandible, incompetent protrusive lips
with 7 mm of interlabial gap, upturned prominent nose,
deep mentolabial sulcus, and lower lip trap habit.

Intraoral examination of dentition revealed mixed dentition stage. Maxillary and mandibular
arch were ovoid in shape with proclined upper incisors and generalized spacing. In occlusion,
there was Angle′s class II division 1 relationship with overjet of 13 mm. The overbite was 6 mm.
The molar relationship was class II bilaterally. Canine relationship was class II on the right side
and was not established on the left side. Upper and lower dental midlines were coinciding with
each other and with facial midline.

The lateral cephalometric values showed a convex hard tissue profile with a severe skeletal
ANB difference of 7°. The maxilla was slightly prognathic relative to the cranial base with an
SNB at 83°. The mandible was retrognathic relative to the cranial base with an SNB at 76°. There
was proclination of upper and lower incisors with average growth pattern.

Diagnosis
Angle′s class II division 1 dentoalveolar malocclusion on class II skeletal base due to retrognathic
mandible.
Treatment plan
Growth modification with myofunctional appliance therapy (activator) immediately followed by
final detailing of occlusion with fixed pre-adjusted edgewise appliance was planned.

Results
Saggital correction (skeletal class I) was achieved through growth modification with improvement in
the facial profile and lip incompetency and reduction of the severe overjet and deep overbite. At the end
of the treatment, the patient had very good facial profile , class I molar and canine relationship, normal
overjet and overbite , root parallelism, and normal tooth position.

Evaluation of the cephalometric tracings demonstrates reduction of the skeletal class II with a 4° decrease in
the ANB angle through forward growth of the mandible. The post-treatment value of SNA was 82° and of
SNB was 79°. Proclination of upper as well lower incisors was also corrected.
Comparison of pretreatment, mid treatment and post treatment Cephalometric values

REFERENCES
 Gurkeerat Singh ( second edition )
 Synopsis of orthodontics
 Indian dental academy

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