Activator/certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
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Introduction
 A functional appliance is one that changes the posture
of the mandible, by holding it open or open and
forward, stretches the soft tissues and changes the
tone of muscles creating pressures which are
transmitted to the dental and skeletal structures,
moving teeth and modifying growth.
 The goal of the functional appliance therapy is to
favorably influence the growth of the mandible
achieving optimal growth direction and amount and
to eliminate any dysfunction or posteriorly retarded
habitual occlusion.

 Definition – activators are those appliances
which can activate muscle forces.
 The term coined by Andersen & Haupl jointly
in 1936.

Historical background
 1880- Kingsley’s vulcanite plate-
 “jumping the bite” for retruded mandible
 Found to be a difficult job
 No longer in use
 Towards the end of 19th century- Vorbissplate-
 Hotz’s modification of Kingsley plate for
treatment of deep bite with functional retrusion of
mandible.

 Hawley’s inclined bite plane-
 A direct descendant of the kingsley plate.
 Frequently used in TMD therapy.
 1902- Robin’s monoblock-
 For bimaxillary expansion
 Advocated its use for glossoptosis in 1923 as it
positioned mandible forward.

 1908- Viggo Andersen in Denmark-
 Modified Kingsley plate with addition of
horseshoe shaped acrylic extension in the
mandible.
 Used on his own daughter.
 Named “active retainer or retention activator”

 1925- Andersen-Haupl activator-
 Teamed up with Karl Haupl in Oslow, Norway.
 Haupl was the one to explain it extensively,
(Funktions- Keiferorthopaedic, Leipzig,1936,
Herman Neusser) hence the name.
 Some called it “Monoblock of Andersen”
 Also called “Norwegian activator”

 Haupl justified their working hypothesis on writing of
Roux- shaking the bone hypothesis in 1883- became
background of both general orthopedic 7 functional
dental orthopedics.
 In 1918- Dr Alfred P Rogers conceived idea of
functional aspects of muscles in treatment of
malocclusion & is important correlation of activator
treatment therapy- no success reported without
concomitant use of appliance therapy.

 1933- Oppenheim published his investigation
under title “crises in orthodontics”. Noticed
potential tissue damaging side effects of heavy
orthodontic forces.
 Throughout Europe, activator became one
universal appliance.

 1938- introduction of expansion plates by A.M
Schwarz – added to development of activator.
 Basically activator was loose appliance that
works intermittently on Farrar’s biological
principle “labor & rest”. Appliance uses m.
action & hence it is an “myodynamic
appliance”- meant for night time wear only.

 Conversion of myodynamic activator into
myotonic- increase in interocclusal distance
when Petric joined the group- Myotonic
appliance of Andersen, Haupl & Petric.
 1949- Bilmer appliance- developed his own
system of functional appliances consisting of 3
types & 6 variations- “Elasticher
Gebissformer”.

 1950- Bionator
 Herren’s activator-
 Learned about activator from Petric
 Co-authored the 6th addition of the Andersen-
Haupl’s classic text book “functions- Kleifer
Orthopedic”
 Later he modified the activator.
 Utilizes the extreme sagittal displacement of the
mandible.

 Elastic open activator- 1960-
 Designed by G.Klammt, discipline of Bilmer in
1960, as Bilmer appliance was too fragile.
 Harvold & Woodside (1971)-
 The designs of their activator utilizes extreme
vertical displacement.
 Palate free activator- 1974- a modification of
activator by Metzelder in 1974.
 Propulsor- 1980- conceived by Mulhemann &
refined by Hotz.

Force analyses in activator therapy
 Static forces- gravity & posture & elasticity of
soft tissues
 Dynamic forces- produced during various
actions like swallowing, opening & closing.
 Rhythmic forces- associated with respiration &
circulation.
 Active forces- forces produced by springs,
jackscrews, pads & magnets.

Mode of action of activator
 Force elimination
 Force application

Force application
 Types of force employed in Activator Therapy:
 The growth potential including the eruption and
migration of teeth gives rise to natural forces.
These can be guided, promoted or inhibited by
activator.
 Muscle contractions and soft tissue stretching
initiate forces when the mandible is relocated. The
contractions are stimulated and transformed by the
activator. These artificial functioning forces can be
effective in all three planes of space.

a) In the sagittal plane, the mandible is propelled
forward and muscle force is delivered to condyle and
strain is produced in the condylar region. A slight
reciprocal force is transmitted to the maxilla.
b) In the vertical plane, teeth and alveolar processes are
either loaded with or relieved of normal forces. with a
high construction bite, greater strain on maxilla, can
have an inhibitory effect on growth increments and
direction and can influence the inclination of
maxillary base.

c) In the transverse plane it is possible to create
forces with midline corrections.
 Various active elements like springs and
screws can also be incorporated.

3 concepts explaining mode of action of activator
 Original Andersen-Haupl concept-
 New function can change the internal structure of
bone.
 During growth, new function can change external
shape of bone also.
 Induces musculo-skeletal adaptation by
introducing new pattern of mandibular closure.
 Myodynamic appliance- uses kinetic energy
through stretch reflex.

 The forward positioning of the mandible
activates superior head of LPM, induces a cell
proliferation in the condyle & a growth
response (Petrovic)
 Acc to Grude (1952) , this action is observed
only if the mandible is not displaced beyond
postural rest position.

Drawback-
 When mouth is opened only 3-4 mm by the
appliance 1 or 2 things can happen-
 Appliance may fall out
 The wider open position does not permit it to
mandible & result- ineffectiveness

Concept of visco-elastic property
 The concept was to overcome the drawback of
previous theory.
 If the mandible opens beyond the 4mm limit, the
appliance does not work in the manner Andersen &
Haupl had suggested.
 Clasp-knife reflex is initiated that builds up potential
energy.
 Herren overextends in the sagittal plane moving mandible
into anterior cross bite position
 Woodside opens as much as 10-15mm beyond the postural
rest position.

 Depending upon the magnitude & duration of
the applied force, the viscoelastic traction can
be divided into the following stages-
 Emptying of vessels
 Pressing out of the interstial fluid
 Elastic deformation of the bones
 Bioplastic adaptation

Concept of combined principles
 Uses m. contraction & viscoelastic properties
of the soft tissues.
 Greater bite opening than Andersen & Haupl
but don’t over compensate as Woodside (4-
6mm opening)
 Ultimate mechanism depends on value on
malocclusion, interocclusal clearance, head
posture, state of mind & level of conciousness.

 Escher (1952)- works alternately with isotonic
& isometric contractions.
 Cycle- at insertion of appliance mandible
elevated by isotonic m. contraction – in contact
with the appliance isometric m. contractions
start. As mandible cant reach postural rest
position, elevators remain stretched- fatigue &
mandible drops & cycle begins again.

Objectives of activator treatment
 To achieve major changes in facial esthetic
 To achieve major occlusal changes in the M-
D, vertical & transverse planes of space.
 To remodel arch form
 To achieve moderate reductions in skeletal dysplasia
b/w maxilla & mandible.
 To change the direction of the mandibular growth by
vertical manipulation.
 Correction of incisor cross bite by vertical
manipulation.

Limitation of activator treatment
 Mandible anchorage loss
 Relative retrusion
 Cant be used itself for decrowding & doesn't
perform detailed tooth positioning.
 Effective in growing pts only
 Tends to produce moderate mandibular
rotations so contraindicated in pts with excess
lower facial height.

Indications of activator treatment
 used in moderate skeletal dysplacias between the midfacial
area and the mandible in which case moderate amounts of
mandibualr growth and maxillary- incisor retraction may
combine for successful treatment primarily in actively growing
individuals with favourable facial growth pattern.
 Well aligned maxillary and mandibular teeth and mandibular
teeth should be upright over basal bone structures.
 It provides a superb treatment in children with lack of vertical
development in lower face height because differential vertical
alveolar development can be readily obtained in either the
maxillary or arch as desired. mandibular
 It provides a useful preliminary treatment before major fixed
appliance mechanotherapy.
 It is useful for post treatment retention in children with a deep
overbite caused by overclosure.

Facial morphology best suited for activator therapy
 1. Correction of dentoalveolar Class II malocclusions: As
activator is a form of intermaxillary therapy, it can cause
mandibular dentition slip labially and maxillary dentition
lingually. Hence it is suitable for correction of dentoalveolar
Class II malocclusions characterized by lingually positioned
mandibular dentition and labially positioned maxillary
dentition.
 2. Moderate skeletal dysplasia: Moderate skeletal dysplasia in
which moderate amount of mandibular growth and maxillary
incisor retraction may combine for successful treatment. It is
not suitable for management of skeletal dysplasia of any
morphological type that exhibits extremes dysplasia between
the mid facial area and the mandible unless it is to be used as
the first stage of 2-stage treatment.

 3. Ideal for management of Class II malocclusion
resulting from environmental influences e.g. thumb
sucking and chronic mouth breathing if some growth
still remains and the oral habit can be eliminated. The
exact prevalence of this type of malocclusions is not
known but should be suspected in any Class II
malocclusion exhibiting excessive lower facial height
is not due to environmental factors, the activator can
propude further deterioration in the facial aesthetic.

CLASS II MALOCCLUSIONS BEST MANAGED BY THE ACTIVATOR .
 The activator constitutes a form of class II intermaxillary
therapy and if it is used, correctly, it can cause the mandibular
dentition to slip labially. Thus activator can correct
dentoalveolar class II characterized by lingually positioned
mandibular dentitions.
 Activator is less appropriate in skeletal problems associated
with extreme apical base dysplasias due to mandibular
retrognathism. Unless the patient has a favorable amount and
dereliction of growth in the midfacial and mandibular areas,
the, maxillary dentition must be retracted bodily to camouflage
the skeletal dysplasia. The activator is not suited to perform
active bodily retractions of incisor teeth.

 The activator is more suited for class II resulting from
midfacial prognathism when the direction of and
amount mandibular growth are favorable. Retraction
maxillary dentition of is avoided to prevent
overemphasizing nose prominence. The activator
does not perform active bodily retractions of teeth, it
is suited for use in children who need minimal
amounts of maxillary incisor movement while
mandible develops forward to camouflage the
midface prognathism.

 Activator is suitable for the not management of
skeletal dysplasias of any morphological type
that exhibits extreme dysplasia midfacial
between the area and the mandible.

 Class-II division-I malocclusion has the
midfacial area and the mandible were
harmoniously related. With permanent
alteration in the rest position of the mandible
as an chronic nasal obstruction the mandible
assumes an environmentally increased
retrognathic position. This represents a
neuromuscular malocclusion, since its origin
involves the alteration of some very basic
neuromuscular reflexes.

 It is ideal for the management of class II resulting
from environmental influences such as thumbsucking
and chronic mouthbreathing. If some growth still
remains and the oral habit can be eliminated. These
are probably environmental stimulations of skeletal
problems.
 However, if the lower face height excess is not due to
environmental factors, the activator can produce
further deterioration in facial esthetics.

 There is another class II neuro-muscular
malocclusion characterized by a normal path
of closure, excess freeway space and
overclosure may appear class I in overclosed
positioned but they are real class II in rest
position. Obviously this is not a case of deep
bite. But rather of apparent overbite, more
correctly be classified as a complete open bite.

 The cause of this excess freeway space or the complete open
bite is an abnormal posture of the tongue during rest in this
individual. Because tongue rests on the occlusal surfaces, teeth
are not permitted to erupt but the jaws continue their normal
downward and forward growth. As growth continues, the
inhibition of tooth eruption creates an increasing excess
freeway space.
 Orthodontic treatment for this patient would more correctly be
planned around the jaw relationships indicated by the rest
position tracing rather than the overclosed centric occlusion
tracing which actually gives a more prognathic position of the
mandible than actually exists.
 The activator is an ideal appliance to effect the differentia
tooth eruption in the maxillary and mandibular buccal
segments.

CONTRADICATIONS
 Activator is not useful in correction of class I
class II malocclusion with crowding. It may
be used to assist in the correction of
disharmony between in tooth size and jaw size
has been being managed concurrently through
serial extractions.
 Activator is contraindicated in children with
extreme LAFH.
 It should not be used in case where there is
mandibular incisor procumbency at start of
treatment.

 The appliance cannot be used in children with
nasal stenosis caused by structural problems
within the nose or chronic untreated allergy.
 appliance has limited application in the non
growing individuals though it may be used
successfully in cases where clinician has
determined that the patient's facial
morphological condition will tolerate increase
in lower face height.

SKELETAL AND DENTOALVEOLAR EFFECT OF
ACTIVATOR
 During craniofacial growth the activator is
capable of influencing the third level of
articulation, as outlined by MOFFET, i.e. the
sutures and the TMJ. This efficiency is
determined by construction bite.
 SKELETAL EFFECT - is dependent on the
growth potential.

 Two divergent growth vectors propel the jaw bases in
an anterior direction.
 Sphenooccipital synchondrosis moves the cranium base.
 and nasomaxillary complex upward and forward.
 The Activator can, to a limited degree control this
upper growth vector which moves the maxillary base
in a forward direction. If the mandible cannot be
positioned anteriorly, the growth and translation of
the nasomaxillary complex can be influenced.
 The vertical skeletal relationship must be assessed
and can be altered, if need be by the activator.
 Rotations of mandibular growth vectors can be
compensated by changing the maxillary base
inclination.

 A downward displacement of the maxillary base allows an
adaptation of the maxilla to a vertical rotation of the mandible.
 Activator constructed with vertical opening only effect
primarily the midface development in the subnasal area.
 Both vertical maxillary growth and eruption of teeth are
restricted.
 DONALD WOODSIDE believes that a small vertical opening
restricts only the horizontal midface development whereas a
wide vertical opening achieves the restriction by the
downward displacement of the midface area.
 A decrease in SNA angle can be observed unless the bite
opening is extreme. In such cases the maxillary plane is then
tipped forward and point 'A' moves a little forward.

 The second growth vector, the condyle translates the
mandible in a downward and forward direction. The
activator is most effective in controlling this vector or
the downward and forward growth of the mandible.
 This effect can be designated as an articular
one, because of the promotion or redirection of
condylar growth.
 Only the upward and backward growth of the condyle
is capable of moving the mandible anteriorly.
 According to MOSS, PETROVIC, Condylar growth
is an expression of a locally based homeostasis for the
establishment and maintenance of a functionally
coordinated stomatognathic system.

 PETROVIC's research has shown- the lateral
Pterygoid m. plays decisive role.
 Forward posturing of the mandible activates
the superior head of lateral pterygoid &
induces cell proliferation & growth in young
individuals.

Effect on mandible
 Birkebaek et al (1984): laminographic implant
study-
 1.1mm increase in condylar growth in 10 months
 Slight forward displacement of glenoid fossa
 1.1mm increase in LAFH
 Increase in MPA by 2.5 degree
 Demner el al (1961), Vargervik & Harvold
(1985) found similar increase in mandibular
length.

 Pancherz (AJO 1984):
 Evaluated 30 class II div I children in the mixed
dentition who were treated sucessfully
 Only 0.3mm increase per year, not statistically
significant.
 Bjork (AJO 1951), Watson (AJO 1981)
observed similar results.

Effects on maxilla
 Williams & Melsen (AJO 1982)- demonstrated
backward rotation of mandible due to increase
in posterior maxillary height.
 Forseberg & Odenrik (EJO 1981) noted a
significant decrease of the SNA angle
 Vagervik & Harvold (AJO 1985)- inhibited
horizontal growth of maxilla by 2mm
 Pancherz (AJO 1984) found restriction by
1.7mm

Dental effects
 Various tooth movements have been observed
during activator therapy-
 Forward displacement of anterior segment (Bjork
1969)
 Bodily displacement of incisors (Jacobsen in 1967)
 Labial tipping of lower incisors (Richardson in
1982)
 Lingual tipping of lower incisors (Moss in 1962)

 Studies by Bjork, Weislander & Harvold
showed following effects-
 Class I occlusion was achieved through distal
tipping of maxillary teeth & mesial mov. Of
mandibular dentition.
 70% of overjet was corrected by incisal tipping-
50% by lingual movement of maxillary incisor
while 22 % by mandibular incisor flaring.

Effect on soft tissues
 Forsberg & Odenrick (EJO 1981)-
 Significant lip retrusion
 No difference in nose growth
 Significant forward positioning of soft tissue
pogonion
 Lip balance was not achieved in pts with relatively
retrognathic profiles or those with steep MPA’s

WHY ARE ORTHOPEDIC DEVICES MORE
EFFECTIVE ON MANDIBLE
AND NOT ON MAXILLA?

EFFICACY OF ACTIVATOR
 With the proper construction of the appliance,
muscles of mastication that are extended
slightly past resting position are automatically
stimulated to contract (stretch or myotatic
reflex) according basic muscle physiological
principles. The same contractive tendency
occurs when the sublingual muscles are
extended by the forward positioning causes
labial tipping or Labial bodily movement of
lower incisors.

 ANDRESEN and HAUPL believed that the presence
of a loosely fitting activator increases muscles of
mastication against the appliance.
 Intermittent movements of the appliance in
swallowing and biting deliver distal and intrusive
forces to maxillary teeth engaged in the appliance.
 Activator being trimmed loosely, it will drop when
the jaws relax. The patient must be conditioned to
bite into the appliance to keep it in position, and if
correctly motivated, a conditioned reflex is soon
developed and this act is performed while sleeping.

 So when the mandible moves mesially to
engage the appliance, the elevator muscles of
mastication are activated, the myotatic reflex is
activated, so that in addition to the muscular
force delivered during swallowing and
biting, the reflex stretch stimulation of the
muscle spindles also elicits reflex muscle
activity.

 Thus forces elicited result in tooth movement
and bone remodelling and may prevent further
forward movement of maxillary dentoalveolar
process or move it slightly distally.
 The activator of ANDRESEN & HAUPL
works by using kinetic energy.

Why appliance s/b loose fitting
 The superior heads of the lateral pterygoid have
the most important role, since they assist in
skeletal adaptation.
 The fundamental requirement for stimulation is
ability the to activate pterygoids.
 An appliance holding the mandible rigidly in
anteriorly displaced position does not activate LPM
m. & hence does not stimulate condylar growth.

Timing of treatment

Fabrication of activator appliance
 Diagnostic preparation- Patient compliance is
essential. It is important to clinically assess the
somatic and psychological aspects for each patient
also determine the patient's motivation potential. This
may be enhanced by creating an instant correction in
class II by moving the mandible forward into a more
normal sagittal relationship. Patient sees the potential
and objectives of the correction to be brought about
by the appliance and is more likely to work toward
this goal of esthetic improvement.

 In some cases of maxillary protrusion and
excessive vertical dimension with reduced
symphyseal prominence, A forward
positioning will not make the profile look
better, in which case other treatment measures
are employed.

VTO

PRETREATMENT CONSIDERATIONS
 Before treatment with the activator is started, the
forward movement of the mandible should be
checked to see that it is not blocked by the occlusal
interferences that make the correction of the
distocclusion impossible, which is usually by,
 Narrow intercanine dimension.
 Lower second molar slightly over erupted distal to the first
molar, it will impede the forward movement of the
mandible.
 Overeruption of maxillary second deciduous molar into the
space created by the premature loss of its antagonist.
 A quite common and easily overlooked causes for
interference is the buccal cross bite of an upper premolar.

Before bite registration few analyses have to be done.
 Study Hodel Analysis:
 1. The 1st permanent molar relationship.
 2. Nature of midline discrepancy if any
 3. Symmetry of the dental arches is determined.
 4. Curve of spee is checked to see if it can be leveled with the activator.
 5. Crowding and any dental discrepancies
 Functional Analysis:-
 1. Rest position
 2. Path of closure
 3. Prematurities
 4. THJ examination
 5. Interocclusal clearance
 6. Respiration
 Cephalometric Analysis
 1. The direction of growth
 2. The difference between the position and the size of the Jaw bases.

 ANDRESEN'S first activators did not displace mandible
beyond the physiologic rest position relative the vertical and
was 3 mm short of the limit of the patient's tolerance relative
to the protrusion.
 First to oppose was SELMER-OSLEN
 1. Muscles couldn't be stimulated at night, for this was the
time nature used to give them rest.
 2. Forces delivered to the teeth by the appliance were a
form of potential energy and not kinetic energy.
 3. Andresen's 2-4 mm opening in molar region is beyond
physiologic rest position.
 4. He said Andresen is wrong if he thought an appliance
holding the jaws a 2 mm beyond is a truly functional
passive appliance.
Construction bite

 PAUL HERREN- activator didn't work according to
Andresen's theories at all, even if it was constructed within the
physiological limits of rest position. His construction bite is in
sagittal direction, the mandible is positioned in an
overcompensated by 3-4 mm. Vertical opening - 2-4 mm plus
the deep bite that is already present.
 The Louisiana state university acivator of ROBERT SHAYE
(1982) essentially follows the same design and principles.
 HARVOLD (1974) said you have got to go Stretch the
muscles, the more stretch, the better. His construction bite - 3
mm short of patient's limit of tolerance in .protrusive position
but with a 8-10 mm vertical opening beyond the rest Position.

 WOODSIDE (1974-75) - said to go even further
beyond rest position to 12-15 mm
 GRABER and NEUMANN said use a combination of
bite opening and protrusion to equal to 10 mm. In
other words, if you open the bite 4 mm between the
occlusions posteriorly then advance the mandible by
6 mm.
 BALTERS of Germany advocated protrusive incisal
end-to end with an interincisal opening of 2-3 mm.

 Construction s/b made considering
vertical, horizontal & transverse planes

Horizontal posturing of mandible
1. The original sagittal jaw relationship may be maintained.
2. Mandible may be positioned forward to change the sagittal
relationship equally on both sides.
3. The bite is changed on one side but is maintained as much as
possible on the other side as with a unilateral Class II Div. 1 or
class II Div. 2 or class III. This means that a normal midline
relationship exists in postural rest, but a midline swing to the
side that is forced in the habitual occlusal relationship.
4. The mandible is postured backward as much as possible in the
fossa, opening the bite enough to try for an end to end incisal
relationship or as close to this as possible, in class III
malocclusions.

Vertical opening of mandible
 Dependent on three major considerations:
 (1) The kind dysgnathic problem (Sagittal and
vertical relationships, morphogenetic growth
pattern)
 (2) the developmental state, sex, and age of the
patient (potential incremental change)
 and (3) the type of activator to be used.

Type of malocclusion:
 Different sagittal and vertical dysplasias require
different construction bite registrations. For example,
in deep bite Class II, Division 2 and Class III
malocclusions, it is necessary to record the vertical
distance between incisal of lower incisors the upper
and margins determining how wide open the
construction bite should
 In permanent dentition cases (specifically in Class II
Division II malocclusions or class I Division 2
symptoms, or in anterior cross bites, e.g., Class III
malocclusions), it is best to open the bite the for the
construction registration a distance of 1.5mm to 3
mm, vertically beyond the incisal edges.

 In the mixed dentition, it should be increased to 4
mm. to 7 mm. Thus, the original overbite is a
determining factor.
 In the Class II, Division malocclusion 2 a severe in
the permanent dentition, the bite may have to be
opened up to 9 mm. in the molar region and
occasionally more.
 Woodside feels it improves the chances of retention
during sleep and enlists the viscoelastic properties of
the stretched soft tissues.

 The reason the bite can be opened so far is that type
of Class II, Division 2 malocclusion most frequently
has a palatal plane that is tipped down anteriorly
along with a deep bite and an excessive curve of spee.
A large bite opening can improve the maxillary
incisor inclination because the anterior end of the
palatal plane is with held or tipped up and this also
reduces the deep overbite because the lower incisors
are under intrusive action as the maxillary base
rotates upward and forward.

 The wide open construction bite brings the mandible
out of the range of any tooth guidance and resultant
retrusive effect on the condyle and the path of
closure. Also such cases usually do not have a severe
sagittal malrelationship and usually have a good chin-
button morphological appearance so rocking open the
bite, which drops the symphysis down and back, does
not have a deleterious effect on the profile. This is
particularly true since in most of these cases there is a
horizontal growth pattern.The large vertical opening
improves the growth direction and allows the full
eruption of the posterior teeth, which are usually in
marked infraocclusion.

 If only mandibular positioning is needed, or a
small anterior posturing is required the (only
maxillary teeth spaced & labially inclined ) ,
the vertical opening should be rised more in
order to elicit more positive functional and
viscoelastic response from musculature.
 Class II, Division 1 problems demanding
more horizontal posturing to establish correct
maxillomandibular relationship, a smaller
vertical opening is needed, particularly if the
growth direction axis is along the y axis.

 In cases with a more vertical growth direction
and a deep overbite, a larger bite opening is
desirable for the construction bite registration
This allows some downward and backward
compensation of maxillary growth (and palatal
plane) to fit the mandibular growth pattern.

 In Class II, Division I malocclusions in which
 (1) the sagittal malrelationship is the width of a
whole premolar;
 (2) there is a severe curve of Spee
 (3) the lower incisors are over erupted, impinge on
the palatal mucosa, the construction bite should not
be higher than vertical end to end relationship.

 This is because the interocclusal distance in the molar
region, with infraocclusion of the molars and
supraocclusion of the lower incisors, might exceed 7
mm which would be excessive because of the
possible lateral spread of the tongue.
 If moderate curve of Spee vertical opening s/b
increased to allow for posterior eruption & getting
favorable muscle balance. In such cases, 4mm.
Between incisal edges is desirable, and it can
occasionally be even more.

 In the case of a synchronous downward and backward
arciform growth pattern and an average incisor
overbite, caution is the watchword, so as not to
accentuate the molar eruption too much, which will
create a more retrusive profile and possibly induce an
anterior open bite that will be difficult to close.
 The interocclusal space should not exceed 4 mm in
the molar region. The same applies to anterior open
bite problems. The interocclusal acrylic table or tooth
bed should not be ground away in such cases, but
rather should maintain constant intrusive contact on
the upper and lower posterior teeth in both arches.

Type of activator

Transverse posturing of mandible
 If the upper and lower midlines do not coincide, a
determination must be made as to the fault - maxillary
or mandibular. The patient is observed in postural rest
position to check the midlines and is then asked to
slowly close the mouth into full habitual occlusion.
 1. Midlines of postural rest position and occlusion
coinciding - construction bite no change.
 2. Postural rest position coincides with midlines while
occlusal position does not, this is due to shift from one side
to other, occlusal interferences should be checked.
Construction bite should follow the resting Position midline
relationship.

 3. Midlines of both in rest and occlusion - caused
by shifting of teeth in one jaw or the other. The
construction bite should line up with the midlines
of maxilla and mandible regardless of shifting of
teeth. Dental midline discrepancies caused by
shifting and malposition of the teeth can be
corrected late with the fixed appliances.
Occasionally a short pretreatment fixed appliance
to correct midline.

Construction bite planning
 The purpose of the construction bite is to
fabricate an appliance that induces the
following effects:
 (1) to bring the lower jaw into a tolerable forward
position with every occluding action of the
mandible
 and (2) to "block the bite“ depressing the lower
anterior teeth and stopping their eruption, while
attempting to stimulate eruption of the posterior
segments.

 Taking the construction bite one should look at
the bite in three different planes of space:
sagittal , vertical and frontal.
 Therefore it is first necessary to clarify three
points using the procedure developed by
Schwartz.

Anterior positioning mandible
 The usual intermaxillary relationship for the
Class II problem is that of end to end an
average incisal relationship. However. it
should not exceed 7 mm to 8mm. Or quarters
of the mesiodistal dimension of the first
permanent molar. Anterior positioning of this
magnitude is contraindicated in the following
instances:

 If the overjet is too large (in extreme cases
approach 18 mm) the anterior positioning
becomes a stepwise progression to be
accomplished in two or three phases.
 If there is severe labial tipping of the maxillary
incisors. they should probably be uprighted
first if possible by a prefunctional appliance.

 If one of the incisors usually the lateral incisor
has erupted markedly to the lingual the
mandible must be postured anteriorly to an
edge to edge relationship with the lingually
malposed tooth otherwise labial movement of
this tooth would not be possible. Eschler
termed this a "pathological" construction bite.

THE EXTENT OF MAXIMUM FORWARD MOVEMENT OF THE
MANDIBLE (SCHWARZ)
 In a normal case, the maximum forward movement of
the mandible averages 9-10mm, but as little as 6-
7mm. The optimal forward movement of the
mandible for the construction bite is usually half the
individual’s maximum range. There are three reasons
for this –
 more uncomfortable for the patient
 The distance of 5mm is approximately is the same as that
between the points of the buccal cusps of the first molars.
This is the amount of distance necessary to change a class
II malocclusion into a class I occlusion.

 It is claimed that one of the best positions for
obtaining the desired histological transformation of
the TMJ from a Class II malocclusion into a Class
I is l approximately half the distance that the
condyle can move forward along the anterior wall
of the fossa to the articular tubercle.

Opening the Bite
 There are some guiding principles in
maintaining a proper horizontal vertical
relationship and determining the height of the
bite-
 The mandible must be dislocated from the resting
position in at least one direction - sagittally or
vertically. This is essential in order to activate the
associated musculature and induce a strain in the
tissues.

 If the magnitude of the forward position is great
(7mm- 8mm), the vertical opening should be
minimal so as not to overstretch the muscles. This
type of construction bite means an increased force
component in the sagittal plane, enabling a forward
positioning of the mandible. The primary
neuromuscular activation is in the elevator muscles
of the mandible.

 If the vertical opening must be extensive, the mandible
must not be anteriorly positioned. If the bite opening is
more than 6 mm, mandibular protraction must be very
slight. Myotatic reflex activity of muscles of mastication
can then be observed as can a stretching of the soft tissues.
A more extensive bite opening is possible in functionally
true deep-bite cases. If the bit registration is high both the
muscles and the viscoelastic properties of the soft tissues
are enlisted.
 The vertical force is increased and the sagittal force is
decreased. This type of construction bite is not effective in
achieving anterior positioning of the mandible, but the
inclination of the maxillary base can be influenced.

 One possible indication of this type of construction
bite is in the case vertical growth pattern. In such
cases, the vertical relationship, either deep bite or
open bite, can be therapeutically affected the
activator.
 The disadvantages of a wide construction bite are the
difficulty in wearing appliance, with increased
difficulty of patient to adaptation. Muscle spasms
often occur in such cases, and appliance tends fall out
of mouth. The wide open construction bite also
makes the lip seal difficult. Yet the reestablishment of
a normal lip seal is essential requisite of functional
appliance therapy.

The Extent of the Individual's Occlusal Clearance in the Resting
Position: (Schwarz)
 Clinical experience indicates that the opening
of construction bite in excess by approximately
2mm individual's position is optimal. Resting
individuals the interocclusal clearance amounts
to 2 mm to 3mm in the molar area. and 4mm.
to 5mm in the incisor area. An opening of 4
mm to 5mm in the Molar area and 6mm to
7mm in the incisor area frequently will
desired.

 As we know from the study of rest position
when mandible is open beyond this position.
the condyle moves downward and forward on
the articular eminence. Thus the bite open
more than 5 mm. in the molar area, forward
movement of 4mm. will suffice.

 Highly experienced clinicians such as Petrik and
Herren entirely disregard the rest position.
 Petrik – The upper and lower incisal edges should
meet in as close to an to edge relationship as possible
in a horizontal plane. This maneuver will generally
leave the incisors 1mm to 4mm. Apart at most, with a
posterior bite opening of 4mm. to 7mm. Contrary to
many other clinicians, Petrik also given preference to
bring the mandible forward to the complete desired
distance at once, not in stages.

 The configuration of the original malocclusion and
the movability of the mandible must be studied
carefully before deciding which technique to follow.
 Taking the construction bite is a most important step
in the treatment. It should be done directly in the
patient's mouth. No articulator duplicates the exact
condylar pathway as in the patient.

General rules for the construction bite:
 If the forward positioning of the mandible is 7mm to
8mm the vertical opening must be slight to
moderate(2mm-4mm).
 If the forward positioning is not more than 3mm to
5mm the vertical opening should be 4mm to 6mm.
 Lower midline shifts or deviations can be corrected
by the activator only if there is actual lateral
translation of the mandible itself. Functional cross
bites that are observed in the functional analysis can
be corrected by taking the proper construction bite.

 Both experimental research and clinical experience
have shown that an increase in muscle activation with
overextended appliances does not increase the
efficiency of the activator.
 Acc to Sander- the frequency of maximal biting into a
6mm. high construction bite is 12.5 percent of the
sleeping time, whereas in an 11mm construction bite
it is only 1.1 percent of the time. If the height is
increased to 13mm as prescribed by Harvold,
maximal biting takes place only 0.8 percent of the
time.

EXECUTION OF THE CONSTRUCTION BITE
TECHNIQUE
 First, a horseshoe-shaped wax bite rim is
prepared for insertion between the maxillary
and mandibular teeth.
 Choice to keep bite on lower or upper arch

 Before taking the wax bite registration, the
patient is seated in an upright position. The
posture should be relaxed and not strained. The
mandible is then gently guided the
predetermined position. The operator guides
but not force the jaw into the desired sagittal
relationship. This exercise is repeated three or
four times.

 The patient is asked to repeat the exercise
alone and then hold the forward position for a
while to set up an exteroceptive engram that
can be replicated when wax is placed between
the teeth.

 After the operator is relatively sure that the patient
can replicate the exercise, the softened wax bite
placed in the mouth in the manner already described.
 Wax should not be too soft. During the closing
movement, the operator controls the edge to edge
incisal relationship and the midline registration.
 To visualize the midlines & to establish correct
reproduction of the incisal relationship, wax should
be cut away from the labial surface of the central
incisors.

 In the final step, the wax is carefully removed from
the mouth without distorting and is checked on the
upper and the lower models and chilled.
 After it has been fitted on casts, the margins are
trimmed with a scissors, so the operator can be sure
the wax is in close approximation to all the cusps of
the teeth.
 The hardened wax bite is then checked once again in
the mouth.

Sequential steps for the construction bite: Schwartz
 The following step by step procedure for taking the construction bite is
suggested:
1. Reproduce the maximum forward movement of the mandible and the correct
occlusal clearance of postural rest. Observe whether a functional lateral
shift occurs and register the true mandibular midline with a pencil on the
labial surfaces of the upper and lower incisors on the casts and in the
patient's mouth.
2. Determine the amount of mesial and vertical mandibular displacement
necessary for the construction bite. It is helpful to mark the amount of
mesial shift with a pencil on the buccal surfaces of the first molars.
3. Show the patient on the casts and in the mirror in which direction the
mandible should be moved. Practice the forward mandibular movement by
gently guiding the mandible in the desired direction.

 Advise the patient to move the jaw slowly according to the
verbal instructions and to stop movement immediately when
asked to do so. Talk to the patient in a calm, reassuring
manner.
4. Soften a sheet of beeswax and make a tight roll, approximately
1 cm in diameter.
5. Shape the roll to conform to the lower dental cast, leaving the
seam on the inside. Press the softened roll of wax on the lower
arch so that only the buccal teeth are covered. In the front, the
wax roll lies just lingual to the lower incisors. Make a groove
on the wax to indicate the midline. Remove any excess wax
that extends onto the retromolar tissue. The distal half of the
last molar tooth should not be covered with wax.

6. Transfer the wax to the patient's mouth, fitting it on the
lower arch in the same manner that it was fitted on the
plaster cast.
7. Move the mandible forward as was previously practiced.
If the registration fails, make a new wax roll and repeat.
8. Remove the wax bite from the mouth and chill it. With a
sharp knife, trim the excess buccal wax until the occlusal
surfaces of the molars are visible. By carefully checking
the plaster casts, also remove all wax that is contacting
the soft tissues, the interproximal papillae, and the
palate. If this is not done, the wax bite cannot be seated
properly on the casts.

9. Place the wax bite between the casts and check
that the mandible is moved forward the desired
amount in the three planes of space. If the
construction bite is incorrect, replace it on lower
cast, and soften its superior surface add a layer
of warm wax. Repeat the procedure from No.6
through No.1O.
10.Replace the hard wax bite in the patient's
mouth and have the patient close the jaw slightly
more firmly to assure the correct fit.

Mounting & fabrication of appliance
 After the construction bite is taken and
checked in the patient and rechecked on stone
working models, the working models are
mounted on the fixator.
 Fixator- Allows upper and lower parts to be
made separately.

Making of wire elements
 Labial bow – horizontal portion can be kept
above or below area of greatest convexity
depending on overbite.
 Passive- .8mm
 Active- .9mm

 Labial guide bow philosophy- when appliance
in mouth- pt can close only by bringing
mandible forward.
 When pt speaks or moves jaw up or down, the
sensory n’s of the maxillofacial complex sense
the smooth coordinated action the labial bow
as it slides up & down over the 6 anterior
teeth.

 These receptor help activate the oro-facial muscles to
keep the mandible in the protruded position as it
closes to keep the appliance moving vertically in a
smooth and coordinated motion.
 The labial guide bow also acts to hold the inner
surface of the upper lip away from the premaxilla and
anterior teeth. The space or clearance of I mm
between the wire and labial surface of teeth which is
sufficient to break the directness of the force vector
of the weight and strain of the upper lip in this area.

 Due to the increased vertical dimension of the
appliance the perioral musculature is put to
increased myotonic tension. This myotonic
tension is further increased when lips attempts
to seal during swallowing. This increased
pressure can rotate a premaxilla, teeth and all
in a distal direction without something to stop
to it.

 The labial bow anchored against the acrylic
base of the appliance and by means of this,
through force vectors to the mesial of first
molars holds the lip away from the teeth and
bone just enough that no movement of this
type will occur. Therefore the myotonic stretch
placed on the orofacial muscles by the
appliance causes a distal drive to be exerted
through the interproximal evaginations of
acrylic.

 Since the premaxilla and anteriors are not
bound by either the labial bow or appliance
acrylic, they feel none of this distal drive. As a
result they stay in the same relative
cephalometric position while the posterior
segments of teeth and the appliance itself drifts
distally

 The greatest amount of myotonic tension exists
during the first 3 months. The appliance is worn
before the muscles and mandible have repositioned
themselves, the labial bow is usually kept off of the
front teeth at this time to take full advantage of the
distallizing forces made available to push the
maxillary posterior segments.
 In the fourth month it is adjusted to contact, to assist
in the rotation of the teeth and bone to a more
conventional arch form.

How made

 The coffin spring- Shaped like the greek letter
Omege, introduced into orthodontics around in 1880,
it serves three main functions to the activator.
 First, it acts as a tongue trainer, helps correct the deviant
swallowing pattern and tongue thrust by causing the base of
tongue to seal itself against the soft palate during
swallowing and thus prevented the tip of the tongue from
scamming up against the lingual surfaces of the anterior
teeth and the premaxillary rugae area.

 Secondly, the coffin spring can be used .as an
active component in moving the buccal posterior
segments laterally.
 Thirdly, for entirely practical reasons the coffin
spring is great for giving the appliance strength,
durability and stability in the mouth.

FABRICATION OF THE ACRYLIC PORTION
 The appliance consists of upper, lower and
interocclusal parts. The dental and gingival
portions can be differentiated in lower.
 If the construction bite is high, the extension of
the flanges is greater than for as horizontal
type of activator, which positions the mandible
more anteriorly.

 This extension is important to enhance the retention
of the appliance, particularly for the vertical activator,
because the patients habitually have an open mouth
posture.
 The flanges for the upper part are 8-12 mm high in
the gingival area, covering the alveolar crest.
 If the acrylic part is thin in the palatal region, it may
cause too much appliance flexibility. To increase the
rigidity a palatal bar can be used.

 The lower acrylic plate is 5-10 mm wide in the
molar area. It is sometimes greater with
flanges 10-15 mm.
 After the appliance has been carefully checked
for proper fit in the mouth, an exact plan of
needed tooth movement is developed.
Approximate trimming can be done on plaster
casts. However, the final grinding must be
done in the mouth.

 Any undercoat acrylic surfaces that might
interfere with the planned tooth guidance must
be removed This potential problem can be
checked with an explorer or visualized by
checking the shadows created on the acrylic by
undercut surfaces.

 Since there is always a bit of adjustment and to
be expected while the appliance is worn during
the first couple of weeks, the final trimming is
not done until the second visit in most cases to
achieve the best possible efficiency.
 The acrylic areas that contact the teeth are
likely to become polished & thus area of force
delivery can be well identified. Then careful
grinding can be done.

PRINCIPLE OF THERAPEUTIC TRIMMING FOR
TOOTH GUIDANCE
 Selective guidance of the eruption of teeth and
development of arch form is necessary in
addition to the elimination of all possible
functional retrusive muscle activity and
attempts to get the best possible condylar
growth adaptation to the more correct sagittal
relationship.

 The aim of trimming is to achieve a loosely fitting
appliance that patient can yet manipulate the one that
maintains the sagittal relationship while stimulating
or restricting selective eruption and movement of
anterior and posterior teeth.
 The acrylic transmit the desired intermittent force and
contact. The teeth are called guiding planes. The
magnitude of force is determined by the amount of
actual acrylic contacting the tooth surface.
 Larger the contacting surface lesser is the force
delivered.

 Trimming in to control tooth movement in 3
planes of space-
 Vertical
 Transverse
 sagittal

Advantages
 Forces employed are physiological and produce no
damage to teeth or supporting tissues.
 Intervals between adjustments are less (6.8 wks).
 Minimum hygiene tissue oral problems, minimum
irritation and damage.
 Appliance worn at night.
 Appointments are brief.
 Uses existing growth of the jaws to the maximum.
 Provides in excellent control vertical direction
particularly overclosure.

 Useful in correction of malocclusions
associated with habits Thumb sucking, Tongue
thrusting.
 After treatment appliance, itself acts as a
retainer saving cost & professional time.
 Cost factor is low.

DISADVANTAGES
 Careful case selection.
 No detailed precise finishing of occlusion.
 Full reliance on patient for successful
treatment.

Biological effects of appliance in corrections class-II
division-l malocclusion
 Following findings by McNamara, Moyers
into 6 categories:
1. Remodelling of mandibular condyle -
 Adaptive changes in 3 general layers of condylar
cartilage.
 Surface changes at anterior aspect of posterior
glenoid fossa.

2 Retardation or redirection of horizontal maxilla
growth- Basal area of maxilla are retarded in their
normal forward development.
3. Mandibular rotation- Increased height of mandibular
alveolar process and variable degree of rate of
eruption of teeth in buccal segment resulting in
backward rotation of mandible.
 This may be compensated by vertical growth of condyles at
a later age. An increase of LAFH is inevitable.

4. Dental arch changes –
 Distal migration of maxillary molars.
 Mesial migration of mandibular molars.
5. Altered eruption of teeth in buccal segments-
vertical eruption of maxillary posterior teeth
inhibited. Eruption of antagonist take place can
undisturbed and free of occlusal imbalances.

6. Incisor tipping
 Immediate to anterior displacement of response
mandible occurs within dental arch - incisor
region.
 Average activator treatment
 Initially - dental changes predominate
 Later - Increase in SNB, Decrease in SNA, skeletal
effect.

Modifications of activator

ANDRESEN-HAUPL ACTIVATOR
 As already mentioned the term activator was coined jointly by
Andersen and Haupl in their textbook "Functions Keifer
orthopedic" published in 1936.
 Hence the first activator is known as "Andresen Haupl
activator ".
 The original appliance combined an upper and lower plate of
the occlusal level and was made vulacanite rubber.
 Only one wire element was used – a maxillary labial bow
made of -0.8 to 0.9mm SS wire. The appliance had to be
remade several times to complete the treatment. For expansion
the appliance was split in the centre and a flexible coffin
spring was incorporated.

 Later the body was replaced by acrylic and the labial
bow incorporated was with two U- loops in the
canine regions with the retaining arm passing through
canine and 1st deciduous molar or 1st premolar. The
labial bow could be active or passive.
 Later when Andresen and Haupl incorporated with
Petrik and published the fifth edition of their back in
1957 many additional wire elements were described.

 Several modifications have been done
thereafter which will be discussed later.

Harvold Woodside activator
 The initially small inter-occlusal distance with a
construction bite was increased in subsequent edition
of the Andersen-Haupl text. The vertical
displacement of the mandible was increased first in
order to prevent the loss of appliance during sleep in
some cases. When Petrik got involved in the team the,
myodynamic appliance of Andersen & Haupl became
myotonic appliance. Importance of the change over
escaped attention until it was pointed out by
Slagsvold.

 Important aspects of Harvold-Woodside activator -
1. Vertical construction bite: Harvold in 1971
originated the idea of using viscoelastic properties of
the muscles and soft tissues as force generators. He
places the mandible approximately 3mm distal to the
most protrusive position that the patient is able to
achieve whereas vertically an extreme separation of
the jaws is used so that the mandible maybe opened
8 - 10 mm beyond the free way space. Woodside uses
vertical separation of approximately 12mm - 15mm
beyond the daytime rest position of the mandible.

The proponents of this concept contend that the use of
myotatic reflex along with attempts to increase the
frequency of biting and swallowing should be largely
ignored, letting passive tension (vjscoelastic
properties) in the stretched labial and oral
musculature deliver the primary force to the
appliance. Thus the power to produce alveolar
remodeling is obtained from the inherent elasticity of
muscles, tendinous tissues and skin without motor
stimulation. This is mediated through clasp knife or
autogenic inhibition reflex.

2. Functional occlusal plane and use of differential control of
teeth eruption –
 If there is minimal eruption of the maxillary posterior teeth
and over eruption of the mandibular posterior teeth there
will be a distinct tendency for the establishment of a Class
III MO or the functional occlusal plane established itself at
a higher level. Conversely, if there is a minimal eruption of
the mandibular buccal segment and an over eruption of the
maxillary buccal segments, the functional occlusal plane
will be established at a lower level and the mesial
component of the maxillary buccal segment eruption will be
over emphasized. These changes may contribute to the
establishment of Class II relationship.
 In Class II activators Harvold Woodside used this principle
of differential control of tooth eruption and allows eruption
of mandibular posterior teeth.

 APPLIANCE:
 Similar to Andersen Haupl activator with some
differences -
 Flanges: To further assist appliance in position during
sleep, the mandibular flanges extended deeply lingual to
the molars to condition the patient to retain the activator in
the mouth. If an attempt is made to remove it with tongue,
the deep flanges will rub on the under cut surfaces of the
mucoperiosteum and irritate the tissues. The patient quickly
learns that this discomfort can be avoided by biting firmly
into the appliance. The under cut lingual flanges are
therefore another conditioning device.

 Labial arch wire:
 The labial arch wire is made of 0.9 cm SS round wire. The
labial arches are commonly of two designs.
 a. Hawley retainer type.
 b. Andresen type.
 A modified Andresen design is used when there has
been considerable narrowing of the maxillary arch in
the canine region resulting from muscle contracture
force. This design release the force of the cheeks
from themaxillary canine area and permits normal
arch formed to be restored.

 Dislodging Springs: Heavy gauge dislodging springs
are placed passively against maxillary 1st permanent
molars and are adjusted distally 05. mm.-They are not
intended to move the molars distally but are intended
to create a dislodging action within the appliance.
Such action helps pt. to bite into the appliance to keep
it in position. For this reason the dislodging springs
act as additional activators of the muscle of
mastication. They also provide friction against the
mesial surface of the maxillary first molar and in the
activators in which the acrylic has been trimmed
occlusally in the maxillary buccal segments; they tend
to prevent its eruption. Thus dislodging springs may
assist in the correct manipulation of the functional
occlusal plane.

Herren’s activator
 Herren was disappointed by low success rate of
Andresen - Haupl- Petrik activator, which was less
that 50%.
 While observing patients wearing activator at night
and watching his own musculature while using the
activator he realized that the activator acted only like
a passive splint at night. Herren's research cleared up
the mystique about active jaw movements that the
appliance supposedly elicited at night.

 The Herren or LSU activator of Robert Shyae
is as such modified as follows:-
 1. Overcompensating construction bite for the
positioning of the mandible.
 2. Upper molar clasps, which secures a
positive splinting effect during the whole
night.

 Modus Operandi -
1. Any inert activator acts like a splint. It is a "myotonic
appliance", to use the term rightfully coined by
Graber. In class II, malocclusion, the construction
bite of Herren activator dislocates the mandible
forward by a total of 8mm or more. When a child
inserts the activator the mandible is purposefully
carried forward until it is possible to bite completely
into the positioning splint. The mandibular teeth then
fit comfortably in the inert appliance which braces the
incisors and canines as well as the lingual surfaces of
the posterior teeth.

 The lower dental arch is supported against the
pull of the stretched retractor muscles. The
mandible is kept from being retracted because
the activator take the load of these forces and
transmit them in an occlusal direction to the
maxillary dental arch. Since action equal
reaction, a force of equal magnitude and
opposite direction acts against the mandibular
dental arch.

 According to Graf, an average of 100N of force was
measured for every millimeter of mandibular forward
shift. When mandible is displaced forward by 8 mm,
around 300g of force is generated.
 The activator holds the retractive musculature of the
mandible " passively stretched. In contrast the
protractors are slackened.
 Auf der Maur - found that two patients who were
wearing a Herren activator showed no
electromyographic activity within the lateral
pterygoid muscle.

2. Although forces are generated in a transverse
direction but not sufficient to cause expansion. Hence
an expansion screw may be used.
3. Moreover, 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 tooth, provided that the acrylic occlusal stops
of posterior teeth are ground away from the
appliance. It should be kept in mind that this effect
lasts for only about 9 hours of sleeping time and
might be counteracted by strong occlusal forces
during day time.

 Construction Bite
1. Positioning the mandible in sagittal direction dominates
over the vertical direction
2. Anterior positioning: - From the post normal
distoocclusion the mandible is carried forward not only to
class I molar relation but also an additional 3 mm to 4mm
beyond neutro occlusion.
3. Vertical positioning: -In deep bite cases, the incisor edges
are kept 2-4mm apart to allow sufficient amount of
acrylic to be present between incisors. This allows
removal of acrylic along the lingual surfaces of Maxillary
when needed. Therefore the posterior vertical opening
depends upon the amount of anterior overbite. The
vertical interocclusal distance in deep overbite totals the
amount of overbite plus 2 to 4 mm.www.indiandentalacademy.com

 In an open bite, the incisor relationship
furnishes no indicator for the vertical thickness
of the construction bite. In such instances, the
interocclusal distance between upper and
lower molars is decisive (4mm to 6mm). Thus,
the wax bite keeps the mandible constantly
open beyond the rest position in the sleeping
patient.

 In Class II mesiocclusions without midline
deviation, care must be taken that upper and
lower dental arch, midline coincide in the
construction bite. When properly taken, the
over compensating construction bite it class II,
Div I mesiocclusions often brings the incisors
into an edge to edge & when the upper
incisiors are not markedly relationship and
occasionally proclined, even beyond. In class
II Div 2 Malocclusions the incisal edge
relationship may approach an anterior cross-
bite while the construction bite is taken.

 Peculiar feature of Herren's Activator:
 Retention of activator by arrow head & Jackson or
Duyzings clasps - Herren argues that different position of
mandible during sleep will not allow activator to be
retained in its place hence; he advocates use of clasps to its
retention.
 Incorporation of Expansion Screw- In the majority of
patients a midline expansion of the maxillary dental arch is
required to obtain a normal buccolingual occlusal
relationship between the dental arches when positioning the
mandible forward into the desired class I relationship. An
expansion screw, placed in the palatal vault at the level of
the first premolars and activated by the patient (90 degrees
as a quarter terms every second week), will correct the
transverse arch width discrepancy.

3. In all activators, the horizontal arches of the clasps
and labial bows should be inserted into the middle of
the interocclusal distance and not too close to the
lingual surface of the teeth. In contrast, the active
pallets may cross closely over contact points.
4. Use of Springs:- Moderate irregulations in the
alignment of the maxillary- incisors can be corrected
by the use of springs while the postnormal occlusal is
being treated. Since the appliance is firmly seated on
the upper teeth, these springs act efficiently, as in
active plats.

5. Restriction of mandibular mobility:- Mobility of the
mandible is restricted by extending the lingual flanges
of the activation as for as possible toward the floor of
the mouth. These flanges guide the mandibular dental
arch in its path to the proper position in the splint.
Hence in taking the impressions, special attention
must be given to a faithful reproduction of the depth
of the posterior part of the alveolar processes. In the
laboratory undercuts resulting from the lingual
inclination of the alveolar processes are leveled with
the application of wax before the flange are
fabricated. If the flange prevents the sitting of the
activator, their transverse width is reduced but never
the depth.

 Treatment of class III- In case of class III
malocclusion, activator therapy is
recommended only when the orthodontist can
guide the child's mandible from anterior cross
bite into an edge-to-edge relationship. In the
most retruded position of the mandible, the
construction bite is taken with the incisal edges
2 or 3mm from each other.

 The activator acts simultaneously in 3 ways:-
 holding the mandible back, splinting in the
maxillary dental arch
 tipping the maxillary incisors in a labial direction
and
 inducing a more anterior relationship of the
maxillary dental arch to the mandibular dental
arch.

 Potentiality of Herren activator -
1. To correct the class II malocclusion in an expedient,
reliable and economic way.
2. To retard forward growth of maxilla.
3. To reposition the mandible during mandibular
growth, either in horizontal or in vertical direction.
4. To archive these permanence in the mixed as well as
early permanent dentition.
5. To provide a high rate of stability of the treatment
results.

“H” activator (GRABER & NEWMANN)
 Constructed with a low vertical opening
registration and forward bite registration
(atleast 3 mm posterior to the most protrusive
positioning possible) .
 Myotatic reflex is activated.
 Muscle force arising during biting and swallowing.
Maxillary incisors can be uprighted and the
anterior growth vector of the maxilla will be
slightly inhibited.

 This type of appliance is most effective when
an anterior sagittal relationship of the mandible
is the primary treatment objective.
 It is indicated in class-II division-l
malocclusion with sufficient overjet with
a) functional retrusion b) result of growth
deficiency

“V” activator (GRABER & NEWMANN)
 Mandible is positioned only 3-5 mm a head
anteriorly to habitual rest position the vertical
opening.
 A maximum of 4 mm beyond the postural
resting vertical dimension.

 Activation of myotatic reflex. Additional force is
elicited with the stretching of the muscles and soft
tissues causing a response of the viscoelastic
properties of the soft tissues involved.
 The frequency of maximal biting into the appliance is
less than in the HI activator.
 The stretch reflex activation with the increased
vertical dimension may well influence the inclination
of the maxillary base.

 This appliance is indicated in cases with
vertical growth patterns and is properly
designated as the vertical “V” activator.
 Disadvantages - Dual bite is commonly
observed.

THE BOW ACTIVATOR OF A.M. SCHWARZ
 Consists of upper and lower halves of the bow activator connected with
an elastic bow made up of 0.9 to1 mm wire. In the anterior area
between the halves a layer of rubber is attached to act as a shock
absorber and to open the bite in the jaw.
 For the treatment of Class II Division 1 Malocclusion, a beginning can
be made with a small forward positioning, increasing this gradually by
periodic adjustments.
 There is possibility of activating only the bow on the side of unilateral
distoocclusion.
 Maxillary or mandibular expansion can be carried out with the
incorporation of the expansion screws.
 Drawbacks:
 1. Appliance easily disturbed.
 2. Results not up to the theoretical expectations.

U BOW ACTIVATOR OF KARWETZKY
 Constructed quite similarly to the Schwarz bow
activator, but with an improved technique and an
apparently increased efficiency.
 The KARWETZKY appliance consists of maxillary
and mandibular active plates joined by a U bow in the
region of first permanent molars.
 The active plates, both maxillary and mandibular
extend over the occlusal aspects of all teeth.
 The height of the construction bite varies with the
modifier
[Herren, Schwarz, Demisch, Woodside, etc.].

 Depending on the placement of the ends of U
bows three type of appliance: -
 Type I - class II malocclusions, in which the short
anterior leg in upper, the lower longer leg is placed
posteriorly.
 Type II For class III malocclusions, in which lower
longer leg is placed anteriorly to shorter leg in
upper leg in upper half.
 Type III Influence in a transverse direction where
there seems to be a displacement to one side or
other, that is a facial asymmetry or lateral cross
bite.

 KARWETZKY's appliance exerts a delicate influence
on the dentition and on the-TMJ.
 The mobility of the parts allows various mandibular
movements which makes the activator more
comfortable and tends to reinforce the functional
stimuli.
 The delicate forces, plus the gradual and sequential
forward positioning of the lower jaw will avoid the
exertion of undue pressure.
 The KARWETZKY activator may be combined with
the fixed appliances.
 An exciting potential for the appliance is the possibility
of use with certain types of orthognathic surgery in
adults, particularly with corticotomies and subapical
resections.

Reactivator
 Modification developed by ROBERT SHAYE
and positioner Laboratories. An anterior
Jackscrew is incorporated in the acrylic to
permit gradual advancement of the lower jaw
in stages, instead of only one 6-7 mm of
forward posturing as done by conventional
activator techniques.

 This is in line with petrovic's research showing a
more favorable and continuing tissue response to the
new stimuli. This is more desirable from a cybernetic
approach as well.
 Histologic studies of the condylar response show
improvement in the incremental and directional
reaction to reactivating procedures. The superiority of
this approach has been stressed by Rolf Frankel.

THE REDUCEDACTIVATOR OR
CYBERNATOR OF SCHMUTH
 Designed by Prof. G.P.F. Schmuth of Bonn. According to him
it is an adaptation of the activation to use it in the simplest
manner.
 The acrylic part is removed in a similar manner to that of
Bionator.
 Has coffin spring made of 1.1 or 1.2mm wire for expansion &
labial bow of regular activator to hold the upper lip.
 Lower incisors are covered by acrylic to hold them in a stable
position. .
 Protrusion loops for upper anterior teeth.
 A molar spur can be incorporated to prevent mesial drift of
upper first molars.

 Although the edge to edge bite of the Bionator
maybe used. Schmuth prefer the customary
bite of the activator.
 Full times wear except meals, spats or special
occasion.
 May be combined with fixed appliance of
different kinds that can be worn
simultaneously.
 Even headgear tubes can be incorporated.

THE PROPULSOR
 Conceived by "Mulhemann and refined by Hotz
(1980).
 Combination of Monoblock and Oral screen.
 No wire configuration is used
 As the oral screen covers the alveolar process, it not
only transmits distal force to upper anterior teeth but
also to the alveolar bone. Hence it suitable for
maxillary dento-alveolar protrusion.
 Construction bite:
 Similar to activator but in a more forward position.

 Periodic modification:
1. Appliance is reactivated by adding acrylic to
the area that contacts the upper anterior
segment.
2. The acrylic between the occlusal surfaces of
the first molars serves to stabilize the
appliance when therapy is initiated. As
treatment progresses however, this acrylic is
removed progressively to allow for unhindered
eruption of the molars and resultant reduction
of the deep overbite if present.

 If selective eruption of the mandibular teeth is
desired to reduce Class II buccal segment
relationship by upward and forward eruption
of the lower teeth while preventing forward
eruption of the upper teeth, more acrylic can
be removed opposing the lower molars leaving
them free.

Elastic Open activators (EOA)
 Daytime activators.
 Designed by G. Klamnt from East Germany in 1960.
 Klamnt, a disciple of Bimler, designed this appliance.
Appliance was very fragile.
 Combination of Activator and Bimler appliance.
 The reduced size increased patient compliance.
 It resembles Bionator as EOA has no acrylic anteriorly and
with more wires. There is, however, a substantial difference.
The Bionator, though freely movable in the oral cavity, is
carefully stabilized on posterior occlusal surfaces or the lower
incisors, as the occasion demands. The
 EOA almost completely lacks such stabilization, and thus its
vertical mobility is unimpeded.
 It is a myodynamic appliance.

 Standard EOA consists of –
 1. Bilateral acrylic parts.
 2. An upper and lower labial wire
 3. A palatal arch, and
 4. Guiding wires.

Construction bite:
 According to Klamnt, the construction bite is taken
with the incisors into an edge to edge bite. According
to him even with an overjet as large as 10 mm, it is
possible to get the incisors into an edge to edge bite
without any problem in TMJ. In event that an edge to
edge bite can not be achieved, the mandible is
brought into an intermediate position. During the
progress of treatment, the appliance may then be
modified to permit an edge to edge bite.
 It is preferable, however, to make a new appliance for
this purpose.

CUT OUT OR PALATE FREE ACTIVATOR
 A modification of activator by Dr Klaws Metzelder in 1974.
 It is an attempt to combine the advantages of the bionator with
some of those of the original Andresen-Haupl activator.
 In the maxillary portion, however, the acrylic covers only the
palatal or lingual aspects of the buccal teeth and a small part of
the adjoining gingiva. Thus, the palate remains free, making it
easier for the patient to wear the appliance continuously.
 The narrow anterior portion of the appliance is reinforced by a
small screw if expansion is needed, otherwise a wire can be
used for this purpose.
 The labial wire (0.9 mm) is the same as that used with
activator. There is no coffin spring.

 Stabilization is achieved by carrying the acrylic over
the occlusal surfaces of some of the buccal teeth, or
by a small rim of acrylic that forms a little groove for
the mandibular incisal margins. Capping of lower
incisors is necessary to prevent procumbancy.
 The technique is essentially the same as described for
the Bionator, and the choice among the different
types of possibilities of treatment is made according
to the principles established by Baiters.
 Construction bite-
 Preferably edge-to-edge.

 Advantages:
 1. Easier to make.
 2. Carries almost all the appurtenances described
for the activator e.g. Jackscrew for
expansion, Petric finger springs for moving
individual teeth, springs for labial tipping of lower
incisors etc.
 3. The labial tipping of upper incisors can be done
in a number of ways e.g. by addition of acrylic, use
of springs.

Bimler Appliance
 The first publication on Bimler appliance came
in 1949. The original name was Gebbisformer
(German). .
 Basic appliance: Simple circular arrangement
of an upper labial arch wire and a lower
lingual wire, which were connected by two
acrylic palatal wings and completed by a lower
acrylic cap.

 Main characteristics:
 Myodynamic appliance
 Prefabricated wire components
 Redoubling of U-Ioops : Provides mechanical
stability& Allows dimensional and positional
changes i.e lengthening and shortening, and raising
and lowering & Screens check pressure
 Prefabricated parts

 Appliances types:
 Based on Incisor Classification-
1. Protrusive Incisors -Type A appliance
2. Retrusive incisors - Type B appliance
3. Reversed Incisors - type C appliance

 Six variations in each type:
1. Variation 1: Standard -More or less normal arches
with only minor occurrence of crowding.
2. Variation 2:Special-lnterdental springs designed to
perform special task
3. Variation 3: Hypo - Indicated in midface deficiency
with uni or bilateral open -bite.
4. Variation 4: Extra - Severe crowding requiring
1stpremolar extraction
5. Variation 5: Contra - Telescopic bite.
6. Variation 6: Bipro - Bimaxillary dental protrusion

Thank you
For more details please visit

Activator/certified fixed orthodontic courses by Indian dental academy

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