activator- Myofunctional appliances

1. FACULTY OF DENTAL SCIENCES

2. ACTIVATOR

3. HISTORY OF ACTIVATOR
• In 1879, Kingsley introduced the term and concept of "jumping the bite"
for patients with mandibular retrusion
• He inserted a vulcanite palatal plate consisting of an anterior incline
that guided the mandible to a forward position when the patient closed
on it.
• This maneuver corrected the sagittal relationship without tipping the
lower incisors forward.
• Vorbissplatte was devised by Hotz a modified form of Kingsley plate.

4. Robin had created an appliance quite similar in its objectives. The monobloc,
as he called it (because it was a single block of vulcanite), positioned the
mandible forward in patients with glossoptosis and severe mandibular
retrognathism who risked occluding their airways with their tongues.
• Impressed by Kingsley's concepts and appliances, Andresen developed a
mobile, loose fitting appliance modification that transferred functioning muscle
stimuli to the jaws, teeth, and supporting tissues.
• The progenitor of the appliance was a modified Kingsley plate that Andresen
used as a retainer over summer vacation for his daughter after he removed
fixed appliances used to correct a distocclusion.
Seeing the continued improvement with this retainer, he called it a
biomechanic working retainer.

5. Mode of Action Of Activator
• The appliance loosely fits into the mouth . The mandible moves forward
to engage the appliance .
• This results in stretching of the elevator muscle of mastication , which
starts contracting thereby setting up myotatic reflex
• According to Andersen And Haupl , the activator induces
musculoskeletal adaptation by introducing new pattern of mandibular
closure

6. Indications of activator :
• It is primarily used in actively growing individuals with favorable growth pattern.
• The maxillary and mandibular teeth should be well aligned.
• The mandibular incisors should be upright over the basal bone.
• The following are some of the indications for the use of activator :
1. Class II, Division 1 malocclusion
2. Class II, Division 2 malocclusion
3. Class III malocclusion
4. Class I open bite malocclusion
5. Class I deep bite malocclusion
6. As a preliminary treatment before major fixed appliance therapy
to improve skeletal jaw relations
7. For post-treatment retention
8. Children with lack of vertical development in lower facial height.

7. Contra-indications of activator therapy
1. The appliance is not used in correction of Class I problems of crowded teeth
caused by disharmony between tooth size and jaw size,
2. The appliance is contraindicated in children with excess lower facial height and
extreme vertical mandibular growth
3. The appliance is not used in children whose lower incisors are severely
procumbent.
4. The appliance cannot be used in children with nasal stenosis caused by
structural problems within the nose or chronic untreated allergy.
5. The appliance has limited application in non-growing individuals.

8. Advantages of activator therapy
1. It uses existing growth of the jaws.
2. During treatment the patient experiences minimal oral hygiene problems.
3 .The intervals between appointments is long.
4. The appointments are usually short due to need for minimal adjustments.
5. Due to the above reasons they are more economical

9. Disadvantages of activator therapy
1. Requires very good patient cooperation.
2. The activator cannot produce a precise detailing and finishing of the
occlusion. Thus post-treatment fixed appliance therapy maybe needed
for detailing of the occlusion.
3. It may produce moderate mandibular rotation (anteriorly downwards).
Thus activators are not used in cases of excessive lower face height.

10. CONSTRUCTION BITE
• Proper activator fabrication requires the
determination and reproduction of the correct
construction or working bite.
• the plaster casts
• cephalometric
• panoral head films
• the patient's functional pattern.

11. 1. In a forward positioning of the mandible of 7 to 8 mm the vertical opening
must be slight to moderate (2 to 4 mm).
2. If the forward positioning is no more than 3 to 5 mm the vertical opening
should be 4 to 6 mm.
3. The activator can correct lower midline shifts or deviations only if actual
lateral translation of the mandible itself exists.
If the midline abnormality is caused by tooth migration, no asymmetric
relationship exists between the mandible and maxilla. An attempt to correct
this type of dental problem could lead to iatrogenic asymmetry. Functional
crossbites in the functional analysis can be corrected by taking the proper
construction bite.

12. CLINICAL PROCEDURE OF RECORDING THE
CONSTRUCTION BITE
1. Guiding the patient
2. Manipulating the wax
3. Transferring the wax bite to patients mouth.

13. • Rolled wax in 'W shape for
recording the construction bite
• Rolled wax adapted on to the
lower cast.

14. Trimming the excess wax

16. • Checking the construction bite on the casts will help us
in determining the amount of horizontal and vertical
displacement and the validity of the construction bite to
fabricate the activator.
CHECKING THE CONSTRUCTION BITE

17. TO CHECK THE VERTICAL OPENING
• We will occlude the cast in centric occlusion.
• We will place four marks, two each on the upper and lower casts in the
region of premolars both on right and left sides.
• We will measure the distance between the upper and lower marks on
both the right and left sides and note it. We will relate the casts once
again using the constructed wax bite. We wil measure the distance
between the same marks on either side of the casts and note it.
• The difference between the two readings show the amount of vertical
displacement. It must be symmetrical .

18. TO CHECK THE HORIZONTAL DISPLACEMENT
• We will occlude the casts in centric occlusion. We will draw two
vertical lines, one each on left and right sides of the upper cast on the
mesiobuccal or distobuccal cusp of first molar and extend them
downwards onto the lower cast. We will relate the casts using the
constructed wax bite.
• The vertical line will be split into two lines due to horizontal
displacement of the casts. We will extend the vertical line of the upper
cast once again on to the lower cast. The distance between the two
lines on the lower cast will give us the amount of horizontal
displacement. It should be symmetrical

19. • FIG. - Checking the wax bite for vertical and
horizontal displacement.

20. Technique for a Low
Construction Bite
with Markedly
Forward Mandibular
Positioning-
H activator

21. • Technique for a
High Construction
Bite with Slightly
Anterior
Mandibular
Positioning-
• V activator

22. • Technique for a
Construction Bite
without Forward
Mandibular
Positioning

23. • Construction Bite
with Opening and
Posterior
Positioning of the
Mandible

24. TRIMMING OF ACTIVATOR
• A finished activator is generally delivered untrimmed to the patient.
When the finished activator is delivered to a patient without trimming
the bite part, it will help in bringing about the desired skeletal
changes i.e., forward positioning of the mandible.
• Trimming the bite part of the activator will help the clinician in
guiding the teeth to erupt into the desired position.

25. Finished activator (untrimmed)
positioned on the casts.
Marks placed on the activator to
help in trimming.

26. Method of trimming the upper
part of activator to allow
distal movement of the
teeth.
Method of trimming the
lower part of activator to
allow the mesial
movement of the teeth.

27. Trimming the lingual aspect of upper
anterior teeth to allow for retraction
of the teeth.
Section of model showing the
trimming which allows the
buccal and occlusal drift of
posterior teeth.

28. PROCEDURE OF TRIMMING
• Trimming the bite part of the activator is done using a vulcanite trimmer.
Before the trimming is commenced, marks can be placed using a glass
marking pencil in the regions which are not to be trimmed.
• The upper part of the activator corresponding to the maxillary arch
should be trimmed in such a way that the teeth will move buccally,
distally and occlusally.
• The lower part of the activator corresponding to the mandibular arch
should be trimmed in such a way that the teeth will move buccally,
mesially and occlusally.

29. MANAGEMENT OF THE APPLIANCE
1. The patient should be convinced about the benefits of the
appliance .
2. Patient should be taught how to use ,place and remove the
appliance .
3. Timing have to be increased gradually over a period of time .
4. Trimming plan should be personalized for every patient .

30. PROBLEMS ENCOUNTERED WITHACTIVATOR
• Difficulty in tolerating the appliance
• Discomfort
• Pain
• Difficulty in Breathing
• Rejection of Appliance
• Distortion of Labial Bow

31. Modifications
1. The Bowactivator of A.MSchwarz
2. Herrenactivator (L.S.U.activator)
3. Wunderersmodification
4. Reducedactivator or cybernator of Shmuth
5. The Karwetzkymodificaton

32. The Bow activator of A.MSchwarz :
• The bow activator is a horizontally split activator having a
maxillary portion and a mandibular portion connected
together by an elastic bow. This kind of modification
allows step wise sagittal advancement of the mandible
by adjustment of the bow.

33. Wunderers modification
• This is an activator modification that is mostly
used in treatment of Class III malocclusion.

34. Reduced activator or cybernator of Shmuth:
• This modification of the activator is proposed by Professor G.P.F.
Schmuth. This appliance resembles a bionator with the acrylic
portion of the activator reduced from the maxillary anterior area
leaving a small flange of acrylic on the palatal slopes.
• The two halves may be connected by an omega shaped palatal wire
similar to bionator.

35. Cut out or Palate free activator
This is a modification proposed by Metzelder to
combine the advantages of bionator and the
Andresen's activator.
• The mandibular portion of the appliance
resembles an activator while the maxillary
portion has acrylic covering only the palatal
aspect of the buccal teeth and a small part of the
adjoining gingiva.
• The palate thus remains free of acrylic thereby
making the appliance more convenient for
patients to wear the appliance for longer hours.
• Due to the greater amount of wearing time,
success should be greater with the palate free
activator.

36. The Karwetzky modificaton:
• This consists of maxillary and mandibular plates joined by a 'U'
bow in the region of the first permanent molar.
• Type I: This is used in the treatment of Class II, Division 1. In
this modification, the larger lower leg is placed posteriorly. Thus
when the two arms of the U bow are squeezed the lower plate
moves sagitally forwards
• Type II : This is used for the treatment of Class III
malocclusion. In this appliance the larger lower leg is placed
anteriorly. Thus when the U bow is squeezed the mandibular
plate moves distally.
• Type III: They are used in bringing about asymmetric
advancements of the mandible. The U bow is attached
anteriorly on one side and posteriorly on the other side to allow
asymmetric sagital movement of the mandible

38. Herren activator (L.S.U. activator):
• A modification of the activator developed by P. Herren (also
known as the Louisiana State University modification of the
same appliance).
• It is essentially an activator made to a construction bite that
positions the mandible forward and downward to a significant
degree.
• According to P. Herren, the wearing of this appliance is not
supposed to increase the activity of the lateral pterygoidmuscle