BRIEF DESCRIPTION ONLY

1. A SEMINAR ON TWIN BLOCK
APPLIANCE
Dr ACHU R BABU
Dept. orthodontics
K.V.G. DENTAL COLLEGE SULLIA

2. TWIN BLOCK APPLIANCE
• First used on Sept 7th, 1977 by William Clark Clark W.J. Twin Block Functional
Therapy: Applications in Dentofacial Orthopedics (3rd Edition)
• As the saying goes, necessity is the mother of all inventions. Even the
Twin block was evolved in response to a clinical problem.
• A young patient Colin Gove, son of a dentist fell and completely
luxated an upper central incisor.Fortunately, he kept the tooth and
within few hours of the accident the tooth was reimplanted using
temporary splint and later on with stabilizing splint

3. • After 6 months, the occlusal relation was Cl-II div 1 with overjet of
9mm and lip trap. This lip trap was causing mobility and root
resorption.
Then it was necessary to design an appliance that could be
worn full time to posture the mandible forward. That time due to
unavailability of such appliance simple bite block were constructed
with an inclined plane of 90° with incisors edge to edge with 2mm of
vertical separation.
• Fortunately, the young patient successfully made an effort to wear
the appliance and then this technique came into being. The first
Twin block appliances were fitted on 7th September 1977 in the
same patient whose age was 8 yrs, 4 months and in a span of 9
months, overjet reduced from 9 to 4mm.

4. PHILOSOPHY BEHIND TWIN BLOCK THERAPY
Considerable forces are applied through the muscles of mastication to
the teeth and the underlying bony structures to influence both the
internal and external structure of the basal bone

5. It is this natural mechanism of bony remodeling by occlusal force
vectors that forms the basis of functional correction by the Twin
Block technique.

6. Occlusal inclined plane
Fundamental functional mechanism of the natural dentition
The occlusal inclined plane acts as a guiding mechanism causing mandible
to be displaced downward and forward.
Twin block appliances: simple bite blocks
Rapid functional correction: by transmission of favourable occlusal forces
to inclined planes

7. Major advantage of using twin blocks was that it could be worn 24 hours,
hence the masticatory forces can be transmitted via the appliance to the
dentition from where they are transmitted to the bony trabaculae according
to wolfs law

8. Twin block technique
The main force: increased the active tension in the stretched
muscles.(AJO DO-1999)
Enhanced response of glenoid fossa.(Rabie and Urban)
Adaptive changes in the glenoid fossa

9. Advantages
Comfort
Aesthetics Patient friendly appliance
Function- there is less interference with normal
function.
Patient compliance-can be fixed to the teethntemporarily or
permanently to guarantee patientncompliance.
Full functional correction of occlusal relationships can be achieved
in most cases without the addition of any orthopedic or traction forces

10. Facial appearance
Speech is not drastically affected
Facial asymmetry can be treated
High Efficiency
Integration with fixed appliances
Treatment of temporomandibular dysfunction

11. Disadvantages
*Mandibular incisor proclination
*An increase in the vertical facial dimension is seen
*Clockwise rotation of the maxillary plane
*Limited increase in mandibular growth.
*Relapse : Initial treatment changes in both the vertical and
horizontal dimensions partially relapses during the initial 3 month
post treatment phase.

12. Timing
*The timing of treatment by any functional appliances lends itself to the
interception of malocclusion at an earlier stage of development, attempting to
resolve skeletal and occlusal imbalance by improving the functional
environment of the developing dentition before the malocclusion can become
fully established in the permanent dentition.

13. VISUAL TREATMENT OBJECTIVE
*An important diagnostic test undertaken before making
a decision to use a functional appliance
*The test enables us to visualize how the patient’s profile
would be after functional appliance therapy.
*It is performed by asking the patient to bring the
mandible forward.
*An improvement in the profile is considered a positive
indication for the use of an appliance.

15. Bite registration
Activation aims to achieve reduction of over jet,
correction of distal occlusion and midline correction.
General guidelines:
*The amount of sagittal advancement of the mandible is
planned.
*A horse-shoe shaped wax block is prepared for insertion
between the upper and lower teeth.(it should be 2-3mm
thicker than the planned vertical opening).
*The patient is made to sit in an upright and non-strained
position.

16. *The mandible is guided to the desired sagittal position.
*The patient is asked to practice placement of the mandible at
the desired sagittal position a few times before registration of
the bite.
*The patient should be instructed to occlude with the midlines
coincident.
*The wax block is placed over the occlusal surface of the lower
cast and is gently pressed so as to form the indentations of
the lower buccal teeth

17. *The wax block is placed on the lower jaw and the patient is
asked to bite at the desired sagittal position.
*It is then removed and placed on the models and checked.
*If found all right , the excess wax is trimmed off.
*The hardened wax block is again tried in the patient’s mouth.

18. *Exacto biteprojet bite- Interocclusal record for accurate control.
*Variable amount of sagittal activation can be done by selecting the
appropriate groove to engage the maxillary incisors in registering the
protrusive

19. George bite gauge- Used to register the protrusive path of mandible in patients
with vertical growth pattern and weak orofacial musculature

20. APPLIANCE DESIGN
Base plate
A midline screw to expand the upper arch
Occlusal bite blocks with inclined plane
Clasps on upper molars
Clasps on lower premolars and incisors

21. Occlusal inclined plane
• During the evolution of the technique…the angulations used
were 45 degree.
• Drawbacks of 45 angulations…posterior open bite.
• An angle of 45 also results in equal downward and forward
force on the mandibular dentition.
• Finally changed to 70…to apply a more horizontal
component of force.

23. *Position of the inclined plane is determined by the lower block
*Inclined plane on the lower block-angled from the mesial surface of the
second premolar or deciduous molar.
*Its thinner buccolingually in the lower canine region (reducing the bulk-
improves speech).
*Upper inclined plane- is angled from the mesial surface of the upper second
premolar to the mesial surface of the upper first molar
*The distal portion covers the posterior teeth in a
wedge shape.

24. Retention elements
*The Delta clasp:designed by William J Clark(1985)
Originally retentive loops-triangular . Alternatively the loops-circular

25. Labial bow: is given in the maxillary arch
Mc Namara : stated that a labial bow in the mandibular arch can
be used to improve retention.

28. Twin block Schwarz appliance(1996

29. Magnetic Twin blocks:
Magnets should be used only where speed of treatment is an
importantconsideration , or where the response to nonmagnetic appliances is
limited.
Role of magnets- is to accelerate correction of arch relationships.
Two types of rare earth magnets are used:
Samarium cobalt
Neodymium iron boron : greater force.

30. Fixed Twin Block
Advantage: Increased control by the operator.
Aesthetic appliance design: Integration of the Twin Block
with Wilson 3D modular lingual appliances

31. Mini Block Appliance
Was introduced to overcome some of the limitations of
conventional Twin Block appliance.
Modifications:
*Stepwise advancement of the mandible is done.
*Vertical dimension of the occlusal bite blocks are reduced.
*Maxillary incisor torquing spring is used(designed by Bass).
*Maxillary incisor capping is done with acrylic

32. FOR TRANSVERSE DEVELOPMENT
*It is nothing but a combination of Schwarz appliance and twin block.
Screws are incorporated in the upper and lower twin blocks.
*When screw is added in lower plate the appliance is also termed as
BOWBEER APPLIANCE

33. Twin Block Mc Namara appliance
*Modified by placing two screws in the mid palatal region.One in
anterior region in line with premolars and the other in posterior
region in line with molar.
• The advantage is that we can obtain only
anterior or only posterior expansion as
required

34. Transverse and sagital appliance
A three way screw can be used in the anterior part of the palate. The
disadvantage with such a screw
is that it may interfere with the speech because of its bulk

35. Twin Block with a Spinner to control tongue thrust.

36. Neuromuscular Twin Block
Introduced By Dr. Jay Gerber -to improve stability and for neuromuscular
treatment.
-Upper and lower expansion screws may be used for lateral development
A face bow, or reverse headgear, may be incorporated Fixed/removable Twin Block and full
banded versions can be made using a Wilson 3D type of appliance or a full banded style

37. CLARK TRANSFORCE TRANSVERSE AND SAGITTAL APPLIANCE
Specifically designed for anterior arch development in upper or lower arches. Often
indicated for simultaneous use in both arches.

38. Made of surgical stainless steel and incorporates a Nickel Titanium
TWINFORCE spring module, which generates 100 to 200 grams of
smooth continuous force while developing arches

39. TRANSFORCE appliance is inserted into lingual sheaths on molar
bands and are pre-activated via the "TWIN FORCE " springs.
An expansion module is incorporated to increasethe inter-canine width (expands at
the cuspids).
May be used in the upper or lower arches when expansion is required to
accommodate crowding
in the labial segments, or to correct arch width in contracted arches.

40. BITE JUMPING SREW FOR TWINBLOCK APPLIANCE

41. SELECTION CRITERIA FOR SIMPLE TREATMENT
1.Class II division 1 malocclusion (ideal but CII D2 & CIII can
also be treated)
2. Uncrowded or decrowded dentition
3. 3. Full unit distal occlusion
4. Well-developed arches
5. OJ < 10mm & deep overbite
6. Profile improve when the mandible is brought forward to
correct OJ
7. Active grower

42. Bite registration
1.Vertical opening
- 2mm interincisal space
- Equivalent to an inter premolar space 5-6 mm
2.AP
- • For most patients: edge to edge (if not uncomfortable)
• Facial profile should improve
• Maximum ~ 10mm
• Must not exceed 70% of the total protrusive path (OJ measured with the mandible retruded
and in the position of maximum protrusion)
Important to
-Open the bite beyond the freeway space patient cannot retrude the mandible when in rest
position
- Avoid making the blocks too thick patient should be able to eat and speak comfortably with
the appliances in the mouth

43. Treatment of Class II division I
Adjustment and clinical management:
Stage 1:active phase
o First visit: Twin blocks are fitted and instructions are given to the
patient Temporary fixation of Twin blocks.
o Initial adjustment-after ten days:
o Adjustment visit after four weeks:
o Routine adjustment-time interval is six weeks

44. Reactivation of Twin blocks
Is done by addition of acrylic on the anterior surface of the upper bite block
Indications for progressive reactivation of Twin Blocks:
If the over jet is greater than 10mm.
In vertical growth pattern.
In adult treatment.
In treatment of TMJ dysfunction.
In any case where full correction of arch
relationships is not achieved after the initial
activation, an additional activation is necessary.

45. Stage 2-Support phase
Antero- posterior and vertical control
Retention: done using Anterior inclined plane:

46. Pterygoid response: Described by McNamara
• Results from altered activity of the medial head
ofthe lateral pterygoid muscle in response to
mandibular protrusion.
• A new pattern of muscle behavior is quickly established
whereby the patient finds it difficult and later impossible to
retract the mandible into its former retruded position. After a
few days, it is more comfortable to wear the appliance than to
leave it out

47. In the pursuit of ideals in orthodontics, facial balance
and harmony are of equal importance to dental and
occlusal perfection. We cannotafford to ignore the
importance of orthopaedic techniques in achieving
these goals by growthguidance during the formative
years of facial and dental development.
CONCLUSION

48. REFERENCES
*Aggarwal P, Kharbanda OP, Mathur R, Duggal R, Parkash H
Muscle response to the twin-block appliance: an electromyographic
study of the masseter and anterior temporal muscles. Am J Orthod
Dentofacial Orthop. 1999: Oct. 116(4): 405-14.
*Broadbent JM Transitional Twin Block. Funct Orthod 1997: May-
Jul; 14(3): 4-8, 10-6.
*Caldwell S, Cook P. Predicting the outcome of twin block
functional appliance treatment: a prospective study. Eur J Orthod.
1999: Oct; 21(5): 533-9.
*Clark W The twin block technique Dent Today. 1991:
Mar; 10(2):50-1.
*Clark W. The twin block technique Funct Orthod 1991:
Jan-Feb;8(l): 24-5, 27-8. 42:
*Clark W.J. Twin Block Functional Therapy Application in
Dentofacial Orthopedics: Mosby – Wolfe; 1995.
*Clark WJ More on the Clark Twin Block Am J Orthod
Dentofacial Orthop 1990: Mar;97

49. THANK YOU