Twin block appliance

1. TWIN BLOCK APPLIANCE
DR. AJAY SRINIVAS
PG STUDENT

2. INTRODUCTION
Our branch of dentistry; Orthodontics as it is
commonly known as “Orthodontics and
Dentofacial Orthopedics” which consists of two
terms both of which are important in order to
describe the treatment given to improve the
dental and orthopedic relationships in the
stomatognathic system.

3. HISTORY
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

4. 4
Development Of The
Twin Block
Before Treatment
IOPA Showing
Luxated 11
Post Treatment
IOPA Showing An
Endodontic Pin To
Stabilize 11

5. 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.

6. 6
Different Stages Of Treatment Using Twin Block
Combination Therapy With Fixed Appliance In
Later Stage

7. 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.

8. 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.

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

10. Occlusal inclined plane
 Fundamental functional mechanism of the natural
dentition
Twin block appliances:
simple bite blocks
Rapid functional correction:
by transmission of favorable
occlusal forces to inclined planes.

11. If the mandibular inclined planes are in a distal
relation to that of maxilla then the force acting on
the mandibular teeth will have a distal force vector
leading to a class II growth tendency.

12. Occlusal inclined plane
The occlusal inclined plane acts as a guiding mechanism
causing mandible to be displaced downward and
forward.

13. Use of masticatory force
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

14. 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

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

16. Other advantges…
 Facial appearance
 Speech is not drastically affected
 Facial asymmetry can be treated
 High Efficiency
 Integration with fixed appliances
 Treatment of temporomandibular dysfunction

17. Disadvantages
Mandibular incisor proclination
An increase in the vertical facial dimension is seen
Clockwise rotation of the maxillary plane

18. 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.

19. 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.

20. 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.

21. VISUAL TREATMENT OBJECTIVE

22. Functional treatment objective
This method is suitable for use with visual
imaging techniques using superimposition
of cephalometric and photographic records.
FTO predicts the facial changes
that result from mandibular
advancement.

23. Bite registration

24. 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.

25. 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.

26. 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.

27.  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
bite.

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

29. George bite gauge
George bite gauge Has
a sliding jig attached to
a millimeter
scale,designed to
measure the protrusion
path of the mandible
and can record a
protrusive bite of no
more that 70% of the
total protrusion path.

30. APPLIANCE DESIGN

31. 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

32. Occlusal inclined plane
 During the evolution of the technique…the
angulations used were 45 degree.
 Drawbacks of 45 angulations…posterior open
bite.

33. 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.

34. 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).

35. 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.

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

37. Advantages of closed loop:
clasp does not open with repeated insertion and
removal
maintains its shape
requires less adjustment
less prone to breakage
Excellent retention on lower premolars
Suitable for use on most posterior teeth.

38. Methods of construction of the delta clasp:
According to the area of best retention:
Retentive loops are angled to follow the curvature
of the tooth into mesial and distal undercuts…if the
tooth is favourably shaped with good undercuts
mesially and distally.
Loop is constructed at right angles to the bridge of
the clasp and is directed interdentally to gain
retention from adjacent teeth…if the tooth is not
favourably shaped.

39. Delta clasps can be given:
In permanent dentition:
On upper first molars and lower first premolars
Ball ended clasp mesial to lower canines and distal
to upper canine is given-
• To improve retention and
• Provide resistance to anteroposterior tipping
In mixed dentition:
• C-clasps-on are given on deciduous molars and
canines.

40. 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.

41. Treatment of Class II division I

42. Bite registration:
Amount of anterior advancement and vertical
opening
 In a growing child, an over jet of up to 10mm can
be corrected on the initial activation by registering
an incisal edge to edge bite with 2mm inter incisal
clearance
 Larger overjets(>10mm)- partial correction(7-
8mm)- reactivation after initial partial correction.

43. Differences between young and adult patients
 In young patients- there is more freedom of movement
In class II division I malocclusion- with protrusive path
of 13mm- activation can be done only up to 10mm-
beyond this range, the muscles and ligaments cannot
adopt to altered function- hence patient will tend to
posture out of the appliance.
 In adults- movements are more restrictive

44. Treatment of Class II division I
Appliance design : Standard Twin Block

45. Standard Twin Block
Appliance design

46. 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

47. Management of deep overbite:
Establishing the correct vertical dimension

48. Reactivation of Twin blocks:
Is done by addition of acrylic on the anterior
surface of the upper bite block.

49. 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.

50. Benefits of progressive mandibular advancement
Gradual training of the protractor muscles of the
mandible
Enhanced mandibular growth due to repeated
stimulation of the lateral pterygoid muscle
Reduced tooth movement due to the generation of
the reduced viscoelastic forces.

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

52. Growth studies:
Pterygoid response:
Described by McNamara
Results from altered activity of the medial head of
the lateral pterygoid muscle in response to
mandibular protrusion.

53. 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.

54. Treatment of Class II division II

55. Twin blocks have the effect of unlocking
the malocclusion by releasing the mandible
from an entrapped position of distal
occlusion and thereby encouraging a rapid
transition to class I arch relationship.

56. Treatment of Class II division II
Bite registration:
Incisors should be in edge to edge occlusion.
When the overbite is excessive, the clearance
between the posterior teeth is correspondingly
increased.
The amount of mandibular advancement is
limited.

57. Appliance design:
Sagittal appliance:
Two sagittal screws for antero posterior arch
development

58. Combined transverse and sagittal appliance:
The triple-screw Twin Block appliance
Designed to improve arch form in anteroposterior
and transverse dimensions and simultaneous
correction of arch relationship.

59. The three-way screw Twin Block appliance:
Three screws housed in a single unit and operated
independently.
Disadvantage-bulky in the anterior palate area.

60. Sequence of trimming:

61. Treatment of Class III

62. Reverse Twin Blocks:
Functional correction- by reversing the
angulations of the inclined planes.
The occlusal blocks are placed over the upper
deciduous molars and the lower first molars.
The occlusal force exerted on the mandible is
directed downwards and backwards by the reverse
inclined planes.

63. Bite registration:
There is less scope for distal displacement of the
mandible.
There should be atleast 2mm interincisal clearance
in the fully retruded position.

64. LATERAL AND OCCLUSAL VIEW

65. Appliance design:
The sagittal appliance:
Sagittal screw -To advance the maxillary incisors
The threw screw appliance -for lateral expansion
of the arch.
Lip pads -to enhance forward movement of the
upper labial segment.
Reverse pull facial mask

67. Treatment of anterior open bite

68. Bite registration:
4mm- of interincisal clearance and 5mm clearance
between the cusps of the first premolars or
deciduous molars should be present.

69. Appliance design:
Extends distally to the lower molar region
Clasps are fabricated on the lower first molars
Occlusal rests are made on the second molars to
prevent their eruption.

70. A palatal spinner-to control anterior tongue thrust.
A tongue guard.
A labial bow

71. Intraoral traction to close anterior open bite:
Intra oral elastics-Dr Christine Mills
Advantages of elastics:
It helps to maintain occlusal contact(esp in
patients with weak musculature).
Reinforcement of intrusive force on the bite
blocks to close the bite.

72. IMPORTANT…
Second molars should not be allowed to over
erupt.
To prevent this: Occlusal cover
or occlusal rests is extended distally
to second molars.
 Upper block should NOT be trimmed
in reduced overbite cases.
As this increases the
anterior open bite.

73. Treatment of mixed dentition
Appliance design:
For improving retention in mixed dentition:
C-clasps- are given on deciduous molars.
Bonding composite to the buccal surfaces of
deciduous teeth to create an additional undercut.

74. Treatment of mixed dentition
Ready- made undercuts- can be made by
extending retention grooves into the buccal
surfaces of deciduous teeth.

75. Twin block Schwarz appliance(1996)

76. Treatment of Permanent dentition
Initial functional correction of early permanent
dentition should be done followed by fixed
appliances to detail the occlusion.
The benefits of combined dental orthopedic and
orthodontic therapy are not temporary but
permanent.
It also helps to avoid surgical correction at a later
stage of development.

77. The Twin traction technique

78. Orthopedic traction should be limited to treatment of
severe malocclusion where growth is unfavorable for
conventional fixed or functional therapy.
Indications:
Severe maxillary protrusion.
To control a vertical growth pattern by the addition of
vertical traction to intrude the upper posterior teeth.
In adult treatment where mandibular growth cannot assist
the correction of a severe malocclusion.

79. In the early years-tubes were added to clasps for
extra oral traction on the upper appliance.
This is a combined method of extra oral and
intermaxillary traction by adding a labial hook to
conventional face bow and extending an elastic to
attach to the lower appliance in the incisor region.

80. The Concorde face bow:
A new means of applying intermaxillary and extra
oral traction to restrict maxillary growth.
It encourages mandibular growth in combination
with functional mandibular protrusion.

81. A conventional facebow is taken and a recurved
labial hook postured extraorally 1mm clear of the
lips is soldered at its anterior end. A elastic is
taken around the hook over to the mandibular
appliance

82. Directional control of orthopedic force:
Intrusion of the upper posterior teeth allows the
bite to close by a favorable forward rotation of
mandible in vertical growth discrepancies.
Additional orthopedic force may help to apply an
intrusive force on the upper posterior teeth.

83. The Concorde face bow is a unique method
of delivering an intrusive force to upper
molars and at the same time, a protrusive
force to the mandible and the lower
dentition.

84. Magnetic Twin blocks:

85. Magnetic Twin blocks:
Magnets should be used
only where speed of
treatment is an important
consideration , or where the
response to nonmagnetic
appliances is limited.
Role of magnets- is to
accelerate correction of arch
relationships.

86. ATTRACTING MAGNETS
Attracting magnets can be used when an increased
activation is necessary at the initial stage of activation.
The functional mechanism stimulates a proprioceptive
response by repeated contact on the occlusal inclined
planes.
Its useful in patients with weak muscular tonicity who
do not make any muscular effort to engage the
appliance.

87. REPELLING MAGNETS
Used in Twin blocks with less mechanical
activation built into the occlusal inclined planes.
Induces additional forward mandibular posture
when the patient bites without reactivation of the
blocks

88. Disadvantages:
The amount of activation is not clear.
The reactivation of the inclined planes will
deactivate the magnets
Also produces large open bites in the
posterior segments.

89. Two types of rare earth magnets are used:
Samarium cobalt
Neodymium iron boron : greater force.

90. Treatment of Facial Asymmetry
The occlusal inclined plane is an ideal functional
mechanism for unilateral activation, and Twin
Blocks are extremely effective in the correction of
facial and dental asymmetry .
The sagittal Twin Block is the appliance of choice
for correction of asymmetry because the sagittal
design allows unilateral activation to restore
symmetry in buccal and labial segments.

91. Fixed Twin Block

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

93. Wilson 3D lingual tube-
retentive element on molar
tube provides a means of
attachment for occlusal
Twin Block components,
which may be fixed or
removable, under our
direct control.

94. Phases of treatment:
First phase:Early intervention and arch
development by the Wilson modular appliance
system.
Second phase:Orthopedic treatment by the Twin
block system.
Third phase: detailed orthodontic correction by
fixed appliance therapy.

95. Functional components:
The twin block transpalatal arch
The Twin block hyrax appliance: For rapid
maxillary expansion.

96. The Twin block lingual arch:Used in mixed
dentition,when functional correction can be
combined with interceptive treatment for arch
development by the lingual arch.

97. Twin blocks in TMJ therapy
The treatment success depends on the timing of the
click.
Early opening click :- up to 22mm opening can be
easily resolved.
Mid opening click :- 22-35mm opening moderate
to resolve.
Late opening click :- over 35mm of opening,
difficult to resolve.

98. Objectives achieved in the first phase of treatment:
Pain is relieved immediately when Twin blocks
are fitted or in more difficult cases,within 4 days.
The muscles are restrained automatically to a
healthy pattern- because of rapid improvement in
facial balance.

99. The disc is recaptured by posturing the mandible
downwards and forwards to advance the condyles.
Rather than act as a passive splint, Twin blocks are
designed to move the teeth that are causing occlusal
imbalance.

100. Selective trimming of the upper block over the
lower first molars only.
To continue to rest the joint, a posterior occlusal
stop is maintained by occlusal contact of the
blocks with the second or third molars to support
the vertical dimension.

101. Appliance design:
The sagittal twin block is used to relieve
compression on the joint.
It is important to maintain posterior occlusal
support at all times in order to relieve
compression.
An anterior inclined plane is incorporated to
support the corrected occlusion.

102. The Twin block biofinisher:
An alternative method of extruding lower molars
by vertical traction in order to stabilize the TMJ.
It has a hook for an elastic that extends above the
upper molar in the vestibule.
The objective is to achieve a longer elastic span for
extrusion of lower molars.

103. The attachment is inserted in horizontal tubes over
the interdental embrasures in the molar region.
The biofinisher attachment is removable and may
be worn at night and removed during the day.
Alternately, elastics may be attached directly to
the delta clasps to be worn full time.

104. The effects of Twin Block
Skeletal changes:
A mean forward growth/repositioning of the
mandible.
An increase in the SNB angle.
An increase in lower anterior facial height.

105. The effects of Twin Block
Dental changes :
Retroclination of the upper incisors.
Proclination of the lower incisors.
Distal movement of the upper molars.
Lower molar eruption in an anterior and
superior direction.

106. Deleterious effects on the hard tissues:
Demineralization seen on :
Incisal edges of lower incisors and canine
cusps.
Occlusal surfaces of posterior teeth covered
by the bite blocks.

107. Growth response to Twin Block
treatment
An atlas of craniofacial growth:Riolo et al(1979) :
Mixed longitudinal study of growth and
development :Prahl Anderson et al(1979) :
o It should not be expected that all patients who
undergo functional therapy will show increased
mandibular growth.

108. Growth response to Twin Block
treatment
o A lack of growth response may be related to the
level of endocrine activity that prevails at the
time of treatment.
o If the treatment occurs during a resting
phase of growth, the potential for increased
mandibular growth is more limited.

109. Comparative studies
Illing et al-compared Twin block , Bionator
and Bass appliances
Twin block is more advantageous because of:
Rapidity of correction
Greater restraint in forward movement of
point A

110. Modifications of Twin Block

111. 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.

112. Reduction in over jet: is achieved due to the
effects of sagittal mandibular growth alone.
Drawbacks of the appliance:
Reduced esthetics.
Over jet relapse

113. 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

114. TWIN BLOCK SCHWARZ APPLIANCE

115. Twin block Crozat appliance
• Is suitable in adult treatment
with minimum palatal and
lingual coverage.
• Disadvantage of this type of
appliance is that it requires
careful adjustment to
maintain symmetry

117. 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

118. FOR SAGITAL DEVELOPMENT
Twin block sagital appliance
• Anteroposterior arch
development is achieved by two
screws which are aligned
anteroposteriorly in the palate

119. 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

120. Twin block appliance with a labial bow:
Treatment effects:
Retroclination of the maxillary incisors.
Increased Lower facial height.

121. Twin block appliance with torquing spurs and high
pull head gear.
Treatment effects:
Significant increase in maxillary restraint-no
increase in Lower facial height.
Significant reduction in the ANB angle.
Anterior relocation of the mandible.
Reduced retroclination of the upper incisors.

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

123. Modified Twin-Block Appliance
with Advancement screws :
Advancement screws are incorporated in the
maxillary appliance blocks and activated by the
insertion of cylindrical acetyl resin spacers of
various thickness.

124. Bite blocks with Standard 12mm, 16mm and
20mm advancement screws are available.
Bite reactivations of as much as 7mm can be
readily achieved.
Advantages:
Minimal inconvenience
to staff and patient.
Allows controlled, stepwise
bite advancements to be carried
out easily at the chair side.

125. 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

126. Neuromuscular Twin Block Design
• 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.

127. 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.

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

129. TRANSFORCE appliance is inserted into lingual
sheaths on molar bands and are pre-activated via
the "TWIN FORCE " springs.

130. An expansion module is incorporated to increase
the 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.

131. REVIEW OF LITERATURE

132. McNamara In 1972
McNamara (1972) gave the lateral pterygoid
hypothesis, which suggests that both postural
and functional activity in the masticatory
muscles increases after functional appliance
insertion. This increased activity especially in
superior head of lateral pterygoid muscle, acts
as a stimulus to mandibular condylar growth.

133. McNamara In 1980
With a few days of fitting of twin block
appliance the position of muscle balance is
altered so greatly that the patient experiences
pain when retracting the mandible. This has
been described as the pterygoid response
(McNamara 1980) or the formation of a
tension zone distal to condyle (Harvold and
Woodside).

134. McNamara In1990
McNamara (1990) found that the placement
of appliances results in an immediate
change in the neuromuscular proprioceptive
response.

135. Aggarwal et al In 1995
Aggarwal et al (1995) evaluated muscle
response to the twin block appliance. They
found that insertion of twin block appliance in
mouth causes a change in EMG pattern of both
anterior temporalis and masseter muscle during
six months observation period. Both muscles
were stimulated, however the masseter showed
a more definite pattern of change.

136. Toth.LR In 1999
Toth.LR (1999) compared the treatment effects
produced by twin block appliance and Fr-II
appliance. They concluded that Class II
correction with twin block appliance is achieved
through normal growth in addition to mandibular
skeletal and dentoalveolar changes. Class II
correction with the Fr-II is more skeletal in
nature with less dentoalveolar changes noted.

137. Chintakanon et al In 2000
Chintakanon et al (2000) found that lateral
pterygoid muscle was not responsible for new
position of mandible after treatment with
Clark's twin block. It is due to displacement of
mandible by condylar growth and surface
remodeling of fossa.

138. Mills.CM and McCalloch.KJ In 2000
Mills.CM and McCalloch.KJ (2000) found
that during the active treatment phase, the
twin block group experienced an average
increase in mandibular unit length by
6.5mm

139. Baccetti.T et al In 2000
Baccetti.T et al (2000) carried out the
cephalometric study to evaluate skeletal and
dentoalveolar changes induced by the twin
block appliance. They found that optimal
timing for twin block appliance therapy of
Class II disharmony is during or slightly after
onset of pubertal peak in growth velocity.

140. G.D. Singh et al In 2002 AO
G.D. Singh et al In 2002 evaluated the changes
in bimaxillary morphology in patients with Class
II division 1 malocclusion treated using Twin
Block appliances. They found that improvements
in facial balance following TBA treatment are
associated with a relative restriction of
anterior displacement within the midfacial
complex as well as maxillary dento-alveolar
effects.

141. Kevin O’Brien et al In 2003 AJODO
Kevin O’Brien et al In 2003 evaluated the
effectiveness of Herbst and Twin-block
appliances in Class II Division I malocclusion.
They found there were no differences in
treatment time between appliances, but
significantly more appointments were needed
for repair of the Herbst appliance than for the
Twin-block

142. Phil Banks et al in 2004 AJODO
Phil Banks et al in 2004 evaluated the
effectiveness of incremental and maximum bite
advancement during treatment of Class II
Division 1 malocclusion with the Twin-block
appliance . They found that Incremental bite
advancement produced no advantages over
maximum advancement.

143. Stanley Braun et al In 2004 AO
Stanley Braun et al In 2004 studied the Effect
of Frankel II and Modified Twin Block
Appliances on the ‘C’-axis (The Growth
Vector of the Dentomaxillary Complex).They
found that Favorable changes observed in the
correction of Class II malocclusions are likely
because of dentoalveolar alterations buttressed
by favorable mandibular growth.

144. Ashok Kumar Jena, Ritu Duggal In 2006
AJODO
Ashok Kumar Jena, Ritu Duggal in 2006
evaluated the skeletal and dentoalveolar effects of
the Twin-block and bionator appliances . They
concluded that Twin-block was more efficient
than the bionator in the treatment of Class II
Division 1 malocclusion.

145. Nicole et al In 2010 AO
Nicole et al (2010) evaluated the Long-
Term Dentoskeletal Changes with the
Bionator, Herbst, Twin Block Functional
Appliances. They concluded no significant
dentoskeletal differences were observed
long-term, among the various treatment
groups and matched controls

146. Omar Yaqooba In 2012 AO
Omar Yaqooba In 2012 evaluated the Use of
Clarks Twin Block functional appliance with
and without an upper labial bow. They found
that the addition of a maxillary labial bow to
the Twin Block has no influence on
dentoalveolar or skeletal changes, or on
rate of overjet reduction.

147. Ashok Kumar Jena In 2013 AO
Ashok Kumar Jena ( 2013) evaluated effectiveness
of twin-block and Mandibular Protraction
Appliance-IV(MPA-IV) in the improvement of
pharyngeal airway passage(PAP) dimensions in
Class II malocclusion. They found that twin-block
appliance was more efficient than the (MPA-IV)
in the improvement of PAP dimensions.

148. Ersin et al In 2014 AO
Ersin et al (2014) evaluated the condylar changes
through cone-beam computed tomography
(CBCT) images in patients treated with Twin-
Block functional appliance. They found that Twin-
Block appliance increases condylar volume,
mandibular length, and intercondylar distance by
stimulating growth of condyle in an upward and
backward direction

149. Veronica et al In 2015 AO
Veronica et al (2015) compared the
dentoskeletal changes produced by the Twin-
block appliance vs the Forsus Fatigue
Resistant Device. They found that Twin Block
appliance produced greater skeletal effects in
terms of mandibular advancement and growth
stimulation while the Forsus caused significant
proclination of the mandibular incisors

150. Dalia et al in 2017
Studied the effect of Treatment with Twin-
Block Appliances on Body Posture in
Class II Malocclusion Subjects and
concluded that the body posture changes
during treatment with Twin-block appliance
were an expression of the physiological growth,
not a response to improvement in occlusion.

151. CONCLUSION
In the pursuit of ideals in orthodontics, facial
balance and harmony are of equal importance
to dental and occlusal perfection. We cannot
afford to ignore the importance of orthopedic
techniques in achieving these goals by growth
guidance during the formative years of facial
and dental development.

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