Twin block /certified fixed orthodontic courses by Indian dental academy
INDIAN DENTAL ACADEMY
Leader in continuing dental education
The Clark Cephalometric Analysis
Appliance design and construction
Treatment of Class II div 1 malocclusion
Treatment of Class II div 2 malocclusion
Treatment of anterior open bite
Treatment of Class III Malocclusion
Twin block therapy in mixed dentition
Magnetic Twin Blocks
Twin Blocks in TMJ Therapy
Fixed Twin Blocks
Twin block traction technique
• Myofunctional Appliances :•
According to Moyers,
Myofunctional appliances are loose
removable appliances designed to alter
neuromuscular environment of orofacial
region to improve occlusal development of
craniofacial skeletal growth.
• Historical Perspective:•
The concept of advancing the
mandible by way of inclined planes is not new,
with the notion of “jumping the bite”(1880)
• “Vorbissplate” of Schwarz (1966).
• The Oliver “ guide plane”
• DeVincenzo and coworkers used appliance
similar to developed by clark but angulation
used, 90 degree to occlusal plane as opposed to
70 degree recommended by Clark.
• In all the experimental animals, including,
most importantly, the mature adult, a large
amount of bone had formed in the glenoid
fossa, especially along the anterior border
of the post-glenoid spine.The glenoid
fossa appeared to be remodeling
Introduction of Twin Block:
• The functional occlusal inclined plane is the
fundamental functional mechanism of the natural
• Cuspal inclines play an important role in
determining the relationship of the teeth as thery
erupt into occlusion.
• Occlusal forces transmitted through the dentition
provide a constant proprioceptive stimulus to
influence the rate of growth and the trabecular
structure of the supporting bone.
Development of Twin Block
“ It is true that necessity is the
mother of invention.”
Twin Blocks evolved in response to a
clinical problem when a young patient ,
having Class II div 1 malocclusion fell
down, the upper right central incisor was
avulsed. Within few hours of the trauma
the tooth was reimplanted .
• In order to prevent the adverse lip action ,
upper and lower bite blocks were
designed which were engaged 90 degree.
The first Twin Block appliance was
fitted on 7th September 1977.
It was found that, within 9 months of
starting the Twin Block therapy the
occlusion and overjet reduced from 9mm
to 4mm in 9 months.
THE CLARK CEPHALOMETRIC
The various angular and linear measurements are as follows:
Cranial Base angle
Mandibular plane angle
Facial plane angle
Facial axis angle
Condylar axis angle
Upper incisor angle
Lower incisor angle
Position of dentition
Position of upper dentition
Position of lower dentition
Soft tissue analysis
Lower lip to E- plane
ADVANTAGES OF TWIN BLOCK
Age of the treatment (Early childhood to the adulthood)
Integration with fixed appliances
Treatment of TMJ dysfunctions
APPLIANCE DESIGN AND
A midline screw to expand the upper arch
Occlusal bite blocks
Clasps on the upper molars and premolars
Clasps on the lower premolars and incisors
A labial bow to retract upper incisors
Springs to move individual teeth and to improve
the archform as required
• Provision for extraoral traction in some cases
• STANDARD TWIN BLOCK:
They are essentially for the treatment
of uncrowded Class II div 1 malocclusions
with good arch form and overjet large
enough to allow unrestricted forward
translation of the mandible to allow full
correction of the distal occlusion.
STANDARD TWIN BLOCK
Twin Block for arch development :• SAGITTAL DEVELOPMENT
• Transverse and Sagittal Development :• Twin Blocks to Close anterior Open bite:-
• Treatment of Class II div 1 Malocclusion
( DEEP OVERBITE)
•Protrusive bite is registered
•Initially, 5-10 mm activation can be achieved
•Edge to Edge bite with 2 m m interincisal clearance.
•Bite activation should not exceed 70 % of total protrusive
•Larger overjets require partial correction
•Center lines should coincide.
•Open the bite slightly beyond the clearance of freeway
space, to prevent dropping off the mandible out of the
•In vertical dimensions 2mm interincisal is equivalent to
clearance in first premolar region by 5 to 6 mm and 3mm
in molar region. ( It allows, supraeruption of molars and
deep bite correction.)
Twin Block in mixed dentition
• Objectives :
• Reduce the overjet and correct distal
• Control overbite if the overbite is deep or
an anterior open bite is present
• Improve arch form by sagittal or
• [C- shaped clasps can be bonded to
deciduous teeth for improved retention.]
Treatment of Class II div 2
• An edge to edge construction bite is
registered to correct the distal occlusion,
in class II division, 2 malocclusion.
• Management of Class II div 2
malocclusion by advancing the mandible
and proclining the upper incisors with
sagittal screws. Eruption of lower molars
corrects the vertical dimensions.
Treatment of Class III malocclusion
Reverse twin blocks are designed to
encourage maxillary development by the
action of reverse occlusal inclined planes
cut at a 70 degree angle to drive the upper
teeth forwards by the forces of occlusion
and at the same time, to restrict forward
Teeth closed to the maximum retrusion, leaving
sufficient clearance between posterior teeth for occlusal
bite blocks .This is normally achieved by recording bite
with 2 mm interincisal clearance in fully retruded
Appliance design:In many cases, the maxilla is contracted in addition
to occluding in distal relation to the mandible.
The three –way expansion screw to combine
transverse and sagittal expansion.
Opening the screw has reciprocal effect of driving
upper molars distally and advancing the incisors.
MAGNETIC TWIN BLOCKS :
Use of the magnets in occlusal inclined
plane, is a new concept.
Darendeliler, Joho (1991,93,95)
reported correction of Class II div 1
malocclusion with magnets.
Twin Blocks in Temporomandibular
joint therapy :• Temporomandibular joint pain and dysfunction
are related to occlusal disharmony with
premature occlusal contact, causing posterior or
lateral shift of the mandible from centric relation
and distal displacement of the condyles.
• Distal displacement of the condyle is associated
with anterior displacement of the articular disc.
Goals of the therapy:
• Relieve the pain caused by distal displacement
of the condyle
• Retain the muscles to a healthy pattern
• Recapture the disc when possible by advancing
the displaced condyles.
• Move the teeth that are causing occlusal
imbalance and mandibular misguidance.
• Increase the vertical dimension to reduce the
The Twin Block Biofinisher
• It extrudes the lower molars by vertical
• It stabilize the TMJ by uncreasing vertical
• It has a hook for elastic, that extends
above upper molars in the vestibule
Temporary fixation of twin block
Twin block appliances may be
designed for direct fixation to the teeth by
The patients co-operation is assured if
appliance is either fixed to the teeth or
removable only by the operator
• Integration of Twin Block with fixed
A combined fixed and functional
approach is necessary for correction of
more complex malocclusions, in which
skeletal and dental factors require a
combination of orthopaedic and
The twin Block traction
technique:• The twin Block traction technique:• The cases in which, response to functional
correction is poor , the addition of orthopaedic
traction force may be considered.
• In treatment of severe maxillary protrusion.
• To control a vertical growth pattern by the
addition of vertical traction to intrude upper
• In adult treatment where mandibular growth can
not assist the correction of severe malocclusion.
The Concorde Face Bow
In the early years of Twin Blocks, tubes were
added to clasp for extraoral traction on the upper
appliance to be worn at night so as to reinforce
the functional component for correction of a
Class II buccal segment relationship.
It provides intermaxillary and extraoral
traction to restrict maxillary growth and at the
same time, encourage mandibular growth in
combination with functional mandibular
Correction of Class III malocclusion with
fixed reverse twin blocks in deciduous
• It makes easier to correct the
malocclusion at early stage.
• Patient compliance need is eliminated
• Appliance, working whole day long,
reduces the treatment time.
• Tooth movements are slower in older patients and the
skeletal response diminishes with patients age.
• In adult orthodontic treatment we should anticipate a
dentoalveolar response with limited skeletal adaptation,
this still leaves scope for significant facial changes, but
only when the skeletal discrepancy is not severe.
• Surgical correction should be considered for cases of
severe skeletal discrepancies in adults.
Twin block functional therapy, applications in dentofacial
….William J Clark.
Dentofacial orthopaedics with functional appliances
Twin block technique, a functional orthopaedic appliance system
AJO-DO 1988, (jan 1-18) –Clark.
The action of three types of functional appliances on the activity of
AJO-DO 1997, (Nov 560-572)
Darendeliler MA, Joho JP, MAGNETIC ACTIVATOR DEVICE (MAD
II) for correction of Class II div 1 malocclusion ( JCO 103, 223-229)
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