Twin block1

TWIN BLOCK
www.indiandentalacademy.com

 Development of twin block.
 Mechanism of action.
 Bite registration & fabrication.
 Stages of treatment.
 Modifications for treating various
malocclusions.
 Recent studies.
 Advantages

Development Of The
Twin Block
 “Necessity is the mother of all inventions”.
 Evolved in response to a clinical problem.
 Young patient who was son of a dental
colleague fell and luxated upper incisor.
 Pt. had Class II Div I malocclusion with a
overjet of 9mm.

Development Of The
Twin Block
 After 6 months-tooth partially reattached.
-severe root resorption.
 To prevent this- posture mandible
- full time.
 No such appliances were available at
that time.

Development Of The
Twin Block

Development Of The
Twin Block
 First Twin Block-7th
sep 1977 .
 To surprise jet reduced in 9 months.
 Incisor was stabilized
 Upper fixed appliance was used then to
complete the treatment.

Basic mechanism
 Occlusal inclined planes are
fundamental functional mechanism of
the natural dentition.
 Inclined planes act as a servo system
mechanism that locks the mandible in
distal occlusion.
 Twin block simulates IP of natural
dentition.

Basic mechanism

Basic mechanism
 Occlusal forces transmitted to the
dentition provide a proprioceptive
system.
 Sensory feedback mechanism exists
that inhibits growth.
 Altering the position of the teeth ,a new
functional behavioural pattern is
established.

Basic mechanism
 Bone remodeling is seen in response to
the functional stimuli.
 A new occlusal force vector is
established.
 Forces of occlusion that are applied
during mastication.

Basic mechanism
 This follows the principle of form an
function.
 With the appliance in the mouth pt.
cannot occlude in the former relation .
 So it aims at intervening treatment at
earlier stage of development.

Diagnosis & Treatment
Planning
 Orthodontic records-study models
-radiographs
-photographs
 Thorough TMJ examination.
 Detailed cephalometric analysis.

Diagnosis & Treatment Planning
 Clinical inspection –fundamental
guideline for a proper case selection
 VTO -patient
-study models

Visual Treatment Objective

Bite registration
 Most important step in the fabrication of
the appliance.
 Equal importance for both sagittal and
vertical activation.

Bite registration
 Acc. to Woodside-1977
-mand should be positioned protruded
approx. 3mm distal to the most
protrusive position that the pt. can
achieve ,while vertically the bite is
registered within the limit of the freeway
space.

Bite registration
 Roccabado –quantifies normal
physiologic TMJ movement as 70% of
the total joint space.
 Overjet upto 10mm-a single activation-
edge to edge incisor relation with 2mm
interincisal clearance.

Bite registration
 Project bite is a very useful gauge –
helps in accurately registering the bite.
 Sagittal activation –choosing the
appropriate groove.
 Vertical –blue colour gauge gives 3mm
interincisal clearance

Bite registration

Bite registration
 Mirror is given to the patient.
 Pt. is shown to bite correctly using the
gauge.
 During protrusion midlines should be
matching.
 Firm wax is used to register the bite.

Bite registration
 Overjet greater than 10mm-
initial activation of 7-8mm
followed by further activation.
 Vertical dimension-blocks should be
thick enough to open the bite slightly
beyond the freeway space.

Stages of twin block
 Three stages-
1. Active phase-sagittal and vertical
dimensions are established.
2. Support phase-support the corrected
position as teeth settle in occlusion.
3. Retention

 Active phase-
AIM-is to correct - distal occlusion
- overjet
- overbite
Duration -6-9 months
 Support phase-
AIM-to maintain corrected incisor relation until
buccal segment occlusion is fully
interdigitated.

 Duration-3-6 months.
 Retention phase-
-upper and lower inclined planes.
-duration- 9 months.

Appliance design
 Two key factors –
1. Patient comfort.
2. Esthetics.

Evolution of appliance
1. Midline screw.
2. Occlusal bite block.
3. U/L clasps.
4. Labial bow.
5. Springs to move individual teeth.
6. Provision of extra oral traction.

Standard twin block
1. Labial bow-early stages of
development
-overcorrect incisor angulation.
-limit the scope of functional correction.
-good lip seal is achieved naturally

Standard twin block

Standard twin block
Clasps-difference from the conventional
design.
Delta clasp-basic principle is the same
with slight modification.
Either-triangular/circular

Standard twin block
 Acc. to area of retention-
1. Mesial and distal undercuts
2. Interdental undercut.
 Used on-upper 1st
perm. Molar
-lower 1st
perm. Pre molar

Standard twin block
 Ball end clasps-mesial to lower canines
-upper pm.
-dec molar
 C clasp -dec molar
- canines

Standard twin block
Base plate
Cold cure Heat cure
 Occlusal inclined planes-

Standard twin block
 Arch development-
Transverse
 U/L Schwarz appliance.
 Twin block Crozat Appliance

Standard twin block
Twin block
Schwarz appl.

Standard twin block
Twin block
Crozat appliance

Standard twin block
Twin block
Sagittal appl.

Standard twin block
Transverse and sagittal dev.-
 Three way screw housing.
 Three screw sagittal appliance.
 Midline screw with lingual wires.

Fabricating the appliance
 Once the bite is taken it is transferred on to
the set of patients models.
 This is then mounted on to a fixator.

 Individual wire
components are
then fabricated
 Wax up is done

 This is followed by flasking ,dewaxing
,packing and curing.
 Cured appliance is then removed.
 Finishing and polishing
 Checking on the models for proper
fitting.

Twin block technique

 Treatment of Class II div I.
 Treatment in mixed dentition.
 Twin block traction technique.
 Treatment of ant. open bite
 Treatment of Class II div II.
 Treatment of Class III.

 Treatment of facial asymmetry.
 Magnetic twin block
 Adult treatment with twin block.
 Twin block for TMJ therapy.
 Fixed twin block.

Treatment of Class II Div I
Deep Bite
 Bite registration-
-Exactobite / Project Bite Guage..
 On an average-5-10 mm
(70% protrusive path) .
 Reactivation of appliance.

Deep Bite
 Appliance design
-inclined planes must
be clear of the lower
molars .

Deep Bite
 Temporary fixation of twin block.
1. Appliance may be fixed using cement
on the tooth bearing areas.
2. Bonded directly on clasps-esp. on
deciduous molars

Deep Bite
 Management of deep bite-
-this is achieved by trimming the occlusal
block, so as to encourage eruption of
the lower molars
Elastic separators
Trimming occlusodistally

Deep Bite
Trimming -1-2 mm /visit
Molars erupt 6-9 months
Triangular wedge shaped area
Eruption of the pre molar

Deep Bite

Deep Bite
 Intergingival height-used to establish
correct vertical dimension.

Deep Bite
 Comfort zone-17-19 mm.
 This is used as a guide to establish the
correct vertical dimension during
treatment.

Deep Bite
 Reactivation of twin block-
-In case of larger overjet.
-Full correction not achieved with initial
activation.
-Growth is less favourable.
-In adult treatment.
-In TMJ therapy
-Restricted protrusive pathway.www.indiandentalacademy.com

Deep Bite
 Extending the ant.
incline of upper twin
block
 Preformed inclined
wedges may be
used.

Treatment in Mixed Dentition
 Skeletal discrepancies are not
delayed until the permanent dentition.
1. Prominent upper incisors.
2. Early treatment of crowding.

 Bite registration-same…
 Appliance design-modified to meet the
requirement of mixed dentition
- limited by decd. teeth
- unfavourable contour

 C –clasps are commonly used –
1. Temporary fixation.
2. Grind retention groove.
 Ball end clasps
 Synthetic crown contours

Twin block Traction Technique
 In most cases ,full functional
correction can be achieved with twin
block alone.
 In minority of the cases-
1. Severe maxillary protrusion.
2. To control vertical growth pattern.
3. Adult treatment.

 The Concorde Facebow-
-Before the dev. of twin block ,author
used extraoral traction with removable
appliance as means of anchorage.
-A method was developed to combine
extraoral and intermaxillary traction .

 Concorde facebow helped in restricting
maxillary growth, at the same time
encouraged maxillary growth in
combination with the functional
appliance.
 Patient comfort and acceptance was
similar to the conventional facebow.

 The labial hook is
positioned
extraorally 1cm
clear of the lips.
 Traction component
are worn only at
night.
 Careful selection of
case is very
essential www.indiandentalacademy.com

 Directional control of
orthopedic force-

Treatment of Ant. Open Bite
 May be due to -skeletal.
-soft tissue.
 Airway obstruction.
 Early treatment –helpful in controlling
functional imbalance
 Prognosis-extent of skeletal/soft tissue
- growth pattern

 Pitfalls in Treatment –
Necessary to be attentive to avoid
overeruption of 2nd
molars behind the
appliance.

Trimming of the upper twin block

-Sagittal activation-two step activation to
be done in cases with increased jet.
-Vertical activation-4mm interincisal
clearance, so as to open bite beyond
the free way space

Vertical control-increase
thickness of block.
-occlusal rest on 2nd
molars
- no acrylic on ant. teeth.

 Closing Ant. Open
bite
- Palatal spinner.
- Tongue guard.
- Labial bow.

 Intra oral traction .
-This may be used to accelerate bite
closure-alternative to high pull
headgear.
-Idea was taken from Dr Mills, who used
elastics to maintain occlusal contacts.

 Intrusive effect of the blocks is
reinforced by vertical elastics.
 Elastics may be worn at night/full time.
 Additional advantage of increasing
occlusal contact on the inclined planes.
 Magnets can also be used for the same
purpose.

Treatment of Class II Div II
 Retroclined upper incisors are
responsible holding the mandible.
 Twin block aims at unlocking the
malocclusion by releasing the mandible
from entrapped position.

 Bite registration
-Bite is taken with incisors in edge-edge.
-These pt. usually have a deep bite, so
they require more vertical development.
-However amount of sagittal
advancement is limited

Sagittal Dev.-formerly sagittal appliances
were used (Witzig and Sphal 1987).
-Two sagittal screws are placed in the
horizontal plane and angled along the
line of buccal segment.

 Can be used for
both upper and
lower arches.

 Combined
transverse and
sagittal development

Treatment of Class III
 Functional
correction of Class
III malocclusion can
be achieved by
simply reversing the
angulation of the
inclined planes.

 One important point-
-position of the
condyles.

-Differs from Class II malocclusion.
-2mm interincisal clearance in full
retruded position.

 Appliance design-
-sagittal design is
usually made.
-combination of
transverse and
sagittal.

 Another
modification-lip pads
may be used to
support the upper lip
clear of the incisors.

 Reverse pull facial
mask
 As an additional
component to
advance the maxilla
by elastic traction

Magnetic Twin Block
 Used to accelerate correction of the
arch relationship.
 Two types-samarium cobalt.
-neodynium boron.
 Vardimon et al 1890-90-carried out
various animal experiments in
mandibular advancement

Magnetic Twin Block
 Author modified the
twin block by
addition of attracting
magnets .
 Magnets are placed
on to the inclined
planes.

Magnetic Twin Block
 Attracting magnets
-Increase activation
- Increase frequency
-Increased force of contact
 Repelling magnets
-Less mechanical activation.
-Additional stimulus.

TMJ Therapy
 Case history & diagnosis-
-Full case history –cause and effect
relationship of occlusal disharmony and
mandibular displacement to pain .
- Radiographic examination of the
- TMJ.

TMJ Therapy
 Timing of the click-
- Early opening click-22mm
- Midopening click-22-35mm
- Late opening click-35mm

TMJ Therapy
 Goals of TMJ therapy-
-relieve pain by distal displacement
-restrain muscles to healthy pattern.
-recapture disc by advancing mandible.
-move teeth causing occlusal imbalance.
-increase the vertical dimension.

TMJ Therapy
 Stages of treatment-
I-sagittal
development-

TMJ Therapy
 II Functional repositioning
Pain relieved immediately
Muscles are restrained
Disc is recaptured

TMJ Therapy
 III Vertical development
Trimming the upper blocks
Vertical traction
Twin block biofinisher

TMJ Therapy
 Twin block
biofinisher-

TMJ Therapy

Treatment of Facial Asymmetry
 Occlusal inclined
planes are capable
of unilateral
activation.
 Use of magnets.

Fixed Twin Blocks
 Increase control by the operator
 Limited indications-
1. Growth status of the pt.
2. Pt. cooperation.
3. One phase treatment is planned.

Fixed Twin Blocks
 Three distinct phases-
1. First –arch development.
2. Second –orthopaedic treatment with
fixed functional twin block system.
3. Third – detailed orthodontic treatment

Fixed Twin Blocks
 Functional
components-
Twin Block
Transpalatal Arch-

Fixed Twin Blocks
 Twin block lingual
arch

Fixed Twin Blocks
 Twin Block Hyrax
Appliance

Fixed Twin Blocks
 Clinical Management & Maintenance
-appliance is tried in mouth –bite is checked
-Once cemented-if correct forward posture is
not achieved
a- lower appliance may be removed and
trimmed
b- provision of Class II elastics

Fixed Twin Blocks
 Appointment should be after 3-4 weeks.
 Support phase-anterior inclined plane is
constructed.
-standard lower appliance
 Comprehensive fixed appliance phase.

Fixed Twin Blocks
 Some disadvantages-
1. Blocks may become loose.
2. Control of vertical dimension is limited.
3. Compromised oral hygiene.

Twin block1

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