Twin block

TWIN BLOCK
www.indiandentalacademy.com

Introduction
• These are functional appliances designed
to enhance forward mandibular growth in
the treatment of distal occlusion by
encouraging a functional displacement of
mandibular condyles downards and
forwards in the glenoid fossa.
• Repositioning creates a positive
proprioceptive response in the muscles of
mastication. www.indiandentalacademy.com

The occlusal inclined plane
• This is fundamental functional mechanism of
habitual dentition
• occlusal forces transmitted through the dentition
provide a constant stimulus to influence the rate
of growth and trabacular structure of supporting
bone
• this sensory feed back mechanism controls
muscular activity and provides a functional
stimulus or deterrent to mandibular bone growth.

Principle
• A technique that would maximise the
growth response to functional mandibular
protrusion by using an appliance system
that is comfortable,simple and esthetically
pleasing to the patient.
• The unfavourable cuspal contacts of a
distal occlusion are replaced by favourable
proprioceptive contacts on the inclined
planes of the twin block to correct the
malocclusion.www.indiandentalacademy.com

History
• Evolved in response to a clinical problem
when a young patient, son of a Dental
collegue fell and luxated an upper incissor
• The first Twin block was fitted on
september 7th 1977

Early Twin Blocks

Standard Twin Block

Standard Twin blocks

Angulation of the inclined plane
• Initially the angulation between the blocks
were made at 90 degrees
• since it was difficult to hold the mandible
forward at this angle, the angulation was
changed to a 45 degree one
• the angulation was changed to 70 degrees
to the occlusal plane to apply a more
horizontal force encouraging a more
forward mandibular growth.www.indiandentalacademy.com

Ideal case selection
• Angles class II Division I with proper arch
form
• lower arch that is uncrowded or decrowded
and aligned
• upper arch that is aligned or can be easily
aligned
• an overjet of 10 - 12 mm and a deep over
bite

• A full unit distal occlusion in the buccal
segments
• a good buccal occlusion should result
when the model is advanced
• Profile should improve clinically when the
patient advances the mandible
• Patient should be in active growth phase.

Phases of treatment
• Active phase
• a)Sagittal correction
• b)vertical correction
• c)correction of occlusion
• Support phase
• Retentive phase

Treatment time
• Active phase : 6 -9 months
• Support phase : 3 -6 months
• Retentive phase: 9 months to reducing the
wear time gradually
• Total time : Average 18 months
inclusive of retention
period

Diagnosis and Treatment planning
• Essential orthodontic records supported
by
• study models
• X-rays
• photographs
• along with a diagnostic report

CLINICAL GUIDELINES
• Improvement of facial profile when the
mandible is advanced forward with the lips
tightly closed indicates Twin block as the
treatment of choice.
• This change is a preview of the anticipated
result of functional treatment.

Functional Treatment objective
• To predict the change in facial profile as a
result of functional treatment.
• This can be done with the Photographs and
by superimposition on a cephalogram.
Method
1.Pre treatment cephalogram taken in
centric occlusion and tracing of the
landmarks are done

3. A template of the mandible and the lower
teeth are drawn on a second tracing that
also registers the cranial base for
referance.
4.The template is advanced to place the
incisor teeth in correct contact with the
lower incisor occluding with the base point
of the upper incisor.
5.lip outline is redrawn with the lips closed
and the mandible forward.

Bite registration
• The construction bite determines the
degree of activation built into the
appliance,aiming to improve jaw
relationship
• Originally the bite registration for twin
blocks was aimed for a single activation-
edge to edge bite for an over jet of upto
10mm

• In an overjet of greater than 10mm initial
advancement of 7 - 8mm and later further
correction
• Patients with a vertical growth pattern find
it difficult to protrude the mandible
consistently due to a weak musculature
• in these cases activation has to be
decreased by trimming the inclined planes
• The George Bite gauge is used to determine
the protrusive position of the mandible
and the amount of activation of the bite.

• Functional activation within normal
physiologic limits should not exceed 70 %
of the protrusive path
• Class II Division I cases usually have a
protrusive path of 13 mm and will tolerate
activation of upto 10 mm

Vertical activation
• It is imperative that the bite blocks be
made thick enough so that the bite is
opened beyond the freeway space
• Average thickness is 5mm in the premolar
region or an inter- incisal clearence of 2
mm in a class II Division I case with a deep
bite
• In Class II Division II edge to edge bite is
sufficient www.indiandentalacademy.com

• In the treatment of anterior open bite cases
it is necessary to have greater inter-incisal
clearance of 4 -5 mm
• Twin Blocks may be activated unilaterally
to correct postural mandibular
displacements

Technique
1. The centric occlusial position is checked
2.Lines are marked on the upper and lower
incissors
3.The patient is asked to bite in a different
occlusial position with the mandible in a
protruded position
4. At this position there must be at least 6 mm
of interocclusial space at the premolar
region www.indiandentalacademy.com

5.The patient is asked to bite in this manner
for a couple of times to get used to the new
bite
6.Construction bite is taken with a red base
plate wax heated in a hot water bath and
moulded to appropriate the arch
7. A minimum of 2 -3mm vertical clearance
between the incisors is a must
8.Mandible is advanced depending on the
degree of over jet
9.Models with the bite is articulated

Appliance design and construction
• These appliances are tooth and tissue
borne
• The appliance is designed to to link teeth
together as anchor units to limit individual
movement and to maximise the orthopedic
response to treatment

Parts of Upper bite block
1.The delta clasp
2.Ball end interdental clasps
3.C-clasps
4.Labial Bow
5.Screws
I) Midline screws
2) Anterior sagittal screw
3)Three dimensional screws

Parts Of Lower Bite Block
• Delta Clasps
• c-clasps
• Ball end clasps

Base plate &Bite blocks
• Appliances are made in heat cure or cold
cure acrylic
• cold cure has the advantage of speed and
convenience but the strength is poor
• preformed bite blocks made of heat cure
acrylic can be used with cold cure base

Heat cured Bite Blocks

Lower Heat Cured Bite Block

Inclined plane &extension of the upper bite
block
• Angulation of 70 degrees
• Buccolingual thickness
• Vertical thickness

Inclined plane angulation & Lower bite block
• Angulated at 70 degrees
• Buccolingual thickness

Modification of standard Twin block
• In class II Div I cases with deep bite
• Combination Twin blocks with fixed
appliance therapy &management in mixed
dentition
• For transverse arch
development”SCHWARTZ TWIN BLOCKS”
• Twin Block for the treatment of adult
cases-”CROZAT APPLIANCE”

• Twin block for sagittal arch development
• For both anteroposterior and transverse
development
• For anterior open bite
• Reverse Twin blocks
• With Orthopedic traction
• with intra oral elastics-class II elastics
• With attracting or repelling magnets
• For correction of facial assymetry
• For TMJ therapy
• Fixed Twin blocks

Mixed Dentition treatment

Mixed dentition trt-cont’d

Magnetic Twin Blocks

Treatment of class II Div II

continued

During treatment

Alligning after therapy

Treatment of Class III cases

Edge to Edge bite

End of Twin Block therapy

Advantages of Twin Blocks
• Comfort
• Aesthetics
• Function
• Patient Compliance
• Facial appearance
• Speech
• Clinical management
• Arch developmentwww.indiandentalacademy.com

• Mandibular repositioning
• Vertical control
• Facial assymetry
• Safety
• Efficiency
• Age of treatment
• Integration with fixed appliance
• Treatment of TMJ Dysfunction

Conclusion
• Facial balance and harmony are of equal
importance to Dental Occlusal perfection.One
cannot ignore the importance of Orthopedic
techniques in achieving these goals by Growth
guidance during the formative years of Facial and
Dental development
• In the new millienium,the integration of
Orthodontic &Orthopedic techniques offer a new
initiatiye in restoring facial balance.

Twin block

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