orthodontic myofunctional appliance

1. TWIN BLOCK

2. Twin Block Functional
Therapy
 Guided by :-
 Dr. Shantanu Sharma
 Dr. Anurag
 Dr. Anamika
 Presented by:-
 Dr. Chitra Agarwal
 1st
Year PG

3. CONTENTS
 Introduction
 History
 Design of twin block
 Response to twin block treatment
 Pterygoid response
 Skeletal changes
 Dental changes
 Standard twin block
 Diagnosis and treatment planning
 Stages of treatment
 Indications
 Contraindications
 Modifications
 Advantages
 References

4. INTRODUCTION
 The goal in developing the Twin Block approach to treatment was to produce
a technique that could maximize the growth response to functional
mandibular protrusion by using an appliance system that is simple,
comfortable and aesthetically acceptable to the patient.
 Twin Blocks are constructed to a protrusive bite that effectively modifies the
occlusal inclined plane by means of acrylic inclined planes on occlusal bite
blocks.
 The purpose is to promote protrusive mandibular function for correction of
the skeletal Class II malocclusion.

5. Comprises of separate upper
and lower units which are
not joined together.
Simple bite blocks designed
to be worn 24 hours a day
Achieve rapid functional
correction of malocclusions
by transmitting favourable
occlusal forces to occlusal
inclined planes that cover
all posterior teeth.

6. Twin blocks are
simple bite blocks
with occlusal
inclined planes.

7. HISTORY
The first Twin Block appliance was fitted
on 7th
September 1977 by William Clark.
Evolved in response to a clinical problem.
Young patient who was son of a dental
colleague fell and luxated the upper
incisor
The twin block technique A functional orthopedic appliance system. WJ Clark - American Journal of Orthodontics and Dentofacial …, 1988

8. The incisor was reimplanted and a splint was given .
After 6 months, the tooth was partially reattached but severe root resorption.
Pt. had Class II Div I malocclusion with this, overjet of 9mm and lower lip trapped lingual to
upper incisors.
This was causing mobility and resorption.
To prevent this, it was necessary to design an appliance.
To harness the forces of occlusion to correct the distal occlusion and also reduce the overjet
without applying direct pressure to the upper incisors.
The bite block was place mesial to 1st
molar at 90-Degree angulation.

9. DESIGN OF TWIN BLOCK
Occlusal inclined plane
The occlusal inclined plane is the fundamental functional mechanism of dentition.
Cuspal inclined planes play an important part in determining the relationship of the teeth
If the mandible occludes in a distal relationship to the maxilla (in class II) the occlusal
forces acting on the mandible in normal function have a distal component of force that is
unfavorable to normal forward mandibular development.

10. Twin-blocks constructed in a protrusive bite ,effectively
modifies the occlusal inclined planes by means of bite-
blocks

11. The bite blocks acts as a guiding mechanism
causing the mandible to be displaced downward
and forward.
The unfavorable cuspal contacts of a distal
occlusion are replaced by favorable
proprioceptive contacts on the inclined planes of
twin-blocks to correct the malocclusion & to free
the mandible from its locked distal functional
position.

12. RESPONSE TO TWIN BLOCK TREATMENT
The twin block technique A functional orthopedic appliance system. WJ Clark - American Journal of Orthodontics and Dentofacial …, 1988
When the mandible postures downward
and forwards, there is an area of
immense cellular activity above and
behind the condyle referred as Tension
Zone.
This area is quickly invaded by
proliferating blood vessels and
connective tissue.

13. McNamara JA. Neuromuscular and skeletal adaptations to altered function in orofacial
PTERYGOID RESPONSE
A new pattern of muscle behaviour is quickly established
whereby the patient finds it difficult and impossible to retract
the mandible to its former retruded position.
The muscles are the prime movers in growth, followed by
bone remodelling as a secondary response.
Hence muscle function must be altered over a sufficient
period of time to allow adaptive bone remodelling changes to
occur, in order to reposition the condyle in the glenoid fossa.

14. SKELETAL CHANGES IN TWIN BLOCK THERAPY
Forward growth/repositioning of the mandible is seen after
twin block therapy.
Increase in SNB angle.
Little change in SNA angle indicating maxillary restraint, but was not
detected because of dentoalveolar remodeling disguising the skeletal
effect.
Forward growth/repositioning of the mandible does result in a significant
change in ANB, thus severity of the class II skeletal pattern is reduced.
Increase in lower anterior facial height.

15. Dental changes as a result of Twin Block
therapy
Overjet reduction
Retroclination of the upper incisors
Proclination of the lower incisors.
Buccal segment correction occurred by distal movement of the upper
molars
Lower molar eruption in an anterior and superior direction.

16. STANDARD TWIN BLOCK
Treatment of an uncrowded
class II div 1 malocclusion with
a good arch form.
Clark’s twin block appliance
consists of:
Base plates
Bite block
Wire components: the delta
clasp and ball end clasp
Other related components

17. • HEAT CURE- Additional
strength and good accuracy
• COLD CURE- Faster and
easier manipulation.
BASE
PLATE

18. BITE BLOCK
The inclined plane on lower bite block is angled from the mesial surface of the second premolar or
deciduous molar whichever present.
the lower bite block does not extend distally to the marginal ridge on the lower second premolar.
This allows the leading edge of the inclined plane on the upper appliance to be positioned mesial
to the lower first molar so as not to obstruct eruption

19. The inclined planes are mostly angled at 70 degrees to the occlusal plane, although the angulation may be reduced to 45
degrees if the patient fails to posture forwards consistently.

20. WIRE COMPONENTS
Delta clasps
• Designed by clarke
• Retentive loops are shaped as a closed triangle or a
circle
• Gives excellent retention on lower premolars
BALL END CLASP
• Are routinely placed mesial to lower canines and in
the upper premolar or deciduous molar regions for
interdental retention from adjacent teeth

21. BITE REGISTRATION
Woodside DG (1977) The activator. In: Graber TM, Neumann B, editors. Removable Orthodontic Appliances. Philadelphia: Saunders; pp. 269-336.
Mandible should be positioned protruded approximately 3mm distal to
the most protrusive position that the patient can achieve ,while
vertically the bite is registered within the limit of the freeway space.-
Woodside-1977
Normal physiologic TMJ movement as 70% of the total joint
displacement. (Roccabado)
Overjet up to 10mm -Edge to edge incisor relation with 2mm
interincisal clearance.

22. The Exactobite or the project
bite gauge is used to record a
protrusive interocclusal record
for the construction of the Twin
Block.
The George bite gauge has a
millimeter gauge to measure the
protrusive path of the mandible
and determine accurately the
amount of activation registered
in the construction bite.

23. Activation should be within the masticatory muscle physiologic limit and
ligament attachment limit.
Total protrusive movement = Overjet in centric occlusion – Max protrusion
possible
Functional activation should not be more than 70% of above value
Sagittal activation –Choosing the appropriate groove.
Vertical –Blue colour gauge gives 3mm interincisal clearance

24. • Initial activation of 7-8mm
• Followed by further activation.
Overjet >10mm
• Should be 4 – 5mm(First premolar region).
Vertical Dimension

25. SUMMARY OF BITE REGISTRATION
• Inter incisal clearance (2mm)
• In first premolar region (5-6mm)
• Molar region (1- 2mm)
Design and management of Twin Blocks: Reflections after30 years of clinical use-William Clark

26. Diagnosis and Treatment Planning
 CLINICAL EXAMINATION
 ORTHODONTIC RECORDS
 Radiographic Examination
 Photographs
 Models
 CEPHALOMETRIC ANALYSIS

27. Clinical Examination
 A retrusive mandible can be detected by examining the
profile and the facial contours with the teeth in
occlusion.
 The patient is then instructed to close the incisors in
normal relationship by protruding the mandible, with the
lips closed lightly together - preview of the anticipated
result of functional treatment.
 If the profile improves with the mandible advanced, this
is a clear indication that functional mandibular
advancement is the treatment of choice.

28. Angles in Clarks analysis- skeletal
Cranial base plane to FH 27±3
Mandibular plane angle 26±4
Cranio-maxillary angle 27±3
Mandibular arc 26±4
Facial axis angle 27±3
Condyle axis angle 27±4
Craniomandibular angle 53±5
Facial plane angle -3±3
Maxillary deflection 0±3

29. Dental Analysis
Upper incisor to anterior vertical 25±7
Lower incisor to anterior vertical 25±4
Interincisal angle 128±6
Position of upper dentition Pterygoid vertical to distal of upper
M1-Age + 3mm
Position of lower dentition Lower incisor to A-Pog 1+2

30. Linear Factors
Convexity – A point to facial plane
• 2.5 at age 8; decreases by 0.1 mm per year
Maxillary position=
• 0 mm in mixed dentition; mean = +1 mm in
adult
Mandibular Position
• –10 mm at age 8; decreases by 0.75 mm per
year

31. 31
Soft Tissue Factors
Nasal angle
• Nasal dorsum to anterior
vertical
Lower lip to E plane -
• –2 mm at age 8; decreases
by 0.2° per year.

32. Parallelism In Dentofacial Development
• Ricketts stated that parallelism exists between three planes:
• Facial axis
• Condyle axis
• Upper incisors
• Upper incisor should be positioned parallel to the facial axis
for stability and balance after treatment.
• Bilmer proposed that parallelism exists between FH plane and
maxillary plane.

33. STAGES OF TWIN BLOCK TREATMENT
Active
phase
Support
phase
Retention

34. ACTIVE PHASE (6-9 Months)
The appliance is used to achieve correction of sagittal jaw
position.
After correction vertical discrepancy is corrected by
selectively trimming the posterior bite blocks.
AIM
• Achieve correction to class I occlusion and control of the vertical
dimension by a three-point contact with the incisors and the molars.
• At this stage the overjet ,overbite and sagittal relationship is full
corrected.

35. SUPPORT PHASE (4-6 Months )
• To maintain the corrected
incisor relationship until the
buccal relationship is fully
interdigitated.
• To achieve this objective an
upper removable appliance is
fitted with an anterior
inclined plane with a labial
bow to engage the lower
incisors and canines.
AIM

36. RETENTIVE PHASE (9 Months)
Treatment is followed by
retention with upper anterior
inclined plane appliance.
Appliance wear is reduced to
nighttime wear only when the
occlusion is fully established.

37. FIXED APPLIANCE PHASE
Final detailing of the
occlusion is completed
using fixed appliance
therapy

38. INDICATIONS
Class II div I malocclusion.
• The following is a good general selection criterion:
• Permanent dentition and active grower
• Uncrowded dentition with well developed arches
• 10mm or less overjet with normal to deep overbite
• Improved facial esthetics once the mandible is brought forward to class I
• Normal growth direction
If patient is Class II div 2 with limited overjet or Class II div 1 with
crowded and irregular incisors, align the upper incisors with a fixed or
removable appliance before starting a twin block.

39. CONTRAINDICATIONS
Class II skeletal by maxillary prognathism
Vertically directed grower
Labial tipping of lower incisors
Crowding

40. MODIFICATIONS OF TWIN BLOCK
Twin block for arch
development
Transverse development
Sagittal development
Sagittal and transverse development
To close anterior open bite

41. TWIN BLOCK FOR TRANSVERSE DEVELOPMENT
By combining twin-block
with schwarz appliance.
Screws in upper & lower
twin block to develop arch
form in mixed dentition.

42. TWIN BLOCK FOR SAGITTAL DEVELOPMENT
For anteroposterior arch
development two screws
which are aligned
anteroposteriorly.

43. TWIN BLOCK FOR BOTH TRANSVERSE AND SAGITTAL
DEVELOPMENT
In cases of laterally contracted
maxillary arch; combined
sagittal and transverse
expansion is required.
This is brought about by
• Three-way sagittal appliance.
• Triple screw sagittal appliance.

44. This is mainly due to a combination of skeletal and soft tissue factors.
Bite registration
• A 4mm interincisal clearance is achieved, resulting in approximately 5mm clearance between the
premolars or the deciduous molars.
Sufficient block thickness is needed so as to open the bite beyond the freeway
space – for intrusion of the teeth and at the same time makes it difficult for the
patient to disengage the blocks.

45. TWIN BLOCK TO TREAT
ANTERIOR OPEN BITE
The lower appliance
• Extends distally to the molar region with clasps on the
lower first molars and
• Occlusal rests on the second molars to prevent their
eruption.
The upper appliance
• Expansion screws for arch expansion
• A palatal spinner to control the tongue thrust
• A tongue guard
• A labial bow may be added to retract the upper incisors.

46. Pitfalls in the treatment of anterior
open bite arise from careless
management of the occlusal bite blocks.
Two common mistakes are to be
avoided:
• The over eruption of the second molars behind
the appliance
• Trimming of the upper bite block occlusally which
allows the lower molars to erupt thereby
propping the bite open and increasing the open
bite

47. TREATMENT OF CLASS II, DIV I MALOCCLUSION
Edge to edge bite with 2mm interincisal
clearance.
Center lines should coincide.
In vertical dimension 2mm interincisal clearance
is equivalent to clearance in first premolar region
by 5-6mm and 3mm in the molar region

48. APPLIANCE DESIGN
Inclined planes must be clear
of the lower molars .
This is achieved by
• Trimming the occlusal block, so as to
encourage eruption of the lower
molars and
• Elastics

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

50. TREATMENT OF MIXED DENTITION
Reduce the overjet and correct distal
occlusion.
Control overbite if the overbite is deep
or an anterior open bite is present .
Improve arch form by sagittal or
transverse development.
“C” clasps can be bonded to deciduous
teeth for improved retention.

51. TREATMENT OF CLASS II DIV 2
MALOCCLUSION
An edge-to-edge construction bite is registered to correct
the distal occlusion in class Il division, 2 malocclusion.
Management of Class Il div 2 malocclusion by advancing the
mandible and proclining the upper incisors with sagittal
screws.
Eruption of lower molars corrects vertical dimensions

52. APPLIANCE DESIGN
For the treatment of Class II Div 2 malocclusions ,
sagittal arch development is necessary.
Sagittal Twin Blocks are used
• Upper block is modified by addition of two sagittal screws set in
the palate for anteroposterior arch development.
• The sagittal design is suitable for both upper and lower arches to
increase the arch length.

53. TREATMENT OF CLASS III
MALOCCLUSION
Reverse twin blocks are designed to encourage maxillary
development.
Reverse occlusal inclined plane cut at a 70-degree angle
drive the teeth forwards by the forces of occlusion
Restrict forward mandibular development.

54. POSITION OF THE CONDYLES
Teeth closed to the maximum
retrusion, leaving sufficient clearance
between posterior teeth for occlusal
bite blocks .
Achieved by recording bite with 2 mm
interincisal clearance in fully retruded
position.

55. Modification
• Lip pads may be
used to support
the upper lip clear
of the incisors.

56. Appliance design:-
In many cases, the maxilla is contracted in relation
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.

57. MAGNETIC TWIN BLOCK
• Samarium Cobalt
• Neodynium Boron
• ATTRACTING MAGNETS
• REPELLING MAGNETS
Two Rare
Earth
Magnets
used

58. ATTRACTING MAGNETS
Increased activation can be built into the initial construction bite for the appliance.
Attracting magnets pull the appliances together and encourages the patient to occlude actively and consistently
in a forward position.
Attracting magnets may accelerate progress by increasing the frequency and force of contact on the inclined
planes.

59. REPELLING MAGNETS
Apply additional stimulus to forward
posture the jaw as the patient closes into
occlusion.
• Amount of activation is not clear
• Reactivation of the inclined plane
would deactivate the magnets.
Disadvantage

60. TWIN BLOCK IN TMJ THERAPY
GOALS
• Relieve pain by distal
displacement.
• Restrain muscles to healthy
pattern.
• Recapture disc by advancing
mandible.
• Move teeth causing occlusal
balance.
• Increase the vertical dimension.

61. STAGES OF TREATMENT
Disc is recaptured
Muscles are restrained
Pain relieved immediately
Functional repositioning
SAGGITAL DEVELOPMENT
Twin block Biofinisher
Vertical traction
Trimming the upper blocks
Vertical development

62. TWIN BLOCK BIOFINISHER
Extruding lower molars by vertical traction to stabilize the TMJ

63.  It is important to recognize that if pain is not relieved by forward posture,
and the disc does not appear to be recaptured, there may be internal
derangement, or folding of the disc. which will not respond to Twin Block
therapy.
 In bite registration the Exactobite is used to guide the mandible downwards
and forwards to a comfortable position.
 Myofunctional therapy after maximum and stepwise advancement with the
Twin Block appliance showed a favourable effect in the temporomandibular
joint region.
 Stepwise advancement showed greater vertical growth and more
favourable anteriorly directed horizontal growth in the temporomandibular
joint region on a short-term basis
Doshi et al, Effective temporomandibular joint growth changes after stepwise and maximum advancement
with Twin Block appliance, Journal of the World Federation of Orthodontists 3 (2014) e9-e14

64. ADVANTAGES OF TWIN BLOCK
The twin block is the most comfortable , the most
aesthetic and the most efficient of all the
functional appliances .
• Comfort of the patient
• Aesthetics
• Function
• Patient compliance
• Facial appearance
• Speech
• Clinical management
• Arch development
• Vertical control
• Facial asymmetry
• Age of treatment
• Integration with fixed appliances
• Treatment of TMJ dysfunctions

69. REFERENCES
 Tan et al,A preliminary report of a new design of cast metal fixed twin-block appliance,
Journal of Onhodottíics, Vol. 34. 2007, 213-219
 Woodside DG (1977) The activator. In: Graber TM, Neumann B, editors. Removable Orthodontic
Appliances. Philadelphia: Saunders; pp. 269-336.
 McNamara JA. Neuromuscular and skeletal adaptations to altered function in orofacial region.
AJO 1973)
 The twin block technique A functional orthopedic appliance system
 WJ Clark - American Journal of Orthodontics and Dentofacial …, 1988
 Design and management of Twin Blocks:reflections after30 years of clinical use William Clark
 Doshi et al, Effective temporomandibular joint growth changes after stepwise and maximum
advancement with Twin Block appliance, Journal of the World Federation of Orthodontists 3
(2014) e9-e14
 Dixon et al,Mandibular incisal edge demineralization and caries associated with Twin Block
appliance design, Journal of Orilwitonfics, Vol. 32. 2005, 3 10

70.  Trenouth et al,A randomized clinical trial of two alternative designs of Twin-
block Appliance, Journal of Orthodontics, Vol. 39, 2012. 17-24
 The effects of Twin Blocks: A prospective controlled study ( David Ian Lund
1998 AJO)
 Management of severe Class II malocclusion with sequential modified twin
block and fixed orthodontic appliances
 Effectiveness of treatment for Class II malocclusion with the Herbst or Twin-
block appliances: A randomized, controlled trial
 Treatment effects produced by the Twin-block appliance and the FR-2
appliance compared with an untreated Class II sample
 Linda Ratner Toth, and James A. McNamara, Jr AJO 99