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Twin block appliance. Dr. Ajay

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Twin block appliance. Dr. Ajay

  1. 1. TWIN BLOCK APPLIANCE DR. AJAY SRINIVAS PG STUDENT
  2. 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. 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. 4 Development Of The Twin Block Before Treatment IOPA Showing Luxated 11 Post Treatment IOPA Showing An Endodontic Pin To Stabilize 11
  5. 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. 6 Different Stages Of Treatment Using Twin Block Combination Therapy With Fixed Appliance In Later Stage
  7. 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. 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. 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. 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. 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. 12. Occlusal inclined plane The occlusal inclined plane acts as a guiding mechanism causing mandible to be displaced downward and forward.
  13. 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. 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. 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. 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. 17. Disadvantages Mandibular incisor proclination An increase in the vertical facial dimension is seen Clockwise rotation of the maxillary plane
  18. 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. 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. 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. 21. VISUAL TREATMENT OBJECTIVE
  22. 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. 23. Bite registration
  24. 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. 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. 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. 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. 28.  George bite gauge- Used to register the protrusive path of mandible in patients with vertical growth pattern and weak orofacial musculature
  29. 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. 30. APPLIANCE DESIGN
  31. 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. 32. Occlusal inclined plane  During the evolution of the technique…the angulations used were 45 degree.  Drawbacks of 45 angulations…posterior open bite.
  33. 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. 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. 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. 36. Retention elements: The Delta clasp:designed by William J Clark(1985) Originally retentive loops-triangular Alternatively the loops-circular
  37. 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. 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. 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. 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. 41. Treatment of Class II division I
  42. 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. 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. 44. Treatment of Class II division I Appliance design : Standard Twin Block
  45. 45. Standard Twin Block Appliance design
  46. 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. 47. Management of deep overbite: Establishing the correct vertical dimension
  48. 48. Reactivation of Twin blocks: Is done by addition of acrylic on the anterior surface of the upper bite block.
  49. 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. 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. 51. Stage 2-Support phase: o Antero- posterior and vertical control o Retention: done using Anterior inclined plane:
  52. 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. 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. 54. Treatment of Class II division II
  55. 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. 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. 57. Appliance design: Sagittal appliance: Two sagittal screws for antero posterior arch development
  58. 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. 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. 60. Sequence of trimming:
  61. 61. Treatment of Class III
  62. 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. 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. 64. LATERAL AND OCCLUSAL VIEW
  65. 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
  66. 66. Treatment of anterior open bite
  67. 67. Bite registration: 4mm- of interincisal clearance and 5mm clearance between the cusps of the first premolars or deciduous molars should be present.
  68. 68. 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.
  69. 69. A palatal spinner-to control anterior tongue thrust. A tongue guard. A labial bow
  70. 70. 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.
  71. 71. 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.
  72. 72. 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.
  73. 73. Treatment of mixed dentition Ready- made undercuts- can be made by extending retention grooves into the buccal surfaces of deciduous teeth.
  74. 74. Twin block Schwarz appliance(1996)
  75. 75. 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.
  76. 76. The Twin traction technique
  77. 77. 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.
  78. 78. 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.
  79. 79. 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.
  80. 80. 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
  81. 81. 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.
  82. 82. 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.
  83. 83. Magnetic Twin blocks:
  84. 84. 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.
  85. 85. 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.
  86. 86. 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
  87. 87. 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.
  88. 88. Two types of rare earth magnets are used: Samarium cobalt Neodymium iron boron : greater force.
  89. 89. 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.
  90. 90. Fixed Twin Block
  91. 91. Fixed Twin Block Advantage: Increased control by the operator. Aesthetic appliance design: Integration of the Twin Block with Wilson 3D modular lingual appliances.
  92. 92. 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.
  93. 93. 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.
  94. 94. Functional components: The twin block transpalatal arch The Twin block hyrax appliance: For rapid maxillary expansion.
  95. 95. 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.
  96. 96. 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.
  97. 97. 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.
  98. 98. 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.
  99. 99. 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.
  100. 100. 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.
  101. 101. 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.
  102. 102. 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.
  103. 103. 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.
  104. 104. 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.
  105. 105. 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.
  106. 106. 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.
  107. 107. 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.
  108. 108. 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
  109. 109. Modifications of Twin Block
  110. 110. 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.
  111. 111. Reduction in over jet: is achieved due to the effects of sagittal mandibular growth alone. Drawbacks of the appliance: Reduced esthetics. Over jet relapse
  112. 112. 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
  113. 113. TWIN BLOCK SCHWARZ APPLIANCE
  114. 114. 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
  115. 115. 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
  116. 116. FOR SAGITAL DEVELOPMENT Twin block sagital appliance • Anteroposterior arch development is achieved by two screws which are aligned anteroposteriorly in the palate
  117. 117. 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
  118. 118. Twin block appliance with a labial bow: Treatment effects: Retroclination of the maxillary incisors. Increased Lower facial height.
  119. 119. 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.
  120. 120. Twin Block with a Spinner to control tongue thrust.
  121. 121. 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.
  122. 122. 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.
  123. 123. 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
  124. 124. 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.
  125. 125. 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.
  126. 126. 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.
  127. 127. TRANSFORCE appliance is inserted into lingual sheaths on molar bands and are pre-activated via the "TWIN FORCE " springs.
  128. 128. 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.
  129. 129. REVIEW OF LITERATURE
  130. 130. 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.
  131. 131. 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).
  132. 132. McNamara In1990 McNamara (1990) found that the placement of appliances results in an immediate change in the neuromuscular proprioceptive response.
  133. 133. 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.
  134. 134. 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.
  135. 135. 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.
  136. 136. 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
  137. 137. 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.
  138. 138. 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.
  139. 139. 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
  140. 140. 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.
  141. 141. 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.
  142. 142. 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.
  143. 143. 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
  144. 144. 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.
  145. 145. 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.
  146. 146. 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
  147. 147. 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
  148. 148. 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.
  149. 149. 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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