Twin block

FUNCTIONAL APPLIANCE

1. TWIN BLOCK

2. CONTENTS INTRODUCTION HISTORY DESIGN OF TWIN BLOCK RESPONSE TO TWIN BLOCK TREATMENT SKELETAL CHANGES DENTAL CHANGES

3. STANDARD TWIN BLOCK STAGES OF TREATMENT INDICATIONS CONTRAINDICATIONS MODIFICATIONS ADVANTAGES

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

5. INTRODUCTION

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

7. THE PATIENT WAS 8YRS AND 4 MONTHS

8. ENDODONTIC PINS WERE PLACED TO STABILIZE THE INCISOR, 4 MONTHS AFTER TREATMENT

9. DESIGN OF TWIN BLOCK Occlusal inclined plane

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. MANDIBLE UNLOCKED

13. RESPONSE TO TWIN BLOCK TREATMENT 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. The   twin block  technique A functional orthopedic appliance system WJ Clark - American Journal of Orthodontics and Dentofacial …, 1988

14. 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. PTERYGOID RESPONSE 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. McNamara JA. Neuromuscular and skeletal adaptations to altered function in orofacial region. AJO 1973)

15. SKELETAL CHANGES IN TWIN BLOCK THERAPY

16. Dental changes as a result of Twin Block therapy

17. 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

18. BASE PLATE HEAT CURE COLD CURE additional strength and good accuracy speed and easier manipulation .

19. BITE BLOCK

20. 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 consistantly

21. WIRE COMPONENTS DELTA CLASP designed by Clarke retentive loops are shaped as a closed triangle or a circle gives excellent retention on lower premolars

22. 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

23. BITE REGISTRATION -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 Woodside DG (1977) The activator. In: Graber TM, Neumann B, editors. Removable Orthodontic Appliances. Philadelphia: Saunders; pp. 269-336.

24. normal physiologic TMJ movement as 70% of the total joint displacement. Roccabado edge to edge incisor relation with 2mm interincisal clearance . Overjet upto 10mm

25. 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 millimetre gauge to measure the protrusive path of the mandible and determine accurately the amount of activation registered in the construction bite.

26. 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

27. Overjet greater than 10mm- initial activation of 7-8mm followed by further activation. Vertical dimension - should be 4 – 5mm(in the first premolar region).

28. 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

29. STAGES OF TWIN BLOCK TREATMENT

30. ACTIVE PHASE 6-9 MONTHS

31. the appliance is used to achieve correction of sagittal jaw position . After correction vertical discrepancy is corrected by selectively trimming the posterior bite blocks. 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. AIM

32. SUPPORT PHASE 4-6 MONTHS

33. AIM 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.

34. ANTERIOR INCLINED PLANE

35. RETENTIVE PHASE 9 MONTHS

36. 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

39. CONTRAINDICATIONS

40. MODIFICATIONS OF TWIN BLOCK

41. Twin block for arch development

42. TWIN BLOCK FOR TRANSVERSE DEVELOPMENT

43. TWIN BLOCK FOR SAGITTAL DEVELOPMENT

44. FOR BOTH TRANSVERSE AND SAGITTAL In cases of laterally contracted maxillary arch; combined sagittal and tranverse expansion is required.This is brought about by Three way sagittal appliance . Triple screw sagittal appliance.

45. 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.

46. TWIN BLOCK TO TREAT ANTERIOR OPEN BITE

47. APPLIANCE DESIGN 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 . For 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.

48. Pitfalls in the treatment of anterior open bite arise from careless management of the occlusal bite blocks. Two common mistakes are to be avoided: 1. The over eruption of the second molars behind the appliance 2. Trimming of the upper bite block occlusally which allows the lower molars to erupt thereby propping the bite open and increasing the open bite

49. 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

50. APPLIANCE DESIGN

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

52. 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- shaped clasps can be bonded to  deciduous teeth for improved retention. TREATMENT OF MIXED DENTITION

53. 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  

54. 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.

55. 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.

56. POSITION OF THE CONDYLES

57. Modification- lip pads may be used to support the upper lip clear of the incisors.

58. Teeth closed to the maximum retrusion , leaving sufficient clearance between posterior teeth for occlusal bite blocks . A chieved by recording bite with 2 mm interincisal clearance in fully retruded position. 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.  

59. MAGNETIC TWIN BLOCK Two rare earth magnets used Samarium Cobalt Neodynium Boron ATTRACTING MAGNETS REPELLING MAGNETS

60. ATTRACTING MAGNETS

61. 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

62. TWIN BLOCK IN TMJ THERAPY

63. 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.

64. STAGES OF TREATMENT SAGGITAL DEVELOPMENT

65. Functional repositioning Pain relieved immediately Muscles are restrained Disc is recaptured

66. Vertical development Trimming the upper blocks Vertical traction Twin block biofinisher

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

68. 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.

69. 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

70. TREATMENT OF FACIAL ASYMMETRY Occlusal inclined planes- capable of unilateral activation. Use of magnets.

71. FIXED TWIN BLOCK Increase control by the operator Limited indications- Growth status of the patient Patient cooperation. One phase treatment is planned .

72. Clinical Management & Maintenance Blocks are checked for comfortable occlusion. Deep bite correction- twin block lingual component is fixed to permanent molars. Vertical elastics and lingual hooks placed after occlusal blocked removed. Appointment should be after 3-4 weeks

73. FUNCTIONAL COMPONENTS

74. TWIN BLOCK TRACTION TECHNIQUE The cases in which , response to functional correction is poor, the addition of orthopaedic traction force may be considered. Indications : In treatment of severe maxillary protrution . To control vertical growth pattern by addition of vertical traction to intrude upper posterior teeth. In adult treatment where mandibular growth cannot assist correction of severe malocclusion.

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

76. Concorde facebow helped in restricting maxillary growth, at the same time encouraged mandibular growth in combination with the functional appliance.

77. The labial hook is positioned extraorally 1cm clear of the lips. Traction component are worn only at night .

78. Directional control of orthopedic force-

79. Dixon et al, Mandibular incisal edge demineralization and caries associated with Twin Block appliance design, Journal of Orilwitonfics , Vol. 32. 2005, 3 10

80. The use of a Southend clasp on the upper and lower incisors of a Twin-block appliance : • reduces retroclination of the upper incisors; • reduces proclination of the lower incisors; • applies control to the incisors which may enhance the skeletal correction. Trenouth et al, A randomized clinical trial of two alternative designs of Twin-block Appliance, Journal of Orthodontics, Vol. 39, 2012. 17-24

81. DESIGNER TWIN BLOCK

82. ADVANTAGES OF TWIN BLOCK

83. The effects of Twin Blocks: A prospective controlled study ( David Ian Lund 1998 AJO) OBJECTIVE: This study was designed to investigate the maxillomandibular skeletal and dentoalveolar changes produced by the Twin Block appliance compared with those changes experienced by an untreated control group.

84. The treatment group consisted of 36 subjects, mean age of 12.4 years The control group consisted of 27 subjects with a mean age of 12.1 years. These patients were observed for a mean time of 1.2 years

85. ANGULAR MEASUREMENTS

86. LINEAR MEASUREMENTS

87. Is mandibular growth increased?

88. statistically significant increase in mandibular length measured from Articulare-Pogonion , with some forward movement of Pogonion , both of which are desirable outcomes of treatment. It was not possible to determine whether the increase in Ar-Pog was due to an increase in mandibular length or a repositioning of the mandible. Baumrind and Korn and Haynes found similar changes in Ar-Pog . . (1986 AO,AJO 1981) However, the Twin Block appliance produced a greater change over a shorter treatment period

89. Do Twin Blocks restrain maxillary forward growth?

90. When forward growth of the maxilla was assessed little change in SNA was observed thus indicating little maxillary restraint. The results do not suggest any significant headgear effect associated with the Twin Block some degree of maxillary restraint might have occurred but was not detected because of dentoalveolar remodeling disguising the skeletal effects of the treatment.

91. Is there a beneficial sagittal change? the forward growth of the mandible does result in a significant change in ANB thus the severity of the Class II skeletal pattern is reduced.

92. Does tooth tipping contribute greatly to correction? There was a significant amount of tipping of the labial segment teeth in both arches. The maxillary incisors were retroclined , mandibular incisors were proclined as a result of treatment, which greatly contributed to correction of the overjet .

93. Does anteroposterior molar movement aid correction of the malocclusion? A restraining effect on the upper molars was demonstrated to the extent that there was slight distalization along with a statistically significant forward movement of the lower molars. This change in molar position aids the correction of the disto -occlusion

94. Do Twin Blocks control the vertical position of the teeth? There was a significantly increased eruption of the lower molars during treatment after judicious trimming of the bite blocks. This not only contributes to overbite reduction and closure of lateral open bites but also helps with Class II molar correction.

95. The following case report documents a 12-year-old boy with 11 mm overjet treated by a phase I growth modification therapy using twin block appliance with lip pads in a stepwise mandibular advancement protocol  [4] , [5] , [6]  followed by a phase II preadjusted Edgewise appliance therapy to settle the occlusion and correct the remaining dental discrepancy. Management of severe Class II malocclusion with sequential modified twin block and fixed orthodontic appliances

96. Enhance forward growth of the mandible to improve facial profile and mandible/cranial base relationship. Reduce overjet and overbite. Achieve Class I incisor and buccal segment relationships. Eliminate lip trap and improve lip competency. Relieve crowding and align teeth. Aims of treatment

97. Phase I: Growth modification therapy An acrylic twin block appliance with lip pads was given for full-time wear with an initial mandibular advancement of 6 mm and interocclusal clearance of 5 mm in the 1 st  premolar region.

98. After 6 months , the appliance was activated by advancing the mandible by 5 mm to achieve an edge to edge incisor relationship. The patient was instructed to turn the maxillary expansion screw once a week and was reviewed every 4 weeks. Bite blocks were trimmed to achieve proper vertical eruption of the posterior dentition to reduce the deep bite. The twin block appliance was removed after 12 months of treatment. Normal overjet , overcorrected molar relationship, and lip competency were achieved by phase I orthopedic stage

99. Post functional appliance photographs

100. Phase II: Fixed appliance

101. Utility intrusion arch fabricated using 0.016” × 0.022” SS wire was placed in the maxillary arch for 3 months for incisor intrusion  . The archwires were subsequently changed to 0.017” × 0.025” stainless steel wire for torque control. Class II elastics were worn full time to maintain the buccal relationships and overjet . Root paralleling was carefully adjusted, and cusp seating was carried out by vertical elastics at the end of treatment. The total treatment was completed in 25 months. Upper and lower Hawley's retainers were given immediately after the fixed orthodontic appliance was removed

102. Results : The post treatment facial profile of the patient demonstrated noticeable improvement with good facial esthetics, straight facial profile, and balanced competent lips . The intraoral occlusion revealed satisfactory result with characteristics of well-aligned dentition . Overjet and overbite were reduced to 3 mm and 2.5 mm, respectively. Class I canine and molar relationship with good buccal interdigitation were also achieved.

103. The twin block appliance due to its acceptability, adaptability, versatility, efficiency, and ease of incremental advancement without changing the appliance has become one of the most widely used functional appliances in the correction of Class II malocclusion. It can eliminate etiologic factors such as sucking habits and lip trap, restore normal growth, and reduce the severity of skeletal abnormalities.

104. Effectiveness of treatment for Class II malocclusion with the Herbst or Twin-block appliances: A randomized, controlled trial Kevin O’Brien

105. The aim of this study was to evaluate the effectiveness of Herbst and Twin-block appliances for established Class II Division I malocclusion. The study was a multicenter, randomized clinical trial carried out in orthodontic departments in the UK. A total of 215 patients (aged 11-14 years) were randomized to receive treatment with either the Herbst or the Twin-block appliance .

106. Treatment with the Herbst appliance resulted in a lower failure-to-complete rate for the functional appliance phase of treatment (12.9%) than did treatment with Twin-block (33.6%). There were no differences in treatment time between appliances, but significantly more appointments (3) were needed for repair of the Herbst appliance than for the Twin-block . There were no differences in skeletal and dental changes between the appliances;however , the final occlusal result and skeletal discrepancy were better for girls than for boys. Because of the high cooperation rates of patients using it, the Herbst appliance could be the appliance of choice for treating adolescents with Class II Division 1 malocclusion. The trade-off for use of the Herbst is more appointments for appliance repair. (Am J Orthod Dentofacial Orthop 2003;124:128-37)

107. DESIGN OF TWIN BLOCK

108. DESIGN OF HERBST APPLIANCE

109. Conclusions • Phase I treatment is more rapid with the Herbst appliance, but overall duration of treatment is similar to that with the Twin-block • The Herbst appliance is prone to debonding an component breakage • There are no differences in the dental and skeletal effects of treatment

110. 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 cephalometric study compares the treatment effects produced in 40 patients treated with the Twin-block appliance 40 children treated with the FR-2 appliance 40 untreated Class II controls

111. significant increases in mandibular length were observed in both treated groups. The Twin-block achieved an additional 3.0 mm of mandibular length, whereas the Fränkel 1.9 mm more than did the controls. No restriction of midfacial growth in either appliance group relative to controls

112. A increase in lower anterior facial height in both treatment groups. more dentoalveolar adaptation was observed in tooth-borne Twin-block appliance than with the tissue-borne FR-2.

113. The Twin-block and FR-2 samples both showed significant retroclination and extrusion (eruption) of the maxillary incisors. The Twin-block patients exhibited distal movement of the upper molars; however, there was no extrusion. Slight lower incisor proclination was noted greater in the Twin-block group compared with the other .

114. CONCLUSION Facial harmony and balance are of equal importance to dental occlusion perfection. One cannot ignore the importance of orthopaedic techniques in achieving these goals by growth guidance during the formative years of facial and dental development. The integration of orthodontic and orthopaedic techniques offer a new initiative in restoring facial balance.

115. 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  

116. 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