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Twin block /certified fixed orthodontic courses by Indian dental academy

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Twin block /certified fixed orthodontic courses by Indian dental academy

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Case selection criteria 1. 2. 3. 4. 5. 6. 7. Angles Class II division I malocclusion with good arch form Uncrowded or well aligned lower arch Upper arch that is aligned or can be aligned An overjet of 10-12 mm and a deep overbite A full unit distal occlusion in the buccal segments Clinically good VTO Patient in active phase of growth
  3. 3. Construction 1. Good set of impressions 2. Accurate construction bite 3. Models mounted on an articulator
  4. 4. Bite registration There are two types of bite gauges used to register bite for twin block: 1. George bite gauge 2. Exactobite gauge
  5. 5. 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.
  6. 6. Exactobite or Projet Bite Gauge Incisal portion has three incisal grooves to be positioned on the incisal edge of the upper incisor A single groove on the opposing side that engages the incisal edge of the lower incisor. The appropriate groove is selected
  7. 7. • Designed to record a protrusion bite for construction of twin blocks. • Registers 2 mm vertical clearance between the incisal edges of the upper and the lower incisors. • 5 or 6 mm of clearance in the first premolar region and 2 mm of clearance distally in the molar region • Ensures that space is available for vertical development of posterior teeth to reduce the overbite.
  8. 8. Procedure First rehearse the procedure of bite registration with patient using a mirror. The patient is instructed to close correctly into the bite gauge before applying the wax. The patient should be instructed to occlude with the midlines coincident and the upper incisors occluding in the appropriate groove to reduce the overjet when the mandible closes into the incisal guidance groove. A relatively firm wax which is dimensionally stable is used to register the occlusion.
  9. 9. Guidelines Horizontal consideration: According to the Roccabado (1992), the position of maximal protrusion is not a physiological position and the range of physiological movement of the mandible is only 70% of the total protrusive path. This is also called freedom of movement.
  10. 10.  Total protrusion path is calculated by measuring the overjet in most retruded position and then in the most maximal protrusion and finding the difference between the two.  The initial activation should not exceed 70% of the protrusive path.  Average 5 – 10 mm on initial activation, depending upon the freedom of movement in protrusion function.  This degree of activation allows an overjet as large as 10 mm to be corrected.
  11. 11. Midline consideration: Centre lines should be coincident provided no dental asymmetry is present
  12. 12. Vertical consideration: Two factors determine the amount of vertical clearance. They are: 1)Thickness of the bite block Adequate vertical clearance must be available between the cusps of the upper and lower first premolars or deciduous molars to accommodate blocks of sufficient thickness to activate the appliance.
  13. 13. 2)The vertical activation must open the bite beyond the freeway space to ensure that the patient can not drop the mandible into rest position and negate the proprioceptive functional response of the inclined planes.
  14. 14. Intergingival height To establish the correct vertical dimension Measured from gingival margin of upper incisor to gingival margin of lower incisor when teeth are in occlusion. Comfort zone for intergingival height for patients is generally found to be 17-19 mm. Height of upper & lower incisors minus overbite
  15. 15. Horizontal Vs Vertical growth pattern Horizontal growth pattern - maintain edge to edge incisor relationship more easily (provided the overjet is not excessive) Vertical growth patterns - may not tolerate the same degree of sagital activation. A smaller initial activation is necessary Gradual mandibular advancement
  16. 16. Clinical management Two phases: • Active phase • Support phase ACTIVE PHASE Twin blocks are worn full time. The objective is to correct arch relationships in the anterior-posterior, vertical and transverse dimensions. Normally overjet and overbite are corrected within 6 months and the lower molars have erupted into occlusion into 9 months. The average time is 6 – 9 months
  17. 17. Clinical management during active phase Instructions to the patient 1st visit 1. Ways to insert and remove the appliance. 2. Operation of screw – The screw that is turned for the first time after the appliance has been worn for one week. 3. Patient should be instructed to eat with the appliance 4. Proper cleaning especially after eating
  18. 18. • 1st visit -The clinician should check that the patient bites comfortably in a protrusive bite. -Overjet is measured for future reference -The lingual acrylic of the appliance must be relieved. - The clasps are adjusted. - If a labial bow is present, it should be out of contact with the upper incisors.
  19. 19. • – – – – 2nd visit : after 10 days Should be comfortable with the appliance. If the patient is failing to posture forward consistently, reduce activation by trimming the inclined planes to achieve patient compliance. Activation of screw under supervision in the beginning. Trimming of upper block occlusodistally by 1mm in case of deep overbite. No trimming should be done in case of reduced overbite or open bite.
  20. 20. • 3rd visit : after 4 weeks. -review of progress – reduction of OJ & correction of molar relationship. -adjustment of labial bow to keep out of contact. -check up for screw activation & its effects. -trimming of upper block as needed. • 4th visit : after 6 weeks -similar pattern of adjustment.
  21. 21. Reactivation of twin blocks: To increase the forward posture by the addition of the cold cure acrylic to extend the anterior incline of the upper twin block.
  22. 22. Reactivation is needed when: a) Overjet is greater than 10mm b) In vertical growth pattern when patient cannot tolerate 10mm protrusion. c) In adult treatment, when the muscles and ligaments are less responsive to a sudden large displacement of the mandible. d) TMJ dysfunction
  23. 23. SUPPORT PHASE   The aim is to retain the corrected incisor relationship until buccal segment occlusion is fully established. An upper removable appliance with steep anterior inclined guide plane.
  24. 24.  The lower appliance is left out at this stage and the posterior bite blocks are removed to allow the posterior teeth to erupt into occlusion.  The upper and lower buccal teeth are usually in occlusion within 4 -6 months.  Important phase. Stability is excellent after twin block treatment; can be attributed partly to the supportive phase.
  25. 25. Retention phase: A normal period of retention follows treatment after occlusion is fully established. During the retention period the appliance wear can be gradually reduced to night time wear.
  26. 26. Average treatment time 1.Active phase- 6-9 months 2.Support phase- 3-6 months 3.Retention phase- 9 months Average treatment time 18 months
  27. 27. Monitoring condylar position during Rx • X-rays to evaluate: Position of condyle in the glenoid fossa – Before Rx with the teeth in contact – Downward and forward position of the condyle when the appliance is inserted – After the overjet has been reduced – On completion of Rx
  28. 28. Treatment of deep overbite:  Trimming upper twin block occlusodistally to encourage eruption of the lower molars  1-2 mm clearance over the lower molars.  The inclined plane must remain intact, however to maintain the activation to propel the mandible down and forward.
  29. 29.  Vertical development slower than sagital correction. Should therefore be made as early as possible in treatment to allow vertical development to proceed concurrently with sagital correction.
  30. 30. Treatment of reduced overbite Bite registration Activation should not be more than 70% of the total protrusive path Yellow Projet or exactobite to register a 4mm interincisl clearance with a 5mm clearance in premolar region
  31. 31. Appliance designs  All posterior teeth must be in occlusal contact with the opposite bite blocks to prevent the over eruption  Second molar eruption should be controlled by placing occlusal rests or extending the upper twin block distally Pitfalls
  32. 32. Palatal spinner  Application of intrusive orthopedic forces may be used to help control vertical growth
  33. 33. Intraoral elastics – first used by Dr Christine Mills
  34. 34. Magnetic forceattracting or repelling force on the inclined plane
  35. 35. Treatment of Class II Div 2 Bite registration Incisors in an edge to edge occlusion Cut off the handle of exactobite later and ask the patient to close fully in an edge to edge relation
  36. 36. Appliance designs • Sagital screws • Three way screw • Sagital and transverse
  37. 37. Springs
  38. 38. •Triple screw
  39. 39. Treatment of class III Reverse Twin Blocks Reverse the angulation of inclined planes to advance the maxilla Important that the patients condyles are not displaced superiorly and or posteriorly in the glenoid fossae at full occlusion
  40. 40. Bite registration • Not the same degree of activation because of less scope for distal displacement of the mandible • Downward and backward forces absorbed at the gonial angle
  41. 41. Appliance design • Three way expansion screw
  42. 42. • Lip pads
  43. 43. • Reverse pull face mask
  44. 44. Treatment during mixed dentition Appliance modification Limited retention in deciduous teeth Methods to improve retention:  Use of C clasp  Bond composite on to the buccal surface of to create an undercut or  Bond C clasp directly to deciduous molar
  45. 45.  Synthetic crown contours (Truax), which are bonded on buccal surface to improve retention  Grinding a concavity for a ball clasp  Grinding retention grooves into buccal surface
  46. 46. Treatment of asymmetry • Effective in correction of facial and dental asymmetry • Occlusal inclined plane ideal for unilateral activation Appliance design Sagital screws More frequent turning of screw on the side that requires more distal movement Use of magnets
  47. 47. Treatment of TMJ • Indicated in-early click when condyle is displaced distal to the disc. Following objectives are attained: – Immediate relief from pain – Retraining of muscles to a healthy pattern & relief of muscle spasm – Recapturing of disc by downward & forward posture of mandible – Movement of teeth causing occlusal imbalance
  48. 48. • Sagital twin block –relieves compression on the joint • Important to maintain posterior occlusal support at all times • Full time commitment from patient
  49. 49. • • • Advantages of Twin block therapy Comfort – Patient wear twin blocks 24 hr per day and eat comfortably. Aesthetics – Twin blocks can be designed with no visible anterior wires without losing efficiency in correction of arch relationships. Function - There is less interface with normal functions because the mandible can move freely in anterior and lateral excursion without being restricted by a bulky one piece appliance. 1.
  50. 50. • Patient compliance – Twin blocks maybe fixed to the teeth temporarily or permanently. Removable twin blocks can be fixed in the mouth for the first week or 10 days of treatment • Facial appearance –the appearance is noticeably improved when twin blocks are fitted. Improvements in the facial balance are seen progressively in the first three months of treatment.
  51. 51.  Speech: Patients can learn to speak normally with twin blocks. Do not distort speech by restricting movements of the tongue, lips or mandible.  Clinical management:  Adjustment and activation is simple.  The appliances are robust and not prone to breakage.  Chairside time is reduced in achieving major orthopedic correction.
  52. 52. • Arch development: • Twin blocks allow independent control of upper and lower arch width. • Appliance design is easily modified for transverse and sagittal arch development. • Mandibular repositioning: Full time appliance wear consistently achieves rapid mandibular repositioning that remains stable out of retention.
  53. 53.  Vertical control: Twin blocks achieve excellent control of the vertical dimension in treatment of deep over bite and anterior open bite.  Facial asymmetry: Asymmetrical activation corrects facial and dental asymmetry in the growing child.
  54. 54.  Safety : Twin blocks can be worn during sports activities with the exception of swimming and violent contact sports, when they may be removed for safety.  Efficiency: Twin blocks achieve more rapid control of malocclusion compared to one piece functional appliances because they are worn full time.
  55. 55.  Age of treatment: Arch relationships can be corrected from early childhood to adulthood. However treatment is slower in adults but the response is less predictable.  Integration with fixed appliances: Simultaneous skeletal correction and alignment. During the support phase an easy transition can be made to fixed appliances.
  56. 56.  Treatment of TMJ dysfunction: The twin blocks may at times also be used as an effective splint in treatment of patients who present TMJ dysfunction due to displacement of the condyle distal to the articular disc. Full time wear allows the disc to be recaptured when disc reduction is possible in early stage TMJ problems and at the same time sagital,vertical and transverse arch development proceeds to eliminate unfavourable occlusal contacts.
  57. 57. Effects of Twin Block Effects on hard tissue Morris et al 1998 compared the skeletal and dentoalveolar effects of three appliances : Bass,Bionator,Twin Block. Results showed : – Greatest anterior movement of mandible in Twin block group – Greater restriction of the anterior movement of point A – Significant reduction in the inclination of upper incisors to the maxillary plane.
  58. 58. McNamara et al 1999 studied the Rx effects produced by Twin block and FR-II appliance compared with an untreated control group. 1)Increase in mandibular length in – Twin Block -3.0mm – Frankel -1.9mm 2)Increase in lower anterior facial height was more in Twin block group 3)More extensive dentoalveolar adaptation was observed more with the tooth borne Twin block appliance.
  59. 59. Mills & McCulloch 2000 evaluated the post treatment changes after successful correction of class II malocclusion with the Twin Block appliance. Found that during the active Rx phase increase in the mandibular length in: Twin Block group -6.5 mm (14 months) Control group- 2.3 mm (13 months) In the post Rx phase Twin Block grp-6.0 mm(36 months) Control grp-6.7 mm (34 months)
  60. 60. Trenouth 2000 evaluated the Rx effects of • • • • Twin Block as compared with the natural growth changes. Following results were found: The twin block appliance reduced the class II relation to a significant level Correction was found to be comparable to that of Herbst appliance Some dentoalveolar compensation was also found Improved response was due to a 24 hr wear
  61. 61. Parkin et al 2001 compared the effects of 2 modifications of Twin block1. Twin block with labial bow 2. Twin block with high pull headgear and torquing spurs – Greater reduction in the ANB angle in 2nd group – Increased maxillary growth restriction – Less retroclination of upper incisors due to torquing spurs.
  62. 62. • O’Brien et al 2003 did a randomized clinical trial to evaluate the effectiveness of Twin block and Herbst appliance. • Twin block with labial bow was used • Changes in mandibular length : Twin Block --3.46mm Herbst ---3.36mm Concluded : No difference in dental & skeletal effects of Rx.
  63. 63. Effects on soft tissue  Rapid changes in craniofacial musculature due to altered muscle function  As appliance is worn full time , even during eating, rapid soft issue adaptation occurs.  Significant facial changes within 2-3 weeks.  Twin Block appliance increases the intermaxillary space so difficult to form an anterior oral seal by contact between the tongue and the lower lip, and patients adopt a natural lip seal without instruction.  Good lip seal is a functional necessity to prevent food and liquid escaping from the mouth So, no need for lip exercises.
  64. 64. • Within a few days of fitting the appliances, the position of muscle balance is altered so that it becomes painful for the patient to retract the mandible. This has been described as the “Pterygoid Response” (McNamara) • Formation of a tension zone distal to the condyle (Harvold)
  65. 65. Sampson et al(2000) evaluated whether the protrusive muscles were responsible for mandibular repositioning after Twin Block therapy. Found that fatiguing these muscles did not alter mandibular position in Twin block group after 6 months of treatment Hypothesized that Twin block therapy may have shortened the protrusive muscles and consequently slowed the increase of muscle force
  66. 66. • 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
  67. 67. • References Twin Block Functional Therapy-Applications in Dentofacial Orthopaedics.William J Clark WJ Clark. The twin block technique. A functional orthopedic appliance system.AJODO1988;93(1):118 Illing et al. A prospective evaluation of Bass,Bionator and Twin block appliances. Part Ithe hard tissues. EJO1998;20:501-516 Chintakanon et al. Effects of Twin block therapy on protrusive muscle functions.AJODO2000;118:392-6.
  68. 68. Baccetti et al. Treatment timing for Twin block therapy.AJODO2000;118:159-70 Mills et al.Post treatment changes after successful correction of class II malocclusion with Twin block appliance. AJODO2000;118:24-33 Parkin et al.comparison of 2 modifications of the Twin block appliance in matched class II samples.AJODO2001;119:5727. Read et al .The intergation of functional and fixed appliance treatment. J of Orthodontics2001;28:13-18 Singh et al.Localization of mandible changes in patients with class II Division I maloclusions treated with twin block appliances: Finite element scaling analysis.AJODO2001;119:419-25 O’Brien et al.Effectiveness of Treatment for class II malocclusion with the Herbst or Twin block appliances:A randomised controlled trial.AJODO2003;124(2):128-137
  69. 69. Thank you For more details please visit