Twin Block Appliance

Presentation regarding Functional orthopaedic appliance

1. Twin Block Appliance Dr. Sanjida Haque & Dr. Anas Imran Presented to Dr. Muhammad Khursheed Alam

2. Introduction Twin Blocks are simple removable bite blocks with occlusal inclined planes which act as functional appliance. Functional appliance: “Change the posture of mandible by holding it open (or) open and forward. ( Profitt ) Cuspal inclined planes guide the relationship of teeth to provide constant proprioceptive stimulus for favorable growth of supporting bone. Devised by William J. Clark 1982

3. History In 1880 Kingsley’s “Jumping the bite” gave the concept of advancing mandible by inclined plane. Followed by Vorbissplate of Schwarz 1966 Then “Oliver” guide plane Devincenzo and coworkers used 90⁰ occlusal plane as opposed to 70 recommended by Clark.

4. Indications Uncrowded Class II Div I Deep bite Class II Div I Class II Div II Deep overbite Reduced overbite Class III Mixed dentition Asymmetry Also indicated in early click when condyle is displaced distal to the articular disc.

5. Contraindications Crowding Very narrow maxilla Skeletal Class II by maxillary prognathism Skeletal asymmetry

6. Advantages Comfortable Aesthetic Function Patient compliance ( Can be worn Full-time) Speech Clinical management Arch development Mandibular repositioning

7. Advantages Vertical control Facial asymmetry Safety Efficiency Age of treatment( Can be worn in all ages) Integration with fixed appliance

8. Modifications Twin Block for Transverse Development with Schwarz appliance Sagittal Twin Block Combination of both sagittal and transverse Twin block with Habit breaker Reverse Twin Block Magnetic Twin Block Twin Block with Extraoral attachment for advancement Twin Block with biofinisher

9. Twin Block for Transverse Development with Schwarz appliance

10. Sagittal Twin Block

11. Combination of both sagittal and transverse

12. Twin block with Habit breaker

13. Reverse Twin Block

14. Magnetic Twin Block

15. Twin Block with Extraoral attachment for advancement(Reverse Pull Face Mask)

16. Twin Block with biofinisher for TMJ therapy

17. Other Designs

18. Parts Twin block consists of two separate removable appliances. 1. Upper part has expansion screw Labial bow 3/3 Adams clasps Sometimes Lip Pads 2: Lower part Double Adams clasps 'C' clasps Ball ended clasps

19. Dental Effects of Twin Block After studies on primates, carefully designed studies were done on human beings Dental effects include Retroclination of upper incisors Uprighting of lower incisor into ideal incisor relationship (Lund and Sandler AJO1998) Restrainment or slight distalization of upper molars Significant advancement of lower molars correcting the distocclusion . Vertical selective eruption of lower molars aids in OB correction Duggal R. J Ind Orthod Soc 2006; 39:30-41,

20. Musculo -Skeletal effects Harvold 1983 described it as ( Tension Zone ) Mc Namara as Pterygoid Response Pain felt by patient after wearing functional appliances in response to altered occlusal function. From the studies of histological changes in animal experiment , it may be deduced that retraction of the condyle results in compression of connective tissue and blood vessels and that ischaemia is cause of pain. A new pattern of muscle behavior is quickly established whereby patient finds it difficult and later impossible to retract the mandible to its former rertruded position. This results due to medial head of the lateral pterygoid muscle.

21. The lateral pterygoid muscle hypothesis Suggests that both postural and functional activity in the masticatory muscles increase after functional appliance insertion. This increased activity , especially in the superior head of the lateral pterygoid muscle, then acts as a stimulus to mandibular growth (McNamara JA. Neuromuscular and skeletal adaptations to altered function in orofacial region. AJO 1973)

22. Effects on Bone Skeletal changes as a result of Twin block therapy Forward growth/repositioning of the mandible Increase in the angle SNB. No significant maxillary restraint Increase in low anterior facial height. (Morris et al. 1998)(Mc Namara 1999)

23. 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.

24. Construction Good set of impressions Accurate construction bite Models mounted on an articulator

25. Bite registration There are two types of bite gauges used to register bite for twin block: 1. George bite gauge 2. Exactobite gauge

26. 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.

27. Exactobite gauge or Project 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.

28. 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.

29. Procedure First rehearse the procedure of bite registration with patient using a mirror. 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 table is used to register the occlusion.

30. Pictorial Procedure

31. Pt bites with incisors edge to edge. ~ 6mm separation of molars

32. Fold wax lengthwise twice to 1/3 size(6mm) Do not flatten

33. Turn folded wax lengthwise and fold once with spatula in between

34. Crimp lower edge against spatula Do not flatten

35. Bite edge to edge on incisor area

36. Registered Bite

37. 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 .

38. Total protrusion path is calculated by measuring the overjet in m ost 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 5-10mm 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.

39. Midline consideration: Centre lines should be coincident provided no dental asymmetry is present

40. Vertical consideration: Two factors determine the amount of vertical clearance. 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. 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.

41. 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 17-19mm Height of upper & lower incisors minus overbite.

42. 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

43. Clinical Management Selectively 1-2mm trimmed upper bite blocks at the region of lower 6 and 7s Active Phase is finished after achieving correct class I Molar ideal OJ and OB three-point contact with incisors and molars . Clark , W. J. (2002) Twin Block Functional Therapy. Fife, UK:Elsevier Active Phase: Fig A, B & C (6-9 Months)

44. Clinical Management Support Phase: (Fig D & E) 3-6 Months Aim is to maintain correct incisor relation until buccal relationships are fully established. For this Upper removable appliance with inclined plane and a labial bow is fitted Retentive Phase: ( 9 months) Only night time wear is sufficient for retention . Clark, W. J. (2002) Twin Block Functional Therapy. Fife, UK:Elsevier

45. Patients Instructions With co-operation, results can be achieved in the least amount of time. How to insert the Twin Block – when placing the upper and lower plates in your mouth, first position them on your teeth and then firmly press the appliances into place using your thumbs. Never position them with your tongue and bite into place. When removing the plates, ease the appliance off from each side. Do not flip the appliance on and off your teeth with your tongue as this will result in a breakage. Full-Time Wear – both the upper and lower plates must be worn together full time, including while you eat and sleep. The only exceptions are when you remove them for cleaning and for contact sports and swimming (to avoid loss).

46. Patients Instructions (Cont.) Activation of the Screw – Always follow directions from your orthodontist. When instructed, turn the screw once/twice every seven days in the direction of the arrow, until advised to stop turning. Eating with the Twin Block – Eating with the appliance will give you much faster results. Leaving the plates out for one meal is equivalent to losing 24 hours of wearing. It may take a while to get used to eating, so initially eat foods which are soft and easy to chew. Comfort – There should not be much discomfort, apart from some tenderness of the facial muscles in the first few days, but this should soon disappear. Full-time wear and eating with the appliance maintains proper fit and minimizes discomfort

47. Patients Instructions (Cont.) Difficulty Speaking and Excessive Saliva – It is normal that there will be some difficulty with speech and excessive saliva the first few days, but this diminishes with time. Oral Hygiene – Always keep your Twin Block and teeth clean. Brush the appliance regularly using a toothbrush and soapy water or toothpaste, and if you can’t brush, rinse the appliance and your mouth after eating. Appointments – keep all appointments. The upper plate needs to be adjusted once a month. Breakages – are costly in both time and money. Don't fiddle with your plate or try to alter or repair it yourself.