Tweed merrifield edgewise. /certified fixed orthodontic courses by Indian dental academy


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  • The dentition is now ready for mandibular anchorage preparation.
  • Tweed merrifield edgewise. /certified fixed orthodontic courses by Indian dental academy

    1. 1. THE TWEED - MERRIFIELD EDGEWISE APPLIANCE INDIAN DENTAL ACADEMY Leader in continuing dental education
    2. 2. Seminar by Dr. Siddhartha Dhar Under the guidance of Prof. Ashima Valiathan BDS, DDS, MS (USA) Head of Dept and Director of PG Studies , Dept of Orthodontics and Dentofacial Orthopaedics, Manipal College of Dental Sciences, Manipal.
    3. 3.      Introduction Basic Concepts Diagnostic Aspects Treatment with the Tweed – Merrifield Edgewise Appliance. Conclusion
    4. 4. Introduction   For over 50 years the Tweed philosophy played a dominant role in American orthodontics. Dr Tweed is considered by many to be the greatest clinical orthodontist of his time, and his reputation, technique and skill as a teacher attracted thousands of students to study at the Tweed Foundation, Tucson, Arizona.
    5. 5.   Although it produces, outstanding results in terms of improving the occlusion and facial profile, the classic Tweed technique is demanding for both the orthodontist and for the patient. It requires a high degree of technical skill, lengthy sequence of archwires, excellent patient co-operation, and a relatively modest patient load to maintain control and achieve its results.
    6. 6.   In 1960, Tweed selected one of his most outstanding students, Levern Merrifield from Ponca City, Oklahoma, to continue his work on the Edgewise appliance and be the co-director of his course with him. At the time of Tweed’s death, in 1970, he became course director.
    7. 7.   From 1965 onwards, Merrifield and members of his study group began to develop a series of modifications that taken collectively, constitute the course currently taught at Tucson, Arizona. This is known as the TweedMerrifield Edgewise Appliance.
    8. 8. Basic Concepts These include: 1. The fundamental concept of the dimensions of the dentition. 2. Dimensions of the lower face. 3. Total space analysis 4. Guidelines for space management 5. Directional control during treatment 6. Sequential tooth movement 7. Sequential mandibular anchorage preparation. 8. The organization of treatment into four orderly steps.
    9. 9.  Merrifield’s innovations in diagnosis and experience in the use of the Edgewise appliance have improved on Tweed’s contributions and concepts to give the modern orthodontist a more accurate, reliable, precise efficient, and practical protocol of diagnosis and treatment.
    10. 10.     Adherence to this protocol allows the clinician to achieve the following: Define objectives for the face, dentition and skeletal pattern. Properly diagnose the malocclusion Use the Edgewise appliance to reach the predetermined objectives efficiently.
    11. 11. Dimensions of the Dentition.    There are three dimensions of the denture, length, width, and height. These dimensions allow the teeth to be moved in six directions, mesially, distally, laterally, lingually, intrusively, and extrusively. All these movements, which are easily accomplished with orthodontic appliances, are limited and restricted by the physical environment of bone, muscle, and soft tissue that exerts influence on the teeth and the jaws.
    12. 12. Arch length- The anterior limit   Anterior expansion of the denture is characterized by a protrusion of the lips, a lack of balance and harmony of the lower face, and a lack of health of the bone and investing tissue. Unless the musculature is very weak, the muscular environment will reassert itself and cause a collapse or crowding of the teeth, a deepening of the bite, an increase in overjet, and finally a deterioration of the investing tissues.
    13. 13.   Charles Tweed concluded that mandibular incisor position must be maintained or that these teeth must be contracted lingually so that they are positioned over basal bone and in harmony with the muscles of this region. Otherwise, either facial esthetics or denture stability or both would be in jeopardy.
    14. 14. The use of Tweed's diagnostic facial triangle is a very simple and accurate means of determining the dimensions of the denture in the mandibular incisor area.
    15. 15. Arch length-The posterior limit   The orthodontist, while considering the anterior end of the denture, must put an equal amount of thought and consideration into the posterior end. The bony environment of the mandibular molars effectively prohibits significant posterior expansion of the mandibular molar teeth.
    16. 16.    Because the maxilla does not have heavy bone support at the tuberosity, it seems to invite one to attempt to use orthodontic forces to move maxillary molars distally into "normal Class I" inclined plane relationships. However, strong muscular pressure being exerted by the buccinator, the masseter, the temporalis, and the internal pterygoid muscles, limits posterior expansion. Class II malocclusions, if treated to Class I inclined plane relationships by any combination of distal driving forces, when space does not exist, show certain characteristic symptoms.
    17. 17.    The maxillary second molars will, if banded, be driven distally off the tuberosity. If unbanded, these second molars will be driven both distally and buccally. The third molars will, in most cases, be deeply impacted because there is generally not enough tuberosity growth to accommodate these teeth in the arch. This illustration brings home the point that to create a posterior discrepancy in an attempt to correct an anterior discrepancy is not sound reasoning.
    18. 18.   It is important to note that uprighting mesially inclined maxillary or mandibular molars that are in a forward position as a result of habits or the premature loss of deciduous teeth is not a form of posterior expansion. It is a proper treatment objective if the original malocclusion arch length, both anteriorly and posteriorly, is respected.
    19. 19. Arch width     Robert Strang did a great deal of work on denture stability and lateral expansion. He stated, "The mandibular cuspid width, as measured across the arch from one canine to the other, is an accurate index of the muscular balance of the individual and dictates the limit of denture expansion in this area.“ He further stated, "With very minor exception, the original mandibular malocclusion width must also be respected in the premolar and molar areas." The recent studies reported in the literature by Little, et al. seem to confirm Strang's hypothesis that mandibular canine width is inviolate.
    20. 20.   According to Merrifield, (AJODO 1994) orthodontists must accept the original tooth position as the extreme width of the buccal segments in patients with normal muscular balance. He also suggested that the environment will tolerate some contraction in the buccal segments and that further contraction will occur after the cessation of treatment.
    21. 21. Vertical dimension     Tooth movements that can be involved are intrusion and extrusion. The muscles of mastication limit this dimension of tooth movement. Vertical expansion of either the maxillary or mandibular posterior teeth causes many undesirable reactions. Included among these could be (1) mandibular rotation, (2) freeway space impingement, (3) maxillary reorientation to cranial base, and (4) an unstable orthodontic treatment result.
    22. 22.      Extrusive forces that cause vertical expansion create a downward descent of the anterior part of the lower face. One millimeter of vertical expansion in the maxillary molar area results in a 1.3 mm descent in the maxillary incisor area. This reaction is not complimentary to facial balance and certainly does not enhance a facial pattern that needs horizontal development. Vertical control should be monitored with lateral head films during the course of treatment. The relative relationship of the palatal plane, the occlusal plane and the mandibular plane when superimposed on head film tracings could be the best guide to control of vertical expansion. These three planes should remain parallel or flatten slightly posteriorly as treatment progresses.
    23. 23.    Vertical expansion, like lateral expansion, seems to occur with posterior expansion. If maxillary molars are moved distally into Class I relationships when there is no space for this movement, there is a wedging open in the posterior part of the mouth. This wedging effect encourages a drop of anterior nasal spine and pogonion. These reactions result in the convex face which has been described as the "orthodontic look."
    24. 24. Diagnostic aspects 1. 2. 3. 4. According to Merrifield and coworkers, any valid identification and classification of orthodontic and orthognathic disharmony should be based on four major areas: Facial Cranial Dental Environmental
    25. 25. I. Facial disharmonies- Factors in differential diagnosis 1. Positions of the teeth     Facial balance is affected by marked protrusion and/or crowding of the teeth. Lip protrusion is a reflection of the amount of maxillary incisor protrusion. Merrifield and others have shown that the upper and lower lips are very responsive to maxillary incisor tooth movements. The lower lip follows the upper anterior tooth retraction very closely, and the upper lip recontours with retraction and some thickening.
    26. 26.     Merrifield (AJO 1966) concluded that 4 mm of upper incisor retraction is accompanied by 3 mm of upper lip retraction and 1 mm of upper lip thickening. Proper directional tooth repositioning can also enhance the chin-lip relationship. The chin-lip relationship can be defined in relation to the nose, nasal-labial contour, smile line and vertical proportions of the face. Lower facial contour is a direct responsibility of the orthodontist.
    27. 27. 2. Frankfort Mandibular Plane Angle (FMA):  This is a crucial skeletal value in differential diagnosis.  Dental compensation for a high FMA requires additional upright positioning of the mandibular incisors.  Conversely, dental compensation for a low FMA requires less mandibular incisor upright positioning
    28. 28. 3. Soft tissue measurements: a. Total chin thickness (mm) b. Upper lip thickness (mm)  Total chin thickness should equal upper lip thickness. If it is less than upper lip thickness, the anterior teeth must be positioned further upright to facilitate a more balanced profile.
    29. 29. 4. Profile line:  The profile line and its relationship to facial structures and FH plane can be used to give an idea of lip procumbency.  The ideal relationship of profile line is tangent to the chin and the vermilion border of both lips, and bisecting the nose.
    30. 30.
    31. 31. 5. Z angle:  This is the angle made by the profile line with the FH Plane.  It has a normal range of 70-80 degrees.  It is an adjunct to the FMIA and is more indicative of the soft tissue profile than FMIA.  It quantifies the combined abnormalities in the values of FMA, FMIA and soft tissue thickness, and gives immediate guidance relative to anterior tooth positioning.
    32. 32. 6. FMIA  Tweed believed this angle was significant in establishing balance and harmony of the face.  He established a standard of 68˚ for individuals with FMA of 22-28˚.  The standard should be 65˚if FMA is 30˚or more, and the FMIA will increase if the FMA is lower.
    33. 33. II. Cranial DisharmonyDifferential Diagnosis 1. FMA:  The FMA defines the direction of lower facial growth in both the horizontal and vertical dimensions.  An FMA greater than the normal range indicates excessive vertical growth, and an FMA less than the normal range indicates deficient vertical growth.
    34. 34. 2. IMPA  Defines the axial inclination of the mandibular incisor in relation to the mandibular plane.  Guide to use in maintaining or positioning teeth in relation to the basal bone.  The standard of 88˚indicates an upright position and with normal FMA, reflects optimal balance and harmony of the lower facial profile.
    35. 35. 3. SNA:  Indicates the relative horizontal position of the maxilla to cranial base. The range at termination of growth ranges from 80-84 degrees.
    36. 36. 4. SNB:  Expresses the horizontal relationship of mandible to cranial base. Range of 7882˚indicates a normal horizontal mandibular position.  Values below 74˚or greater than 84˚indicate a large maxillomandibular discrepancy, and could require orthognathic surgery, in addition to orthodontics.
    37. 37. 5.ANB:  The normal range is 1-5˚. With higher ANB angles, Class II relationships become proportionately more difficult to handle.  An ANB angle greater than 10˚or less than -3˚indicates a need for surgery as an adjunct.
    38. 38. 6. AO-BO:  Indicates horizontal relation of mandible to maxilla.  More sensitive to malrelations than the ANB angle because it is measured at the occlusal plane.  Treatment becomes more difficult when AO-BO is greater than the normal range of 0-4mm.  It changes in direct proportion to the occlusal plane angle.
    39. 39. 7. Occlusal Plane:  The occlusal plane value expresses the relation of the occlusal plane to the FH plane.  A range of 8-12˚is normal with variations of about 2˚between males and females.  In most orthodontic corrections, the original value should be maintained or decreased.  An increase in occlusal plane angle indicates a loss of control during treatment.
    40. 40. 8. Posterior facial height:  Linear measurement in mms from articulare to the mandibular plane tangent to the posterior border of the ramus.  An increase in ramus height is essential for downward and forward mandibular response.  Relationship of posterior facial height to anterior facial height determines the FMA and lower facial proportion.
    41. 41. 9. Anterior facial height:  Linear measurement in mms of the vertical distance between the palatal plane and menton.  In Class II correction it is essential to limit increase in AFH.  Accomplished by controlling mandibular and maxillary molar extrusion and using anterior high pull force on the maxilla.
    42. 42. 10.Facial Height Index:  Andre Horn studied the relationship of AFH to PFH, and found that normal PFH is 69% of the AFH. (FHI= 0.69).  Normal range is 0.65-0.75.  Index values approaching 0.60 and 0.80 indicate divergent and convergent patterns respectively.
    43. 43. 11. Facial Height Change Ratio:  A ratio of two times as much increase in PFH as AFH increase during treatment is ideal for correction of Class II div 1 and dento-alveolar protrusion malocclusions.  However, the actual volume of change is more important than simply the ratio.  Merrifeld and Gebeck ( AJODO 1995) evaluated successfully and unsuccessfully treated Class II malocclusions, and found that successful cases were associated with greater increase in PFH, while the opposite was true of unsuccessful cases.
    44. 44. Gramling’s Probability Index.    Over a period of 15 years, till his untimely death in 1993, Jim Gramling of Jonesboro, Arkansas was director of the Tweed Foundation. During this period he studied large samples of successfully and unsuccessfully treated Class II cases. Based on the evidence gathered he formulated a Probability Index (published in J Charles Tweed Foundation 1989 and posthumously in AJODO 1995)
    45. 45.  The elements of the Probability Index are five key cephalometric angles. When properly integrated, they appear to be reliable in predicting the prognosis of a given orthodontic treatment.
    46. 46. The following conditions might be necessary for Class II treatment success: 1. 2. 3. 4. 5. FMA should be 20 -30˚. ANB should be 6˚or less. FMIA should be greater than 60˚. Occlusal plane should be 7˚ or less. SNB should be 80˚or more.
    47. 47.
    48. 48.
    49. 49.
    50. 50. The Cranial Facial Analysis.    The Cranial Facial Analysis has been developed from Gramling's work, from Merrifield and Gebeck's work, and from Andre Horn's ratio studies. The Z angle has been substituted for the FMIA because it is a better indicator of facial form. Horn's Facial Height Index was added to further define horizontal and vertical relationships of the craniofacial complex.
    51. 51. Dental Disharmony    Along with a consideration of the face and skeletal pattern, the orthodontist must also consider the dentition. Total space analysis as described by Merrifield is divided into three parts anterior, midarch and posterior. This is done for simplicity in identifying the area of space deficit or surplus, as well as accuracy in differential diagnosis.
    52. 52. Anterior Space Analysis 1.Measurement in mms of the space available in mandibular arch, from canine to canine, as well as measurement of the mesiodistal dimension of each of these anterior teeth. Difference is referred to as surplus or deficit. 2.The Tweed diagnostic triangle is also used to analyze this area. The cephalometric discrepancy i.e. the amount of space required to position the mandibular incisors for facial balance is added.
    53. 53. 3.Soft tissue thickness is also considered. Total chin thickness should equal upper lip thickness. If it is less than upper lip thickness, anterior teeth need further uprighting, for a more balanced profile.
    54. 54.   The anterior discrepancy = Anterior tooth surplus/ deficit + cephalometric discrepancy + Soft tissue imbalance. Each of these three values has a difficulty factor so that a difficulty value can be calculated.
    55. 55. Midarch Space Analysis     Midarch area includes the mandibular first molars, and first and second premolars. Analysis of this area reveal mesially inclined first molars, rotations, spaces, deep curve of Spee, crossbites, missing teeth, habit abnormalities, blocked out teeth, occlusal disharmonies. This area being in center of arch, allows easiest method of space management for malocclusion correction. In addition to the arch length discrepancy and curve of Spee, the occlusal disharmony is to be measured.
    56. 56.     Occlusal disharmony (Class II or Class III) is measured by articulating the casts and using the maxillary 1st premolar cusp as reference. Measurement is made mesially or distally from maxillary first premolar buccal cusp to the embrasure between mandibular first and second premolars. Average of both sides measurement is taken to get the occlusal disharmony. The difficulty factor is “2”, so the measurement is doubled when added to the midarch difficulty.
    57. 57. Posterior Space Analysis    The required space in the posterior space analysis is the mesiodistal width of the 2nd molars and 3rd molars in the mandibular arch. Space available is the measurement in mm from distal border of 1st molar to the anterior border of ramus along occlusal plane. An estimate of posterior arch length increase based on age and gender is added to this value.
    58. 58.     The literature reveals an increase of 1.5 mm each side per year after full eruption of 1st molars, till age of 14 years for girls and 16 years for boys. It is important not to create a posterior discrepancy while adjusting the other areas. On the other hand posterior space surplus should be used to alleviate midarch and anterior discrepancies. Posterior space analysis value has a low difficulty factor of 0.5 because a deficit can easily be resolved by extraction of third molars.
    59. 59.
    60. 60. Differential Analysis System.   The Cranial Facial Analysis and the Dentition Space Analysis together make up the Differential Analysis System. Sum of Cranial Facial Difficulty and Dentition Space Difficulty gives the Total Difficulty.
    61. 61.
    62. 62. The Tweed Merrifield Edgewise Appliance.    The approach used at the Tweed Foundation employs a “straight bracket” appliance. It consists of posterior bands and anterior mesh pads with single, double width 0.022 brackets on the six anterior teeth; intermediate single width brackets on the premolar bands; twin brackets on the first molars; and heavy edgewise 0.022 tubes with mesial hooks on the second molars. Lingual hooks and cleats are also provided on molars and premolars respectively.
    63. 63.
    64. 64.    Each of the brackets and tubes is placed at right angles to the long axis of the tooth. No tip, torque, variations in thickness are present in the bracket. According to Merrifield “ this prescription, in my opinion is the only one that provides sufficient versatility to provide for individualized tooth positioning.”
    65. 65.     The commonly used archwire sizes are 017 x 022, 018 x 025, 019 x 025, 020 x 025, 0215 x 028. These wire dimensions give a great deal of versatility with the 022 x 028 bracket slot. Knowledge of first, second and third order bends and their interactions is crucial. The commonly used auxiliaries include elastics, directionally oriented headgear ( High pull J hook, straight pull J hook.)
    66. 66. Treatment with the Tweed Merrifield Edgewise Appliance.   Using Tweed’s treatment concepts as a foundation, Merrifield developed force systems that simplify the use of the Edgewise appliance. The twelve sets of arch wires used by Tweed have been reduced to four or five sets of wires.
    67. 67. Essentially five concepts compose the treatment philosophy. 1. Sequential appliance placement 2. Sequential tooth movement 3.Sequential Mandibular Anchorage Preparation 4. Directional Force 5. Treatment Timing. 
    68. 68. 1.Sequential Appliance Placement     In a 1st premolar extraction patient, second molars and 2nd premolars are banded. Initially 1st molars are left unbanded. Incisors and canines are bonded, any malaligned anteriors are not ligated to the archwire. Less traumatic to patient, easier for orthodontist. After the engaged teeth respond to forces of archwire and auxiliaries, the maxillary and then mandibular 1st molars are banded.
    69. 69. 2.Sequential tooth movement   Tooth movement is sequential. It is rapid and precise because they are moved individually or in small units.
    70. 70. 3. Sequential mandibular anchorage preparation.    Unlike Tweed who prepared mandibular anchorage using Class III elastics and place all the compensation bends in the archwire at one time. Merrifield’s technique allows mandibular anchorage to be prepared quickly and easily, tipping only two teeth at a time, using headgear rather than Class III elastics for support. Known as Merrifield “10-2” system.
    71. 71. 4. Directional Force    Defined as controlled forces that place the teeth in the most harmonious relationship with their environment. The resultant vector of all forces should be in an upward and forward direction to enhance the possibility of favorable skeletal change, especially in dentoalveolar protrusion, Class II correction. To achieve this, vertical control is crucial.
    72. 72.
    73. 73. 5. Timing of treatment   Should be initiated at a time when treatment objectives can be most readily accomplished. This may mean interceptive treatment in the mixed dentition, selected extractions in mixed dentition, or waiting for second molar eruption before starting active treatment.
    74. 74. Steps of treatment 1. 2. 3. 4. Denture Denture Denture Denture preparation correction completion recovery
    75. 75. 1. Denture preparation Objectives:  Leveling  Individual tooth movement and rotation correction  Retraction of maxillary and mandibular canines.  Preparation of terminal molars for stress resistance. (Takes approximately 6 months.)
    76. 76.      Teeth of the original malocclusion are sequentially banded and bonded. 018 x 025 resilient mandibular archwire and 017 x 022 resilient maxillary archwire are inserted. The stop loops are flush with the second molar tubes in each arch. Mandibular 2nd molars receive effective tip of 15 degrees from the archwire and maxillary 2nd molars receive 5 degrees distal tip. Offset placed mesial to 2nd premolar is in each archwire, to prevent outward expansion of canines
    77. 77.
    78. 78.     High pull J hook headgear used to retract both maxillary and mandibular canines. After first month of treatment, maxillary first molars are banded and after second month, mandibular first molars. After each month, terminal molar tip in mandibular archwire is increased to maintain effective tip of 15 degrees. As canines retract and arches are leveled, lateral incisors are ligated, and power chain force to aid canine retraction can be used. Note: During each visit, archwires are removed, carefully coordinated, 1st, 2nd and 3rd order bends checked, and religated.
    79. 79.
    80. 80. At end of denture preparation stage of treatment: 1. Dentition should be fully banded and leveled. 2. Canines should be retracted. 3. All rotations should be corrected 4. Mandibular terminal molars tipped distally into an anchorage prepared position.
    81. 81.
    82. 82. 2. Denture correction      Spaces are closed with maxillary and mandibular closing loop archwires. Mandibular archwire: 019 x 025 working archwire with 6.5 mm vertical loops distal to the lateral incisor brackets. Maxillary archwire: 020 x 025 archwire with 7 mm vertical loops distal to lateral incisor brackets. Stop loops in both arches are immediately distal to brackets of 1st molars. Stop loop in mandibular archwire incorporates a compensation to maintain the 15 degree terminal molar tip.
    83. 83.
    84. 84.  At end of space closure the curve of occlusion in maxillary arch should be maintained and mandibular arch completely level with a 15 degree distal tip in the second molar.
    85. 85. The dentition is now ready for mandibular anchorage preparation.
    86. 86. Sequential mandibular anchorage preparation  Archwire produces an active force on only two teeth while remaining passive to the other teeth in the arch, which act as anchoring units.  Referred to as 10-2 anchorage system  Anchorage preparation is supported by high pull headgear worn on anterior vertical spurs, soldered distal to mandibular central incisors.
    87. 87.       At end of mandibular space closure, the lower 2nd molars are tipped to 15 degrees distal angulation. First molar anchorage is initiated with an 019 x 025 archwire with loop stops bent flush against second molars, and 10 degree distal tip placed just mesial to loop stop. Compensating bend is given to maintain second molar tip. After 1 month, the 1st molars should show 5 -8 degrees distal inclination of 1st molars. Third and final step involves placement of 5 degree distal tip 1 mm mesial to 2nd premolar brackets. Compensating bend is given mesial to first molar, so that arch wire is passive to 1st and 2nd molars
    88. 88.
    89. 89. At end of anchorage preparation, a readout will show distal axial inclinations as follows:  2nd molars: 15 degrees.  1st molars: 5-8 degrees.  Second premolars: 0-3 degrees. This brings to an end, the denture correction step for Class I malocclusion.
    90. 90. The Class II force system 1.For patients with end-on or full-cusp Class II dental relationship of buccal segments a new force system is required to complete denture correction.  Final decision for Class II correction is made on basis of ANB relationship, maxillary posterior space analysis and patient co-operation.
    91. 91. Guidelines for use:   The Class II force system achieves best results when ANB is 5 degrees or less, patient is co-operative, and maxillary 3rd molars are missing. If present and approaching eruption, they should be removed to facilitate distalization of maxillary teeth.
    92. 92. 2.If a co-operative patient has a mild Class II dental relationship, normal vertical skeletal pattern, ANB of 5-8 degrees, and normally erupting maxillary 3rd molars, extraction of 2nd molars is most advantageous for distalizing maxillary arch.
    93. 93. 3.If ANB is greater than 10, maxillary 3rd molars are present and patient cooperation is questionable, either first molars should be removed after space closure, or surgery should be considered.  Note: The Class II force system needs excellent compliance from patient, else maxillary anterior teeth will be pushed forward off basal bone.
    94. 94. Class II force system- the procedure.    At end of Sequential mandibular anchorage preparation, mandibular 0215 x 028 stabilizing archwire with ideal 1st, 2nd , 3rd order bends is fabricated, with the stop loop 0.5 mm short of molar tubes. Gingival spurs soldered distal to mandibular lateral incisors. Wire seated and terminal molar cinched to loop stop.
    95. 95.      Maxillary archwire (020 x 025)with closed helical bulbous loops bent flush against 2nd molar tubes is fabricated. Ideal 1st, 2nd order bends and 7 degrees of progressive lingual crown torque in molar segment. Gingival spur immediately distal to 2nd premolar. Gingival high pull headgear hooks soldered distal to central incisors. Class II lay on hooks with gingival extension for anterior vertical elastics are soldered distal to lateral incisors.
    96. 96.     Closed helical bulbous loops are opened 1mm each side and wire ligated in place. Eight ounce Class II elastics from hooks on 2nd mandibular molar tubes to Class II hooks on maxillary wire. Anterior vertical elastics, as well as maxillary high pull headgear are worn. The helical loops are activated 1mm monthly till second molars have Class I molar relationship.
    97. 97.
    98. 98.   Then, first molar is distalized using a coil spring wound and compressed mesial to it, as well as E chain from second molar. Class II elastics, anterior vertical elastics and high pull headgear (14 hours per day) are continued. After 1st molars have been distalized into overcorrected Class I relationship, second premolars followed by canines are moved distally
    99. 99.    After overcorrection of maxillary posterior segment, an 020 x 025 maxillary archwire with 7mm closing loops distal to lateral incisors is fabricated. Wire is activated 1 mm per visit Light Class II elastics, anterior vertical elastics and high pull headgear are used .
    100. 100. 3.Denture completion     Ideal 1st 2nd 3rd order bends are placed in finishing mandibular and maxillary 0215 x 028 resilient archwires. The mandibular archwire duplicates the previous wire used. The maxillary archwire has artistic bends and hooks for highpull headgear, anterior vertical elastics and Class II elastics. This stage can be regarded as a mini treatment of the malocclusion.
    101. 101. At the end of this stage the following objectives should be achieved: 1. 2. 3. 4. 5. 6. 7. Alignment of incisors. Occlusion over treated to Class I relation. Anterior teeth edge to edge. Maxillary canines and 2nd premolars locked tightly into Class I dental relation. Mesiobuccal cusp of upper 1st molar occluding in mesiobuccal groove of lower 1st molar. Distal cusps of 1st molars as well as 2nd molars out of occlusion. All spaces from 2nd premolar forward closed tightly.
    102. 102. 4. Denture recovery.    Orthodontist should not strive for ideal final result at the end of treatment. This ideal result will occur after all treatment mechanics are discontinued and uninhibited functional and environmental influences in the post treatment period stabilize and finalize the position of the total dentition. This recovery phase occurs when all appliances are removed and retainers are placed.
    103. 103.   Orthodontists not familiar with the concept of overtreatment express concern about the posterior disclusion achieved at completion of treatment. Often referred to as Tweed occlusion, but properly identified as transitional occlusion.
    104. 104. Transitional occlusion
    105. 105.  The concept of transitional occlusion followed by a period of recovery is based on the belief that an individual’s own oral environment will determine the ultimate position of the dentition and overtreatment allows greatest opportunity for maximal stability and functional efficiency.
    106. 106. Stable occlusion achieved
    107. 107. Conclusion:    Since Angle through Tweed and to date with Levern Merrifield, the Edgewise appliance has endured the test of time. Although the Tweed Merrifield appliance is the direct descendant of Angle’s original appliance in 1928, it is used with a totally different philosophy of treatment. The introduction of concepts of differential diagnosis, directional force and sequential wire manipulation have made it the most precise and efficient instrument for the correction of major malocclusions, that exists in the world today.
    108. 108.  1. 2. 3. References: Gebeck TR, Merrifield LL. Orthodontic diagnosis and treatment analysis: concepts and values, Part I, Am J Orthod Dentofac Orthop 1995; 107: 434-443. Gebeck TR, Merrifield LL. Orthodontic diagnosis and treatment analysis: concepts and values, Part II, Am J Orthod Dentofac Orthop 1995; 107: 541-7. Gramling JF. The probability index. Am J Orthod Dentofac Orthop 1995; 107: 165-71.
    109. 109. 4.Horn A. Facial height index. Am J Orthod Dentofac Orthop 1992; 102: 180-183. 5.Merrifield LL, Klontz HA, Vaden JL. Differential diagnostic analysis system. Am J Orthod Dentofac Orthop 1994; 106: 641-648. 6. Merrifield LL. The dimensions of the denture: Back to basics. Am J Orthod Dentofac Orthop 1994; 106: 535-41. 7.Merrifield LL, Directional forces. Am J Orthod 1970; 57: 435-464. 8.Merrifield LL. The sequential directional force edgewise technique. In Johnston L, editor: New vistas in orthodontics, Philadelphia, 1985, Lea and Febiger.
    110. 110. 9. Vaden JL, Dale JG, Klontz HA. The Tweed Merrifield Edgewise appliance: Philosophy, Diagnosis and Treatment. In Graber , Vanarsdall, Vig, editors: Orthodontics-Current principles and techniques, 4th edn, St. Louis, 2005, Mosby.Pgs: 675-715.
    111. 111. Thank you For more details please visit