Tweed merrifield philosophy /certified fixed orthodontic courses by Indian dental academy


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Tweed merrifield philosophy /certified fixed orthodontic courses by Indian dental academy

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education 3/5/2014
  2. 2. Contents:  Introduction  Historical perspective  Tweed’s philosophy  Levern Merrifield  Tweed-Merrifield philosophy  Tweed-Merrifield Edgewise Appliance  Steps of treatment  Conclusion  References 3/5/2014
  3. 3. Introduction The Tweed – Merrifield edgewise appliance is the direct descendent of the appliance invented in 1928 by Edward H. Angle, but it is used with a totally different philosophy of treatment. 3/5/2014
  4. 4. Historical perspective 3/5/2014
  5. 5. •Simplicity •Stability •Efficiency •Delicacy •Inconspicuousness Dr. Edward H. Angle 3/5/2014
  6. 6. The Edgewise Appliance  To overcome the deficiencies of his previous appliances, Angle changed the form of the bracket  Placed the slot in the centre and placing it in a horizontal plane 3/5/2014
  7. 7. Edgewise appliance 3/5/2014
  8. 8.  Edgewise bracket when formed consisted of a rectangular box with 3 walls within the bracket.  0.022 x0.028” 3/5/2014
  9. 9.  Unique feature  rectangular wire in rectangular slot  twisting / torquing forces could be imparted to control the axial inclination of teeth  Possible to move teeth in all 3 planes of space with a single arch wire. 3/5/2014
  10. 10. Dr. Charles H. tweed 3/5/2014
  11. 11. Charles H. Tweed  Graduated from an improved Angle course (George Hahn) in 1928 at the age of 33yrs.  Helped Dr. Angle in publishing an article in the Dental Cosmos  Dr. Angle urged his dear student to : Dedicate his life to the development of the edgewise appliance To make every effort to establish orthodontics as an specialty within the dental profession.  Dr. Tweed instigated the passing of first orthodontic specialty law in the U.S.. In 1929 first law limiting the practice of orthodontics to specialists was passed  Dr. Tweed-first certified specialist in orthodontics in the U.S. 3/5/2014
  12. 12. •Aug 11, 1930, Angle died at age of 75yr. •Tweed held to Angle’s conviction, but this lasted for only 4yrs.In 1932 published article in Angle orthodontist “reports of cases treated with Edgewise Arch mechanism.” •Upright mandibular incisors frequently were related to post treatment facial balance and successful treatment. •To position mandibular incisors upright ,he concluded one must prepare anchorage and extract teeth. 3/5/2014
  13. 13. • He selected failed cases and treated them with premolar extractions. • 1936- paper on extraction of teeth for orthodontic malocclusion correction. • Was called a traitor ,faced criticism. • In 1940 he produced case reports of the retreated cases. 3/5/2014
  14. 14.  “just put your plaster on the table”- let the treatment speak for itself.  Dr. Robert Strang- supporter  1947- Charles H. Tweed Foundation for Orthodontic Research 3/5/2014
  15. 15. Tweed’s contributions: •Emphasized four objectives of orthodontic treatment. 1.the best balance and harmony of facial lines 2.Stability of dentures after treatment 3.Healthy mouth tissues 4.An efficient chewing mechanism •Concept of uprighting teeth over basal bone. •Extraction of teeth acceptable. •Enhanced clinical application of cephalometrics. 3/5/2014
  16. 16. •Diagnostic facial triangle. •Anchorage system as a major step in treatment. • Serial extraction 3/5/2014 Diagnostic facial triangle
  17. 17. 3/5/2014
  18. 18. 1.Type A growth trends : • middle and lower face growing forward and downward in unision with no change in the ANB angle. • growth is approximately equal in both vertical and horizontal dimensions. • Type A subdiv growth trend. • Prognosis good 3/5/2014
  19. 19. Type B growth trend : • middle face growing forward more rapidly than the lower, ANB increases in size with growth. • ANB <4 deg prognosis is fair. • ANB 7-12 deg prognosis poor. 3/5/2014
  20. 20. Type C growth trend: • lower face growing forward and downward more rapidly than the middle face, with a decrease in the size of the ANB. 3/5/2014
  21. 21. 2)That the establishment and maintenance of stable anchorage is the fundamental factor in successful orthodontic treatment and should be the initial concern of the operator.  Outstanding feature of Dr.Tweed’s philosophy 3/5/2014
  22. 22. Anchorage preparation •It was believed at that time that-“An undisturbed tooth affords the best resistance to movement.” •Tweed-It is impossible to band a tooth that’s in tight contact with a neighbor and have it undisturbed. •Reatin –when teeth are tipped distally as during Anchor preparation, osteoid tissue is laid down adjacent to mesial surface of the tooth being moved distally. 3/5/2014
  23. 23.  In the use of intermaxillary force, it was Dr.Tweed’s contention that the teeth in the anchorage denture must be placed in distal axial inclination if they are to be expected to resist forward and occlusal strain of elastics. 3/5/2014
  24. 24. Anchorage preparation 1. First degree anchorage preparation:  Minimal anchorage preparation required. applicable in : malocclusions with ANB 0-4deg ,facial esthetics are good, total discrepancy does not exceed 10mm.  Mandibular anchor molars uprighted /maintained in their upright positions to prevent being elongated by Class II elastics.  The direction of pull of the elastics in function, will not exceed 90 deg when related to the long axis of the terminal molars. 3/5/2014
  25. 25. 2. Second degree anchorage preparation:  necessary for malocclusions in which ANB > 4.5 deg  facial esthetics demand that point B moved anteriorly and point A posteriorly.  Class II cases, accompanied by type A, type A subdivision, type B growth trends.  Distal marginal ridge of terminal molar at gum level. 3/5/2014
  26. 26. 3.Third degree anchorage preparation : • total anchorage preparation necessary in severe malocclusions where total discrepancy 14- 20mm ,ANB doesn’t exceed 5 deg. • Class I cases with exceedingly irregular teeth. • all three posterior teeth tipped distally 3/5/2014
  27. 27. Levern Merrifield 3/5/2014
  28. 28. Dr. Levern Merrified 3/5/2014 LEVERN MERRIFIELD 1953 : took TWEED course 1960 : selected by Dr.Tweed to be codirector and continue his work on edgewise appliance. 1970 : Director  study of orthodontic dentistry & development of edgewise appliance
  29. 29. A.Diagnostic concepts: Introduced diagnostic analyses which allow clinicians to determine whether and when extractions are necessary, if indicated which teeth to be extracted. 1. Fundamental concept of dimensions of the dentition 2. Dimensions of the lower face 3. Total space analysis 4. Guidelines for space management decisions a. facilitate maximal orthodontic correction b. Define areas of skeletal, facial, and dental disharmony 3/5/2014
  30. 30. B. Treatment concepts: 1. 2. 3. 4. 5. Sequential appliance placement Sequential tooth movement Sequential mandibular anchorage preparation Directional force Proper timing of treatment 3/5/2014
  31. 31. Dimensions of the dentition  Premise 1: anterior limit exists  Premise 2: posterior limit exists  Premise 3: lateral limit exists  Premise 4: vertical limit exists 3/5/2014
  32. 32. Anterior limit  Mandibular incisors positioned over basal bone.  Tweed’s diagnostic facial triangle 3/5/2014
  33. 33. Posterior limit  Muscular pressure: buccinator, masseter, temporalis, medial pterygoid- limit for posterior expansion  “to create a posterior discrepancy in an attempt to correct an anterior discrepancy is not sound reasoning” - Dimensions of the denture L. Levern Merrifield. AJODO 1994;106:535-42 3/5/2014
  34. 34. Lateral limit  “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.”  “ with very minor exception, the original mandibular malocclusion width must also be respected in the premolar and molar areas” - Robert Strang 3/5/2014
  35. 35. Vertical limit  Muscles of mastication limit this dimension.  Functional balance allows a normal freeway space and efficient functioning of the temporomandibular joint 3/5/2014
  36. 36. Facial disharmony 3 factors affect facial balance:  Position of teeth: protruded teeth  Skeletal pattern  Soft tissue thickness : total chin thickness and upper lip thickness must be equal 3/5/2014
  37. 37. Upper lip thickness and total chin thickness If the total chin thickness is lesser than upper lip thickness, the anterior teeth must be positioned upright further to facilitate a more balanced facial profile because lip retraction follows tooth retraction 3/5/2014
  38. 38. Some measurements to judge facial balance 1. Profile line 2. Facial balance on frontal view- vermilion border of the lower lip should bisect the distance between the bottom of the chin and the ala of the nose. 3. Z angle 4. FMIA 3/5/2014
  39. 39. Profile line in a balanced face When facial balance is present, the ideal relationship of profile line is to be tangent to the chin and the vermillion border of both the lips and should lie in the anterior 1/3rd of the nose. 3/5/2014
  40. 40. Profile line drawn on a protrusive face 3/5/2014
  41. 41. FMIA : Tweed believed this angle was significant in establishing balance and harmony of the lower face. Related to FMA. • FMA 22-28 deg, FMIA 68deg • FMA 30 deg or more ; FMIA 65deg. • dental compensation for a high FMA requires additional uprighting of flared mandibular versa. Z – angle : indicative of soft tissue profile and more responsive to maxillary incisor retraction than FMIA 3/5/2014
  42. 42. Z angle and FMIA Z- angle : 70-80 deg range 75 -78 deg ideal Maxillary incisor retraction of 4mm allows 4mm of lower lip retraction and 3mm of upper lip response 3/5/2014
  43. 43. Cranial disharmony Skeletal analysis factors • FMA • IMPA • SNA • SNB • ANB 3/5/2014
  44. 44. • • • • • • Ao-Bo Occlusal plane angle- 812 deg PFH AFH- 65mm facial height index 0.65-0.75 facial height change ratio Merrifield and Gebeck reported a 2:1 increase in PFH compared to AFH in successfully treated class II patients. 3/5/2014
  45. 45. Craniofacial analysis • Jim Gramling’s probability index: observed that in successfully treated Class II patients FMA was controlled , FMIA increased, IMPA reduced , Z-angle increased , SNB remained same, AO-BO reduced. • Probability index suggests that the following pre treatment conditions might be necessary for Class II treatment success : FMA should be 22-28 deg . ANB should be 6 deg or less . FMIA should be greater than 60 deg . Occlusal plane should be 7 deg or less . SNB should be 80 deg or more . 3/5/2014
  46. 46. Dental disharmony 3. Total space analysis: 3 parts: a. Anterior space analysis:  anterior tooth arch surplus/deficit : difference between space available in mandibular arch from canine to canine and sum of mesiodistal dimension of six anterior teeth.  anterior discrepency: surplus/deficit + cephalometric discrepancy (the amount of space required to upright the mandibular incisors for optimum facial balance) 3/5/2014
  47. 47. Mid arch discrepancy : mid arch tooth discrepancy = diff b/t available midarch space and mesio distal width of 1st premolar, 2nd premolar,1st molar, space required to level curve of spee. + occlusal disharmony : measure distance b/t maxillary premolar buccal cusp to embrasure b/t mandibular 1st and 2nd premolar. 3/5/2014
  48. 48. c. Posterior space analysis: Posterior tooth arch discrepancy: space available = distal of mandibular first molar to anterior border of ramus along occlusal plane. required space = sum of mesio-distal width of 2nd molar and 3rd molars. Most easily recognizable sign of posterior space deficit is late 2nd molar eruption. 3/5/2014
  49. 49. Differential Diagnostic Analysis System  Craniofacial analysis + total dentition analysis  Craniofacial difficulty + total dentition space analysis difficulty is called total difficulty  Mild : 0-60  Moderate : 60-120  Severe: >120 3/5/2014
  50. 50. 3/5/2014
  51. 51. Merrifield’s treatment philosophy 1. Sequential appliance placement 2. Sequential tooth movement 3. Sequential mandibular anchorage preparation 4. Directional force 5. Proper timing of treatment 3/5/2014
  52. 52. Sequential appliance placement Advantages: • Less traumatic • Easier • Less time consuming • Allows greater efficiency in arch wire action (longer inter bracket span in posterior segment) 3/5/2014
  53. 53. Sequential tooth movement 3/5/2014 Advantage : Rapid and precise tooth movement because they are moved individually/in small units
  54. 54. Sequential mandibular anchorage preparation:  developed by MERRIFIELD- “10 – 2” system.  Tweed : En masse anchor preparation ; all compensation bends placed at one time in the archwire and Class III elastics used for support ---- result : Labially flared and intruded mandibular incisors 3/5/2014
  55. 55. Merrifield technique –  `10 – 2’ Force systems(10 ten teeth used as  Anchor units to tip 2 teeth)  High pull head gear for support rather than Class-III elastics  Tooth movement is controlled, sequential and precise. 3/5/2014
  56. 56. Directional force :  Hallmark of modern edgewise treatment. Tweed-Merrifield  Controlled forces which place teeth in the most harmonious relationship with their environment 3/5/2014
  57. 57. Resultant force vector of all forces should be upward and forward (counterclockwise), giving opportunity for favourable skeletal change, especially in dentoalveolar protrusion Class II malocclusion correction Upward and forward force system 3/5/2014
  58. 58. Mandibular incisors upright over basal bone needed so that the maxillary incisors can be moved distally and superiorly 3/5/2014
  59. 59. If point B is allowed to move down, mandibular incisors are tipped off the basal bone and maxillary incisor drops down and back instead of being moved up and back. Downward and backward force system 3/5/2014 This leads to a patient with lengthened face, a gummy smile, incompetent lips and a more recessive chin.
  60. 60. 5. Timing of treatment: Treatment should be initiated at the time when treatment objectives can be most readily accomplished. This may mean interceptive in the mixed dentition, or waiting for second permanent molar eruption before starting active treatment. 3/5/2014
  61. 61. Tweed- Merrifield Edgewise appliance 3/5/2014
  62. 62. Brackets and Tubes 3/5/2014
  63. 63. Arch wires  0.017 x0.022”  0.018 x0.025”  0.019 x0.025”  0.020 x 0.025”  0.0215 x0.028”  Different wire dimensions allow greater versatility and allow sequential application of forces at different stages. 3/5/2014
  64. 64. First-, second-; and third- order bends  First-order bends:  Expansion or contraction 3/5/2014
  65. 65.  Second-order bends 3/5/2014
  66. 66. Third-order bends Mandibular arch  Objective is to place some degree of lingual crown torque on all mandibular teeth.  Ideal 3rd order bends in mandibular segment:  Incisor : -7deg  Canines : -12 deg  2nd premolars and molars : -20 deg 3/5/2014
  67. 67. 3/5/2014
  68. 68. 3/5/2014
  69. 69. 3/5/2014
  70. 70. 3/5/2014
  71. 71. Maxillary arch  Anterior segment needs no torque (0 deg) or slight lingual root torque.  Posterior segment needs lingual crown torque:  Canines and 1st premolar : -7 deg  Second premolars 3/5/2014 : -12 deg
  72. 72. Auxiliaries used:  Elastics  Directionally oriented headgear: high pull J-hook headgear straight pull J- hook headgear 3/5/2014
  73. 73. STEPS OF TREATMENT with Tweed – Merrifield Technique 3/5/2014
  74. 74. By: Samprita Sahu M.D.S 1st Year Department of Orthodontics and Dentofacial Orthopedics GITAM Dental College and Hospital 3/5/2014
  75. 75. STEPS OF TREATMENT CLASSIC TWEED MERRIFIELD EDGEWISE DIRECTIONAL FORCE TREATMENT can be organized into four force systems : 1) Denture preparation 2) Denture correction 3) Denture completion 4) Denture recovery 3/5/2014
  76. 76. 1.DENTURE PREPARATION (approx 6 months) OBJECTIVES: a) Leveling b) Individual tooth movement and rotation correction c) Retraction of both maxillary and mandibular canines d) Preparation of terminal molars for stress resistance 3/5/2014
  77. 77. Denture preparation  Initial archwires 0.017 x 0.022 maxillary arch wire  0.018 x0.025 mandibular arch wire  J-hook head gear for canine retraction. 3/5/2014
  78. 78.  Maxillary molars Banded after 1st month of treatment  Arches getting leveled off  Power chain force to aid Canine retraction. 3/5/2014
  79. 79. End of Denture preparation  Terminal anchorage: molar  The mandibular terminal molar should be tipped to anchorage prepared position at the end of denture preparation. 3/5/2014
  80. 80.  Full dentition bracketed and leveled  Canines retracted , all rotations corrected 3/5/2014
  81. 81. 2.Denture Correction – OBJECTIVES: 1. Complete space closure in both the arches 2. Class I intercuspation of canines and premolars 3. Sequential anchorage preparation 3/5/2014
  82. 82.  Mandibular wire: 0.019 x0.025 with 6.5mm vertical loop distal to lateral incisor bracket.  Maxillary archwire: 0.020 x0.025 with 7mm vertical loop.  Loop stops immediately distal to brackets of first molars  Loop stop in mandiblar arch wire incorporates a compensation to maintain 15deg terminal molar tip 3/5/2014
  83. 83.  Closing loop application: 3/5/2014 maxillary and mandibular closing loops are used to close spaces mesial to the distalized canines  Vertical support in maxillary arch through J hook Headgear (hook b/t central and lateral)  Vertical support for mandibular anterior teeth through anterior vertical elastics
  84. 84. After space closure is complete, mandibular arch is leveled, curve of occlusion in maxillary arch maintained and the terminal molars remain tipped to an anchorage prepared position. 3/5/2014
  85. 85. Sequential Mandibular Anchorage Preparation  Sequential tooth movement concept - Arch wire exerts active force on only 2 teeth, while remaining passive to other teeth in the arch. Remaining teeth act as stabilizing anchor units as 2 teeth are tipped. “10-2” anchorage system 3/5/2014
  86. 86. 1. Tipping the 2nd molar to a 15° distal inclination Readout 3/5/2014
  87. 87. 2. 1st molar anchorage preparation • 10° distal tip • Compensating bend mesial to loop stop • 10-2-6 3/5/2014
  88. 88.  3. 5° distal tip 1mm mesial to 2nd premolar brackets 3/5/2014
  89. 89. Class II Force Systems  A different system of forces may be used in patients with end-on or full cusp Class II dental relationship.  A final diagnostic decision made and treatment planned based on – the ANB relationship, maxillary posterior space analysis and patient cooperation…using the following guidelines: 3/5/2014
  90. 90. 1. If the maxillary 3rd molar is missing or if ANB<= 5deg and patient is cooperative… best prognosis. If 3rd molar erupting, it is best to remove it to facilitate distal movement of maxillary teeth. 2. If patient is cooperative, has a mild Class II dental relation, normal vertical skeletal pattern, ANB 5-8deg and normally erupting 3rd molars…then advantageous to extract 2nd molars. 3. If ANB >10deg, poor patient cooperation, 3rd molars present…after maxillary and mandibular first premolar extraction space closure, either first molar extraction or surgical correction considered.( poor prognosis) 3/5/2014
  91. 91. Orthodontic Correction of Class II dental relationships • Mandibular anchorage preparation with 0.0215x0.028” stabilizing archwire • Maxillary arch wire with 0.020x 0.025” arch wire 3/5/2014
  92. 92. Maxillary second molar distalization: helical bulbous loop placed against maxillary second molar 3/5/2014
  93. 93. Helical bulbous loop pushes the maxillary molar distally 3/5/2014
  94. 94. Coil spring trapped mesial to the first molar 3/5/2014
  95. 95. Maxillary first molar distalization 3/5/2014
  96. 96. Maxillary second premolar and maxillary canine distalization 3/5/2014
  97. 97. Maxillary anterior space closure. 0.020x0.025” maxillary loop arch wire is used to close the maxillary anterior space 3/5/2014
  98. 98. 3. Denture Completion Maxillary and mandibular stabilizing wires, along with proper elastics and head gear force, are used to complete orthodontic treatment. 3/5/2014
  99. 99. At end of denture completion following characteristics should be readily observed: • Incisors must be aligned. • Occlusion overcorrected • Anterior teeth edge-edge relation • Maxillary canines and 2nd premolars locked tightly into Class I relation. • Mesiobuccal cusp of maxillary 1st molar must occlude in mesiobuccal groove of mandibular first molar. • Distal cusp of first molar and second molars must be slightly out of occlusion. • All spaces must be closed tightly from 2nd premolars forward. 3/5/2014
  100. 100. 4. Denture recovery  Forces involved are those of surrounding environment, primarily muscles and periodontium.  Concept of overcorrection: if mechanical corrective procedures barely achieve normal relationships of teeth, relapse is inevitable. 3/5/2014
  101. 101.  Transitional occlusion: disclusion of second molars 3/5/2014
  102. 102. Final occlusion is characterized by the teeth settling into their most efficient, healthy and stable positionsfunctional occlusion 3/5/2014
  103. 103. Conclusion 3/5/2014
  104. 104.  It is designed to achieve individualized tooth movements and precision to each patient, to achieve functional occlusion and optimal esthetics, to shorten treatment duration through use of sophisticated force systems.  The edgewise appliance has stood the test of time and will be used by many more generations of orthodontics. 3/5/2014
  105. 105. References:  Orthodontics-Current principles and techniquesGraber and Vansardall; 3rd and 4th edition  The tweed philosophy: the Tweed years: James J. Cross; Seminars in Orthodontics;1996:2;231-267  The Tweed-Merrifield Philosophy: James L. Vaden; Seminars in Orthodontics;1996:2;237-240  Differential Diagnosis- L. Levern Merrifield; Seminars in Orthodontics;1996:2;241-253  Tweed-Merrifield Sequential Directional Force Treatment;1996:2;254-268 3/5/2014
  106. 106.  Merrifield L.L. The dimensions of the denture: Back to basics. AJODO 1994;106:535-542  Clinical Orthodontics- Charles H. Tweed, Vol. 1 3/5/2014
  107. 107. Nothing worthwhile ever departs 3/5/2014
  108. 108. 3/5/2014