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Cephalometrics for orthognathic surgery

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Cephalometrics for orthognathic surgery

  1. 1. Cephalometrics for Orthognathic Surgery www.indiandentalacademy.com
  2. 2. INTRODUCTION  Successful treatment of the orthognathic surgical patient is dependent on careful diagnosis  Cephalometrics can be an aid in the diagnosis of skeletal and dental problems and a tool for simulating surgery and orthodontics by the use of acetate overlays (Tracing sheets). www.indiandentalacademy.com
  3. 3. HISTORY  Earlier Cephalometric analysis highlighting dentofacial patterns and dysplasias are  Wylie’s analysis (1947)  Down’s analysis (1956)  Steiner’s analysis However, www.indiandentalacademy.com
  4. 4. Analysis to help diagnose and plan for orthognathic surgeries came in late seventies and early eighties. www.indiandentalacademy.com
  5. 5.  Cephalometrics for orthognathic surgery burstone 1978 april Journ. of oral surg  Quadrilateral analysis- By Di-paolo AJO-DO 1984 Dec  Proportionate mesh analysis AJO 1987 JUN www.indiandentalacademy.com
  6. 6. More recent venture into Cephalometric treatment planning and predictions has been VIDEOIMAGING www.indiandentalacademy.com
  7. 7. COGS – Cephalometrics for Orthognathic Surgery  Developed at university of Connecticut  Based on a system from Indiana University and further developed by additions at Connecticut www.indiandentalacademy.com
  8. 8. COGS – Cephalometrics for Orthognathic Surgery  Developed by Charles Burstone et al  Presented first in Journal of Oral Surgery. 1978 April  Followed by Soft tissue Cephalometric Analysis for Orthognathic surgery in Journal of Oral Surgery. 1980 www.indiandentalacademy.com
  9. 9.  Data derived from samples obtained from Child Research Centre, Univ. of Colorado school of medicine.  Sample type: Northern european descent  Sample Size = 27  16 females  11 males www.indiandentalacademy.com
  10. 10. Plane of Reference for comparison  A constructed plane called Horizontal Plane which is surrogate Frankfort Horizontal plane constructed by drawing a line 70 from SN plane  Most measurements will be made from projections either parallel or perpendicular to the Horizontal Plane www.indiandentalacademy.com
  11. 11. COGS  Chosen landmarks and measurements can be altered by various surgical procedures.  The appraisal includes all facial bones and a cranial base reference.  Rectilinear measurements can be readily transferred to a study cast for mock surgery. www.indiandentalacademy.com
  12. 12.  Critical facial components can be examined.  Standards and statistics are available for variations in age and sex from 5 to 20  Consists of a series of measurements that can be computerised. www.indiandentalacademy.com
  13. 13. H-Plane www.indiandentalacademy.com
  14. 14. Cranial Base www.indiandentalacademy.com
  15. 15. Cranial Base Males Females Ar-Ptm ( || to HP) 37.1 + 2.8 32.8 + 1.9 Ptm-N ( || to HP) 52.8 + 4.1 50.9 + 3.0 www.indiandentalacademy.com
  16. 16. Horizontal Measurements N-A-Pg www.indiandentalacademy.com
  17. 17. Horizontal Measurements Males Females N-A-Pg angle 3.9 + 6.4 2.6 + 5.1 N-A ( || to HP ) 0.0 + 3.7 -2.0 + 3.7 N-B ( || to HP ) -5.3 + 6.7 -6.9 + 4.3 N-Pg ( || to HP) -4.3 + 8.5 -6.5 + 5.1 www.indiandentalacademy.com
  18. 18. Vertical Measurements www.indiandentalacademy.com
  19. 19. Vertical Measurements Males Females N-ANS ( 1 to HP) 54.7 + 3.2 50.0 + 2.4 ANS-Gn ( 1 to HP) 68.6 + 3.8 61.3 + 3.3 PNS-N ( 1 to HP) 53.9 + 1.7 50.6 + 2.2 MP – HP angle 23.0 + 5.9 24.2 + 5.0 Upper incisor-NF(1 to NF) 30.5 + 2.1 27.5 + 1.7 Lower incisor-MP(1 to MP) 45.0 + 2.1 40.8 + 1.8 Upper molar-NF (1 to NF) 26.2 + 2.0 23.3 + 1.3 Lower molar-MP (1 to 35.8 + 2.6 32.1 + 1.9www.indiandentalacademy.com
  20. 20. Maxilla and Mandible www.indiandentalacademy.com
  21. 21. Maxilla and Mandible Males Females PNS-ANS (|| to HP) 57.7 + 2.5 52.6 + 3.5 Ar-Go (linear) 52.0 + 4.2 46.8 + 2.5 Go-Pg (linear) 83.7 + 4.6 74.3 + 5.8 B-Pg (|| to MP) 8.9 + 1.7 7.2 + 1.9 Ar-Go-Gn angle 119.1 + 6.5 122.0 + 6.9 www.indiandentalacademy.com
  22. 22. Dental Measurements www.indiandentalacademy.com
  23. 23. Dental Males Females OP upper – HP angle 6.2 + 5.1 7.1 + 2.5 OP lower – HP angle A-B ( 1 to OP) -1.1 + 2.0 -0.4 + 2.5 Upper incisor – NF angle 111.0 + 4.7 112.5 + 5.3 Lower incisor – MP angle 95.9 + 5.2 95.9 + 5.7 www.indiandentalacademy.com
  24. 24. The Arnett’s way www.indiandentalacademy.com
  25. 25. Soft tissue Cephalometric Analysis  By William Arnett and Robert Bergman AJODO 1999  Sequale to Facial keys to orthodontic diagnosis and treatment planning. Part I and II AJODO 1993 www.indiandentalacademy.com
  26. 26. “We only treat what we are educated to see. The more we see, the better the treatment we render our patients” -Arnett.... www.indiandentalacademy.com
  27. 27. Arnett and Bergman....... “When attention is directed only to bite correction, facial balance may not improve and can deteriorate. The orthodontist's job is to balance occlusal correction, temporomandibular joint function, periodonal health, stability, and facial balance while moving the teeth to correct the bite.” www.indiandentalacademy.com
  28. 28. Format for examination of face  Natural head posture,  Centric relation (uppermost condyle position),  Relaxed lip posture  True Vertical Line ( TVL ) www.indiandentalacademy.com
  29. 29. Arnett and Bergman By examining the patient in this format, reliable facial-skeletal data can be obtained that enhances diagnosis, treatment planning, treatment, and quality of results. www.indiandentalacademy.com
  30. 30. Why the Natural head position? www.indiandentalacademy.com
  31. 31. Natural head posture is preferred because of its demonstrated accuracy over intracranial landmarks. Natural head posture has a 2° standard deviation compared with a 4° to 6° standard deviation for the various intracranial landmarks in use. www.indiandentalacademy.com
  32. 32. Why Centric Relation?? www.indiandentalacademy.com
  33. 33. Why relaxed lip position?? www.indiandentalacademy.com
  34. 34.  The patient should be in the relaxed lip position because it demonstrates the soft tissue, relative to hard tissue, without muscular compensation for dentoskeletal abnormalities.  Vertical disharmony between lip lengths and skeletal height (vertical maxillary excess, vertical maxillary deficiency, mandibular protrusion, mandibular retrusion with deep bite) can not be assessed without the relaxed lip posture. www.indiandentalacademy.com
  35. 35. Existing positions and needed changes in upper incisor exposure, interlabial gap, lip length, and proportion are lost in the closed lip position. Closed lip position may be adequate for normoskeletal cases but is totally inadequate for skeletal disharmony assessment www.indiandentalacademy.com
  36. 36. What is TVL and Why TVL?? www.indiandentalacademy.com
  37. 37. True Vertical Line ( TVL )  It is a Vertical line passing through the Subnasale with natural head posture.  It may be used to quantify favorable or unfavourable change in the profile after overjet reduction and has a potential role in post treatment analysis and research www.indiandentalacademy.com
  38. 38. Soft tissue Cephalometric Analysis  Data base: Based on 46 white models  Males = 20  Females = 26  All models had natural class I occlusion and reasonably well balanced facially www.indiandentalacademy.com
  39. 39. Metallic Markers are placed on right side of face to mark key midface structures. i.e 1. Orbital rim marker 2. The alar base marker 3. The subpupil marker www.indiandentalacademy.com
  40. 40. Soft tissue Cephalometric Analysis Composed of five components 1. Dentoskeletal factors 2. Soft tissue structures 3. Facial length 4. Projections to TVL 5. Harmony values www.indiandentalacademy.com
  41. 41. Dento skeletal factors  Have a large influence on the facial profile.  When in normal range individually produce a balanced and harmonious nasal base, lip, soft tissue A’ and B’, and chin relationship. www.indiandentalacademy.com
  42. 42. Dento skeletal Factors Females Males Mx occlusal plane 95.6 + 1.8 95.0 + 1.4 Mx1 to Mx occlusal plane 56.8 ± 2.5 57.8 ± 3.0 Md1 to Md occlusal plane 64.3 ± 3.2 64.0 ± 4.0 Overjet 3.2 ± .4 3.2 ± .6 Overbite 3.2 ± .7 3.2 ± .7 www.indiandentalacademy.com
  43. 43. Dento skeletal factors www.indiandentalacademy.com
  44. 44. Soft tissue structures  Soft tissue thickness in combination with dentoskeletal factors largely control lower facial esthetic balance.  Nasolabial angle and upper lip angle are important in assessing the upper lip and may be used by the orthodontist as part of the extraction decision. www.indiandentalacademy.com
  45. 45. Soft Tissue Structures Females Males Upper lip thickness 12.6 ± 1.8 14.8 ± 1.4 Lower lip thickness 13.6 ± 1.4 15.1 ± 1.2 Pogonion- Pogonion’ 11.8 ± 1.5 13.5 ± 2.3 Menton- Menton’ 7.4 ± 1.6 8.8 ± 1.3 Nasolabial angle 103.5 ± 6.8 106.4 ± 7.7 Upper lip angle 12.1 ± 5.1 8.3 ± 5.4www.indiandentalacademy.com
  46. 46. Soft tissue structures www.indiandentalacademy.com
  47. 47. Facial length  The presence and location of vertical abnormalities is indicated by assessing maxillary height, mandibular height, upper incisor exposure and overbite. www.indiandentalacademy.com
  48. 48. Facial Length Females Males Nasion’-Menton’ 124.6 ± 4.7 137.7 ± 6.5 Upper lip length 21.0 ± 1.9 24.4 ± 2.5 Interlabial gap 3.3 ± 1.3 2.4 ± 1.1 Lower lip length 46.9 ± 2.3 54.3 ± 2.4 Lower 1/3 of face 71.1 ± 3.5 81.1 ± 4.7 Overbite 3.2 ± .7 3.2 ± .7 Mx1 exposure 4.7 ± 1.6 3.9 ± 1.2 Maxillary height 25.7 ± 2.1 28.4 ± 3.2 Mandibular height 48.6 ± 2.4 56.0 ± 3.0 www.indiandentalacademy.com
  49. 49. Facial Length www.indiandentalacademy.com
  50. 50. Projections to TVL  They are antero-posterior measurements of soft tissue and represent the sum of the dentoskeletal position plus the soft tissue thickness overlying that hard tissue landmark.  The horizontal distance for each individual landmark, measured perpendicular to the TVL, is termed the landmark’s absolute value. www.indiandentalacademy.com
  51. 51. Projections to TVL Females Males Glabella –8.5 ± 2.4 –8.0 ± 2.5 Orbital rims –18.7 ± 2.0 –22.4 ± 2.7 Cheek bone –20.6 ± 2.4 –25.2 ± 4.0 Subpupil –14.8 ± 2.1 –18.4 ± 1.9 Alar base –12.9 ± 1.1 –15.0 ± 1.7 Nasal projection 16.0 ± 1.4 17.4 ± 1.7 Subnasale 0 0 www.indiandentalacademy.com
  52. 52. Projections to TVL www.indiandentalacademy.com
  53. 53. Projections to TVL Females Males A point’ –0.1 ± 1.0 –0.3 ± 1.0 Upper lip anterior 3.7 ± 1.2 3.3 ± 1.7 Mx1 –9.2 ± 2.2 –12.1 ± 1.8 Md1 –12.4 ± 2.2 –15.4 ± 1.9 Lower lip anterior 1.9 ± 1.4 1.0 ± 2.2 B point’ –5.3 ± 1.5 –7.1 ± 1.6 Pogonion’ –2.6 ± 1. 9 –3.5 ± 1.8 www.indiandentalacademy.com
  54. 54. Harmony Values  Created to measure facial structure balance and harmony.  It is the position of each landmark relative to other landmarks that determines the facial balance.  The harmony values represent the horizontal distance between two landmarks measured perpendicular to the true vertical www.indiandentalacademy.com
  55. 55. HV examines four areas of balance  Intramandibular parts.  Interjaw  Orbits to jaws  The total face www.indiandentalacademy.com
  56. 56. Intramandibular Relations Females Males Md1-Pogonion’ 9.8 ± 2.6 11.9 ± 2.8 Lower lip anterior- Pogonion’ 4.5 ± 2.1 4.4 ± 2.5 B point’-Pogonion’ 2.7 ± 1.1 3.6 ± 1.3 Throat length (neck throat point to Pog’) 58.2 ± 5.9 61.4 ± 7.4 These values assess chin projection relative to other mandibular structures. www.indiandentalacademy.com
  57. 57. Harmony Values www.indiandentalacademy.com
  58. 58. Inter jaw Relations Females Males Subnasale’- Pogonion’ 3.2 ± 1.9 4.0 ± 1.7 A point’-B point’ 5.2 ± 1.6 6.8 ± 1.5 Upper lip anterior-lower lip anterior 1.8 ± 1.0 2.3 ± 1.2 www.indiandentalacademy.com
  59. 59. Orbit to Jaws Females Males Orbital rim’- A point’ 18.5 ± 2.3 22.1 ± 3 Orbital rim’- Pogonion’ 16.0 ± 2.6 18.9 ± 2.8 www.indiandentalacademy.com
  60. 60. Harmony Values www.indiandentalacademy.com
  61. 61. Full Facial Balance Females Males Facial angle 169.3 ± 3.4 169.4 ± 3.2 Glabella’-A point’ 8.4 ± 2.7 7.8 ± 2.8 Glabella’- Pogonion’ 5.9 ± 2.3 4.6 ± 2.2 www.indiandentalacademy.com
  62. 62. Note Landmark values are dependent on TVL placement. HOWEVER www.indiandentalacademy.com
  63. 63. Harmony values are independent of the position of the TVL thus making it very reliable www.indiandentalacademy.com
  64. 64. SURGICAL-ORTHODONTIC CEPHALOMETRIC PREDICTION TRACING By Epker and Fish (1980 JCO) adopted in part from the mechanics developed by Ricketts for cephalometric analysis, growth prediction and visual treatment objective construction as presented by Bench, Gugino, and Hilgers. (Bioprogressive therapy) www.indiandentalacademy.com
  65. 65. Cephalometric Prediction Tracing for Mandibular Advancements. Why do prediction tracings for mandibular surgery? www.indiandentalacademy.com
  66. 66. 1) To accurately assess the profile esthetic results which will result from the proposed surgery, 2) To consider the desirability of simultaneous adjunctive procedures such as genioplasty, suprahyoid myotomy, etc., 3) To help determine the sequencing of surgery and orthodontics (i.e., if the surgery is done first will it be more difficult or easier to do the indicated orthodontics), www.indiandentalacademy.com
  67. 67. 4) To help decide what type of orthodontics might best be employed (i.e., extraction versus non-extraction) 5) To determine the anchorage requirements should extraction treatment be chosen www.indiandentalacademy.com
  68. 68. The Cephalometric x-ray from which the prediction tracing is to be done should be taken with the patient's lips in REPOSE www.indiandentalacademy.com
  69. 69. Step I: Trace the Stable Structures.  The first step in producing a prediction tracing is to overlay a piece of acetate paper on the original cephalometric tracing and trace all structures which will not be significantly altered by the surgery and/or orthodontics www.indiandentalacademy.com
  70. 70.  For mandibular surgery, these structures will include the deep cranial features, the maxilla, the maxillary occlusal plane, the mandibular ramus and the profile to the base of the nose. Draw in Frankfort Horizontal and a line from nasion to indicate the optimum facial depth, i.e., 89° in females, 90° in males www.indiandentalacademy.com
  71. 71. Step 2 - Add Skeletal Portion Changed by Surgery  Slide the prediction tracing to the left and rotate it slightly to position bony pogonion at the optimum facial depth, keeping the mandibular occlusal plane in proper relation to the maxillary occlusal plane. www.indiandentalacademy.com
  72. 72.  Once a satisfactory position is achieved, trace the distal portion of the mandible, the corpus axis, and the soft tissue chin in this position (Fig. 2B).  There is little change in soft tissue chin thickness, so the soft tissue chin may be drawn in just as it was originallywww.indiandentalacademy.com
  73. 73. Step 3 - New A-Po Line.  Construct a new line from Point A to pogonion. If a genioplasty is to be included in the procedure, the anterior portion of this altered chin, be it bone or alloplast, is now construed to be pogonion for purposes of placing the teeth. www.indiandentalacademy.com
  74. 74. Step 4 - Placing the Teeth.  First the lower incisor is placed in its optimum position 1 millimeter ahead of the A-Po line, 1 millimeter above the occlusal plane, and at 22 degrees to the A-Po line. www.indiandentalacademy.com
  75. 75. Step 4 - Placing the Teeth.  Old and new mandibles are then superimposed on Corpus Axis at PM and the change in lower incisor position is noted. Arithmetically adding twice this change to the crowding already present allows calculation of the arch length deficiency or excess. Thus, the anterior-posterior position of the lower first molar can be determined and the molar is traced in this position. www.indiandentalacademy.com
  76. 76.  The upper first molar is then placed in the desired occlusion and the upper incisor is likewise placed in the optimum position with its long axis 5 degrees more upright than the new facial axis (dotted line on the prediction tracing) . www.indiandentalacademy.com
  77. 77. Step 5 - Tracing the New Lip Contours.  Once the teeth are placed, the lip contours are traced to correspond to the new incisor positions. www.indiandentalacademy.com
  78. 78.  Once completed, the prediction tracing must be viewed as a goal toward which one is working.  Once the prediction tracing is as you like it, the prediction tracing can be superimposed upon the original tracings, registering on the structures not significantly altered by the surgery and/or orthodontics, and the previously stated five basic reasons to do prediction tracings for mandibular surgery can be deliberately and intelligently assessed www.indiandentalacademy.com
  79. 79. Cephalometric Prediction for Maxillary Superior Repositioning.  Why do prediction tracings for maxillary surgery cases? www.indiandentalacademy.com
  80. 80. It is even more important to do prediction tracings for maxillary surgery cases, especially when the primary direction of movement is vertical, to ascertain the effects of the prescribed surgery on the mandible. www.indiandentalacademy.com
  81. 81.  The decision to superiorly reposition the maxilla is made primarily from their esthetic features. The amount of superior repositioning is based upon the upper tooth to lip measurement which is made clinically. Still, www.indiandentalacademy.com
  82. 82.  We need to know if the maxilla should be moved posteriorly or anteriorly along with the upward movement  We need to know what orthodontics will be necessary.  Furthermore, we need to know if autorotation alone will produce an adequate chin or if we will wish to add a genioplasty or consider simultaneous mandibular advancement. These questions can be answered from a prediction tracing. www.indiandentalacademy.com
  83. 83. Step 1 - Trace the Stable Structures.  As is the case with all prediction tracings, we again begin by tracing the structures which will not be modified either surgically or orthodontically www.indiandentalacademy.com
  84. 84. Step 2 - Determination of Ideal Vertical Position for the Upper Incisor.  the measurement of the amount of upper central incisor exposed, i.e., that from stomion of the upper lip to incisal edge, be made clinically with the patient standing in a relaxed posture.  This is the single most important measurement in preparation for superior repositioning of the maxilla and can be confirmed cephalometrically. www.indiandentalacademy.com
  85. 85.  Once the amount of incisor exposed beneath the upper lip is determined, the "ideal" amount of superior repositioning of the upper incisor can be determined by the formula x= y-2 0.8  where X is the amount of superior repositioning necessary  Y is the amount of upper incisor showing. www.indiandentalacademy.com
  86. 86. This formula is used because the upper lip tends to shorten approximately 20% of the amount of superior surgical repositioning; thus, a 1:1 relationship between the amount of tooth showing and the amount of repositioning necessary does not exist. www.indiandentalacademy.com
  87. 87.  If the superior movement is to be accompanied by posterior movement of the incisors and an acute nasolabial angle is present, the lip will not shorten quite as much as predicted.  Conversely, with an obtuse nasolabial angle and anterior movement of the incisor, the lip will tend to shorten slightly more. www.indiandentalacademy.com
  88. 88. These slight variations may be disregarded, unless the anterior- posterior change is more than 6 millimeters. www.indiandentalacademy.com
  89. 89. Step 2 - Determination of Ideal Vertical Position for the Upper Incisor.  Once the desired amount of vertical incisor repositioning is determined, draw a line parallel to Frankfort horizontal on the prediction tracing to represent the desired vertical position www.indiandentalacademy.com
  90. 90. Step 3 - Autorotation of the Mandible.  Superimpose the original and prediction tracings and, keeping the mandibular condyle in the same position, rotate the prediction tracing clockwise until the occlusal plane is 1 mm above the line indicating the desired position of the upper incisor. www.indiandentalacademy.com
  91. 91.  Trace the mandible in this position. The corpus axis and the occlusal plane are also traced in at this time  The change in point A and the soft tissue chin contour must be carefully studied at this time. To allow easier observation of these features, one may wish to trace, with dotted lines, the soft tissue chin, the lower incisor, and Point A. www.indiandentalacademy.com
  92. 92. Step 4 - Genioplasty Determination  The next feature which must be noted is the new soft tissue chin position. (This is where the chin autorotates to.) If the chin is adequate, then genioplasty is not necessary.  However, if the chin is still weak, either mandibular advancement or some type of genioplasty must be added to the treatment plan for optimum esthetics.  Conversely, if the chin is too strong, then some procedure to reduce it may be required. www.indiandentalacademy.com
  93. 93. Step 4 - Genioplasty Determination  Cephalometric criteria which may be used to help determine optimum anteroposterior soft- tissue chin position. www.indiandentalacademy.com
  94. 94.  For bony genioplasties, the ratio of anterior- posterior soft tissue change to bony change is about 0.6:1, thus, if 5 millimeters more chin is desired, a bony advancement of 8 millimeters will be required. www.indiandentalacademy.com
  95. 95. If alloplastic material is to be added, this ratio approaches 1:1 thus 5 millimeters of alloplast will produce 5 millimeters more soft tissue chin. Dann, J.A. and Epker, B.N.: Proplast Genioplasty: A Retrospective Study of Treatment Results, Angle Orthodontist, [47:173, 1977.] www.indiandentalacademy.com
  96. 96.  Once the amount of genioplasty has been determined, the new A-Po line can be constructed using the genioplasty as a new pognonion and either the old Point A or new Point A as discussed previously. www.indiandentalacademy.com
  97. 97. Step 5 - Placement of Teeth In Ideal Positions.  The lower incisor is placed in relationship to the symphysis of the mandible, the occlusal plane and the APO plane. The arch length requirements and realistic results dictate its location. www.indiandentalacademy.com
  98. 98. Step 6 - Nasal Outline  With superior repositioning of the maxilla, the nasal tip is generally elevated slightly. This is more pronounced if the maxilla is moved upward and forward, less pronounced if upward and backward. The lower border of the nose is relatively unchanged though it too may be elevated a small amount. Accordingly, the prediction tracing should be placed on the original with the fixed landmarks superimposed and the nasal outline traced with the aforementioned alterations www.indiandentalacademy.com
  99. 99. Step 7 - Upper Lip. The upper lip reacts to superior repositioning in the following ways:  The length from subnasale to upper lip stomion shortens 1/5 of the amount of superior repositioning,  The thickness increases by 1/3 of the amount of incisor retraction, and  The lip thins out slightly if the upper incisor is moved forward, but in all but the most extreme instances this is unnoticeable. www.indiandentalacademy.com
  100. 100. www.indiandentalacademy.com
  101. 101.  To trace the new upper lip one should superimpose on the fixed cranial structures and study the change in incisor position. If the upper incisor is retracted such that it lies posterior to an imaginary line from the labial surface to Point A on the original tracing, then lip support has been reduced and one should trace the new lip in the following manner:  www.indiandentalacademy.com
  102. 102.  Divide the vertical distance from old incisor tip to new incisor tip into fifths and the anterior-posteriordistance into thirds.  Move the prediction tracing down 1/5 and forward 2/3 and draw in the new lip vermillion.  Connect the new lip vermillion to the previously traced subnasale in an artistic manner.  Subnasale is affected so little by superior repositioning that for prediction it can be considered a fixed point. www.indiandentalacademy.com
  103. 103. If the upper incisor has moved directly up the line from the labial surface to Point A of the original tracing, then lip support is unchanged and one should trace the new lip in the following manner:  Divide the vertical distance from old incisor tip to new incisor tip into fifths. Move the prediction tracing down 1/5 and trace the new lip, connecting it to subnasale as above. www.indiandentalacademy.com
  104. 104. www.indiandentalacademy.com
  105. 105. If, the upper incisor is forward of the line from labial surface to Point A of the original tracing, then lip support has been increased and the new lip is traced as follows:  Divide the vertical distance from old incisor tip to new incisor tip into fifths.  Move the prediction tracing down 1/5. Then,  While maintaining this vertical position, rotate and slide the prediction tracing such that the long axis of the upper incisor in the prediction tracing is parallel to, and the labial surface is flush with, the line from the labial surface to Point A of the original tracing.  Trace the new lip in this position This effectively maintains the original lip thickness. www.indiandentalacademy.com
  106. 106. Step 8 - Lower Lip. In most instances the lower lip vermillion is traced in the same relation to the lower incisors as existed prior to treatment. www.indiandentalacademy.com
  107. 107. Step 8 - Lower Lip. Superimpose the lower incisor on the prediction tracing over that on the original and trace the lower lip. Where the lower incisors are retracted 5 millimeters or more, the lip tends to thicken slightly. Thus the lower incisors are not exactly superimposed, but the prediction tracing is moved slightly to the lingual of an exact superimposition (i.e., the lip thickens slightly) and the lip traced in this position www.indiandentalacademy.com
  108. 108. Some artistic freedom must be employed when dealing with a hypotonic lip. the hypotonic lip may increase mildly in tonicity following production of lip competence and added support for the lip via augmentation genioplasty. IN SUCH CASES then the lip would be traced slightly thinner for purposes of prediction www.indiandentalacademy.com
  109. 109. Step 9 - Chin.  If no genioplasty is projected, the soft tissue chin will be relatively unaffected by treatment and should be traced by simply superimposing on the mandibular symphysis.) www.indiandentalacademy.com
  110. 110.  If a sliding genioplasty is done, the chin is traced by first superimposing on the original symphysis and then sliding the prediction tracing back 6/10 of the amount of the genioplasty and tracing the new chin contour. www.indiandentalacademy.com
  111. 111.  If an alloplastic implant is added, the new chin contour can be determined by simply superimposing the alloplastic implant on the original symphysis and tracing the chin www.indiandentalacademy.com
  112. 112.  Once the tracing is completed, we again must study it to determine if indeed we have achieved a satisfactory result. www.indiandentalacademy.com
  113. 113.  To once again gain optimum appreciation for the proposed changes superimposition of the original and prediction tracing is done again superimposing on the structures not significantly altered by the surgery and/or orthodontics. www.indiandentalacademy.com
  114. 114.  Frequently, it is necessary to do several prediction tracings, trying different surgical approaches to a problem (i.e., superior repositioning vs. superior repositioning with genioplasty vs. superior repositioning with mandibular advancement) before one can determine which result is best. www.indiandentalacademy.com
  115. 115. Conclusion  Certainly it is better to retreat a patient on paper than to wish that a different surgical approach had been employed after the fact www.indiandentalacademy.com
  116. 116. www.indiandentalacademy.com

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