Surg analysis ii /certified fixed orthodontic courses by Indian dental academy


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Surg analysis ii /certified fixed orthodontic courses by Indian dental academy

  1. 1. Surgical analysis and prediction INDIAN DENTAL ACADEMY Leader in continuing dental education
  4. 4.   In 1999 Arnett et al purposed the Soft Tissue Cephalometric Analysis (STCA) , with particular emphasis on midface structures that do not show on standard cephalometric analysis. In particular, orbital rim, subpupil,and alar base contours were noted to indicate anteroposterior position of the maxilla.
  5. 5.       Soft Tissue Cephalometric Analysis (STCA) can be used to diagnose the patient in five different but interrelated areas; dentoskeletal factors, soft tissue components, facial lengths, True vertical line (TVL) projections, and harmony of parts.
  6. 6. Dentoskeletal factors,   Dentoskeletal factors have a large influence on the facial profile. These factors, when in normal range will usually produce a balanced and harmonious nasal base, lip, soft A’, soft B’, and chin relationship.
  7. 7. Dentoskeletal factors:  maxillary occlusal plane upper incisor to maxillary occlusal plane, lower incisor to mandibular occlusal plane, overbite, and overjet are measured.
  8. 8. female male
  9. 9.   The dentoskeletal factors, to a large extent, control esthetic outcome How accurately the orthodontist and surgeon manage the dentoskeletal components greatly influences the resulting profile.
  10. 10. 2.Soft tissue structures
  11. 11. Tissue thickness of upper lip, lower lip, B to B’, Pog to Pog’, and Me to Me’ are depicted. Soft tissue thickness in combination with previously described dentoskeletal factors largely control lower facial aesthetic balance.
  12. 12.      Soft tissue structure; ideal values Upper lip thickness –female-12.6 ± 1.8mm male-14.8 ± 1.4 mm Lower lip thickness -:female;13.6 ± 1.4 mm male; 15.1 ± 1.2mm . Pogonion-Pogonion’ --female; 11.8 ± 1.5 mm male;13.5 ± 2.3mm . Menton-Menton’ --female;7.4 ± 1.6 mm male--8.8 ± 1.3 mm.
  13. 13. Upper lip angle and nasolabial angle are depicted. Clinical significance; These soft tissue structures are altered by movement of the incisor teeth. Therefore these angles should be studied before orthodontic overjet correction to assess the potential for changes out of normal range.
  14. 14.  Upper lip angle-- female 12.1 ± 5.1 male 8.3 ± 5.4 degree Nasolabial angle-- female-103.5 ± 6.8 male- 106.4 ± 7.7 degree
  15. 15.   3.Facial length Soft tissue lengths include facial height (Na’ to Me’), lower one-third height (Sn to Me’), upper lip length (Sn to upper lip inferior), lower lip length (lower lip superior to Me’), and interlabial gap (upper lip inferior to lower lip superior).
  16. 16.      Facial height --female-124.6 ± 4.7mm; male137.7 ± 6.5mm Lower 1/3 of face —female;-- 71.1 ± 3.5 mm male;-- 81.1 ± 4.7 Upper lip length –female-21.0 ± 1.9mm male24.4 ± 2.5 mm Interlabial gap– female- 3.3 ± 1.3mm male-2.4 ± 1.1 mm. Lower lip length– female- 46.9 ± 2.3mm; male-;54.3 ± 2.4mm
  17. 17.   Additional essential vertical measurements include: Relaxed lip upper incisor exposure, maxillary height (Sn to Mx1tip), mandibular height (Md1 tip to Me’) and overbite.
  18. 18. Ideal values    Maxillary incisor exposure –female-4.7 ± 1.6mm male-3.9 ± 1.2 mm Maxillary height —female- 25.7 ± 2.1mm male- 28.4 ± 3.2mm . Mandibular height –female-48.6 ± 2.4mm male-56.0 ± 3.0mm
  19. 19.   4.TVL projections are anteroposterior 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.
  20. 20.   When midface retrusion is diagnosed the TVL is moved 1 to 3 mm anterior. Midface retrusion is defined by clinical factors (long nose, deficient midface structures, poor incisor upper lip support) and cephalometric factors (upright upper lip and/or thick upper lip)
  21. 21. Soft tissue profile points measured to TVL are Glabella ( G’), nasal tip ( NT), soft tissue A’ point ( A’), upper lip anterior ( ULA), lower lip anterior ( LLA), soft tissue B’ point ( B’), and soft tissue Pogonion’ ( Pog’).
  22. 22. Ideal values       Glabella –female 8.5 ± 2.4mm male –8.0 ± 2.5 mm Nasal projection –female-16.0 ± 1.4 mm–male-17.4 ± 1.7mm . A point’ –female;-01 ± 1.0 mm male;–0.3 ± 1.0mm . Upper lip anterior--female -3.7 ± 1.2 mm male-3.3 ± 1.7mm . Lower lip anterior- female 1.9 ± 1.4mm, male-1.0 ± 2.2 mm B point’ –female-5.3 ± 1.5m male –7.1 ± 1.6mm . Pogonion’ –female-2.6 ± 1.9mm male –3.5 ± 1.8 mm.
  23. 23. Midface, points measured with respect to the TVL are soft tissue orbital rim( OR’), cheekbone height of contour ( CB’), subpupil ( SP’), and alar base (AB’). Hard tissue measured to the TVL are upper incisor tip and lower incisor tip.
  24. 24. Ideal values        Orbital rims –female;-18.7 ± 2.0mm male; –22.4 ± 2.7mm Cheek bone- female –20.6 ± 2.4mm male –25.2 ± 4.0mm Subpupil- female –14.8 ± 2.1mm male; –18.4.0 ± 1.9mm Alar base- female –12.9 ± 1.1 mm male–15.0 ± 1.7 mm Subnasale female 0mm male 0mm Mx1 female–9.2 ± 2.2 mm male;–12.1 ± 1.8mm Md1 female–12.4 ± 2.2mm male–15.4 ± 1.9 mm
  25. 25. 5.Harmony values    The harmony values were created to measure facial structure balance and harmony. Harmony or balance between different facial landmarks is an important component of beauty. It is the position of each landmark relative to other landmarks that determines the facial balance. Harmony values represent the horizontal distance between 2 landmarks measured perpendicular to the true vertical line (TVL)
  26. 26.       Harmony values examine four areas of balance: A) intramandibular parts, B) interjaw, C) orbits to jaws, and D) The total face. These harmony groupings are essential to excellent dentofacial outcomes.
  27. 27. A) intramandibular parts, Relationships between structures within the mandible that determine balance are measured, lower incisor to Pog’, lower lip to Pog’, soft tissue B’ to Pog’, and neck throat point to Pog’ are depicted.
  28. 28.      Intramandibular relations IDEAL VALUES Md1-Pogonion’ –female 9.8 ± 2.6mm male 11.9 ± 2.8mm . Lower lip anterior-Pogonion’---female 4.5 ± 2.1mm male- 4.4 ± 2.5mm . B point’-Pogonion’—female 2.7 ± 1.1mm male 3.6 ± 1.3 mm. Throat length (neck throat point to Pog’) – female 58.2 ± 5.9mm male 61.4 ± 7.4mm
  29. 29.    Analysis of these structures indicates chin position relative to other mandibular structures and which, if any, structure is abnormally placed. For example, excessive distance from mandibular incisor tip to the chin may indicate an upright lower incisor, or hard tissue pogonion enlargement, or increased thickness of the chin soft tissues (Pog to Pog’). All of these possibilities are examined within the intramandibular harmony group, and a diagnosis is made so that treatment can be rendered to harmonize structures within the mandible
  30. 30. B) interjaw,    Next, interjaw harmony is examined. These relationships directly control the lower one third of facial aesthetics. : relationships between the upper and lower jaw soft tissues that determine balance are measured Values indicate the interrelationship between the base of the maxilla (Sn) to chin (Pog’), soft tissue B’ to soft tissue A’ and upper to lower lips.
  31. 31.     Interjaw relations Subnasale’-Pogonion’--female 3.2 ± 1.9 mm male--4.0 ± 1.7 mm A point’-B point’ --female 5.2 ± 1.6 male 6.8 ± 1.5mm Upper lip anterior-lower lip anterior female; 1.8 ± 1.0mm male -- 2.3 ± 1.2mm
  32. 32. C ), Orbital rim to jaws: relationships between the soft tissue orbital rim and upper and lower jaw that determine balance are measured, soft tissue orbital rim to upper jaw at soft tissue A’ point and lower jaw at Pog’.
  33. 33. Ideal values   Orbital rim’- female A point’ 18.5 ± 2.3mm male 22.1 ± 3mm Orbital rim’-Pogonion’ –female 16.0 ± 2.6mm male- 18.9 ± 2.8mm
  34. 34.      D ) Total face harmony: relationships between the forehead, upper jaw, and lower jaw that determine balance are measured, The upper face, midface, and chin are related via the facial angle (G’-Sn-Pog’). Then the forehead is compared to two specific points, upper jaw (G’-A’) and chin (G’-Pog’). These three measures give the broad picture of facial balance.
  35. 35. Ideal values     Full facial balance Facial angle —female 169.3 ± 3.4 male 169.4 ± 3.2 . Glabella’-A point’ –female 8.4 ± 2.7mm male 7.8 ± 2.8mm . Glabella’- Pogonion’ –female 5.9 ± 2.3mm male 4.6 ± 2.2mm
  36. 36.
  37. 37. SOFT TISSUE CEPHALOMETRIC ANALYSIS - Legan, Dallas, Burstone et al
  38. 38.   Means & standard deviation derived from 40 orthodontically untreated white adults (20 men, 20 women). Class I occlusion, Vertical facial proportions within normal limits.
  39. 39.     Facial convexity – given by angle G – Sn – Pg’. Smaller value – Class III profile. Clockwise angle – Positive. Counterclockwise angle – Negative.
  40. 40.     Maxilla & mandibular are related to a line dropped from glabella perpendicular to horizontal reference plane. Maxillary – Distance to subnasale from this line. Gives amount of maxillary excess or deficiency in A-P dimension. Anterior to line – Positive, Posterior negative
  41. 41.  This & other related A-P measurements are important in planning treatment for anterior maxillary advancement or reduction and for total alveolar or lefort I maxillary horizontal advancement or reduction.
  42. 42.   Mandible – distance from perpendicular line dropped from glabella to Pg’. Gives an indication of mandibular prognathism or retrognathism.
  43. 43.     This measurement must be evaluated in conjunction with others to distinguish between microgenia—small hard tissue chin, micrognathia—small mandible retrognathia—average sized mandible positioned posteriorly Thin soft tissue chin or combination of these
  44. 44. Lower face throat angle (Sn – Gn’ –C)    Formed by intersection of lines Sn-Gn’ & Gn’-C. Critical in planning treatment to correct A-P dysplasias. In case of obtuse angle, clinicians should not use procedure that reduce prominence of chin. C
  45. 45. CLINICAL APPLICATION   Class III patients with short ,heavy throats & obtuse angle usually not have mandibular setbacks. Alternatives – maxillary advancement, mandibular subapical procedure, mandibular setback with advancement genioplasty, compromise tooth position.
  46. 46.   Vertical – ratio of distances G – Sn & Sn – Me’ should be approx. 1. Less than one indicates larger lower third of the face
  47. 47. Lip position     Nasolabial angle – between Cm-Sn-Ls. Important measurement in A-P maxillary dysplasias. Acute angle allow us to surgically retract maxilla or maxillary incisors or both. Obtuse angle – maxillary advancement or proclination of incisors.
  48. 48.  A-P lip position – line is drawn from Sn-Pg’ & amount of lip protrusion or retrusion is measure as perpendicular linear distance from this line to most prominent point of both lips.
  49. 49.    Labiomental sulcus – from depth of sulcus perpendicular to LiPg’ line. Sulcus of about 4mm provides pleasing lower lip to chin contour. Uprighting lower incisors,intruding maxillary incisors,chelioplasty can help in reducing a deep sulcus.
  50. 50.    Distance of upper lip to maxillary incisor (Stm – 1) is a key factor in determining vertical position of maxilla. Normal – 2mm of incisor display. Patients with vertical maxillary excess tend to show a large amount of upper incisor with lips in repose.
  51. 51.     Vertical maxillary deficiency – No incisor display with lips relaxed, edentulous look. Orthodontically extruding maxillary teeth or surgically positioning the maxilla inferiorly – preferable treatment in patients with short face. INTERLABIAL GAP – Approx. 3mm . Patients with maxillary excess have large interlabial gaps & lip incompetency.
  52. 52.   Raising maxilla – shortens facial height, allow patient to close lips without muscle strain. Patient with maxillary deficiency – no interlabial gap, have lip redundancy with a rolling out of upper & lower lips.
  53. 53.      Lower third of face (SnMe’) – divided into thirds. Length of upper lip (Snstm)is one third of total distance of sn-Me’. Stm-Me’ is about two thirds. Sn-stm/stm-Me’ is 1:2 When it becomes smaller than half vertical reduction genioplasty is considered.
  55. 55.  TOMAC an acronym for the author’s name is a surgical orthodontic treatment planning and prediction system designed to identify the best possible soft tissue profile by testing the effects of various orthodontic and surgical options.
  56. 56.   Line from glabella to subnasale – Upper facial contour plane. Line from subnasale to pogonion – Lower facial contour plane.
  57. 57.   The acute angle between these planes is the facial contour angle, which describes the degree of anteroposterior discrepancy of the total face. Normal value – according to Burstone is -11º ± 3º.
  58. 58.    The facial contour angle (FCA) is highly relevant to the analysis because it measures the convexity or concavity of the face Varies according to facial type, with leptoproscopic (long face) individuals tending to be more convex, around -16°, euryproscopic (short face) patients tending to have more acute angles : -7°.
  59. 59. Nasolabial angle   The nasolabial angle is formed by the intersection of a line originating at subnasale and tangent to the lower border of the nose with a line from labrale superius to subnasale Indicates the protrusion of the upper lip relative to the nose but can also be a reflection of the up or down tip of the nose.
  60. 60.    Male-100-110 degree Female-110-120 degree Tip of the nose is more elevated in the females than in males creating a more obtuse angle.
  61. 61. Nasofacial angle     Formed by the intersection of a tangent to the radix and the tip of the nose with a line drawn from glabella to pogonion. Describes the protrusion and slope of the nose relative to the total facial profile. Norms- 30-35 degree O’ Ryan et al 36-40 degree Powell et al
  62. 62. Lower lip chin throat angle      This angle is formed by a line drawn labrale inferius and tangent to pogonion intersecting with a tangent to the throat that passes through throat point and soft tissue menton. determine the position of the lower lip in relation to the chin. Norms-110 SD 8 DEGREE Prognathic mandibleacute Retrognathic mandibleobtuse
  63. 63. LINEAR MEASUREMENTS      Lip protrusion- Bustone’s B line is taken as reference. Drawn from subnasale to pogonion Upper lip-+3.5 sd 1.4 mm Should be used in conjunction with nasolabial angle Lower lip +2.2 mm sd 1.6 mm. Should be used in conjunction with lower lip chin throat angle
  64. 64.     Chin length Measured from constructed soft tissue menton to the intersection of tangents to the chin and the throat. Difficult to measure accurately, because it is subject to a number of variables amount of fat present, the posture of the head and the shape of the mandible and throat. Norms 38-42mm in females 40-45mm in males.
  65. 65.      Upper facial height— measured from eye point to subnasale makes up two fifth Middle facial height or upper lip lengthsubnasale to stomion and contributes one fifth. Female 20mm male 24 mm lower facial height or lower lip length-from stomion to constructed menton makes up final two fifth. Must be used in combination with interlabial gap and maxillary incisor exposure.
  66. 66. Interlabial gap   Is the space between the upper and lower lips when they are relaxed with the head in a normal upright position and the teeth in centric occlusion. Range 3mm >3mm excessive lower facial height
  67. 67. Maxillary incisor exposure      Should be 1-2mm in males and 3-5 mm in females when lips are relaxed. This is a critical measurement on which much of the vertical planning for surgicalorthodontic treatment depends Excessive exposure — increased maxillary height, Under exposure- maxillary height deficiency or teeth attrition Lip length increases with age as much as 1mm (Nanda, Ghosh) – taken into consideration while planning the correction of vertical maxillary excess.
  68. 68.       Measured in both relaxed and lip together postures. Measurement is made from the point of maximum thickness of the upper lip just below subnasale to the underlying bone usually about 3mm below A point. This measurement is compared with that from the incisor crown to the vermillion border. The norm is 14mm –upper measurement 15mm-lower resulting in 1mm of taper. Clinical significance lip taper appears to be more prevalent in older patients and must be allowed for when retracting proclined maxillary incisors. Lip taper
  69. 69. Prediction
  70. 70. Soft tissue changes from various surgical procedure  To predict the soft tissue profile it is vital to have an in depth knowledge of the soft tissue reactions caused by different surgical movements of the jaws.
  71. 71. Mandibular advancement •Soft tissue pogonion advances in an almost 1:1 (100%) ratio with hard tissue pogonion. •The inferior labial sulcus responds in a. 69:1 (70%) ratio with hard tissue B Point. •Labrale inferius advances in a .77;1 (75%) ratio with the lower incisor tip. Mandibular setback •Soft tissue pogonion advances in an almost 1:1 (100%) ratio with hard tissue pogonion. •The inferior labial sulcus responds in a .77:1 (75%) ratio with hard tissue B Point •Labrale inferius responds in a .79;1 (75%) ratio with distal movement of the lower incisor tip.
  72. 72.   The lower lip shortens slightly and becomes more protrusive by curling out and the labiomental fold becomes more accentuated. Only minor effects occur in the upper lip and the nasolabial angle.
  73. 73. Mandibular advancement The soft tissue chin advances in harmony with the underlying bony chin. The thickness of the lip also plays a role the thicker the lip the less it will advance and the thinner the lip the more it will respond. The lower lip advances less than the soft tissue chin because of its status before surgery, when it can be curled,everted and already forward. Mandibular setback The lower lip shortens slightly and becomes more protrusive by curling out and the labiomental fold becomes more accentuated. Only minor effects occur in the upper lip and the nasolabial angle.
  74. 74. genioplasty   In Enhancement as well as reduction genioplasties the soft tissue chin follows the bony contour in a 1:1 ratio. The chin advancement in particular has no influence on the lower lip at labrale inferius but the labial sulcus deepens. Therefore genioplasties should only be performed if they complement and balance lip position .
  75. 75. Maxillary advancement    The nose tip responds in a ratio of .26:1 (25% of the hard tissue movement) measured at maxillary incisor anterius. Subnasale advances in a .52:1 (50%) ratio with maxillary incisor anterius and in a .56:1 (55%) ratio with subspinale (A point). The superior labial sulcus moves horizontally in a ratio of. 69:1 (70%) with maxillary incisor anterius;in other words the middle of the upper lip becomes less concave as it flattens.
  76. 76. Maxillary advancement     Labrale superius responds in a .55:1 (55%) ratio with maxillary incisor anterius. Labrale superius and stomion superius move vertically in a .1:1 (10%) ratio with the maxillary advancement. Thin lips(<15mm) advance 2.8 times farther than thick lips. As a whole as the maxilla advances the nose tip advances slightly the alar bases widen marginally, subnasale advances ,the superior labial sulcus flattens and labrale superius advances.
  77. 77. Maxillary impaction    Undesirable nasal tip elevation due to superior repositioning. 1 mm of elevation for every 6mm of superior repositioning. The alar bases widen with maxillary impaction. And nasolabial angle decreases. The upper lip elevates superiorly with impacted maxilla by 40%. Will shorten more if the maxilla is advanced as well as impacted
  78. 78. autorotation  The soft tissue chin follows the autorotation of the mandible in an approx. 1:1 ratio. The lower lip becomes slightly recessive at labrale inferius and labiomental angle increases.
  79. 79. TOMAC VTO   TOMAC is a unique surgical-orthodontic treatment planning system. The essential underlying principle is that the soft-tissue profile is changed first, setting a goal toward which hard-tissue changes are adapted. The TOMAC VTO is constructed in three stages:
  80. 80. Test VTO Pre surgical VTO Surgical VTO
  81. 81. Test VTO  This is where the various orthodontic and surgical options are tested and the optimum combination is visualized. In the anteroposterior plane, the facial contour angle (FCA) is changed to the chosen ideal. The upper and lower jaws, or both, are traced in their new positions according to the softtissue reactions to surgical movements, and the teeth are then decompensated accordingly.
  82. 82.
  83. 83.   Line from glabella to subnasale – Upper facial contour plane. Line from subnasale to pogonion – Lower facial contour plane.
  84. 84. TEST VTO
  85. 85. Presurgical-Orthodontic VTO   This is constructed from the information in the test VTO. Any necessary incisor decompensations, molar adjustments, and soft-tissue changes become the orthodontic objectives prior to the surgical procedure.
  86. 86.
  87. 87. SURGICAL VTO   The surgical VTO is constructed over the presurgical VTO, with the surgical cuts diagramed on the tracings of the jaws. The simulated surgical movements are governed by the decompensated positions of the incisors. The soft-tissue profile is then drawn according to the expected soft-tissue/hard-tissue ratios of movement
  88. 88.
  89. 89.
  90. 90. VIDEO IMAGING  In the VTO of an orthognathic surgery case, the clinician classically has used acetate templates of the teeth and jaws to predict orthodontic and surgical movements to attain their esthetic and functional goals, and the final profile is determined by the reaction of the soft tissue to the hard tissue movements
  91. 91.   Cephalometric digitizing programs are useful in automating these predictions Video imaging technology allows the orthodontist to gather frontal and profile images and modify them to project overall esthetic treatment goals
  92. 92.
  93. 93.
  94. 94.
  95. 95.
  96. 96.
  97. 97.     The advantage that video cephalometric planning often offers is that (1) it allows facial visualization for better comprehension of the facial response to the dental and/or soft tissue manipulation involved in a particular treatment plan; 2) it allows quantification of the planned dental and/or osseous movements to reduce the guesswork as to the facial response to our orthodontic treatment plan; and (3) it allows the clinician to test various treatment plans before deciding on the final plan. This is the essence of the video imaging concept because it allows us, at least in adult or surgical cases, to determine beforehand the facial result of proposed treatment.
  98. 98. Computer prediction of hard tissue profiles in orthognathic surgery. Loh S, Yow M. 2002  The purpose of this retrospective study was to analyze the accuracy of computer predictions by CASSOS (Computer-Assisted Simulation System for Orthognathic Surgery) 2001 software (2000 SoftEnable, Technology). Forty adult patients who had undergone orthognathic surgery were evaluated. Pre- and postsurgical lateral cephalographs were scanned into the computer,. A customized cephalometric analysis consisting of 14 measurements was used in this study. Predicted and actual postsurgical hard tissue landmarks were compared.
  99. 99.    Results showed good correlation between repeated digitization for all measurements. There were no statistically significant differences in 10 of the 14 measurements. The differences that were statistically significant were in angular measurements for SNA angle, upper incisor to maxillary plane angle (U1-MxP), interincisal angle (U1L1), and upper incisor to anterior cranial base angle (U1SN). The greatest mean difference measured was the interincisal angle (U1-L1) which, although statistically significant, was clinically insignificant. This investigation showed that CASSOS 2001 software provides accurate hard tissue prediction for orthognathic surgical procedures.
  100. 100. The predictability of maxillary repositioning in LeFort I orthognathic surgery. Jacobson R, Sarver DM. (ajo 2002)   The purpose of this retrospective study was to evaluate the surgical accuracy of maxillary repositioning by comparing the objectives obtained from cephalometric prediction tracings with the actual skeletal changes achieved during maxillary and maxillomandibular procedures. The sample consisted of 46 patients from the files of 1 orthodontist. Presurgical and immediately postsurgical cephalometric radiographs were digitized, and the original surgical prediction was reproduced with Dentofacial Planner (Dentofacial Software, Toronto, Ontario, Canada) software.
  101. 101.    Vertical and horizontal measurements to several skeletal landmarks were used to assess the differences between the predicted maxillary position and the actual maxillary postsurgical position. Statistical differences were found for some measurements, particularly those related to the vertical placement of the posterior maxilla.. To assess the overall fit of individual predictions, authors calculated an average discrepancy for each patient; 80% of the actual results fell within 2 mm of the prediction, and 43% fell within 1 mm of the prediction
  102. 102. Predictability of soft tissue profile changes following bimaxillary surgery in skeletal class III Chinese patients. J Oral Maxillofac Surg. 2004.  The aim of this study was to evaluate the accuracy of soft tissue profile predictions generated by a recently developed computer program (Computer-Assisted Simulation System for Orthognathic Surgery [CASSOS] 2001, SoftEnable Technology, Ltd, Hong Kong) in Chinese skeletal Class III patients treated with bimaxillary surgery
  103. 103.    Comparison of the predicted and actual changes found that 16 of the 32 soft tissue measurements were significantly different ( P <.05). Most of the significant prediction errors were observed in the upper and lower lip region. The software tended to underestimate the vertical position of both the upper and lower lip and overestimate the horizontal position of the lower lip. However, the mean differences were relatively small, with the greatest mean difference being 2 mm in the vertical position of stomium inferius. The CASSOS 2001 program produced a clinically useful prediction of soft tissue profile changes following bimaxillary surgery in skeletal Class III Chinese patients.
  104. 104. conclusion   Surgical analysis offers the opportunity to identify treatment goals in the vertical and anteroposterior planes, allowing the clinician to be more confident in making the difficult decision of whether a case can be treated by orthodontics alone or requires orthognathic surgery. Our ability to predict the outcome of any orthognathic procedure relies on the surgeon's ability to accurately reproduce the desired skeletal movements and on our understanding of the soft tissue changes associated with those movements.
  105. 105.   In the future, computerized tracing and video imaging techniques in three dimensions may be faster and more efficient than conventional tracing methods. With soft-tissue responses to hard-tissue movements better understood than in the past, these and other influential factors could be incorporated into computerized technology, to provide extremely accurate treatment planning information.
  106. 106. REFERENCES:_ 1. 2. 3. 4. Burstone CJ, James RB, Legan H: Cephalometrics for orthognathic surgery.J Oral Surg 1979 (36);269-77. Legan H, Burstone CJ: Soft tissue cephalometric analysis for orthognathic surgery.J Oral Surg 1980 (38);744-751. Burstone CJ: Integumental Profile. AJO 1958 (44); 1-25. Di Paolo RJ, Philip C, Maganzini A: The quadrilateral analysis: An individualized skeletal assessment. AJO 1983 (83),1;19-32.
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