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Cephalometrics for orthognathic surgery1 /certified fixed orthodontic courses by Indian dental academy


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Cephalometrics for orthognathic surgery1 /certified fixed orthodontic courses by Indian dental academy

  1. 1. Cephalometrics for Orthognathic Surgery INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2.  Taken from the AJO-DO 1984 Dec (470-482): The quadrilateral analysis - Di Paolo, Philip, Maganzini, and Hirce  --------------------------------  The quadrilateral analysis: A differential diagnosis for surgical
  3. 3.  Taken from the AJO-DO 1983 Dec (508- 520): Projecting the soft-tissue outcome of surgical and orthodontic manipulation of the maxillofacial skeleton - Kinnebrew, Hoffman,  --------------------------------  Projecting the soft-tissue outcome of surgical and orthodontic manipulation of the maxillofacial skeleton
  4. 4.  Taken from the AJO-DO 1980 Dec (657-669): Cephalometric diagnosis and surgical-orthodontic correction of apertognathia - Frost  --------------------------------  Cephalometric diagnosis and surgical-orthodontic correction of apertognathia
  5. 5. Ceph needs innovation not renovation  Ao- 97 vol67 no.5
  6. 6. Factors Influencing the Predictability of Soft Tissue Profile Changes Following Mandibular Setback Surgery  (Angle Orthod 2001;71:216–227.)
  7. 7. 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).
  8. 8. HISTORY  Earlier Cephalometric analysis highlighting dentofacial patterns and dysplasias are  Wylie’s analysis (1947)  Down’s analysis (1956)  Steiner’s analysis However,
  9. 9. Analysis to help diagnose and plan for orthognathic surgeries came in late seventies and early eighties.
  10. 10. More recent venture into Cephalometric treatment planning and predictions has been VIDEOIMAGING
  11. 11. COGS – Cephalometrics for Orthognathic Surgery  Developed at university of Connecticut  Based on a system from Indiana University and further developed by additions at Connecticut
  12. 12. 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
  13. 13.  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
  14. 14. 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
  15. 15. 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
  16. 16. 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
  17. 17. 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
  18. 18. TVL
  19. 19. NHP
  20. 20. The Arnett’s way
  21. 21. Arnett & Bergman.... (1993- Am. J. orthod. & Dentof Orthop. )  Contributed 19 keys to facial esthetics  Used for comprehensive treatment planning. Backed by Soft Tissue Cephalometric Analysis (1999 - Am. J. Orthod. & Dentof. Orthop.)
  22. 22. “We only treat what we are educated to see. The more we see, the better the treatment we render our patients” -Arnett....
  23. 23. 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.”
  24. 24. Format for examination of face  Natural head posture,  Centric relation (uppermost condyle position),  Relaxed lip posture  True Vertical Line ( TVL )
  25. 25. 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.
  26. 26. Why the Natural head position?
  27. 27. 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.
  28. 28. Why Centric Relation??
  29. 29. Why relaxed lip position??
  30. 30.  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.
  31. 31. 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
  32. 32. What is TVL and Why TVL??
  33. 33. 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
  34. 34. 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)
  35. 35. Cephalometric Prediction Tracing for Mandibular Advancements. Why do prediction tracings for mandibular surgery?
  36. 36. 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),
  37. 37. 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
  38. 38. The Cephalometric x-ray from which the prediction tracing is to be done should be taken with the patient's lips in REPOSE
  39. 39. 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
  40. 40.  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
  41. 41. 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.
  42. 42.  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 originally
  43. 43. 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.
  44. 44. 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.
  45. 45. 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.
  46. 46.  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) .
  47. 47. Step 5 - Tracing the New Lip Contours.  Once the teeth are placed, the lip contours are traced to correspond to the new incisor positions.
  48. 48.  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
  49. 49. Cephalometric Prediction for Maxillary Superior Repositioning.  Why do prediction tracings for maxillary surgery cases?
  50. 50. 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.
  51. 51.  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,
  52. 52.  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.
  53. 53. 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
  54. 54. 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.
  55. 55.  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.
  56. 56. 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.
  57. 57.  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.
  58. 58. These slight variations may be disregarded, unless the anterior- posterior change is more than 6 millimeters.
  59. 59. 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
  60. 60. 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.
  61. 61.  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.
  62. 62. 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.
  63. 63. Step 4 - Genioplasty Determination  Cephalometric criteria which may be used to help determine optimum anteroposterior soft-tissue chin position.
  64. 64.  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.
  65. 65. 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.]
  66. 66.  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.
  67. 67. Step 5 - Placement of Teeth In Ideal Positions.  This step is carried out exactly as described by Bench, et al.2 After placing the teeth in their ideal position we are now ready to trace the new profile.
  68. 68. Thank you For more details please visit