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Template analysis /certified fixed orthodontic courses by Indian dental academy


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Template analysis /certified fixed orthodontic courses by Indian dental academy

  1. 1. Template Analysis INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Contents • • • • • • • Introduction History Mooree’s Mesh diagram Mesh coordinate system study Template Analysis Proportionate Analysis Conclusion
  3. 3. Introduction • The cephalometric technique has been used in the field of orthodontics for over 60 years and has become an important diagnostic aid in the formulation of diagnosis and treatment plan as of today. • Cephalometric standards have been useful guidelines but many of their limitations were unrecognized and ignored.
  4. 4. • Many a times clinicians take statistical mean as the norm and tend to treat the patients according to them which in all cases may not be the ideal treatment. • Hence the orthodontic profession has been criticized as a millimeter profession. To overcome this a template analysis was developed.
  5. 5. • A cephalometric template is a set of oriented rulers that permit size and position to be measured in terms of years of development.
  6. 6. History • The grids superimposed on the face of a horse rider and the edentulous man by Leonardo da Vinci (1490) demonstrate the artist's keen appreciation of proportion. • Focus on the proportionate representation of man's face dates back to ancient records from Egypt, and India.
  7. 7. • As early as 1917, D'Arcy Wentworth Thompson studied growth and form of primate skulls comparing them to a human skull by using Cartesian coordinate system. • Lucien de Coster of Belgium, one of the pioneers of contemporary cephalometric methods, led transformation of a mesh coordinate system as early as 1939 for analysis of radiographs in norma lateralis of orthodontic patients.
  8. 8. • But the earliest grid analysis that was developed in a standardized and coordinated manner to assist in a clinical situation giving a clearer perspective for assessing the treatment objectives was originally developed by Moores in 1953. Later more norms were added to this mesh in 1976.
  9. 9. Mooree’s Mesh Diagram • Standardized lateral head radiographs of 46 men and 47 women from the greater Boston area, representing a broad range of normal occlusal variation, were used to construct male and female norms for the mesh diagram. These radiographs were obtained as part of the Longitudinal Studies of Child Health and Development by the Department of Maternal and Child Health, School of Public Health, Harvard University.
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  12. 12. • The Mooree’s mesh can be used to compare growth changes in longitudinal studies where proportions can be visualized rather than the amount of growth. It also helps in circumventing the great variation in facial dimension.
  13. 13. Mesh Coordinate System Study
  14. 14. • Data from longitudinal studies of twins conducted at the Forsyth Dental Center was used. All head radiographs at the Forsyth Dental Center were taken in natural head position. • Extracranial vertical could be used as reference line for cephalometric analysis.
  15. 15. • When serial records were available for an individual, one radiograph was used to standardize the natural head position on all other serial records of that individual, by superimposing the tracings on the cranial base area. • Skeletal landmarks used were based on the standard and classic anthropometric definitions of Martin-Saller.
  16. 16. Construction of the Mesh Diagram • Upper face height, and the length of the anterior skull base (NS), determine the size of the core rectangle within the mesh. • The construction of the grid's core rectangle involves drawing a vertical through nasion, parallel to the extracranial reference line and two horizontal lines perpendicular to this vertical, one at nasion and the second through the anterior nasal spine (ANS). The fourth line is drawn parallel to the vertical at a distance from nasion equal to (NS).
  17. 17. • The sides of the core rectangle are divided into equal parts to provide the scale interval for all the horizontal and vertical grid lines needed to construct the mesh diagram. • One vertical line is added at the front and at the back of the core grid rectangle. One horizontal line is added above the core grid rectangle and three under it. The face is thereby inscribed in a rectilinear coordinate system composed of 24 small rectangles
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  20. 20. • Preference has been given to the female norm, because the vertical through nasion intersects point A and the tip of the mandibular incisor. The anterior and posterior nasal spines are both located on the same horizontal, and a horizontal also intersects both the tip of the mandibular incisor and the anterior aspect of the line representing the functional occlusal plane.
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  23. 23. • Individual variation in the position of facial landmarks and teeth implied that the facial configurations of the subjects studied differed markedly in the degree of prognathism and in facial shape. The contour ellipses illustrating these individual differences at 50% confidence limits showed various shapes.
  24. 24. • The amount and direction of this variation in the location of a given landmark were reflected in the lengths of the major and minor axes of the corresponding ellipses. A very narrow ellipse indicated that most of the variation in the location of the landmark was concentrated along the major axis of he ellipse.
  25. 25. • No variance occurred at nasion because his point served as the origin of the coordinate system. Likewise, no variance occurred for ANS along its Y coordinate because the projection of ANS on the vertical through nasion served to scale the vertical coordinates of the grid. The horizontal coordinates were scaled on the anterior skull base depth (nasion-sella).
  26. 26. • Therefore, the variations in the position of sella turcica reflected individual differences in its cephalo-caudal (vertical) position relative to nasion, ie, the biologic variation in the inclination of the anterior skull base. The small component of variance along the X axis for point sella was contributed by individuals with pronounced caudal (downward) inclination of the anterior skull base.
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  28. 28. • To determine the need for separate age norms of children at various ages, a mesh diagram analysis was undertaken on the purely longitudinal sample of male and female twin pairs defined in the materials section.
  29. 29. • Although the size of the mesh rectangles at 8 and 16 years varied, the average proportionate location of the anatomic landmarks in the mesh coordinate system at 8 years of age, when plotted in the mesh coordinate system of the same individuals at 16 years, showed that the location of landmarks at both ages was remarkably close for all landmarks in the upper face and for the soft tissue profile outline.
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  31. 31. Procedure for Mesh Distortion • The vertical and horizontal location of landmarks in the mesh diagram are compared to the location of corresponding landmarks in the norm. The mesh coordinates are subsequently distorted to display differences in the proportionate location of each landmark in the individual's mesh. This objective is accomplished in two steps:
  32. 32. – By locating the median proportionate position of each landmark in its respective grid rectangle of the patient's mesh diagram, just as in the norm. For example, the mean location of gonion within its small grid rectangle is horizontally at 14% from the anterior vertical line and vertically at 27% from the upper horizontal line. The deviation of the patient's gonion from its median location is represented by an arrow that depicts the displacement factor.
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  34. 34. – Distorting the grid lines of the specific small mesh rectangle to reflect the deviation of each landmark from its normal proportional location. The sides of some rectangles will be elongated while others will be shortened, indicating the sites of facial disproportion or disharmony. The amount of grid transformation is equal to the distance between the actual location of the landmark and its normal proportional location within its mesh rectangle.
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  36. 36. • When a mesh rectangle contains two landmarks, the procedure becomes more complex and consequently two sets of normalizing factors pertain. After the location of all landmarks has been evaluated, distortions are drawn through the points marked on the tracing for various landmarks.
  37. 37. • These distortions are smoothed and thereby constitute trend lines revealing the differences in the individual's facial pattern with respect to the norm. The grid lines are not changed when all landmarks on the tracing and the norm are in the same proportionate position within their respective mesh rectangles.
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  39. 39. • To interpret the mesh diagram of a patient, the reader should realize that sagittal dimensions are proportional to the length of the anterior skull base (nasion-sella turcica). Vertical dimensions are proportional to upper face height (nasion to the projection of the anterior nasal spine on the vertical through nasion).
  40. 40. • When the mesh is drawn on the tracing of the lateral cephalogram of an individual patient, it is important to compare first the size of the individual's small individual rectangles with the size of the small rectangles of the norm. These differences express the shape of the individual patient's face.
  41. 41. • If the height is smaller the face is short in comparison to its depth. If the height is greater, the face is longer. • If the length is greater the face is deep. If the length is shorter, the face is shallow. • If both dimensions of the small rectangles are larger or smaller than those of the norm, but maintain their ratio as in the norm, the individual's face is simply bigger or smaller than the norm face without any proportional difference.
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  48. 48. Template Analysis • It was intended initially to use clear plastic templates inscribed with standardized facial outlines. • Templates – Numeric standards for the sex specific templates were charted out based on the data published by Riolo et al. from the University of Michigan Elementary and Secondary School Growth Study(1974).
  49. 49. – Non-standard enlargement of 13% and so these templates were adjusted to the 6% to 7% magnification which was comparable to the Broadbent-Bolton cephalostat. – Admixture of Class I and Class II malocclusion. – These norms were similar to the Bolton standards (Broadbent et al., 1975) except that they were more retrognathic. They were considered normative rather than ideal.
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  51. 51. Analysis • Each template is a compact set of oriented rulers graduated in years(6 to 16 years). • So a single template can be used for the analysis. • There are no millimeter measurements or degrees. • It becomes easy to rapidly duplicate the essence of any type of analysis.
  52. 52. Cranial base Superimposition • Any localized deviation from the apparent baseline age can be explained by a detailed regional superimposition. • So any kind of comparison must be done with some kind of superimposition. • Commonly used reference planes are SN and FH plane. – FH greater variation – Other planes that may be used Ba-N, PMV, ANSPNS
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  54. 54. • Measurements and methods of superimposition are chosen to evaluate the general relationship of the various landmarks to the age scales on the template. • Point to point matching is not sought but an overall balance is checked for. • Once this is evaluated the nature of the faulty unit can be assessed by regional superimposition
  55. 55. Regional Superimposition • To determine relative size (measured in years) of any given craniofacial dimension, the template is placed over the cephalogram and the pairs of points describing the measurement to be taken is compared with the template scales at symmetric ages until a match is achieved.
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  57. 57. • Some points to be compared will be registratio points which in the event will not require age matching.
  58. 58. Suggested Cephalometric Measurements • Cranial Base length Anterior Posterior Total Register on S, read age at N Register at S and read age at Ba Ba to N at symmetric ages
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  60. 60. • Facial height Upper anterior ANS to N /SN/FH Upper posterior PNS to S/SN/FH Lower anterior ANS to Go Anterior N to Gn Posterior S to Go
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  63. 63. • Maxillary Size Length Effective length PNS to ANS or Point A Ar to Point A*
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  65. 65. • Mandibular size Ramus height Ar to Go Body length Go to Pog/Gn/Point B Overall Ar to Go/Pog/Point B Effective length Ar to Gn
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  67. 67. • Dental position Maxillary dentition Orient the template on palatal plane and register at Point A, and read the molar position at the upper contact point dots and incisor position at 1/1 Mandibular dentition Orient the template on mandibular plane (Go-Gn) and register at Point B, and estimate the molar position by interpolation at the lower terminal points M and incisor position at 1/1
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  69. 69. • Dental extrusion Maxillary Mandibular Palatal plane registered at Point A to Down’s occlusal plane (DOP), M or 1/1 Mandibular plane (GoGn) registered at Point B to DOP or 1/1
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  71. 71. • The given set of values must be treated as examples. • Many of the dimensions an orthodontist can think of can be easily visualized using these templates. • Angular measurements can be visualized as a qualitative or a semi-quantitative measure rather than a quantitative measure. • Experience will prove that many popular analyses can be easily duplicated.
  72. 72. Proportionate Template • The proportionate template is designed for use on adults and is used mainly in treatment planning associated with orthognathic surgery. • Angular measurements rather than linear measurements are used when comparing individuals to “normal” and individuals of different sizes. • Linear measurements are mainly used when the distances 'measured are minimal and can be conveniently measured in millimeters
  73. 73. • A practical and convenient method of identifying dental and skeletal disharmonies is direct visual comparison.
  74. 74. Philosophy of the Template • The proportionate template is based on the principle of the visual comparison of lateral cephalometric tracings with average normal tracings. • It may be argued that a single template cannot be used for all individuals because of variations in body height. • But since body (or craniofacial) proportions of all individuals should be similar regardless of height, only templates of different sizes would be needed for comparison.
  75. 75. • To compare lateral head film tracings of persons with craniofacial skeletal dysplasia, a template having average skeletal proportions was developed from the data of Broadbent and coworkers. These data were based on the recordings of 5,000 individuals.
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  77. 77. • To accommodate variations in skull size, four templates were designed. The average template was developed by averaging geometrically the dimensions of the sample. The large template was intended for larger than average persons, and the small template for persons with smaller than average craniums and jaws. In addition, an extra-large template was designed for much larger than average individuals.
  78. 78. • There were no separate templates made for men and women as the spatial arrangement of the skeletal components and their relation did alter much. • Difference: – Larger frontal sinuses, supraorbital ridges and noses – Prominent chin
  79. 79. Cephalometric Landmarks and Planes
  80. 80. Method of Application • Select the appropriate template • Method 1 – The mid S-J point of the template is superimposed on that of the tracing, and the template is adjusted to the point where the Ba-N lines on the template and the tracing are parallel to each other.
  81. 81. • Method 2 – Points basion and nasion in the correctly selected template will approximately overlie the same points on the tracings. When superimposing Ba-N, both S-J lines will be parallel to each other. The template is then raised or lowered, keeping the Ba-N lines parallel until both of the mid S-J points are equidistant from the Ba-N line.
  82. 82. • Method 3 – Any other plane or points for reference must be used and adjusted and moved around to identify the offending agent. • Interpretation – – – – – – The relative spatial position of maxilla and mandible Length of maxilla. Length of mandible. Vertical dimensions Incisor inclination. Cant of mandibular plane.
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  87. 87. Summary • The expanding scope of temporary orthodontic treatment would seem to demand meaningful diagnostic procedures. Template analysis provides a simple and flexible alternative to the conventional methods. • It demands the active participation of the clinician. It forms more of a “decision tree” when compared to the conventional numerical analyses.
  88. 88. Thank you For more details please visit