Growth prediction1 /certified fixed orthodontic courses by Indian dental academy


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Growth prediction1 /certified fixed orthodontic courses by Indian dental academy

  1. 1. GROWTH PREDICTIONS INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2.  Growth and Development is a remarkable tale of an orderly sequence by which each human being blossoms out from a minute cell to an adult man
  3. 3.  · · · Growth is defined as : Multiplication of living substance (J.S. Huxley) increase n size, proportion and progressive complexity (Krogman) an increase in size (Todd)
  4. 4.  Growth has some characteristics like :  Pattern  Variability  Timing
  5. 5.     Why is understanding growth so important? Growing Non-Growing Brodie in 1938 said “There seems to be a definite correlation between success of treatment and growth. Apparently growth and development accounts for a considerable part of change which takes place during orthodontic treatment”
  6. 6.    Correction of dentofacial malocclusions would be helped immeasurably if he could predict with a degree of certainty the adult features of his patient If the dentist could forecast the child’s adult appearance with or without therapeutic intervention, decisions could be made about the timing, type, and length of treatment In borderline cases, decisions on whether to treat at all could be better weighed
  7. 7.  For growth prediction to be feasible at all, craniofacial growth must be orderly
  8. 8.  What is Fibonacci series ? 0+ 1 + + = 1 + = 2 = 3 5 8 13 21
  9. 9.   It would appear that the principle of the golden section and Fibonacci numbers are basic to this orderly arrangement and growth of the human face Mandible grows on the logarithmic spiral which has a basis the golden triangle, in turn, related to the golden section which is related to the Fibonacci series
  10. 10.   According to Kendall and Buckland “ The process of forecasting the magnitude of statistical variations, at some future point of time” “Specifying the amount and direction of future growth in the context of a base line or reference point”
  11. 11.      Is a change in the vertical or horizontal relationship of the upper to the lower jaw indicated? Should the lower incisor be repositioned both horizontally and vertically? What movement of the upper incisor is required? Should anchorage be prepared or preserved in the lower arch? Is movement or stabilization required for the upper molars?
  12. 12.    Will the tooth movement bring about a desired esthetic result which will still be acceptable at maturity? Will post-treatment growth affect retention? Will there be space for the third molars given a specific treatment?
  13. 13.  The principal proponents of growth prediction Ricketts and Holdaway have suggested that the major value of the technique is the compilation of all the treatment factors (mechanics, growth, skeletal and soft tissue) together on paper to see how they inter-relate
  14. 14.        According to Hirschfield and Moyers : Future size of a part Relationship of parts Timing of growth events Vectors of growth Velocity of growth The effects of orthodontic therapy on any of the above predicted parameters
  15. 15.   Future size of a part The prediction of future size, as Burstone has pointed out, is primarily a problem of predicting future increments which are to be added to a size that is already known Relationship of parts perhaps the most important prediction for the clinician is the future relationship of parts, i.e. the future facial pattern. Johnson found measures of relationship and proportion to be of greater predictive significance than the linear size of anatomic parts.
  16. 16.   Timing of growth events Growth spurts Vectors of growth Most predictive methods thus far presume a continuation of the pattern first seen Therefore, the presumption is made that the vectors of growth present at the time of prediction will remain
  17. 17.  Velocity of growth It would be of use to know the future expected rate of growth Prediction of velocity is most important during the pubescent spurt
  18. 18.  The effects of orthodontic therapy on any of the above predicted parameters Our knowledge of prediction might best proceed by learning to predict untreated growing faces The clinician must always wonder what effects his therapy have on the predicted and actual growth of one specific face
  19. 19.     Theoretical Regression Experiential Time series
  20. 20.       Collection of series of relevant, random data Mathematical construction of a theoretical model Theoretical development of a hypothesis from the model Proving the hypothesis practically The model began theoretically and was proved practically Implication in orthodontics :  Theoretical models of craniofacial growth have not yet been defined mathematically in terms precise enough to permit the application of the method to prediction
  21. 21.  These methods serve to calculate a value for one variable, called dependent, on the basis of its initial state and the degree of its correlations with one or more independent variables. E.g. Johnston grid
  22. 22.   Ultimate accuracy of cephalometric prediction may be limited to some extent by intrinsic errors within the cephalometric method itself Contemporary methods seem inadequate to provide an efficient estimate of individual changes attributable only to growth
  23. 23.   The assumption within the method that the coefficients remain constant over thw whole time period. An individual whose growth is to be predicted in clinical practice may not even be a member of the population upon which the regression equation was based
  24. 24.  They are based on the clinical experience of a single investigator who attempts to quantify his observations of practice in such a way that they can be used by others. E.g. Ricketts
  25. 25.  Theoretical basis is shaky on two counts: The assumption must be made that the individual being predicted will behave as the mean of a population of which he is a not a member  The morphology of the mandible and other parts is a clue to the future growth of the face 
  26. 26.    Accuracy, efficiency and individuality for clinical application “Random walk” type or process These methods consists of two types: time-series analysis smoothing methods
  27. 27.  1. 2. 3. 4. Time-series is considered to be composed of four parts : Trend or long-term movement Oscillations about a trend Cyclic or periodic events Random (unsystematic) components
  28. 28.    Exponential smoothing is a way of estimating the current value of a parameter by means of some sort of average of past values of that parameter Prediction is then based on coefficients derived from the smoothed parameters. Since the coefficients will change in accord with changes in parameter, the predicted coefficients will change in accord with changes in the parameter
  29. 29.       Based on average values individualized prediction manual computerized short range long range
  30. 30. Most predictions of growth are based on some mathematical model of the growth process, two kinds of which can be distinguished: (1) the transformed coordinate method of D’Arcy Thompson (2) Equations producing curves descriptive of processes
  31. 31.     The numeric standards from which the present specific templates were drafted are derived from 3 major studies reports. They are: Michigan Growth study Bolton-Brush Growth study Burlington Growth study
  32. 32.  Existing data sets are too small to allow subdivision in different categories : Bolton’s data is age specific only  michigan has subdivision on the basis of sex  Burlington has subdivision on the basis of facial types 
  33. 33.    All data sets are derived from whites of Northern European descent sample mostly consists of normal children. The patient to be predicted for growth may not have the average amount or direction of growth
  34. 34.   Johnston forecast Grid template methods  schematic template  anatomically complete template  Ricketts prediction  short range  long range  Holdaway soft tissue VTO
  35. 35.   Based on the addition of mean increments of growth by direct superimposition on a printed grid The land marks used are : Sella Nasion Tip of nose Point M Point A Point B Posterior Nasal Spine
  36. 36.    Tracing of landmarks is superimposed along S-N and registered at S The points are then advanced downward and forward one unit per year Vectors for A, B and M were inferred from descriptive templates prepared by Hries and associates and the behavior of N and P was patterned after reports by Ricketts
  37. 37.   When an average cephalometric tracing is made of a group by connecting the average values of each landmark, the composite tracing thus prepared is called a Template There are 2 types of templates : Schematic template  Anatomically complete template 
  38. 38.     Schematic template The schematic templates show the changing position of selected landmarks with age on a single template Michigan and Burlington growth studies have developed this type of templates Michigan templates have sub-divisions on the basis of sex Burlington templates have subdivision on the basis of facial pattern
  39. 39.     anatomically complete template Based on Bolton growth study data. Age-specific A reference template is selected so that the lengths of anterior cranial base are same The growth is predicted by advancing the template ages from the reference templates
  40. 40.    The term VTO is used in two different contexts : VTO as a diagnostic test for functional appliances Growth prediction VTO Holdaway’s VTO  Ricketts’ VTO 
  41. 41.
  42. 42.
  43. 43.  Soft-tissue facial angle
  44. 44.  Nose prominence
  45. 45.  Superior sulcus depth measured to a perpendicular to Frankfort and tangent to the vermilion border to the upper lip
  46. 46.  Soft-tissue subnasale to H line
  47. 47.  Skeletal profile convexity
  48. 48.  Basic upper-lip thickness
  49. 49.  Upper lip strain measurement
  50. 50.  H angle
  51. 51.  Lower lip to H line, Inferior sulcus to H line, soft tissue chin thickness
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  66. 66.  In the case of Steiner Analysis, it can be demonstrated with geometric principles that the sum of the following 4 angles is equal to 180 degrees ANB  Mandibular incisor to the NB plane  Maxillary incisor to the NA plane  Interincisal angle 
  67. 67.
  68. 68.   The first treatment in obtaining the visual treatment objective involves a clinical judgment - determination of the desired angulation of the mandibular incisor to the NB plane In actual planning of treatment, the desired angulation of the lower incisor to the NB plane must be left to the judgment of the individual clinician
  69. 69.   Downs - Interincisal angle 131 degrees Reidel - suggested that the relationship between maxillary and mandibular incisors is best determined by functional and esthetic considerations
  70. 70.   From a functional standpoint the relationship of maxillary lingual crown contour to mandibular incisal edge position is more important than the interincisal angle Considering esthetics, he suggested that the upper and lower incisor facial crown angle should approach 0 degrees or a straight line
  71. 71.
  72. 72.
  73. 73.   Because of variations in crown axis/root axis angulation ass seen in dilaceration, an optimal facial crown angle of 0 degrees does not always correlate to any single “ideal” interincisal angle The interincisal angle most appropriate to a particular case must be determined by drawing a cephalometric incisor “setup” with a facial crown angle of 0 degrees
  74. 74.
  75. 75.      Determine the angulation of lower incisor to NB plane Set upper and lower incisors at a facial crown angle of 0 degrees Measure the resulting interincisal angle Estimate the expected ANB angle following treatment Calculate the required upper incisor to NA angulation
  76. 76.     Growth Estimation - 1957 Cephalometric Analysis and Synthesis-1961 Short-range VTO Long-range VTO - 1972
  77. 77.  The Static Synthesis Estimation is made almost entirely for the movement of the teeth and changes in lips  the lower incisor is positioned with one SD of the normal to the APo  the upper incisor is then adjusted to it with normal overbite and overjet  the necessary anchorage can be envisioned by movement of the posterior teeth 
  78. 78.  The Dynamic Synthesis Growth of the chin - foremost consideration  Cranial areas are employed for basal refernces 
  79. 79.  Cranial Behavior Maxilla seemed to grow forward at almost an identical rate with nasion  SNA angle changed very little  1 mm per year of growth on the SN plane can be expected and Sella-Basion is usually about twothirds of that amount 
  80. 80.  Mandibular Behavior estimating the change in the chin by the direction of the Y axis or growth axis of the face  in the ave. Class II case the Y axis tended to open about one degree during a two year period during treatment  In Class III cases, the Y axis closed one degree or more during orthodontic treatment 
  81. 81.   So the final consideration for estimation of change in the direction of the Y axis revolves around the original facial pattern the amount of growth of the mandible knowledge of average case is the starting point  average yearly expectancy is about 2.5 to 3 mm of growth on the Y axis 
  82. 82.  Change the Y axis and lengthen it for estimated growth, draw the symphysis and establish the mandibular plane backward from the symphysis consistent with the tilt of the mandible
  83. 83.  Maxilla Behavior Behavior of Point A from a vertical and horizontal standpoint is estimated  Point A and the anterior nasal spine usually drop vertically about one-third the total facial height increase during treatment  about two-thirds height increase is measured in the denture area or lower face 
  84. 84.  Cephalometric Tooth Set Up  Lower incisor is related to the A-Pog line depending on the environmental forces operating on the denture and the age of the patient
  85. 85.   Analysis - “where he was” Synthesis - “where to go”
  86. 86.  “The radius of this circle is determined by using the distance from mental protuberance (Pm) to a point at the forking of the stress lines at the terminus of the oblique ridge on the medial side of the ramus (point Eva)”
  87. 87.  By plotting a line through the long axis of the condyle and neck and extending it to the lower mandible, the bending of the mandibular form during growth had been studied
  88. 88.    Bjork’s implant studies had revealed that the lower border of the mandible was resorbing and that the mandibular plane was not acceptable as a reference base for growth analysis The next move toward improving the method was to identify a “central core” cephalometrically External form of mandible
  89. 89.  First, a point (Xi) in the center of the ramus was located
  90. 90.   Occlusal plane holds a strong tendency to pass through Xi point Xi also represents the entrance of the neurotrophic bundle into the mandible
  91. 91.  Second, a point at the superior aspect of the symphysis was selected as suprapogonion (Pm) Stress-center acc. to Ricketts  Site of a reversal line acc. to Enlow 
  92. 92.    Third, point Dc as located Corpus axis Condyle axis
  93. 93. Bending occurred in an orderly manner and therefore the greater the magnitude of growth, the greater the bending Mandible was found to bend about half degree each year
  94. 94.
  95. 95.
  96. 96.
  97. 97.    Constructed an experimental arc bisecting the two previous arcs The use of this arc still bent the mandible a fraction too much Stress lines
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  101. 101. Apposition of the lower border of the symphysis for males occurs at about 1 mm each 8 years From the point Mu the mandible is grown on the arc at the sigmoid notch about 2.5 mm each year
  102. 102. K factor Coronoid is extended upward and outward at a rate of 0.8 mm per year Condyle in this average individual is extended upward and backward 0.2 mm per year
  103. 103. Drift of the mandible occurs almost precisely at a pace of 50% of the total mandibular growth
  104. 104.   Oblique ridge of the mandible shows apposition of about 0.4 mm each year This is a critical point because it helps to determine the space available for the developing mandibular third molar
  105. 105.
  106. 106. Thank you Leader in continuing dental education