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Validity of cephalometrics /certified fixed orthodontic courses by Indian dental academy

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Validity of cephalometrics /certified fixed orthodontic courses by Indian dental academy

  1. 1. VALIDITY OF CEPHALOMETRICS www.indiandentalacademy.com
  2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  4. 4. INTRODUCTION Radiographic cephalometry is a two dimensional representation of three dimensional object. Conventional roentographic cephalometry have not been useful for accurate assessment of craniofacial anomalies and facial asymmetries. The validity of many cephalometric analysis have not been documented. Other limitations of radiographs www.indiandentalacademy.com
  5. 5. Classification of errors of lateral cephalometric radiographs.  Errors in cephalometric measurements a)Radiographic projection error Magnification Distortion b)Errors within measuring system c)Errors in landmark identification Quality of radiographic image Precision of landmark definition Reproducibility of landmark location The operator and registration procedure www.indiandentalacademy.com
  6. 6. Classification of errors of lateral cephalometric radiographs. 2)Errors in growth prediction and superimposition techniques 3)Limitations of cephalometric analysis Sagittal basal relationship Vertical basal relationship Dentoalveolar relationship www.indiandentalacademy.com
  7. 7. Radiographic projection errors  Magnification: It occurs because x ray beams are not parallel with all points on the object to be examined .  The use of long focus object and short object film distance have been recommended in order to minimize such projection errors (Franklin 1952)  Focus film distance > 280 cms doesn’t alter magnitude of projection error (Ahlquvist et al 1986)  Enlargement compensation for lateral ceph. Radiograph is 4.6 to 7.2 % & for frontal film 0.3 to 9.2 % at 60” anode to midsaggital plane distance (Bergersen O E 1980) Use of angular than linear measurement www.indiandentalacademy.com 
  8. 8.  Distortion: Misalignment of patient head and X-ray apparatus (Ahlquvist et al 1983 , 1986)  Different magnification between different planes  Bilateral landmarks – “dual image” on the radiograph  Mild asymmetry- difficult to differentiate between geometric distortion and true subject asymmetry (Cook 1980)  www.indiandentalacademy.com
  9. 9. Factors to Control Radiographic Projection Errors    Standardization of radiographic cephalometry stabilization of patient head Special research applications: stereo- head films and osseous implants (Rune et al 1977) www.indiandentalacademy.com
  10. 10. Errors within measuring system  Conventional v/s Digitized cephalometry      Dentofacial planner Quick ceph image Por dios Digigraph Rocky mountain orthodontics – JIFFY orthodontic evaluation www.indiandentalacademy.com
  11. 11. Errors in landmark identification  Many factors are involved    Quality of radiographic image Precision in landmark definition and reproducibility of land mark location Operator and registration procedures www.indiandentalacademy.com
  12. 12. Quality of radiographic image   It is expressed in terms of sharpness/ blurr , contrast & noise SHARPNESS   Related to blurr and contrast 3 types of unsharpness Geometric  Motion  Receptor   BLURR www.indiandentalacademy.com
  13. 13.  CONTRAST    Magnitude of optical density difference between structure and its surroundings Increased contrast: increases subjective perception but leads to loss of details owing to blackening of regions Deteremined by Tissue being examined  Receptor  Level of kV used  www.indiandentalacademy.com
  14. 14.  NOISE:     it refers to all factors that disturb signal in a radiograph Noise of pattern, structure or anatomy Receptor mottle or quantum noise In recent years the application of digital technology to conventional radiography has enhanced image sharpness , contrast and reduce noise. www.indiandentalacademy.com
  15. 15. Precision in landmark definition and reproducibility of land mark location    Geometrically constructed landmarks and landmarks identified as points of change between convexity and concavity often prove to be very unreliable Rad. Complexity of the region makes it difficult to locate landmarks Baumrind and Frantz pointed out: errors in landmark location is a function of 3 variables 1. 2. 3. Absolute magnitude of error Relative magnitude or linear distance between the landmarks Direction from which the line connecting the landmarks intercept their envelope of errors. www.indiandentalacademy.com
  16. 16.  Errors in landmark identification can be reduced by: Replication of measurements  Localization of landmarks is more exact 2nd time than at first judgement  Specific landmark location – radiologic registration can minimize error  www.indiandentalacademy.com
  17. 17. Operator and registration procedures   Experience and calibration TEST: Land mark identification reliability www.indiandentalacademy.com
  18. 18. Systemic errors depending on design of study     Inter observer variability Intra observer variability Bias due to subconcious expectation of the operator while assessing the outcome of scientific research- double blind expt. Design. Method to reduce error- calibration and periodical recalibration test to establish specific confidence www.indiandentalacademy.com
  19. 19. Errors in growth prediction   Various methods have been proposed most of which are based on mathematical models of growth process Prediction method used in industry and science Theoretical method Regression method Experimental method Time series method www.indiandentalacademy.com
  20. 20.  Growth prediction is difficult for number of reasons • • • • Wide range of marphological difference Varying rates and direction of growth Varying in timing of different area of active growth Lack of correlation b/w size of facial structure at an early age and ultimate adult size www.indiandentalacademy.com
  21. 21.  Rakosi (1982)-source of eror in growth prediction •Variable growth rate in regional growth sites •Growth pattern not being fully taken into account •The relationship of form and function www.indiandentalacademy.com
  22. 22. Limitations of growth predictions    These are derived from means of large samples,there is no reason to suggest that growth pattern under investigation behaves as a mean Past growth does not predict future growth There is no evidence to suggest that appareance of single part such as mandible is clue to future growth of face www.indiandentalacademy.com
  23. 23. Can jaw rotation be predicted?   Skeiller and Bjork-growth rotation of mandible based on morphological criteria using implants Baumrind et al-experiment to determine ability of clinician in distinguishing forward rotation from backward rotation based on head film information 232 treated classII patients-14 groups Each group contain 2 or 3 forward/backward rotation 5 senior board certified orthodontists Result showed none of experts performed at a that was Statistically better than chance. www.indiandentalacademy.com
  24. 24. Errors in superimposition    Reference points are used for superimposition(cranial base,maxilla, mandible) Various technique for superimposition(best fit technique,tracing,punching pin holes,blink method/substraction technique)none of these methods are more accurate than others(Houston and Lee 1985) Study by Ghafari et al showed statistical differences in interpretation of facial changes by different superimposition methods www.indiandentalacademy.com
  25. 25. Reliability of cephalometric analysis  Fundamental to orthodontics is the need to determine the relationship of the various skeletal components, particularly those of the jaws to each other and to the rest of the cranium in the cranio facial complex. The interpretation of the measurements continues to be the subject of much debate. www.indiandentalacademy.com
  26. 26.  Wylie et al compared five analyses in ten individuals who underwent various surgical corrections.Pre treatment cephalometric radiographs of the ten patients were selected to illustrate different dentofacial deformities , each of which was corrected with a different surgical procedure. The pretreatment cephalometric radiographs were blindly The pretreatment cephalometric radiographs assessed by one investigator who used the criteria for each of five popular analyses. www.indiandentalacademy.com
  27. 27. Limitations of horizontal reference planes used in various analysis    FH plane SN plane Functional occlusal plane www.indiandentalacademy.com
  28. 28. Downs – timely warning. It was he who had shown that discrepancies between cephalometric facial typing and photographic facial typing disappear when the Frankfort plane is not horizontal but tilted up or down. www.indiandentalacademy.com
  29. 29. www.indiandentalacademy.com
  30. 30. SN plane www.indiandentalacademy.com
  31. 31. Bjorks studies of facial prognathism also illustrates the unreliability of intra cranial reference lines on cephalograms. Two adult Bantu men were selected to represent maximum and minimum facial prognathism relative to the S-N plane.Bjork illustrates the greatest variation in the inclination of the cranial base rather than the greatest differences in prognathism. www.indiandentalacademy.com
  32. 32. Functional occlusal plane www.indiandentalacademy.com
  33. 33. Natural head position Natural head position is a standardized and reproducible orientation of the head in space when one is focusing at a distant point at eye level. German anthropological society in 1884 – Frankfort Agreement. The plane which passes through the left and right porion landmarks and the left orbitale achieved uniformity in craniometric research. www.indiandentalacademy.com
  34. 34. The simplest procedure to obtain facial photographs and head radiographs is to instruct patients to sit upright and look straight ahead to a point at eye level on the wall in front of them. The conventional use of two ear rods to stabilize the head in radiographic cephalometry is based on the assumption that the transmeatal axis of humans is perpendicular to the mid sagittal plane. The relationship of the left and right ears in their vertical and horizontal relation is frequently asymmetric. www.indiandentalacademy.com
  35. 35. The insertion of ear rods will obviously result in vertical and/or horizontal rotation of the head ,which introduces a deficient and misleading image. Thereby,the attempt to determine facial asymmetry of a patient generally results in a compromise rather than as an exact definition. Only the left ear rod should be used in radiographic cephalometry both for the lateral and frontal projection. The right ear rod should merely be inserted against any part of the ear. www.indiandentalacademy.com
  36. 36. Saggital basal relationship    Short coming of ANB angle Taylor in 1969 Beatty in 1975-AXDangle www.indiandentalacademy.com
  37. 37. Point A revisited – Jacobson- AJO 1980 Point A cannot be accurately identified in all cephalometric radiographs.. In instances where this landmark is not clearly discernible, an alternative means of estimating the anterior extremity of the maxillary base is shown. A point plotted 3.0 mm. labial to a point between the upper third and lower two thirds of the long axis of the root of the maxillary central incisor was found to be a suitable point - (estimated point A) through which to draw the NAE line and one which most closely approximates the true NA plane. www.indiandentalacademy.com
  38. 38. Vertical basal relationship      Different cephalometric parameters are used Different reference lines used Duterloo et al(1985)-distinction between skulls with small and large divergency DiagramGraphical representation-vorhies and adams 1981-overall vertical index www.indiandentalacademy.com
  39. 39. Dentoalveolar relationship   Different cephalometric parameters are used Anterior teeth are more emphasized than posterior teeth www.indiandentalacademy.com
  40. 40.  various cephalometric analyses used in routine orthodontic practice 1) stieners analyses 2) witts 3)Mcnamara 4)Burstones-hard and soft tissue analyse 5)Schwartz analyses 6)Rakosi jaraback www.indiandentalacademy.com
  41. 41. Mc Namara analyses: For determining the anteroposterior relationship to maxilla and mandible , mid facial length is measured from condylion to point A. The effective length of the mandible is measured from condylion to gnathion. Birte Melsen suggests that there are displacements of condyle,pogonion,menton and point B relative to superimposition on implants at a study done on annaual intervals between 8.5 yrs and 15.5 yrs of age. www.indiandentalacademy.com
  42. 42. Limitations of cephalometric radiographic analyses     1)Growth pattern not taken into consideration 2)Mean values are based on different population 3)Two dimensional representation of three dimensional object 4)Form and functions not taken into consideration www.indiandentalacademy.com
  43. 43. Conclusion: A combination of various cephalometric norms and variables should be compiled to arrive at a proper diagnosis.Although innumerable controversies exist in the field of cephalometrics, it is still a very significant & effective diagnostic tool. www.indiandentalacademy.com
  44. 44. References cephalometric radiography-Thomas Rakosi cephalometric radiography-Athenosis radiographic cephalometry-Jacobson           Broadbent BH. A new X-ray technique and its application to Orthodontia. Angle Orhod 1931;1:45-66. Adams JW. Correction of error in cephalometric roentgenograms. Angle Orthod 1940;10:313. Hixon EH. The norm concept and cephlometrics. Am J Orthod 1956;42: 898-919. Salzmann JA. Cephalometrics : Resume of the workshop and limitations of the technique. Am J Orthod 1958;44:901-5. Ricketts RM. Variations of the temporomandibular joint as revealed by Cephalometric laminography. Am J Orthod 1959;36: 877-98. Harvold E (1963) Some biological aspects of orthodontic treatment in the transitional dentition. Am J Orthod 49: 1-14. Salzmann AJ. Limitation of roentographic cephalometry Am J Orthod 1964;64:204-10. Miller AP, Savaras B, Singh JI. Analysis errors in cephalometric measurements of 3dimensional distances on the maxilla. Am J Orthod. 1966;36(2):169-75. Richardson A. An investigation into the reproducibility of some points, planes and lines used in cephlometric analysis. Am J Orthod 1966;52: 637-51. Bjork A. The use of metallic implants in the study of facial growth in children: method and application. Am J Phys Anthropol 1968;29:243www.indiandentalacademy.com
  45. 45.            Frantz RC. The reliability of head film measurements 2. conventional angular and linear measurements. Am J Orthod 1971;60(5):505-17. Hixon EH. Cephalometrics: a perspective. Angle Orthod 1972;42:200-11. Kvam E, Krogstad O. Correspondence of Cephalometric values. A methodological study using duplicating films of lateral head plates. Angle Orthod 1972;42:123-8. Sekiguchi T, Savara BS. Variability of Cephalometric landmarks used for face growth studies. Am J Orthod 1972;61: 603-18. Gravely JF, Benzies PM. The clinical significance of tracing error in cephalometry, Br J Orthod 1974;1: 95-101. Midtgard J, Bjork G, Lander-Aronson S. Reproducibility of cephalometric landmarks and errors of measurement of cephalometric cranial distances. Am J Orthod 1974;44(1):57-6. Greenberg LZ, Johnston LE. Computerized prediction: The accuracy of a contemporary longrange forecast. Am J Orthod 1975; 67: 243-52. Baumrind S, Miller DM, Molthen R. The reliability of head film measuments. 3. Tracing and superimposition. Am J Orthood 1976; 70:617-44. Popovich F, Thompson GW. Craniofacial templates for orthodontic case analysis. Am J Orthod 1977;71:406-20. McWilliam J, Welander U. the effect of image quality on the identification of cephalometric landmarks. Am J Orthod 1978;48(1):49-56. Hurst RVV, Schwaninger B, Shaye R. Interobserver reliability in xeroradiographic cephalometry. Am J Orthod 1979;75:179-83. www.indiandentalacademy.com
  46. 46. www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com