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Cephalometric superimposition

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Cephalometric superimposition

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  2. 2. IntroductionIntroduction A cephalometric super imposition is an analysis of lateral cephalograms of the same patient taken at different times. These super impositions are used to evaluate a patient’s growth pattern between different ages and to evaluate changes in dentoalveolar and basal relationships after a course of orthodontic or surgical m
  3. 3. Early method -- Comparison of linear and angular measurements from consecutive cephalograms Serial superimpositions from cephalograms that have been taken at different times To determine the effect of growth or treatment, tracings of the head films are superimposed on those landmarks least affected by m
  4. 4. The placement of metallic implants for subsequent use as stable structures (BJORK, 1968). Information gathered from these implant studies are useful in identifying areas which are relatively stable or where the changes are of relatively small magnitude. When tracing serial films, start with the smallest age and follow the child towards maturity or start at the most mature stage and work backwards -- Allows examiner to observe gradual morphological changes. Broadbent (1975) m
  5. 5. For superimpositions to be accurate they should be taken under identical conditions of Magnification, Head position, Radiological exposure and Tracing of the superimpositions must be accurate (locate precisely the outlines of the relevant structures and to eliminate the confusing, unusable details) m
  6. 6. DefinitionsDefinitions Validity Validity or accuracy is the extent to which, in absence of measurement error, the value obtained represents the object of interest. Reproducibility Reproducibility, or precession, is the closeness of successive measurements of the same m
  7. 7. Uses of CephalometricUses of Cephalometric superimpositionsuperimposition Evaluate a patient’s growth pattern between different ages Evaluate changes in dentoalveolar and basal relationships after orthodontic or surgical treatment Differentiate the changes due to growth and that due to treatment Construction of m
  8. 8. Color-coding for tracingColor-coding for tracing To facilitate identification of consecutive cephalograms (American board of orthodontists,1990) Pretreatment – black Progress – blue End of treatment – red Retention – green m
  9. 9. When evaluating the dentofacial changes that occur as a result of growth or treatment, specific areas that should be observed for alteration include: Changes in overall face Changes in the maxilla and its dentition Changes in the mandible and its dentition Amount and direction of condylar growth and Mandibular rotation m
  10. 10. Evaluation of the overall changes in overall face Cranial structures have been used for super impositions based on the fact on that both the neurocranium and its related cranial base achieve most of their growth potential at a relatively early age. Therefore, this part of the cranium is considered to be relatively stable. m
  11. 11. Basion Horizontal (Coben,Basion Horizontal (Coben, 1955)1955) m
  12. 12. Broadbent triangleBroadbent triangle (Broadbent, 1931)(Broadbent, 1931) m
  13. 13. Basion – Nasion planeBasion – Nasion plane (Ricketts, 1979)(Ricketts, 1979) m
  14. 14. Sella-nasion line (AmericanSella-nasion line (American Board of Orthodontics, 1990)Board of Orthodontics, 1990) m
  15. 15. Disadvantage of above methods – They incorporate areas of the cranial base that continues to change during most of the growing years. Growth at the spheno-occipital synchodrosis Bone remodeling at the Nasion -- (Knott, 1971) Bone remodeling at the Sella -- (Melsen, 1974). m
  16. 16. Basion – influenced by the remodeling processes on the surface of the Clivus and anterior border of foramen magnum and displacement of occipital bone due to growth at spheno-occipital synchodrosis (Melsen, 1974). Bolton point – It is frequently obscured by the mastoid process in the teenage years (Broadbent, 1975). m
  17. 17. Best fit of anterior cranial base (NelsonsBest fit of anterior cranial base (Nelsons (1960) cephalometric study and Melsen’s(1960) cephalometric study and Melsen’s (1974) histological investigation)(1974) histological investigation) Identified various bony surfaces in the anterior cranial base that are suitable for accurate superimpositions. They include Anterior wall of sella turcica The contour of cibriform plate of ethmoid bone m
  18. 18. Details in trabecular system in ethmoid cells Median border of orbital roof Plane of sphenoid bone (planum spenoidale) Registration should be done on the midpoint between the right and left shadows of the anterior curvatures of the greater wing of the sphenoid bone where they intersect the planum. m
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  20. 20. They compared the above methods and concluded that this study does not suggest a preference among the various methods but the use of best fit of the anterior cranial base may be better than the others as it takes into consideration the detailed individual anatomy of the cranial base, rather than simplifying this anatomy into lines or planes Ghafari, Engel, and Laster (May, 1987) m
  21. 21. Uses of overall superimpositionsUses of overall superimpositions Provide an overall assessment of the growth and treatment changes of the facial structures Amount and direction of maxillary and mandibular growth or displacement Changes in maxillary-mandibular relationship m
  22. 22. Relative changes in soft tissue integument (specifically the nose, lips and chin) Provide information on the overall displacement of the teeth It does not provide for an assessment of the changes in the position of the teeth within the maxilla or mandible. In order to obtain this information, maxillary and mandibular superimpositions are required. m
  23. 23. Grid analysis (Weislander AJOGrid analysis (Weislander AJO 1993)1993) m
  24. 24. Changes in the maxilla andChanges in the maxilla and its dentitionits dentition Maxillary superimposition The purpose of maxillary superimposition is to evaluate the movement of maxillary teeth in relation to the basal parts of maxilla m
  25. 25. Superimposing along the palatal planeSuperimposing along the palatal plane registered at ANS (Broadbent 1937, Mooreregistered at ANS (Broadbent 1937, Moore 1959, Salzmann 1960, Ricketts 1960,1959, Salzmann 1960, Ricketts 1960, Mcnamara 1981).Mcnamara 1981). m
  26. 26. Superimposition on the nasal floorSuperimposition on the nasal floor with films registered at anterior surfacewith films registered at anterior surface of maxilla. (Downs 1948, Brodie 1949)of maxilla. (Downs 1948, Brodie 1949) m
  27. 27. Superimposition along the palatalSuperimposition along the palatal plane registered at pterygomaxillaryplane registered at pterygomaxillary fissure (Moore 1959)fissure (Moore 1959) m
  28. 28. The methods of maxillary superimposition that use the palatal plane are compromised because of the remodeling of the palatal shelves. The hard palate undergoes continuous resorption on its nasal surface and apposition on the oral side making most of these methods of superimposition unsatisfactory. Both points ANS and PNS undergo significant anteroposterior remodeling m
  29. 29. Superimposition on the outline ofSuperimposition on the outline of infratemporal fossa and posterior portion ofinfratemporal fossa and posterior portion of hard palate (Reidel 1974)hard palate (Reidel 1974) m
  30. 30. Superimposition registering the maxilla onSuperimposition registering the maxilla on the common Ptm co-ordinate, maintainingthe common Ptm co-ordinate, maintaining the basion Horizontal relationship (Cobenthe basion Horizontal relationship (Coben 1986).1986). m
  31. 31. Superimposition on the best fit of internalSuperimposition on the best fit of internal palatal structures (McNamara 1981)palatal structures (McNamara 1981) m
  32. 32. Superimposition on metallicSuperimposition on metallic implants (Bjork and skieller 1976).implants (Bjork and skieller 1976). They found that remodeling involves resorptive lowering of the nasal floor -- greater anteriorly than posteriorly. The zygomatic process did not undergo the same remodeling changes .So they recommended the use of headfilm tracing superimposition on the anterior surface of the zygomatic process of the maxilla. m
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  34. 34. Structural superimposition on the anteriorStructural superimposition on the anterior surface of the zygomatic process of thesurface of the zygomatic process of the maxilla. (Bjork and Skieller 1976) with themaxilla. (Bjork and Skieller 1976) with the second head film oriented so that thesecond head film oriented so that the resorptive lowering of the nasal floor isresorptive lowering of the nasal floor is equal to the apposition at the orbital floor.equal to the apposition at the orbital floor. m
  35. 35. Compared the popular “Best fit” method with that of implant and structural superimposition methods Best fit method significantly underestimates the vertical displacement of molar teeth by 30% and that of incisors up to 50%. No statistically significant differences were found between the structural and implant methods in the vertical plane. Nielsen (AJO 1989) m
  36. 36. In the horizontal plane the structural method on average demonstrated posterior displacement of the reference points by 0.5 mm. Hence it has been concluded that the structural method for superimposing head films is a valid and reliable method for determining maxillary growth and treatment changes. m
  37. 37. Disadvantage of using theDisadvantage of using the structural methodstructural method The zygomatic process of maxilla is characterized by double structures, which make it difficult to identify accurately and hence to trace the construction line. If the anterior surface of the zygomatic process is short, superimposition can create rotational effect, which can cause tooth movements to be misinterpreted. So quality head films are required. m
  38. 38. Doppel (AJO 1994)Doppel (AJO 1994) Compared various superimposition methods and concluded that for clinical purposes this method of maxillary superimposition more closely approximates implant superimposition. Anterior and posterior contours of zygomatic arches are superimposed allowing the floor of the orbit to be raised more than the palatal plane in a ratio of 1.5:1 m
  39. 39. Changes in the mandible andChanges in the mandible and its dentitionits dentition It is used to evaluate the movement of mandibular teeth in relation to the basal parts of the mandible Lower border of the mandible and on the inner table of symphysis (Salzmann 1960, 1972). Disadvantage -- Lower border undergoes significant remodeling during growth (Bjork 1963). m
  40. 40. Superimposition on the mandibularSuperimposition on the mandibular planeplane It has low degree of validity, but of high degree of m
  41. 41. Implant studies, Bjork (1963,Implant studies, Bjork (1963, 1969) and Bjork and Skieller1969) and Bjork and Skieller (1983)(1983) Indicated relatively stable structures that could be used for superimposition purposes. Anterior contour of the chin The inner contour of the cortical plates at the inferior border of the symphysis and trabecular structure in the lower part of symphysis. The contour of mandibular canal Lower contour of mineralized molar m
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  43. 43. Evaluation of Amount and direction ofEvaluation of Amount and direction of condylar growth and mandibular rotationcondylar growth and mandibular rotation m
  44. 44. Visual treatment objectiveVisual treatment objective (VTO)(VTO) It is a visual plan to forecast the normal growth of the patient and the anticipated influences of treatment, to establish the individual objectives we want to achieve for that patient. The treatment plan must take advantage of beneficial aspects of growth and minimize any undesirable effects of growth, if m
  45. 45. After setting up teeth ideally within the anticipated or “grown” facial pattern, the orthodontist must decide what mechanics and orthopedics must be used to achieve these goals. m
  46. 46. To effectively forecast and draw an effective treatment design the steps that should be followed are: Understand the individual patients basic facial, skeletal and dental structures (Ricketts analysis). An analysis of normal growth change and treatment design Evaluation of growth and treatment results VTO m
  47. 47. Ricketts VTORicketts VTO Uses of Ricketts VTO Monitoring and measuring the treatment progress Helps in orthodontists self improvement m
  48. 48. Construction of VTOConstruction of VTO The various steps that should be followed in the construction of a VTO are Cranial base prediction Mandibular growth prediction Maxillary growth prediction Occlusal plane position Location of dentition Soft tissue of the face m
  49. 49. CranialCranial base predictionbase prediction m
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  52. 52. 1mm/year m
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  58. 58. Mandibular growth predictionMandibular growth predictionMechanics Convexity reduction – Opens 1°/5mm Molar correction –Opens 1°/3mm Overbite correction –Opens 1°/4mm Cross bite correction –Opens 1°-1½° Facial axis closes with extraction Open or close with headgear Facial pattern S.D on the dolicofacial pattern Opens 1° m
  59. 59. m
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  62. 62. 1mm/year m
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  65. 65. 2mm/year m
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  72. 72. Maxillary growth predictionMaxillary growth prediction m
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  78. 78. Maximum range of point A changes with various mechanics HG -8mm Class II elastics -3mm Activator -2mm Torque -1 to -2mm Class III elastics 2 to 3mm Facial Mask 2 to 4mm m
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  81. 81. m
  82. 82. Occlusal plane positionOcclusal plane position m
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  87. 87. Location of dentitionLocation of dentition m
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  95. 95. 4mm m
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  102. 102. Soft tissue of the faceSoft tissue of the face m
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  106. 106. 1mm/year m
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  124. 124. Take the VTO and superimpose on the five-superimposition areas to establish individual objectives for the patient. The Five superimposition areas are used to evaluate the following in the face in order: The chin The maxilla The teeth in the mandible The teeth in the maxilla The facial m
  125. 125. Superimposition area 1Superimposition area 1 Basion-Nasion at CC point. Establishes Evaluation area 1 (Evaluate the amount of growth of the chin in mm and change in an opening or closing direction that may result from the mechanics used). m
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  128. 128. Superimposition area 2Superimposition area 2 Basion – Nasion at Nasion. Establishes Evaluation area 2 (Changes in the maxilla). The Basion - Nasion – Point A angle does not change with normal growth. Any change in this angle is due to the effect of mechanics. m
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  131. 131. Superimposition Area 3Superimposition Area 3 Corpus Axis at PM. Establishes Evaluation Area 3 (evaluate weather we are going to intrude, extrude, advance or retract the lower incisors which help us determine the type of mechanics that must be used) Evaluation Area 4 (evaluate the lower molars to determine what type of anchorage we need and weather we wish to advance, upright or hold the lower molars) m
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  134. 134. Superimposition Area 4Superimposition Area 4 Palate at ANS. Establishes Evaluation Area 5 (Evaluate what we are going to do with upper molars – hold, intrude, extrude, distalize or bring them forward) Evaluation Area 6 (Evaluate what we are going to do with upper incisors – Intrude, extrude, retract, torque or tip them) m
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  137. 137. Superimposition Area 5Superimposition Area 5 Esthetic plane at crossing of occlusal plane. Establishes Evaluation Area 7 (evaluate the soft tissue profile). m
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  140. 140. VTO (Visualized treatmentVTO (Visualized treatment objective) -- Holdaway (1984 AJO)objective) -- Holdaway (1984 AJO) Systems based on hard-tissue measurements or reference lines alone may produce disappointing results. Develop facial profile outline that is harmonious with the skeletal type of the patient under study. Plan the dental repositioning necessary to bring about the desired change. m
  141. 141. m
  142. 142. Step I m
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  146. 146. .75mm/yearStep II m
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  149. 149. 3mm/yearStep III m
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  153. 153. m
  154. 154. Step IV m
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  158. 158. Step V m
  159. 159. 40% m
  160. 160. m
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  162. 162. Step VI 50% m
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  164. 164. Step VII m
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  173. 173. 15 10 Step VIII m
  174. 174. 4 m
  175. 175. Elimination of lip strain -- 4 mm Upper lip change -- 4 mm. Maxillary incisor rebound -- 1.5 mm. Total incisor repositioning -- 9.5mm. m
  176. 176. m
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  180. 180. Step IX m
  181. 181. m
  182. 182. m
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  184. 184. Arch length loss from reposition --2 x 4 = 8 mm Model discrepancy -- 2 mm Total discrepancy -- 10 mm. m
  185. 185. Lower molar must be moved forward 2.5 mm. Step X m
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  188. 188. Step XI m
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  192. 192. Step XII m
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  198. 198. TEMPLATE ANALYSISTEMPLATE ANALYSIS Johnston JCO 1987Johnston JCO 1987 Templates exist in two forms Schematic (Michigan,Burlington) Anatomically complete (Broadbent- bolton, Alabama) m
  199. 199. Schematic (Michigan) m
  200. 200. Each template is, in effect, a compact set of oriented rulers graduated in years (6 to 16 years). Thus any patient with this age range can be analyzed with a single template. The types of superimpositions that should be used to assess overall facial form and to measure the size of component parts includes Cranial base superimposition Regional m
  201. 201. Cranial base superimposition: The choices of reference planes are SN registered at S FH registered at PtV m
  202. 202. Regional superimposition: To determine relative size (measured in years) of any craniofacial dimension m
  203. 203. THE PROPORTIONATE TEMPLATE Jacobson AJO 1979 The tracing of the individual with disharmony is compared with a normal tracing or template and they are systematically compared. m
  204. 204. m
  205. 205. Tracing with template superimposed on mid S-J point and B-Na parallel Maxilla and mandible sagittal and vertical Mandibular plane Soft tissue lips Chin Nose m
  206. 206. Superimposition on palatal plane registered on Ptm Length Incisor inclination Incisor height Molar height m
  207. 207. Body length Ramus height Gonial angle Incisor height and inclination Molar height Superimposition on mandibular plane registered at pogonion m
  208. 208. Superimposition on the lines representing the vertical dimensions Upper facial height Lower facial height m
  209. 209. Superimposition on the occlusal plane Vertical dimension of the m
  210. 210. The cephalometric superimposition methods used for visualizing, planning, and predicting surgical orthodontic outcomes are Tracing overlay method Template method Surgical treatment objective (STO) m
  211. 211. The purpose of S.T.O. To establish orthodontic and pre- surgical orthodontic goals. To develop surgical objectives To create the predicted facial profile, which can be used as a visual aid in patient consultation. m
  212. 212. Tracing overlay method m
  213. 213. m
  214. 214. Template method m
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  216. 216. ConclusionConclusion • If the tracings are not accurate and the superimpositions and not made on radiographic structures that have been proved to be relatively stable and reliable, the superimposition can be manipulated to show anything the operator wants to show. m