Superimposition techniques

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Superimposition techniques

  1. 1. SUPERIMPOSITION TECHNIQUES INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. Contents        Introduction Methods of assessing dentofacial changes Method of superimposing radiographs Maxillary super-impositions Mandibular superimpositions Ricketts superimposition for treatment design Ricketts four-step method www.indiandentalacademy.com
  3. 3. Definition Superimposition is the placement of an image on top of an already existing image usually to add to overall image effect and to conceal something eg. Such as a different figure is superimposed over an original figure.  The transformation of one or more figures to achieve the geometric relationship to another figure Wikipedia  www.indiandentalacademy.com
  4. 4. Introduction     In 1931 Broadbent (USA) and Hofrath (Germany) - cephalometric technique using a cephalostat. Treatment planning. Evaluation of treatment results by quantifying the changes brought about by treatment Predicting growth related changes www.indiandentalacademy.com
  5. 5. What is cephalometric superimposition ?  “A cephalometric superimposition is an analysis of lateral cephalograms of the same patient taken at different times”. www.indiandentalacademy.com
  6. 6. TO PERFORM ACCURATE SUPER IMPOSITION      Consecutive cepholograms should be taken under identical condition of magnification head position, and radiological exposure The tracing of the superimpositions must be accurate It is of great importance that exactly the same structures and their corresponding radiographic shadows be traced in the consecutive cepholograms One should have the thorough knowledge of anatomy of dentofacial & cranial structures as well as radiographic interpretation They have to be registered on stable reference areas in the face. www.indiandentalacademy.com
  7. 7. CEPHALOMETRIC SUPER IMPOSITIONS INVOLVE THE EVALUATION OF:      ¨ ¨ ¨ ¨ Changes in the overall face Changes in the maxilla and its dentition Changes in the mandible and its dentition Amount and direction of condylar growth Mandibular rotation www.indiandentalacademy.com
  8. 8. Method of superimposing radiographs Superimposing on a stable plane or structure Registration on a stable landmark www.indiandentalacademy.com
  9. 9. Validity and reproducibility   Validity: It is the extent to which the value obtained represents the object of interest.  Planes and landmarks should be anatomically valid and should agree with the anatomic structures they represent Reproducibility: It is the closeness of successive measurements of the same object. www.indiandentalacademy.com
  10. 10. Methods of assessing Dentofacial changes    Brodie and Broadbent AJODO 1987-Dentofacial growth patterns are established at a very early age and thereafter are subject to proportional changes. Downs and Ricketts AJO 1960 -several angles and dimensions change with age but in an orderly and progressive manner Hellman -suggested that the infant face is transformed into that of an adult face by increase in size by changes in proportion and by adjustment in position. www.indiandentalacademy.com
  11. 11. Methods of assessing Dentofacial changes Color coding suggested by ABO:  Pretreatment – Black  Progress – Blue  End of treatment – Red  Retention - Green www.indiandentalacademy.com
  12. 12. Evaluation of overall changes in the face  Superimposition methods:  Broadbent triangle  Sella nasion line  Basion horizontal  Basion nasion plane  De Costers anterior cranial base reference line  Viazis cranial base triangle  Frankl’s occipital reference base www.indiandentalacademy.com
  13. 13. Evaluation of overall changes in the face  Objectives  Overall assessment of growth and treatment changes of the facial structures  Amount of change in direction of displacement and growth of maxilla and mandible.  Changes in soft tissue  Changes in maxillo mandibular relationship  Overall displacement of teeth. www.indiandentalacademy.com
  14. 14. Evaluation of overall changes in the face Superimposition at registration point R with Bolton-nasion planes parallel Broadbent triangle Among the first structures used for superimposition  On observations of dried skulls and a comparative study of cranial base planes (Bolton-nasion, porionnasion, sella-nasion) in persons 3 to 18 years of age.  Bolton point maybe obscured by Mastoid www.indiandentalacademy.com 
  15. 15. Evaluation of overall changes in the face Sella nasion plane:   . SN is a frequently used reference line that has been reported to be relatively stable. Both points S and N are located in the mid sagittal plane and are displaced a minimal degree by movement of the head. www.indiandentalacademy.com
  16. 16. Steiner -SN with registration point  At sella to evaluate sagittal changes in mandibular positions and  At nasion to evaluate the position of the maxilla through changes in the angle SNA www.indiandentalacademy.com
  17. 17. Evaluation of overall changes in the face Sella nasion plane:  Unlike Steiner, Björk used sella as registration point to assess changes in position of both jaws. www.indiandentalacademy.com
  18. 18. Evaluation of overall changes in the face Basion horizontal  Basion is used as the registration point.  The SN planes are made parallel by the help of the Basion horizontal line and it’s constant relationship with SN.  A coordinate grid system is used to superimpose the radiographs. www.indiandentalacademy.com
  19. 19. Evaluation of overall changes in the face Basion - Nasion plane:  Suggested by Ricketts as Facial Axis  He considered Ba-N plane as a line of separation of the face from the skull and hence a basic cranial axis for growth and structural reference. www.indiandentalacademy.com
  20. 20.  Based on studies of laminograph sections, Ricketts suggested that the cranial base angle, while constant on average, exhibits a change of 5° in either direction over a 3-year period www.indiandentalacademy.com
  21. 21. Evaluation of overall changes in the face De Coster lineAjodo1952 The line represents the axis of skull base.  He advocated tracing the inner contour of the frontal bone through the cerebral aspect of the ethmoid , the planumsphenoidale and the anterior aspect of the sella turcica. www.indiandentalacademy.com
  22. 22. Evaluation of overall changes in the face Viazis cranial base triangleJco;25  The anterior wall of sella turcica and the cribriform plate (laminar cribrosa) remain unchanged after age of 5 years. www.indiandentalacademy.com
  23. 23.  Superimposition on the anterior wall of sella turcica and the stable TC (cranial base) line, with registration on T point, provides a practical and reliable formation in both the anteroposterior and vertical planes. www.indiandentalacademy.com
  24. 24. Evaluation of overall changes in the face Viazis cranial base triangle  First priority - to registering on T point, followed by superimposing on the inner structure of the triangle, and finally superimposing on the TC line. This "best-fit" approach meets the realistic expectations of any superimposition technique. www.indiandentalacademy.com
  25. 25. Frankel’s occipital reference base   Among the basal structures of the neurocranium, the occipital bone around the foramen magnum is the first to ossify (between the third and fourth year of life). Minimalpostnatal growth of this structure and surrounding tissues is seen. www.indiandentalacademy.com
  26. 26. Frankel’s occipital reference base  Reference plane – based on natural head posture and parallel to the ground www.indiandentalacademy.com
  27. 27. Evaluation of overall changes in the face Reliability of the various cranial base reference planes used. For meaningful interpretations of superimpositions they have to be registered on stable reference landmarks.  Cranial base superimpositions are subject to error due to the continued growth of the sphenoccipital synchondrosis (Knott).  Bone remodelling at sella and Nasion are also responsible for further errors. www.indiandentalacademy.com
  28. 28.    Nasion position can change in a vertical direction (Nelson and Knott). Melsen’s study’s on human autopsy material has shown that the position of sella may change in a downward or a downward and backward direction. She also showed that the position of Basion changed due to remodelling of the clivus. The Bolton point could be difficult to locate in children due to the shadow of the mastoid process www.indiandentalacademy.com
  29. 29. Growth changes in position of Nasion and sella www.indiandentalacademy.com
  30. 30. Reference structures for overall face superimpositions.  Nelson’s and Melsen’s - stable structures in the anterior cranial base.  Anterior wall of sella turcica  The contour of the cribriform plate of the ethmoid  Trabecular system of the ethmoid air cells  The median border of the orbital roof  Planum sphenoidale www.indiandentalacademy.com
  31. 31. www.indiandentalacademy.com
  32. 32. SUPERIMPOSITION OF THE MAXILLA Evaluates  Movement of maxillary teeth  Rotation of maxilla  Two method for superimposing the maxillary structutres are recommended- the structural method and a modified best fit method. Structural Method : - Suggested by Bjork & Skieller in 1976. is recommended if the details of the zygomatic process of the maxilla are clearly identified in both cephalograms. Modified best fit method : - If the details of zygomatic process of maxilla are not identified in both cephalograms. www.indiandentalacademy.com
  33. 33. Structural method of superimposition of maxilla Pre treatment Tracing Post treatment Tracing Super imposition of pre & post treatment tracing On each cephologram, trace the contours of palate, maxillary 1st molar, central incisors, zygomatic process of maxilla, floor of the www.indiandentalacademy.com orbit N-S line and the construction line.
  34. 34. Modified best fit method Pre treatment Tracing   Post treatment Tracing Super imposition of pre & post treatment tracing On each cephalogram trace the outline of the palate 1st permanent molars and central incisors. Following structures are in a best fit alignment.  Contour of the oral part of the palate  Contour of the nasal floor www.indiandentalacademy.com
  35. 35. Evaluation of changes in maxilla and its dentition in relation to the maxilla Superimposition along the palatal plane registered at ANS Broadbent, Moore, Salzman, Ricketts, McNamara  Compromised by remodelling of the palatal shelves and ANS Bjork and Skeiler  www.indiandentalacademy.com
  36. 36. Evaluation of changes in maxilla and its dentition in relation to the maxilla Superimposition on the nasal floors with films registered at the anterior surface of the maxilla Downs and Brodie.  www.indiandentalacademy.com
  37. 37. Evaluation of changes in maxilla and its dentition in relation to the maxilla Superimposition along the palatal plane registered at the pterygomaxillary fissure Moore  www.indiandentalacademy.com
  38. 38. Evaluation of changes in maxilla and its dentition in relation to the maxilla Superimposition on the outline of the infratemporal fossa and the posterior margin of the hard palate. Reidel  www.indiandentalacademy.com
  39. 39. Evaluation of changes in maxilla and its dentition in relation to the maxilla Superimpostion registered at the common Ptm coordinate maintaining the basion horizontal relationship. Coben  www.indiandentalacademy.com
  40. 40. Evaluation of changes in maxilla and its dentition in relation to the maxilla superimposition on the best fit of the internal palatal structures. McNamara  www.indiandentalacademy.com
  41. 41. Evaluation of changes in maxilla and its dentition in relation to the maxilla   The structural superimposition on the anterior surface of the zygomatic process of the maxilla Bjork and Skeiler www.indiandentalacademy.com
  42. 42. Evaluation of changes in maxilla and its dentition in relation to the maxilla  Neilsen on a study of various maxillary superimposition techniques concluded that:  The best fit method significantly under estimates the vertical displacement of skeletal and dental landmarks  With the structural method ANS showed twice as much vertical displacement as PNS www.indiandentalacademy.com
  43. 43.   Structural method did not show any significant differences The structural method is a valid method of assessing maxillary growth and treatment changes www.indiandentalacademy.com
  44. 44. Mandibular superimposition Evaluates  Movement of the mandibular teeth  Mandibular rotation  Amount & direction of condylar growth www.indiandentalacademy.com
  45. 45. Stable areas according to Bjork and Skieller (1983)  Anterior contour of the chin  The inner contour of the cortical plates at the inferior border of the symphysis  Contours of the mandibular canal  Lower contour of the mineralized molar tooth germ www.indiandentalacademy.com
  46. 46. Step – by – step approach for mandibular superimpositions Pre treatment Tracing Progress treatment tracing Super imposition of pre & progress treatment tracing On each cephologram trace the following  The symphysis with inner cortical bone  The inferior and posterior contour of the mandible  The anterior contour of the ramus  The most labially positioned lower incisor, and  The first molar. www.indiandentalacademy.com
  47. 47. Methods to assess growth Vs treatment changes   Differentiate between changes produced due to growth and changes produced due to treatment. Assess treatment changes against the background of natural growth of the individual www.indiandentalacademy.com
  48. 48. RICKETTS SUPER IMPOSITION TECHNIQUE It is one of the most important superimposition technique used.  Ricketts super imposition is used to differentiate the changes in normal growth and those due to treatment mechanics. This techniques involves five super imposition areas to evaluate  The chin  The maxilla  The teeth in the mandible  The teeth in the maxilla  The facial profile www.indiandentalacademy.com 
  49. 49. Rickett ’s Eleven factor summary analysis   Eleven factors of the basic facial and skeletal structures are recorded from the cephalometric tracing to describe the chin, maxilla, teeth and soft tissue profile. Five areas of superimposition within which are a total of seven areas of evaluation are used to evaluate in amount and direction, change in normal growth and change due to treatment. www.indiandentalacademy.com
  50. 50. Rickett’s Eleven factor summary analysis www.indiandentalacademy.com
  51. 51. Rickett’s Eleven factor summary analysis MEAN CHANGE FACIAL AXIS 90+/-3 No change FACIAL DEPTH 87+/-3 +10 for 3 yrs MAND PLANE 26+/-4 -1o for 3 yrs FACIAL TAPER 68+/-3 No change LFH 47+/-4 No change MAND ARC 26=/-4 Mand arc closes1/2yr Angle inc 1/2yr CON AT A 2mm+/-2mm -1mm / 3 yrs L1 TO APO 1+/-2 No change L1 INCL 22+/-4 No change U6 TO PTV Age+3+2 1mm / year L LIP TO E LINE -2+/-2 Less with age www.indiandentalacademy.com
  52. 52. Rickett’s Eleven factor summary analysis SUPERIMPOSITION AREA 1 – EVALUATION AREA 1 • FACIAL AXIS OPENS 1o FOR DOLICOFACIAL PATTERN •FACIAL AXIS CLOSES 1O FOR BRACHYFACIAL PATTERNS •FACIAL AXIS OPENS 1O FOR 5mm CONVEXITY REDUCTION •FACIAL AXIS OPENS 1O FOR 3mm MOLAR CORRECTION •FACIAL AXIS OPENS 1O OR 4mm OVERBITE CORRECTION •FACIAL AXIS OPENS 1 TO 1.5O FOR CROSS BITE CORRECTION AND RECOVERS ONE HALF BASION-NASION PLANE at CC www.indiandentalacademy.com
  53. 53. Rickett’s Eleven factor summary analysis SUPERIMPOSITION AREA 2 – EVALUATION AREA 2 • THE BASION-NASION-POINT A ANGLE OF 66O DOES NOT CHANGE WITH GROWTH •SO ANY CHANGES PRODUCED MUST BE DUE TO TREATMENT •HEADGEAR - -8mm •CLASS II ELASTICS - -3mm •ACTIVATOR - -2mm •TORQUE- - 1 TO 2mm •CLASS III ELASTICS 2 TO 3mm •FACIAL MASK - 2 TO 4mm BASION NASION PLANE AT NASION www.indiandentalacademy.com
  54. 54. Rickett’s Eleven factor summary analysis SUPERIMPOSITION AREA 3 – EVALUATION AREAS 3 AND 4 • LOWER DENTURE REMAINS CONSTANT WITH THE A Pog LINE •Without treatment, the lower molar will erupt directly upward to the new occlusal plane. •The LOWER INCISAL angle is 22° at +1mm to the APo plane and + 1 mm to occlusal plane, but the angle increases 2° with each mm of forward compromise. CORPUS AXIS AT PM www.indiandentalacademy.com
  55. 55.    OCCLUSAL PLANE TO CORPUS AXIS DOES NOT CHANGE LOWER MOLAR ERUPTS IN A DIRECTION PERPENDICULAR TO THE FH PLANE OCCLUSAL PLANE ERUPTS 0.8mm UPWARDS FROM THE CORPUS AXIS. www.indiandentalacademy.com
  56. 56. Rickett’s Eleven factor summary analysis SUPERIMPOSITION AREA 4 – EVALUATION AREAS 5 AND 6 • THE UPPER MOLAR AND INCISOR FOLLOW THEIR POLAR AXIS WITH GROWTH •CHANGES IN POSITION OF THE MOLAR OR INCISOR IS DUETO TREATMENT. •UPPER DENTAL ARCH ERUPTS DOWNWARD AND FORWARD 0.2 TO 0.3mm PER YEAR PALATE AT ANS www.indiandentalacademy.com
  57. 57. Rickett’s Eleven factor summary analysis SUPERIMPOSITION AREA 5 – EVALUATION AREA 7 • ESTHETIC PLANE AT INTERSECTION OF OCCLUSAL PLANES www.indiandentalacademy.com
  58. 58. Rickett’s four position analysis Takes into consideration two superimposition areas to evaluate skeletal change and two superimposition areas to evaluate dental change against growth. www.indiandentalacademy.com
  59. 59. Rickett’s four position analysis    Position 1 Mandible or chin Central axis 90+/-3 www.indiandentalacademy.com
  60. 60. Rickett’s four position analysis    Position 2 Maxilla Backward moment of .A of 3 help reduce convexity www.indiandentalacademy.com
  61. 61. Rickett’s four position analysis      Position 3 Upper teeth Tracing are superimposed on palatal plane and registered at ans 1 intrusion& retrusion 7mm Molar 2mm forward www.indiandentalacademy.com
  62. 62. Rickett’s four position analysis Position 4 Lower teeth Tracings are superimposed on corpus axis and registered at pm Incisor crown 7mm,root 3mm molar2mm www.indiandentalacademy.com
  63. 63. Pitchfork analysis     Johnston in 1985 Used to evaluate growth/displacement of the max and mand To register moments of max and mand Data recorded in the form of a pitch fork www.indiandentalacademy.com
  64. 64. Pitchfork analysis Growth and displacement of max and mand are measured relation to cranial base(registration at sella) The changes of max and mand molars and incisors are measured relative to basal bone All measurement are executed parallel to MFOP and are given signs appropriate to the nature of their contribution to the molar and overjet corrections or changes. www.indiandentalacademy.com
  65. 65. Pitchfork analysis   Superimposition on D Measurement of molar and incisal changes www.indiandentalacademy.com
  66. 66. Pitchfork analysis  Measurement of amount of molar correction www.indiandentalacademy.com
  67. 67. Pitchfork analysis  Measurement of overjet correction www.indiandentalacademy.com
  68. 68. CONCLUSION    Rickett’s Cephalometric superimposition are a valuable tool in treatment planning. These analysis help in orthodontic diagnosis by enabling the study of skeletal, dental and soft tissue structures of the cranio facial region. These analysis also classify the skeletal and dental abnormalities and establish the facial type. www.indiandentalacademy.com
  69. 69. References:     Orthodontic cephalometry Text book-Athanasios E Athanasiou Radiographic cephalometry second ed.,-Alexander Jacobson(Text book) Bioprogressive therapy-Robert M.Ricketts(Text book) A Four- step method to distinguish orthodontic changes from natural growth:J.C.O,Vol 9,1975 pgs208-228 www.indiandentalacademy.com
  70. 70. THANK YOU www.indiandentalacademy.com

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