Bjorks analysis

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bjork cephalometric analysis

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Bjorks analysis

  1. 1. BJORK'S ANALYSIS PRESENTED BY SUSNA SARAH PAUL DEPARTMENT OF ORTHODONTICS
  2. 2. CONTENTS ● INTRODUCTION ● MANDIBULAR ROTATIONS ● SEVEN SIGNS OF GROWTH ROTATION ● BJORK'S FACIAL DIAGRAM ● ANGULAR AND LINEAR PARAMETERS ● CONCLUSION
  3. 3. Dr ARNE BJORK (1911-1996) ● ● ● Arne Björk was born on 1911 in Dalarne, Sweden. After his dental training in Stockholm, he practised dentistry from 1937 to 1951. During these years he also studied anthropology and genetics at the Swedish Institute for Human Genetics. In 1947 he published the famous dissertation “The Face in Profile”.
  4. 4. ● ● ● ● 1949-1950 chairman of orthodontics in Malmo, Sweden 1951-1981 professor of orthodontics in Royal Dental college, Denmark 1973 received the Ketcham award of Am. Board of orthodontics. 1980 nominated as member of World Federation of Orthodontics
  5. 5. Bjork conducted a study in 1951 using metal implants to find the sites of growth and resorption in individual jaws, and individual variation in direction and intensity. Bjork gave seven structural signs to find the direction of mandibular growth rotation.
  6. 6. FORWARD ROTATION OF MANDIBLE Type I About the centre in the TMJ.
  7. 7. Type II. About the centre located at the incisal edges of the lower anterior teeth.
  8. 8. Type III. Centre of rotation to the of premolars region
  9. 9. BACKWARD ROTATION OF MANDIBLE Type I Centre lies at the TMJ Openbite develops
  10. 10. TYPE II Centre is at the most distal occluding molars. This occurs in connection with growth in the sagittal direction at the condyles. The soft tissue of the chin may not follow this movement and a characteristic double chin may form. Difficulty in closing lips without strain.
  11. 11. The seven signs were: 1.Inclination of the Condylar head. 2.Curvature of the Mandibular canal. 3.Shape of the lower border of mandible. 4.Inclination of the Symphysis. 5.Interincisal angle. 6.Intermolar or Interpremolar angles. 7.Lower Anterior face height.
  12. 12. INCLINATION OF THE CONDYLE Condylar Inclination
  13. 13. CURVATURE OF THE MANDIBULAR CANAL
  14. 14. SHAPE OF THE LOWER BORDER OF MANDIBLE
  15. 15. INCLINATION OF SYMPHYSIS
  16. 16. INTERINCISAL ANGLE
  17. 17. INTER MOLAR AND PREMOLAR ANGLE
  18. 18. LOWER ANTERIOR FACIAL HT.
  19. 19. BJORK'S ANALYSIS Three groups of Scandinavian(Swedish) male school children: Group I – 20 twelve year old Group II – 322 twelve year old Group III -281 high school graduates. Roentgenograms taken at a distance of 155 cms were used. The facial diagram was constructed and analysed.
  20. 20. He put forward a facial diagram in which the linear and angular configurations determine the amount and distribution of facial prognathism. This facial diagram that implicates these changes constitutes the Bjork’s Analysis.
  21. 21. LANDMARKS USED WERE: A – Articulare. Gn – Gnathion. Pg – Pogonion. Id – Infradentale. Sp – spina nasalis anterior (ANS) Dd – Chin angle, pt of intersection of mandibular plane and line tangent to ID and pogonion.
  22. 22. Pr – Prosthion Kk – gonial angle The plane of reference he took was the SN plane.
  23. 23. Construction of facial diagram A line drawn from the prosthion to ANS to the nasion, to the center of sella turcica (S), to articulare to the Gonial angle (KK), to Chin angle (DD), and from these to infradentale (Id).
  24. 24. ANGULAR MEASUREMENTS ● Angles formed by lines at N ● Angles formed by lines at S ● Angle formed by lines at Ar ● Angle formed by lines at KK ● Angle formed by lines at DD
  25. 25. ANGLES AT NASION These measures the facial profile in relation to the cranial base. Max. Alv. Prog. 84±3 Mand. Alv. Prog.79±6
  26. 26. ANGLE AT SELLA ● It provides a means of measuring the shape of the cranial base. 123°±5
  27. 27. ANGLE AT ARTICULARE ● It shows the forward or backward diversion of mandible. 143°±6
  28. 28. ANGLE AT KK 128°±7
  29. 29. ANGLE AT DD
  30. 30. POSITION OF FORAMEN MAGNUM
  31. 31. INCLINATION OF FOREHEAD
  32. 32. LINEAR MEASUREMENTS ● Sella nasion line 71cm±3
  33. 33. ● Sella articulare line 32cm±3
  34. 34. ● Articulare KK line 44cm±5
  35. 35. ● KK to DD 71cm±5
  36. 36. Facial prognathism may be due to – Shortening of the cranial base. – Angular deflection of the cranial base. – A small ramus – cranial base angle. – Increased jaw length.
  37. 37. PARAMETERS BJORK'S NORMS PT. VALUE INFERENCE SADDLE ANGLE 123°±5 124° NORMAL Ar ANGLE 143°±6 141° NORMAL Go ANGLE (KK) 128°±7 126° NORMAL SN LINE 71±3cm 71cm NORMAL SAr LINE 32±3cm 40cm INCREAED THAN NORMAL ArKK LINE 44±5cm 57cm INCREASED THAN NORMAL KK-DD LINE 71±5cm 87cm INCREASED THAN NORMAL

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