Bjorks analysis

bjork cephalometric analysis

1. BJORK'S ANALYSISBJORK'S ANALYSIS
PRESENTED BY
SUSNA SARAH PAUL
DEPARTMENT OF
ORTHODONTICS

2. CONTENTS
●INTRODUCTION
●MANDIBULAR ROTATIONS
●SEVEN SIGNS OF GROWTH ROTATION
●BJORK'S FACIAL DIAGRAM
●ANGULAR AND LINEAR PARAMETERS
●CONCLUSION

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. ●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. 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. FORWARD ROTATION OF
MANDIBLE
Type I
About the centre in the
TMJ.

7. Type II.
About the centre located at
the incisal edges of the lower
anterior teeth.

8. Type III.
Centre of rotation to the region
of premolars

9. BACKWARD ROTATION OF
MANDIBLE
Type I

Centre lies at the TMJ
Openbite develops

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. 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. INCLINATION OF THE
CONDYLE
Condylar Inclination

13. CURVATURE OF THE
MANDIBULAR CANAL

14. SHAPE OF THE LOWER
BORDER OF MANDIBLE

15. INCLINATION OF SYMPHYSIS

16. INTERINCISAL ANGLE

17. INTER MOLAR AND PREMOLAR
ANGLE

18. LOWER ANTERIOR FACIAL HT.

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. 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. 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. Pr – Prosthion
Kk – gonial angle
The plane of reference he took was
the SN plane.

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. 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. 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. ANGLE AT SELLA
●It provides a means of
measuring the shape
of the cranial base.
123°±5

27. ANGLE AT ARTICULARE
●It shows the forward or
backward diversion of
mandible.
143°±6

28. ANGLE AT KK
128°±7

29. ANGLE AT DD

30. POSITION OF FORAMEN
MAGNUM

31. INCLINATION OF FOREHEAD

32. LINEAR MEASUREMENTS
●Sella nasion line
71cm±3

33. ●Sella articulare line
32cm±3

34. ●Articulare KK line
44cm±5

35. ●KK to DD
71cm±5

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.

38. 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