CEPHALOMETRIC ANALYSIS IN DETAILS INCLUDING STEINER, TWEED AND DOWN FOR UNDER GRADUATE

1. Cephalometrics in
orthodontics

2. Cephalometrics
 Cephalometry
• Cephalometrics is the interpretation of lateral skull radiographs
taken under standardized conditions.
• Origin: ‘Cephalo’ means head and ‘Metric’ is measurement
• The analysis and interpretation of standardized radiographs of
facial bones - Using standardized skull radiograph to assess
facial, dental and skeletal relationships as well as airway
analysis

3. History
• Cephalometry was modified from anthropological
studies and craniometry (study of cranium).
• Introduced in 1931 by Broadbent (USA) and Hofrath
(Germany)
• Clinical application of cephalometry was introduced
by Downs

4. Skull: lateral View

5. Skull: frontal View

6. 1) Lateral Cephalogram
• Lateral view of skull
• X-ray beam perpendicular to the patient's sagittal
plane at a specific distance from X-ray source

7. Position of the patient
• Frankfurt Horizontal plane should be parallel to floor.
• Ear rods stabilize the patient on the horizontal plane.
• Forehead clamp should be fixed for vertical plane
stabilization of patient.
• Patient is made to close the mouth in centric
occlusion.

8. Uses
• In orthodontic diagnosis & treatment planning
• In classification of skeletal & dental abnormalities
• In establishing facial types
• In evaluation of treatment results
• In predicting changes associated with surgical
treatment
• Helps in predicting growth related changes.
• Research purpose

9. 2) Posteroanterior (PA) Cephalogram
• Image receptor is placed in
front of the patient,
perpendicular to the
midsagittal plane and
parallel to the coronal plane
• The patient is placed so
that the canthomeatal line
is perpendicular to the
image receptor

10. Uses :
 Provides information related to
skull width
 Skull symmetry
 Vertical proportions of skull,
craniofacial complex & oral
structures
 For assessing growth
abnormalities & trauma

11. Cephalometric imaging system
• X- ray apparatus
• An image receptor
• Cephalostat

12. Goals of Cephalometrics
• Goals of Cephalometrics To evaluate the
relationships, both horizontally and vertically, of the
five major functional components of the face:
 • The cranium and the cranial base
 • The skeletal maxilla
 • The skeletal mandible
 • The maxillary dentition and the alveolar process
 • The mandibular dentition and the alveolar process

13. Cephalometric landmarks
• A conspicuous point on a Cephalogram that serves
as a guide for measurement or construction of planes
– Jacobson
• 2 types :
1. Anatomic: represent actual anatomic
structure of the skull e.g. – N, ANS, pt. A, etc.
2. Constructed: constructed or obtained
secondarily from anatomic structures
in the Cephalogram e.g.– Gn, Go, S

14. Requirements for a landmark
 Should be easily seen
 Be uniform in outline
 Easily reproducible
 Should permit valid quantitative measurement of lines
and angles
 Lines and planes should have significant relationship
to the vectors of growth

15. Cephalometric landmarks
Cephalometric landmarks can be broadly classified
into
• hard tissue and
• soft tissue points.

16. LANDMARKS
• Nasion : the most anterior
point midway between the
frontal & nasal bone on the
fronto-nasal suture.
• Orbitale : the lowest point on
the inferior margin of the orbit.
• Porion : the highest bony point
on the upper margin of the
external auditory meatus.

17. • Sella : the point representing the
midpoint of the pituitary fossa.
• Point A: it’s a deepest point in the
midline between ANS & alveolar
crest between two central
incisors.
• Point B: it’s a deepest point in the
midline between alveolar crest of
the mandible & the mental
process.
• Basion: it’s the median point of
the anterior margin of foramen
magnum

18. • ANS: it’s the anterior tip of the sharp
bony process of the maxilla in the
midline of the lower margin of
anterior nasal spine.
• Gonion: it is at the junction of the
ramal plane & mandibular plane.
• Pogonion: it’s the anterior most point
of the bony chin in the medial plane.

19. • Menton: Most inferior midline
point on the mandibular
symphysis.
• Gnathion: Most antero-inferior
point on the symphysis of the chin.
• Articulare: point at the junction of
the posterior border of ramus &
the inferior border of the basilar
part of occipital bone.
• Condylion: most superior point on
the head of condyle.

20. • PNS: The intersection of a
continuation of the anterior wall of
the pterygopalatine fossa & floor of
the nose, marking the distal limit of
maxilla.
• Ptm point: The intersection of
inferior border of foramen
rotundum with the posterior wall of
pterygoid-maxillary fissure.

21. Cephalometric planes
• Are derived from at least 2 or 3 landmarks
• Used for measurements, separation of anatomic
divisions, definition of anatomic structures of relating
parts of the face to one another
• Classified into horizontal & vertical planes

22. Cephalometric planes
Horizontal planes
 S.N. Plane – sella to nasion.
 F.H. Plane – orbitale to porion.
 Occlusal plane – plane bisecting
posterior occlusion.
 Palatal plane – ANS to PNS of
palatine bone. -

23. Cephalometric planes
Horizontal planes
• Mandibular plane: Different definitions are given in
different analysis
1. Tweed- Tangent to lower border of the mandible
2. Downs analysis – extends from Go to Me
3. Steiner’s analysis – extends from Go to Gn

24. Cephalometric planes
Vertical planes
• Facial plane – nasion to pogonion
• Facial axis – ptm point to gnathion.
• A-Pog line – point A on maxilla to pogonion on
mandible.
• E. plane (Esthetic plane)-Line drawn from the tip of
the nose to the most anterior part of the soft tissue
chin

25. Evaluation of cephalometrics radiograph
• Digitizing
– Illuminated radiograph viewing screen which is connected
to computer.
– Specialized software used to produce tracing
• Hand Tracing
– light viewing box(X-ray viewer)
– Acetate matte sheets used as transparency to facilitates
landmark identification
– Sharp 3H pencil is used
– Acetate sheet to be secured using masking tape

27. Principle of Cephalometric analysis
• To compare the patient with a normal reference
group, so that differences between the patient’s
actual dentofacial relationships and those expected
for his/her racial or ethnic groups are revealed.

28. Classification of Cephalometric analyses
I. Methodological classification
1. Angular analyses – SNA, SNB, ANB, Tweed’s
analysis.
2. Linear analyses – McNamara analysis, COGS.
II. According to area of analysis
1. Skeletal analysis – SNA, SNB, ANB
2. Dentoalveolar analysis – upper 1 to NA
3. Soft tissue analysis – E plane

29. Examples
• Down's
• Steiner
• Tweed
• Rickett
• Harvold
• McNamara
• Sassouni
• Wits

30. Downs Analysis
• First published by Downs in 1948
• Most frequently used cephalometric analysis
• According to Downs, “Balance of face is determined
by position of mandible”
• Frankfurt Horizontal plane used as reference plane
to degree of retrognathism or prognathism
• Downs analysis consists of ten parameters of which
five are skeletal and five are dental

31. Downs Analysis
• SKELETAL:
– Facial angle
– Angle of convexity
– A-B plane
– Mandibular plane angle
– Y axis
• DENTAL:
– Cant of occlusal plane
– Interincisal angle
– Incisor occlusal plane angle
– Incisor mandibular plane angle
– Protrusion of maxillary incisors.

32. FACIAL ANGLE
• Degree of protrusion or retrusion of mandible in relation to the
upper face.
• Nasion pogonion intersects the Frankfort occlusal plane.
• increased angle - Prominent chin
• smaller angle – retrusive chin
• Range: 82 - 95 degrees, mean 87.8

33. • Angle formed at the intersection Nasion-point A to point A –
pogonion.
• Average value: 0( -8.5 - 10).
Significance:
• Positive angle suggest a prominent maxillary dental base in
relation to mandible.
• Negative angle is indicative of prognathic profile
Angle of convexity

34. • A-B plane angle Point A – point B to
nasion – pogonion. Average value: -4.6
( -9 to 0)
Significance:
• Indicative of maxillo mandibular
relationship in relation to facial plane.
- Negative since point B is positioned
behind point A.
- Positive in class III malocclusion or
class I malocclusion with mandible
prominence
Skeletal A-B plane angle

35. • angle formed at the Intersection of mandibular plane
with F.H. Plane.
• Average value: 21.9 ( 17 to 28)
Mandibular plane angle

36. • Sella gnathion to F.H. plane.
• Average value: 59.4 ( 53 to 66)
Significance:
• Indicates growth pattern of a
individual
• Increased in Class II facial patterns
or Vertical growth pattern of
mandible
• Decreased in Class III facial patterns
or Horizontal growth pattern of
mandible
Y-Axis

37. Cant of occlusal plane
• Occlusal plane to F.H. plane
• occlusal plane through region of overlapping cusps of first
premolar & first molars.
• Average value: 9.3 ( 1.5 - 14)
• Gives a measure of slope of occlusal plane relative to F.H.
Plane.
Dental Parameters

38. Inter incisal angle
• Inter incisal angle between long axes of upper and lower
incisors.
• Average value: 135.4 ( 130 - 150.5)
• Smaller angle – incisors tipped forward.
Dental Parameters

39. Incisor occlusal plane angle
• This is the inside inferior angle formed by the intersection
between the long axis of lower central incisor and the occlusal
plane and is read as a plus or minus deviation from a right
angle
• Average value: 14.5 ( 3.5 - 20)
• An increase in this angle is suggestive of increased lower
incisor proclination.
Dental Parameters

40. Dental Parameters
INCISOR MANDIBULAR PLANE:
Intersection MP with a line passing through incisal edge & apex
of root of mandibular central incisors.
Positive angle – forward tipped incisors
Range: -8.5 to 7 degrees, mean 1.4

41. Upper incisor to A-pog line
• This is a linear measurement between the incisal edge of the
maxillary central incisor and the line joining point A to pogonion.
• Average value: 2.7 mm(-1 - 5 mm)
• The measurement is more in patients presenting with upper
incisor proclination.
Dental Parameters

43. Steiner’s analysis
➤ Steiner’s analysis is a cephalometric analysis
introduced by Steiner in 1953.
➤ Steiner’s analysis provides maximum clinical
information with minimum number of measurements.
Steiner’s analysis consists of:
• Skeletal analysis
• Dental analysis
• Soft tissue analysis

44. Steiner’s analysis
Landmarks
The following cephalometric landmarks are used:
➤ Sella (S)
➤ Nasion (N)
➤ Point A (A)
➤ Point B (B)
• Steiner used the sella–nasion
(S–N) plane, the plane obtained
by joining sella and nasion.
• SN plane uses anterior cranial base as the reference
plane.

45. STEINER ANALYSIS

46. SKELETAL ANALYSIS
MAXILLA {SNA}:
• To determine whether maxilla is
positioned anteriorly or posteriorly to
cranial base.
• Mean reading 82 degree
• More angle – relative forward
positioning of maxilla
• Less angle – backward positioning

47. MANDIBLE { SNB};
Mandible protrusive or retrusive
Mean 80 degrees
Greater angle – prognathic mandible.

48. RELATIONSHIP OF MAXILLA TO MANDIBLE {ANB}
ANB provides general idea of anteroposterior discrepancy of
maxilla to mandibular apical bases.
Mean: 2 degrees
Greater – class II skeletal tendency
Lesser – mandible ahead of maxilla

49. OCCLUSAL PLANE:
• Overlapping cusps of first
premolars & first molars.
• Angle of occlusal plane to SN
plane.
• Mean 14 degrees.

50. MANDIBULAR PLANE:
• Drawn between gonion & gnathion
• Mean 32 degrees
• High angle or low angle –
unfavorable growth pattern.

51. DENTAL ANALYSIS:
MAXILLARY INCISOR POSITION:
• Indicates the relative angular
relationship of upper incisor
teeth to N – A line.
• 4mm in front of N-A line & its
axial inclination bears a 22
degrees.

52. MANDIBULAR INCISOR POSITION:
• Relative forward or backward
positioning of teeth to the N-B line.
• Normal value: 4mm, 25 degrees.

53. INTERINCISAL ANGLE:
• Relates the relative position of
upper incisor to that of lower
incisors.
• Normal: 130 degrees.

54. LOWER INCISOR TO CHIN :
• distance between the labial surface of the
lower incisor to N-B line should be equal.
• If difference more than 4mm, corrective
measures are generally indicated.

55. SOFT TISSUE ANALYSIS:
• Includes appraisal of the adaptation of soft tissue to the bony
profile with consideration to size, shape & posture of the lips.
• Acc, to steiners – Lips should touch a line extending from the
soft tissue contour of the chin to middle of S formed by the
lower border of the nose. - S line.
• Lips beyond this line – protrusive.
• Positioned behind – retrusive.

56. Summary of Steiner’s analysis

57. Tweed’s analysis
• Charles Tweed stated that there is a relation between the
inclination of mandibular incisors and mandibular plane angle.
The mandibular incisors should be placed upright over basal
bone for stability and aesthetics.
• Planes used
1. Frankfort horizontal plane: Obtained by joining porion
and orbitale.
2. Long axis of lower incisor: Obtained by drawing a line
along the long axis of incisors.
3. Mandibular plane: Obtained by drawing a tangent to
lower border of mandible.

58. Angles formed
1. Frankfort mandibular plane angle (FMA): It is the angle
formed at the intersection of Frankfort horizontal plane and
mandibular plane. Value is 25° in well-balanced faces.
2. Incisor mandibular plane angle (IMPA): It is the angle
formed at the intersection of mandibular plane and long axis of
lower incisor. Value is 90° in well-balanced faces.
3. Frankfort mandibular incisor angle (FMIA): It is the angle
formed at the intersection of long axis of lower incisor and
Frankfort horizontal plane. Value is 65° in well-balanced faces.

59. Tweed’s analysis
Interpretations
➤ FMA >28° means high angle patient and mandible
grows clockwise.
➤ FMA <23° means low angle patient and mandible
grows counterclockwise.
➤ IMPA >110° means proclined lower incisors.
➤ IMPA <85° means retroclined lower incisors.

60. THANK YOU
We should strive to develop cephalometric norms and
values pertaining to an Indian background instead of
using those meant for Caucasian norms.