The uses and application of cephalometrics in orthodontics

1. 21 January 2015

2.  Introduction
 Types
 History
 Uses
 Equipment
 Positioning of the Patient
 Evaluation of Radiograph
 Landmarks and Planes
 Analysis
 References

3. Cephalometry
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

4. 1) Lateral Cephalogram
• Lateral view of skull
• X-ray beam perpendicular to the patient's sagittal plane
2) Frontal Cephalogram
• Anteroposterior view of skull
• X-ray beam perpendicular to the patient’s coronal plane

5.  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

6.  In orthodontic diagnosis and treatment planning.
› Assesment of horizontal/vertical skeletal relationship,
incisor position/inclination, soft tissue profile
› Orthognathic surgery
 Helps in classification of skeletal and dental
abnormalities.
 Helps in evaluation of treatment results.
› Post-functional to assess skeletal/dental relationship
› Plan retention and monitor post retention phase
 Helps in predicting growth related changes.
 Research purpose

7. • Collimated X-ray source - 5 feet from midsagittal plane of
patient
• Cephalostat - head positioner(with 2 ear rods and forehead
clamp)
• Aluminium wedge/ Barium paste - increases soft tissue
definition
• Film - placed 1.5-1.8 foot behind midsagittal plane of
patient with rare earth metal intensifying screen

8. Cephalostat

9.  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.

10. Important to examine radiograph for any abnormalities or
pathology Eg. Sella turcica increase in size in pituitary tumor
 Digitizing
› Illuminated radiograph viewing screen which is connected to
computer.
› Specialized software used to produce tracing
 Hand Tracing
› Carried out in a darkened room with light viewing box(X-ray viewer)
and all but the areas being traced should be shielded out
› Acetate sheets used as transparency facilitates landmark
identification
› Sharp pencil used ( 0.3mm leaded propelling pencil)
› Acetate sheet to be secured using masking tape and tracing
oriented in the same position as patient when X-ray taken
› Bilateral landmarks, unless directly super imposed, an average of two
should be taken

11. Cephalometry
Tracing

12. Sella :
Centre of the
pituitary fossa of the
sphenoid bone
Nasion :
Junction of
frontonasal suture
Basion :
Most anterior point
of foramen magnum
Anterior Nasal
Spine :
Most anterior
midpoint of ANS
of maxilla
Posterior Nasal
Spine :
Most posterior
midpoint of PNS of
palate
A- Point :
Most concave
point of alveolar
process of
maxilla
B- Point :
Most concave point of
alveolar process of
mandible
Menton :
Most inferior midpoint
of the chin on the
outline of mandibular
symphysis
Pogonion :
Most anterior
midsaggital
point along
convexity of
chin
Gonion :
Midpoint along curvature of
angle of mandible between
inferior border of body and
posterior border of ramus
Condylion :
Most superior
point of
mandibular
condyle
Gnathion :
Most anteroinferior
point on mental
symphysis
Orbitale :
Most inferior point
of infraorbital rim
Porion :
Most superior
point of external
accoustic

13. Landmarks

14. 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.
 Mandibular plane – gonion to
gnathion.
Vertical planes
 A-Pog line – point A on
maxilla to pogonion on
mandible.
 Facial plane – nasion to
pogonion,
 Facial axis – ptm point to
gnathion.
Planes

15. Examples
 Down's
 Steiner
 Rickett
 Harvold
 McNamara
 Sassouni
 Wits by Johnston
 Wylie
 Tweed

16. 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 plan to
degree of retrognathism or prognathism

17. Skeletal Perimeters
 Facial angle
Inferior angle formed by intersection of nasion-
pogonion plane and F.H. plane.
Average value: 87.5o ( 82o - 95o)

18. Significance: Indication of antero- posterior positioning of
mandible in relation to upper face.
- Increased in skeletal class III with prominent chin
- Decreased in skeletal class II

19.  Angle of convexity
Nasion-point A to point A – pogonion.
Average value: 0o ( -8.5o - 10o).

20. Significance:
- Positive angle suggest a prominent maxillary dental
base in relation to mandible.
- Negative angle is indicative of prognathic profile

21.  A-B plane angle
Point A – point B to nasion – pogonion.
Average value: -4.6o ( -9 to 0o)

22. 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

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

24.  Mandibular plane angle
Intersection of mandibular plane with F.H.
Plane.
Average value: 21.9o ( 17 to 28o)

25. Dental Parameters
 Cant of occlusal plane
Occlusal plane to F.H. plane
Average value: 9.3o ( 1.5o - 14o)
Gives a measure of slope of occlusal plane relative
to F.H. Plane.

26.  Inter incisal angle
Angle between long axes of upper and lower incisors.
Average value: 135.4o ( 130o - 150.5o)
Increased in class I bimaxillary protrusion.

27.  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: 14.5o ( 3.5o - 20o)
An increase in this angle is suggestive of increased lower incisor
proclination.

28.  Incisor mandibular plane angle
This angle is formed by intersection of the long axis of
the lower incisor and the mandibular plane.
Average value: 1.4o (-8.2o - 7o)
An increase in this angle is suggestive of increased lower
incisor proclination.

30.  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.

31. Soft tissue Analysis
 Rickett’s E-plane
› Line joining the soft tissue chin and tip of nose. In
balanced face, lower lip lie 2mm (± 2mm) anterior to
this line and upper lip little further posterior

32.  Facial plane
› Line between soft tissue nasion and soft tissue chin. In
well balanced face, the Frankfort plane should
bisect the facial plane at an angle about 86o and
point A should lie on it

33.  The Holdaway line
› Line from the soft tissue chin to upper lip. In a well
proportioned face, if extended, should bisect the
nose

34.  An introduction to orthodontics, Laura Mitchell (3rd
edition)
 Radiographic Cephalometrics, Alexander Jacobson
 Contemporary Orthodontics, William R. Proffit (4th
edition)
 Comparisons of the Consistency and Sensitivity of Five
Reference Lines of the Horizontal Position of the
Upper and Lower Lip to Lateral Facial Harmony, The
Orthodontic Cyberjournal