The presentation contains information related to posteroanterior cephalometrics which is very important in patients with facial asymmetry .

1. PA Cephalometrics
Dr. Gourav Sriwastva
1st Year PGT

2. CONTENTS
• Introduction
• Setup of PA Cephalometry
• Head Positioning for PA Cephalometry
• Interpretation of PA Cephalogram
• Landmarks on a PA Cephalogram
• Planes in a PA Cephalogram
• Grummon’sAnalysis
• Rickett’s Analysis
• Svanholt & Solow Analysis
• Grayson Analysis
• Hewitt Analysis
• Chierici Method
• Limitations of PA Cephalometry
• Application of PA Cephalometry
• References.

3. Introduction
• The frontal view of face, and consequently the posteroanterior (PA) cephalogram,
should be an integral part of facial evaluation, given that we present ourselves to
the world face forward.
• PA Cephalogram is an effective tool in evaluating transverse and vertical
dimension of craniofacial structures.
• Asymmetry of craniofacial skeleton is most readily diagnosed from the frontal (PA
view) rather than lateral view.
Ref : Chebib, F. S., & Chamma, A. M. (1981). Indices of craniofacial asymmetry. The Angle Orthodontist, 51(3), 214–226. https://doi.org/10.1043/0003-
3219(1981)051<0214:IOCA>2.0.CO;2
•

4. Setup for PA Cephalometry
• Image Receptor & Patient Placement :
• Image receptor is placed in front of the patient ,
perpendicular to the mid sagittal plane and
parallel to the coronal plane.
Why ?
• Canthomeatal line forms a 9ᵒ angle with the
Frankfurt plane and the Frankfurt plane is
perpendicular to the image receptor.
• For standard PA skull projection, the
canthomeatal line is perpendicular to the image
receptor.
• Ref : White, S. C., & Pharoah, M. J. (2014). Oral radiology: Principles
and interpretation (7th ed.). Mosby.
Ref : RadiographicCephalometry From Basics to 3D
Imaging Jacobson 2nd ed

5. • Position of Central X- ray Beam :
• The central beam is perpendicular to the image receptor, directed from the
posterior to anterior.
• Parallel to the patient’s midsagittal plane and is centered at the level of the
bridge of the nose.
Ref: White, S. C., & Pharoah, M. J. (2014). Oral radiology: Principles and interpretation (7th ed.). Mosby.

6. • Resultant Image :
• The midsagittal plane ( An
imaginary line extending from the
interproximal space of the central
incisors through the nasal septum
and middle of the bridge of nose.)
should divide the skull image into
two symmetric halves.
• The superior border of the petrous
ridge should lie in the lower third of
the orbit.
Superior Border of Petrous Ridge

7. • The standard distance from the X-ray source to the ear rods is 5 ft.
• Reproduction of head position is crucial because if the head is tilted then
vertical dimension measurements will not be accurate.

8. Head Positioning for PA Cephalogram
• Head can be positioned with the tip of the nose and
forehead in light contact with film cassette holder
sensor.
• The standard method is by keeping the Frankfort
Horizontal Plane parallel to the floor while the
patient is facing the X-ray film cassette as close as
permissible within the limits of nose prominence.

9. • To ensure correct orientation of the head in the
FHP, patient positioning should be guided by
scribing a line on the ear rod assembly at a point
15 mm above the ear rod.
• The height of the orbit is around 3 cm, and the
lateral canthus is essentially at the center of the
orbit, or 15 mm .
• Orienting the head in the natural head position.

10. • Cephalogram should be taken with the mouth of the patient slightly open in
cases of significant mandibular displacement.
• Signs of a good head position :
1.Top of the petrous portion of the temporal bone lies near the centre of the
orbit.
2. The head position and intermaxillary occlusal relationship that appear on
the X- ray should first be checked using an intraoral photograph of the patient,
study casts or by clinical evaluation of the occlusion.
3. No double shadow.

11. Evaluation on a PA cephalogram
• Orbits : Whether normally inclined or
oblique and whether equal or disparate
in size.
• Ramus of Mandible : Whether
present, absent, or underdeveloped as
seen in unilateral or bilateral
hypoplasia.
• Angle of Mandible : Obtuse or Acute.
An obtuse angle is seen on the
unaffected side of ankylosis.
• Body of Mandible : Whether present
,absent or developed on both sides to
an equal extent or not. May deviate to
either side in certain situation.

12. • Chin : Whether present in the centre or deviated
to one side as seen in cases of asymmetry of the
mandible.
• Malar Bone : Whether equally prominent on
either side or just one side as in craniofacial
syndromes.
• Maxillary sinus : Whether equal on both sides
and development is normal or not.
• Width of Dental Arches : May be
underdeveloped or overdeveloped.
• Cant of Occlusal Plane : can be compared at a
single glance in a PA Cephalogram.
• Nasal Width : May be equal or unequal as in
unilateral hypoplasia.

13. Landmarks on a PA Cephalogram
• Zygomatic Point (ZL,ZR) : Bilateral
points on the medial margin of the
zygomaticofrontal suture at
the intersection of the orbit.
• Center of the Roof of Zygomatic
Arch (ZA,AZ) : It is abbreviated as ZA
for left side and AZ for the right side.
• Euron Point (EL,ER) : The most
lateral point on the side of the head in
the region of parital bone.

14. • J Point : Bilateral points on the
jugal process at the intersection of
the outline of the tuberosity of the
maxilla and zygomatic buttress.
• AG (Antegonial tubercle :
Mandible) : Points at the lateral
inferior margin of the antegonial
protuberance. (GA, Left & AG,
Right).
• Crista Galli (Cg)
• ANS (Anterior Nasal Spine) : Tip
of the ANS just below the nasal
cavity and above the hard palate.

15. • Condylon (Cd) : The most
superior part of the condylar
head.(Left and Right)
• A1 Point : A point selected at
the interdental papilla of the
upper incisors at the junction of
the crown and gingiva.
• B1 Point : A point selected at
the interdental papilla of the
lower incisors at the junction of
crown and gingiva.
• ME (Mental) : The most inferior
midline point on the
mandibular symphysis.

16. Planes in a PA Cephalogram
Median Sagittal Reference Plane (MSR
Plane) :
 It follows the visual plane formed by the
subnasale and midpoints between the
eyes and eyebrows thus it’s a key
reference line.
 It runs vertically from Cg through ANS to
the chin area and nearly perpendicular
to the Z plane.
 The Z plane is a line joining the
zygomatico-frontal suture of one side to
the other.

17. • If the location of Cg is in question,then MSR
plane is drawn from the midpoint of Z plane
through the ANS.
• If there is upper facial asymmetry , MSR
plane is drawn from Midpoint of Z plane
through the midpoint of Fr-Fr plane. (
Foramen rotundum of each side).
• To avoid any bias , a best fit vertical line is
drawn in the centre connecting the
midpoints of the line joining the
Zygomaticofrontal Sutures ( Z-Z), Centres of
Zygomatic archs(ZA), Medial aspects of
Jugal processes (J) and the Antegonial
notches (AG-GA) of both sides.

18. Interpretation of PA Ceph
Step 1
• Evaluate calvaria, sutures,and diploic space starting in the area of the left EAM, Mastoid air
cells and petrous ridge of temoral bones of either side.
• Look for intracranial calcifications.
Step 2
• Evaluate upper & middle face. Identify orbit, sinus (frontal, ethmoid, maxillary), zygomatic
process of maxilla, nasal cavity, turbinates, septum and hard palate.
• Look for sinusitis, nasal septal deviation.

19. Step 3
• Evaluate the lower face.Follow the outline of the mandible starting from the right condylar
and coronoid processes,ramus, angle and body through the anterior mandible to the same
anatomic structure on left side.
• Look for any bony prominence or mandibular pathologies.
Step 4
• Evaluate the cervical spine. Identify dens, superior border of C2, and the inferior border of C1
• To find out how much growth has occurred so far and how much growth is still remaining.

20. Step 5
• Evaluate the alveolar bone and teeth.

22. Grummons’ Analysis
• It is a comparative and quantitative PA cephalometric analysis.
• It is not related to normative data.
• It consists of number of components:
1.Horizontal Planes.
2.Mandibular Morphology.
3.Volumetric Comparison.
4. Maxillomandibular comparison of asymmetry.
5. Linear AsymmetryAssessment.
6. Maxillomandibular Relation.
7. FrontalVertical Proportions.

23. • Horizontal Planes :
Four planes can be drawn to show
the degree of parallelism and
symmetry of facial structures.
Three planes connect the medial
aspects of zygomaticofrontal sutures
(Z-Z),centers of ZA and medial
aspects of Jugal processes (J).
Another plane is drawn at the
menton parallel to the Z plane.
The MSR plane has been selected as a
true vertical reference line.

24. • Mandibular Morphology :
 Left and right triangles are formed at the
heads of the condylar processes or
Condyles (Co), antegonial notches (AG),
and the menton and then compared.
 The ANS-ME line parallels the visual
dividing line from the sub – nasale to the
soft tissue menton in the lower face.

25. • Volumetric Comparison : Two
‘volumes’(polygons) are
calculated from the area
defined by each Co-GA-ME and
the intersection with a
perpendicular from Co to MSR.

26. • Maxillomandibular Comparison of
Asymmetry :
Drawing perpendiculars from J and GA to
the MSR plane and connecting lines from
Cg to J and GA produces two pairs of
triangles, each bisected by the MSR plane.
If there is perfect symmetry the four
triangles become 2 : J-Cg-J and AG-Cg-GA.

27. • Linear Asymmetry Assessment : Vertical
offset and linear distances are measured
from the MSR Plane to Co,C,J,AG.

28. Maxillomandibular Relation :
 To allow tracing of the functional posterior occlusal
plane a 0.014” wire is placed across the
mesiocclusal areas of the maxillary first molars.
 The wire should extend about 3mm buccally to
make it easy to recognise on the head film.
 Distances are measured from the buccal cusps of
the upper first molars ( on the occlusal plane) along
the J perpendiculars.
 Ref : Orthodontic Cephalometry . Athanasios E. Arthanasiou. Mosby –Wolfe.

29. • Frontal Vertical Proportions
• Skeletal and dental measurements are made along the Cg-ME line with divisions at
the ANS,A1 and B1.
• The following ratios can be calculated:
1. Upper Facial Ratio : Cg-ANS / Cg-ME
2. Lower Facial Ratio : ANS-ME / Cg-ME
3. Maxillary Ratio : ANS-A1 / ANS-ME
4. Total Maxillary Ratio : ANS –A1 / Cg-ME

30. 5. Mandibular Ratio : B1-ME / ANS- ME.
6.Total Mandibular Ratio : B1- ME / Cg- ME
7. Maxillomandibular Ratio : ANS-A1 / B1-ME.
These values can be compared with common facial aesthetic ratio and
measurements.

31. Ricketts’ Analysis
• Provides normative data of the parameters measured.
• Helpful in determining vertical, transverse, dental and skeletal problems.
• It has 5 components : 1. Dental relations.
2. Skeletal relations
3. Dental to Skeletal
4. Jaw to Cranium
5. Internal structure.

32. • Dental Relations :
1. Molar relation left (A6 – B6)
2. Molar relation right (A6 –B6)
Molar relations indicate the difference in width
between the upper and lower molars measured at the
most prominent buccal contour of each tooth.They are
used to describe the buccal / lingual occlusion of the
first molars.
3. Intermolar width (B6 – B6) : Intermolar width is
measured from the buccal surface of the mandibular
left first molar to the buccal surface of the mandibular
right first molar.This is helpful in determining the
aetiology of cross bite.
4. Intercanine width (B3-B3) : Intercanine width is
measured from the tip of the mandibular right canine
to the tip of mandibular left canine.
5. Denture midline :The denture midline is measured
from the midline of the lower arch.

33. • Skeletal Relations :
It comprises of –
1. Maxillomandibular width right
2. Maxillomandibular width left – measured
from the jugular process to the frontal
facial plane ( constructed from medial
margins of zygomaticofrontal sutures to
the AG point ).
They used to measure skeletal crossbite.
3. Maxillomandibular midline – measured by
the angle formed byANS – Me plane to a
plane perpendicular to the ZR-ZL plane.
4. Maxillary width ( J-J) – Measured as the
transverse distance from J to J.
5. Mandibular width ( AG –GA ) – Measured as
transverse distance from AG to GA.

34. • Dental to Skeletal : It comprises,
1.Lower Molar to Jaw Left ( B6 to J- GA left )
2. Lower molar to Jaw Right ( B6 to J- AG
right ) : Measured from the buccal surface
of the lower molars to a plane from the jugal
process to the antegonial notch.
3. Denture – Jaw midline : Measured from the
midline of denture to the midline of jaws (
ANS- Me )
4. Occlusal planeTilt : Describes the
difference in height of the occlusal plane
from the ZL-ZR plane.

35. • Jaw to Cranium :
1. Comprises a single entity , postural
symmetry, which is measured by the
difference in angles ( left and right )
formed by a plane from the zygomatic
suture to the antegonion to the zygomatic
arch.
2.It is used to determine cause of
asymmetries.

36. • Internal Structure :
1. Nasal width : Measured from the widest aspects
of the nasal cavity. Used to determine cause of
mouth breathing.
2. Nasal height : Measured by distance from the ZL-
ZR plane to ANS.
3. FacialWidth : Measured at the AZ-ZA points . It
essentially describes width at the ZA and can be
useful in maxillary expansion decision making.

37. • Maxillomandibular DifferentialValue & Ratio :
• It is the difference between the mandibular width (AG – GA) and the maxillary
width (J-J).
• NormalValue is 20 mm.
• This value helps us in estimating transverse deficiency and the amount of
expansion required.
• The ratio of the maxilla to mandible is about 80 % , and that of the nasal cavity to
maxilla ranges from 40 % to 42%.

38. Svanholt & Solow Analysis
• This method aims to analyze one aspect of
transverse craniofacial development namely, the
relationship between the midline of jaws and the
dental arches.
• Early orthopedic interception of a deficient maxilla
re-establishes an optimal growth in the sagittal and
transverse dimensions, thus facilitating the
correction of class III mid-facial deficiency and the
elimination of permanent mandibular structural
asymmetry.
Ref :The functional shift of the mandible in unilateral posterior crossbite and the
adaptation of the temporomandibular joints: A pilot study. P.H. Nerder, M. Bakke.

39. Grayson Analysis
• This analysis permits visualization of skeletal
midlines at selected depths of the craniofacial
complex.
• In case of hemicraniofacial microsomia
(unilateral underdevelopment of the mandible,
maxilla, external and middle ear, zygoma,
parotid gland, fifth and seventh cranial nerves,
and associated musculature and soft tissue ) this
analysis can be used because it localizes
asymmetry in posteroanterior and basilar
views.
• Ref : Analysis of craniofacial asymmetry by multiplane
cephalometry. Bary H Grayson, Joseph G McCarthy.
• Shafer’s Textbook of Oral Pathology , 8th ed.

40. Hewitt Analysis
• 63 cephalometric PA radiographs were
traced and area of triangles were
compared with the equivalents on the
contra lateral side.
• The findings suggest an overall
asymmetry with the larger side being the
left.The cranial base and maxillary regions
tended to be larger on the left, the
mandibular and the dento-alveolar
regions exhibiting a greater degree of
symmetry.
• Ref :A Radiographic Study of Facial Asymmetry A. B.
Hewitt .British Journal of Orthodontics, 2:1,37-40

41. Chierici Method
• A line connecting the lateral extent of the
zygomaticofrontal sutures on each side (zmf-zmf line) is
constructed.
• Line X is drawn through the root of the crista galli
perpendicular to zmf-zmf.
• The method focuses on the examination of the
asymmetry in the upper face.
• Examination of the different structures and landmarks on
both left and right sides on the same plane and the
deviation of midline structures can identify craniofacial
asymmetry and reveal its extent.

42. Limitations of PA Cephalometry
• Cants of occlusal and transverse planes are sensitive to head rotation and
tilt.Therefore correct head position is critical while taking a PA
cephalogram.

43. Application of PA Cephalometry
• Diagnosis : For assessing asymmetry of face and widths of the jaws and
cranium.
• Skew of sagittal cephalometrics reflects the sustained use of Edward H.
Angle’s sagittally defined classification of malocclusion.
• In diagnosing deviated nasal septa cases, nasal turbinate hypertrophy,
canine impaction , cervical lordosis and key findings in cleft palate.

44. • Transverse Growth :
• Transverse development of jaws is characterized
by differential growth between maxilla and
mandible. Mandibular width proceeds, on an
average at a ratio of 2:1 relative to maxillary
width between ages 10 and 18 years.
• The posterior width grows more than the
anterior breadth of the jaws. ( Grayson et al.
observation ).
• Dentoalveolar width at the level of first molars (
between right and left buccal surfaces of crowns
and apices) seems to be stable.
• Ref : RadiographicCephalometry from Basics to 3D imaging. Alexander Jacobson 2nd

45. • Treatment : ForAssessment of orthognathic surgery outcomes involving
the patient’s midline or mandibular –maxillary relationship. . ( ref : White, S. C., & Pharoah,
M. J. (2014). Oral radiology: Principles and interpretation (7th ed.). Mosby.)
• To evaluateTMJ Disk Displacement & mandibular asymmetry in skeletal
class III patients. ( ref:The relationship betweenTMJ disk displacement & mandibular asymmetry in skeletal class III
patients. Hyung Joo Chri,Tae-Woo-Kim, AngleOrthodont.2011)

46. • To measure the amount of maxillary expansion required and the amount
that has occurred with treatment.
• To decide in which case Orthognathic Surgery is needed and in which case
Dentofacial Orthopedic treatment can be done.

47. Envelope of Discrepancy
Ref :The CurrentConcepts of Orthodontic Discrepancy Stability, Maen Mahfouz .

48. Envelope of discrepancy has following features-
1) Quantitative: Describes the magnitude and severity of discrepancy in
metric measurements.
2) Qualitative: Describes the quality of discrepancy in classes and types.
3) Dynamics: Describes the stability of discrepancy and its changes by age
either by soft and/or hard tissue.

49. Software Based (RES-NET 18)PA Cephalometry

50. Conclusion
PA Cephalogram are essential diagnostic aids in cases with facial asymmetry
hence PA cephalometric analysis should always be included with lateral
cephalometric analysis for a more clear and understandable treatment
approach in such cases.

51. References :
• Chebib, F. S., & Chamma, A. M. (1981). Indices of craniofacial asymmetry. The Angle Orthodontist, 51(3), 214–226. https://doi.org/10.1043/0003-
3219(1981)051<0214:IOCA>2.0.CO;2
• White, S. C., & Pharoah, M. J. (2014). Oral radiology: Principles and interpretation (7th ed.). Mosby.
• Radiographic Cephalometry From Basics to 3D Imaging Jacobson 2nd ed.
• Orthodontic Cephalometry. Athanasios E Arthanasiou. Mosby- Wolfe.
• The Current Concepts of Orthodontic Discrepancy Stability, Maen Mahfouz .
• The functional shift of the mandible in unilateral posterior crossbite and the adaptation of the temporomandibular joints: A pilot study. P.H. Nerder,
M. Bakke.
• Analysis of craniofacial asymmetry by multiplane cephalometry. Bary H Grayson, Joseph G McCarthy.

52. • A Radiographic Study of Facial Asymmetry A. B. Hewitt .British Journal of Orthodontics, 2:1,37-40
• Shafer’s Textbook of Oral Pathology . 8th ed.
• The relationship between TMJ disk displacement & mandibular asymmetry in skeletal class III patients. Hyung Joo Chri, Tae-Woo-Kim, Angle
Orthodont.2011
• Automatic identification of posteroanterior cephalometric landmarks using a novel deep learning algorithm: A comparative study with human
experts. Hwangyu Lee, Jung Min

53. Thank You