The document discusses postero anterior (PA) cephalometry, which evaluates craniofacial structures in transverse and vertical dimensions. It describes how to properly position patients for PA cephalograms, including orienting the Frankfort horizontal plane parallel to the floor. Various PA cephalometric landmarks related to specific bones are identified. Planes used in PA cephalograms are described, including the median sagittal reference plane. Grummons analysis for PA cephalograms is outlined, involving horizontal planes, mandibular morphology analysis, and other components.

1. Postero anterior cephalometry
Prof : maher fouda
By : Ameen qulah
1. Om Prakash Kharbanda (Diagnosis and M anagement of Malocclusion and
Dentofacial Deformities)
2. Basavaraj Subhashchandra Phula (an atlas on CephalometriC landmarks)

2. Postero anterior cephalometry
The PA cephalogram offers an effective tool in
evaluating the craniofacial structures in transverse
and vertical dimensions. It allows us to look at
the facial skeleton in relative view of the right-
left face and upper-lower face. First attempts
towards analyzing the craniofacial skeleton on PA
cephalograms were limited to absolute linear
^measurements such as face widths and heights
and later ratio and volumetric comparisons were
added to evaluate relative asymmetries.

3. Set-up for PA cephalometry
Patient’s correct orientation is of utmost importance before exposing the
patient to X-ray radiation. The cephalostat head holder is rotated 90°
so that the subject will face the X-ray cassette and the central X-ray
beam passes through the skull in a posteroanterior direction bisecting
the transmeatal axis perpendicularly. Patient is fixed in a headholder with
the use of ear rods.
The standard distance from X-ray source to the ear post axis is 5
feet. The reproduction of the head position is crucial because if the
head is tilted all vertical dimensional measurements will change.

4. Reproducing correct head orientation
1. Conventionally, head can be
positioned with the tip of the nose
and forehead in light contact with
the cassette holder. This position is
good for evaluation of craniofacial
anomalies which require special
attention to the upper face.
2. The standard method is by
keeping the Frankfort’s 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.

5. Reproducing correct head orientation
3. To ensure correct orientation of head
in FH plane, a guided patient positioning
as follows: A line is scribed on the ear rod
assembly at a point 1^5 mm above the ear
rod.
The height of the orbit is about 3 cm,
and the lateral canthus is essentially at
the centre of the orbit, or 15 mm. The
patient should be oriented such that his ear
canals tuck snugly against the top of the
ear rods with the head positioned so that
the lateral canthus of the eye is located
in level with that line

6. 4- Orienting the head in natural
head position (NHP).6
5- Cephalograms are taken with
the mouth of the patient
slightly open for cases with
significant mandibular
displacement.

7. Signs of good head position on PA
cephalogram X-ray film
1. The head position and the intermaxillary
occlusal relationship that appear in X-ray
should be first confirmed using patient’s
photographs, study casts or clinical evaluation
as a guideline.
2. In a properly oriented frontal head film, the
top of the petrous portion of the temporal
bone will lie near the centre of the orbit.

8. Evaluation of PA cephalogram
Important features
1. Orbits - whether normally inclined or oblique
and size of orbits whether equal or
disparate.
2. Ramus of the mandible - whether present or
absent or underdeveloped as seen in unilateral
or bilateral hypoplasia cases.
3. Angle of mandible - whether obtuse or acute.
Obtuse angle is usually seen on the unaffected side
in ankylosis.
4. Body of mandible - whether present or
absent and developed on both sides to an equal
extent or not. May be deviated to either side in
certain situations.

9. 5- Chin - whether present in centre
or deviated to one side as seen in
cases of asymmetry of mandible.
6- Malar bones - whether equally
prominent on either sides or one
side as in craniofacial syndromes.
7- Maxillary antra - whether equal
on both sides and whether the
development is normal or not.

10. 8- Width.of dental arches - may be
underdeveloped or over developed
on either sides.
9. Cant of occlusal plane - can be
compared at a single glance in PA
cephalogram. Cant may be tilted
to the affected side in TMJ
ankylosis cases.
10. Nasal widths - may be equal or
unequal as in unilateral hypoplasia.

11. PA cephalometric landmarks/points
related to specific bones are listed below:
1. Cephalometric landmarks (points) related to
ethmoid bone.
2. Cephalometric landmarks (points) related to nasal
bone.
3. Cephalometric landmarks (points) related to
zygomatic bone.
4. Cephalometric landmarks (points) related to
maxillary bone.
5. Cephalometric landmarks (points) related to
dentition.
6. Cephalometric landmarks (points) related to
mandible.

12. PA Cephalometric
Landmarks Related to
Ethmoid Bone

13. ).
Cg. Critsta galli :
Neck of crista galli, most
constricted point of the projection
of the perpendicular lamina of the
ethmoid (almost at the level of
planum

14. PA Cephalometric
Landmarks Related to
Nasal Bone

15. Top of Nasal Septum
according to athanasios E
athanasiou (tns)
The highest point onto the superior
aspect of the nasal septum
Type
Top of nasal septum is a unilateral,
anatomic, hard tissue PA
cephalometric landmark.

16. Nasal cavity (NC)
according to Robert M Ricketts
Lateral most point on inside surface of the bony nasal
cavity
Type: NC is a unilateral, anatomic, hard tissue
PA cephalometric landmark.

17. Pa Cephalometric
Landmarks Related to
zygomatic Bone

18. (Zyg)zygoma
according to Viken
Sassouni :
Most lateral and superior point of
the shadow of the zygomatic arch
Type:
Zygoma is a bilateral, anatomic,
hard tissue PA cephalometric
landmark.

19. Zygion (zy)
according to Robert M
Ricketts
Zygion is the most lateral
point of each zygomatic arch .
Type
Zygion is a bilateral, anatomic,
hard tissue PA cephalometric
landmark

20. zygomatic arch (ZA)
according to Robert M
Ricketts
Center of zygomatic arch by
inspection for frontal.
Type
Zygomatic arch is a bilateral,
anatomic, hard tissue PA cephalo-
metric landmark.

21. zygomatic Suture Point - Z
according to Robert
M Ricketts
Medial and anterior junction of
the zygomatic bone with the
frontal bone
Type
Zygomatic suture point is
a bilateral, anatomic,
hard tissue PA cephalometric
landmark.

22. Jugal Process ( J)
Bilateral points on the jugal process
at the intersection of the outline of
the tuberosity of the maxilla and
zygomatic buttress (left and right).
according to Robert M Ricketts
Lowest point on the curve
of zygomatic bone used in
the lateral film, also the point
on the jugal process of the
maxilla at a crossing with the
tuberosity of the maxilla
(in the frontal)

23. Pa Cephalometric
Landmarks Related to
Maxilla

24. Maxillare (Mx)
• Maximum concavity on the
contour of the maxilla between the
first molar and malare .
• Maximum concavity on the
contour of the maxilla between
malare (Ma) and the maxillary first molar (U6).Closely
corresponds to the key ridge.
• The intersection of the
lateral contour of the maxillary
alveolar process and the lower
contour of the maxillozygomatic
process of the maxilla (left and right).

25. Pa Cephalometric Landmarks
Related to Dentition

26. Incision Superius Incisalis (Isi)
Incision superius incisalis is the
incisal edge of the maxillary central
incisor.
according to arne Bjork
Incision superius incisalis is the
mid-point of the incisal edge of the
most prominent upper central
incisor.
according to Robert E Moyers
Incision superius incisalis is the
incisal tip of the most anterior
maxillary central incisor.

27. Incision Superius apicalis
Incision superius apicalis (Isa(
Upper incisor apex (UIA)
Incision superius apicalis is the root apex of the
most anterior maxillary central incisor; if this
point is needed only for defining the long axis of the
tooth, the midpoint on the bisection of the apical root
width can be used.
according to Michael L Riolo
The upper incisor apex is the root tip of the maxillary
central incisor. In cases where the root is not
yet completed, the midpoint of the growing root
tip is marked.
SN Bhatia and BC Leighton
The upper incisor apex is the root apex of the most
prominent upper incisor.

28. Maxillary Molar (um)
Definition
according to athanasios E
athanasiou
The most prominent lateral point
on the buccal surface of the
second deciduous or first
permanent maxillary molar

29. Maxillary First Molar
U6–Maxillary first molar
A6—Maxillary first molar
Definition
Maxillary first molar is the tip of the
mesiobuccal cusp of the maxillary
first permanent molar.
Tracing of Maxillary First Molar on Lateral Cephalogram
The labial and lingual and cuspal outlines of the crown
of the maxillary permanent first molar appears as
radio-opaque lines on the lateral cephalogram. Trace
these outlines of crown of the maxillary permanent
first molar, the tip of the mesiobuccal cusp of the
maxillary permanent molar is the point of maxillary
first molar.

30. Cuspid
Abbreviation
A3–Cuspid
Definition
according to Carl F gugino
Tip of the upper permanent canine .
Type
Cuspid is a bilateral, hard tissue
cephalometric landmark.

31. Incision Inferius Incisalis (Iii)
Definition
Incision inferius incisalis is the incisal
edge of the most prominent mandibular
central incisor.
according to arne Bjork
The incision inferius is the incisal point
of the most prominent medial
mandibular incisor.
according to Robert E Moyers
The incision inferius is the
incisal tip of the most labial
mandibular central incisor.

32. Incision Inferius apicalis (Iia)
Definition
Incision inferius apicalis is the
root apex of the most anterior
mandibular central incisor; if this
point is needed only for defining the
long axis of the tooth, the midpoint
on the bisection of the apical root
width can be used.
SN Bhatia and BC Leighton
The lower incisor apex is the
root apex of the most prominent
lower incisor.

33. Incision Inferius Frontale (iif)
Definition
according to athanasios E
athanasiou
The midpoint between the
mandibular central incisors at the
level of the incisal edges .
Type
Incision inferius frontale
is a unilateral, hard tissue
cephalometric landmark.

34. Mandibular First Molar (L6)
Definition
Mandibular first molar is the
tip of the mesiobuccal cusp of
the mandibular first permanent
molar.
Type
Mandibular first molar is a unilateral,
anatomic, hard tissue cephalometric
landmark.

35. mi
Definition
mi is the mesial contact of the lower
molar projected normal to the plane of
occlusion.
Significance
mi is used as one of the reference
points in the construction of plane and
angle in the Bjork cephalometric
analysis.

36. Mandibular Molar (Im)
Definition
according to athanasios E
athanasiou
The most prominent lateral point on
the buccal surface of
the second deciduous or first
permanent mandibular molar
Type
Mandibular molar is
a bilateral, hard tissue
cephalometric landmark.

37. Pa Cephalometric Landmarks
Related to Mandible

38. Menton ( Me)
according to Viken Sassouni
Lower most point of the contour of
the chin.
according to Carl F gugino
Menton is the point on inferior border
of symphysis directly inferior
to mental protuberance and
below center of trigonium
mentali.

39. Articulare (Ar)
Definition
Articulare is the point of intersection the
dorsal contours of the processus articularis
mandibulare and os tempoarle.The midpoint,
a is used where double projection gives rise
to two points
Significance
• Constructions of posterior/ramus border of
the mandible i.e. the line joining the point
articulare and gonion.
• Growth pattern is assessed using Go and Go
angles.
• Rotation of the mandible is also assessed

40. Malare (Ma)
Definition
according to Viken Sassouni
Midpoint of intersection
between the projection of the
coronoid process and the lower
contour of the malar bone

41. antegonial Tubercles (Ag)
Definition
according to Robert M Ricketts
Intersection of the outline of
the dense bone of the
trihedral eminence with the
lower border of the ramus.

42. Antegonion (Ag)
Definition
according to athanasios E
athanasiou
The highest point in the
antegonial notch (left and right)

43. Planes in PA cephalogram
Various horizontal and vertical planes are drawn
in PA cephalogram in different analyses for the
determination of asymmetry, linear dimensions and
angles.

44. Median sagittal reference (MSR) plane
It has been selected as a key
reference line because it closely
follows the visual plane formed by
subnasale and the midpoints between
the eyes and eyebrows. The median
sagittal reference plane normally runs
vertically from crista galli (Cg)
through the anterior nasal point
(ANS) to the chin area, and is
typically nearly perpendicular to the
Z plane (line joining zygomaticofrontal
suture of one side to the other).

45. If the location of Cg is in
question, an alternative method of
drawing MSR is to draw a line
from the midpoint of the Z plane
through ANS. The position of
anterior nasal spine will be
altered in facial asymmetry
involving the maxilla.

46. If there is upper facial asymmetry,
MSR can be drawn as a line from the
midpoint of the Z plane through the
midpoint of the Fr-Fr line (foramen
rotundum of one side to the other). To
avoid any such bias, a best-fit vertical
line is drawn in the center connecting
the midpoints of lines joining
zygomaticofrontal sutures (Z-Z), the
centres of the zygomatic arches (ZA),
the medial aspects of the jugal
processes (J) and antegonial notch
(AG-GA) of both the sides.

47. The best-fit line and all lines
constructed as perpendiculars through
midpoints between pairs of orbital
landmarks have shown excellent
validity.
Besides vertical reference lines,
horizontal best-fit lines have to be
constructed to know the asymmetry
in vertical plane. All horizontal lines
connecting bilateral cranial landmarks
can adequately serve as reference
lines in the analysis of vertical
asymmetry from PA cephalograms, if
landmark identification error is
acceptable.

48. Grummons analysis
Grummons analysis is a
comparative and quantitative PA
cephalometric analysis and is not
related to normative data.
The analysis consists of different
components:
1. Horizontal planes
2. Mandibular morphology
3. Volumetric comparison
4. Maxillomandibular comparison of
asymmetry
5. Linear asymmetry assessment
6. Maxillomandibular relation
7. Frontal vertical proportions.

49. Horizontal planes
Four planes are drawn to show
the degree of parallelism and
symmetry of the facial structures.
Three planes connect the medial
aspects of the zygomatic frontal
sutures (Z-Z), the centres of the
zygomatic arches (ZA), and
the medial aspects of the jugal
processes (J). Another plane is
drawn at menton parallel to the
Z plane. MSR has been
selected as a true vertical
reference line.

50. Mandibular morphology
Left and right triangles are
formed from the heads of the
condylar processes or the
condyles (Co), the antegonial
notches (AG), and menton. These
are split by the ANS-ME line and
compared. ANS-ME parallels the
visual dividing
line from subnasale to soft tissue
menton in the lower face.
Linear values and angles can be
measured while the anatomy can
be determined. Like the horizontal
planes, this data is quite sensitive
to head rotation.

51. 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. A computer can
superimpose one polygon
upon the other to provide a
percentile value of
symmetry.
GA
CO
ME

52. Maxillomandibular
comparison of asymmetry
Perpendiculars are drawn to
MSR from J and GA, and
connecting lines from Cg to J
and GA. This produces two
pairs of triangles, each pair
bisected by MSR. If perfect
symmetry is present, the four
triangles become two, J-Cg- J’
and AG-Cg-GA.

53. Linear asymmetries
The vertical offset as well as the linear distances
are measured from MSR to Co, C, J, AG and ME.

54. Maxillomandibular relation
To allow tracing of the functional posterior occlusal plane, a .014" wire
is placed across the mesio-occlusal areas of the maxillary first molars.
The wire should extend about 3 mm buccally to make it easy to
recognize on the head film.Distances are measured from the
buccal cusps of the upper first
molars (on the occlusal plane)
along the J perpendiculars.
The AG plane, MSR, and the
ANS-ME plane are also drawn to depict
the dental compensations for any skeletal
asymmetries in the horizontal or vertical
planes (maxillomandibular imbalance).
Midline asymmetries of the upper and
lower incisors and ME-MSR are also
provided.

55. Frontal vertical proportions
Skeletal and dental measurements are made
along the Cg- ME line with divisions at ANS,
Al, and Bl. The following ratio are
calculated.
1. Upper facial ratio— Cg-ANS/Cg-ME 42 %
2. Lower facial ratio— ANS-ME/Cg-ME 58%
3. Maxillary ratio— ANS-A1/ANS-ME 54%
4. Total maxillary ratio— ANS-Al/Cg-ME
31%
5. Mandibular ratio— B1 -ME/ANS-ME 55%
6. Total mandibular ratio— B 1 -ME/Cg-ME
32 %
7. Maxillomandibular ratio— ANS-A1/B1-
ME 97%

57. Ricketts analysis
Ricketts analysis gives a normative data of
parameters measured, which is helpful in
determining vertical, transverse dental and skeletal
problems. It has five components:
1. Dental relations
2. Skeletal relations
3. Dental to skeletal
4. Jaw to cranium
5. Internal structure.

58. Dental relations

59. Dental relations
1. Molar relation left (A6-B6).
2. Molar relation right (A6-B6). A differences in
width between the upper and lower molars
measured at the most prominent buccal contour of
each tooth. Used to describe the buccal/lingual
occlusion of first molars
.
2 mmClinical
deviation
1.5 mmnorm
2mmClinical
deviation
1.5mmnorm

60. Intermolar width (B6-B6).
It 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
a crossbite.

61. Intercanine width (B3-B3).
It is measured from the tip of
the mandibular right canine to
the tip of the mandibular left
canine.
Denture midline.
It is measured from the midline
of the upper arch to the midline
of lower arch

62. Skeletal relations

63. • Maxillomandibular width right.
It is measured from the jugal process
to the frontal facial plane
(constructed from the medial margins
of the zygomaticofrontal sutures to
AG point). Used to measure
skeletal crossbite.
• Maxillomandibular width left. It
is measured on left side

64. Maxillomandibular midline.
It is measured by the angle formed
by the ANS-ME plane to a plane
Perpendicular to ZA-AZ plane.
Interpretation:
Determines the mandibular midline
deviation with respect to the
midsagittal plane. This asymmetry
might be the consequence of functional
or skeletal problems

65. 4. Maxillary width (J-J’).
It is measured as transverse
distance from J-J’.
5. Mandibular width (AG-GA).
It is measured as transverse
distance from AG-GA.

66. Dental to skeletal
Clinical deviation

67. 1. Lower molar to jaw left (B6 to J-
GA left).
2. Lower molar to jaw right (B6
to J-AG right). It is measured
from the buccal surface of the
lower molars to a plane from
the jugal process to the
antegonial notch. Norm: 6.3
mm, clinical deviation: 1.7 mm.
increased measure indicates the
likelihood of a buccal mandibular
expansion
Clinical deviation

68. 3. Denture-jaw midline.
It is measured from the midline
of the denture to the midline
of the jaws (ANS-ME).
Clinical deviation

69. 4. Occlusal plane tilt.
It describes the
difference in the height
of the occlusal plane to
the ZL-ZR plane.
Clinical deviation

70. Jaw to cranium
Clinical deviation

71. Postural symmetry. It is
measured by the difference
inthe angles (left and right)
formed by a plane from the
zygomatic suture to
antigonion andantigonion to
the zygomatic arch. Used to
determine cause of
asymmetries.
Interpretation: Used for the
diagnosis of asymmetry
Clinical deviation

72. Internal structure
Clinical deviation

73. Nasal width.
It is measured from the widest
aspects of the nasal cavity. May
be used to determine the cause
of mouth breathing.
Clinical deviation

74. 2.Nasal height.
It is measured by the distance
from the ZL-ZR plane to the
anterior nasal spine.
3. Facial width.
It is measured at AZ-ZA points.
It essentially describes width at
zygomatic arches and can be
useful in maxillary expansion
decision making.

75. Maxillomandibular differential values
and ratio
Maxillomandibular differential
values and ratios obtained
from PA cephalogram help
us in estimating the
transverse deficiency and
also the amount of
expansion required.
Maxillomandibular
differential value is the
difference between mandibular
width (AG-GA, antigonion -
antigonion) and maxillary
width (J- J’). A differential in
total width of about 20 mm
was considered satisfactory

76. A definite ratio exists between maxillary and
mandibular width and also nasal cavity to maxilla,
which will help us in determining the relative
transverse problem in the arches.
The value of ratio of maxilla to mandible is about
80%, and the ratio of nasal cavity to maxilla ranges
from 40 to 42%.

77. Summary
• PA cephalogram is an essential diagnostic aid in cases
with facial symmetry. It can answer the important
aspects of facial symmetry like maxillomandibular
width, occlusal plane level, dental to skeletal
midline, skeletal midlines and chin location.
• It is helpful in determining true asymmetry from the
apparent.
• The PA cephalogarms are used to assess location and its
quantification of transverse problem, skeletal class
III, and for prediction of upper canine impactions.
• PA cephalogram is used to measure the amount of
maxillary expansion required and that has occurred
with treatment.

78. Thank
you