Postero - Anterior cephalometry basics/cosmetic dentistry courses

 Introduction.
 Technical Aspects.
 Different Head Positions.
 Exposure Conditions and Considerations.
 Skull Anatomy : Frontal and Posterior View .
 Radiographic Anatomy.
 Cephalograph Tracing Procedure.
 Structures Included in Postero-Anterior Cephalograph.
 Postero-Anterior Cephalometric Landmarks.
 Purpose Of Postero-Anterior Cephalometry.
 Uses and Limitations of Postero-Anterior Cephalometry.
 Bibliography.
www.indiandentalacademy.com

Mal-occlusions and dento-facial deformities constitute three-Mal-occlusions and dento-facial deformities constitute three-
dimensional conditions or pathologies. Orthodontic treatmentdimensional conditions or pathologies. Orthodontic treatment
requires comprehensive three- dimensional diagnostic examinationrequires comprehensive three- dimensional diagnostic examination
but assessment of postero-anterior and basilar cephalometric viewsbut assessment of postero-anterior and basilar cephalometric views
are particularly important for dento-alveolar and facial asymmetries;are particularly important for dento-alveolar and facial asymmetries;
dental and skeletal crossbites and functional mandibulardental and skeletal crossbites and functional mandibular
displacements.displacements.
With the advent of cephalometric radiography, postero-anteriorWith the advent of cephalometric radiography, postero-anterior
cephalometric projections and relevant analyses constitute ancephalometric projections and relevant analyses constitute an
important adjunct for qualitative and quantitative evaluation of theimportant adjunct for qualitative and quantitative evaluation of the
dento-facial region.dento-facial region.

Equipment ::
1.1. Head-holder orHead-holder or
Cephalostat.Cephalostat.
2.2. X-ray source.X-ray source.
3.3. Cassette holderCassette holder
containing the film.containing the film.

 Patient positioning:
Patient is positionedPatient is positioned
upright facing theupright facing the
film.film.
 X-ray source:
Connection betweenConnection between
the X-ray source andthe X-ray source and
cassette holdercassette holder
containing the filmcontaining the film
should be rigid.should be rigid.

Distance between X-ray
source to patient:
5 feet ( 152.4cm)5 feet ( 152.4cm)
For the postero-For the postero-
anterior projection, theanterior projection, the
distance is measureddistance is measured
to the earpost axis.to the earpost axis.

Fixed Head Position:
The patient is fixed in theThe patient is fixed in the
head-holder with the helphead-holder with the help
of two ear-rods, and theof two ear-rods, and the
patient’s head rests onpatient’s head rests on
the uppermost side of thethe uppermost side of the
rods, which are insertedrods, which are inserted
into the ear holes.into the ear holes.
The Frankfort horizontalThe Frankfort horizontal
plane is parallel to theplane is parallel to the
floor in order to maintainfloor in order to maintain
all vertical dimensions.all vertical dimensions.

Natural Head Position:
It is a standardizedIt is a standardized
orientation of head, whichorientation of head, which
is assumed by focusing onis assumed by focusing on
a distant point at eye levela distant point at eye level
(Moorrees, 1985).(Moorrees, 1985).
Reproducibility of theReproducibility of the
natural head position isnatural head position is
approx. 2approx. 200
, which supports, which supports
its use in Cephalometryits use in Cephalometry..
( Lundstrom and( Lundstrom and
Lundstrom, 1992).Lundstrom, 1992).
The ear rods are placedThe ear rods are placed
directly in front of thedirectly in front of the
tragus so that they lightlytragus so that they lightly
contact the skin, thuscontact the skin, thus
support the head bilaterallysupport the head bilaterally
in transverse plane.in transverse plane.

Other techniques of head positioning:
According to Chierici ( 1981):
Patient’s head should be positioned with the tip of the nose andPatient’s head should be positioned with the tip of the nose and
forehead lightly touching the cassette holder. This head position helpsforehead lightly touching the cassette holder. This head position helps
evaluate craniofacial anomalies of upper face.evaluate craniofacial anomalies of upper face.
According to Faber ( 1985):
In cases of suspected significant mandibular displacement, theIn cases of suspected significant mandibular displacement, the
postero-anterior cephalogram should be taken with the patient’spostero-anterior cephalogram should be taken with the patient’s
mouth slightly opened.mouth slightly opened.
This helps differentiate between functional mandibular displacementThis helps differentiate between functional mandibular displacement
and dento-skeletal facial asymmetry.and dento-skeletal facial asymmetry.

According toAccording to Manson- Hing, 1985:Manson- Hing, 1985: Film exposure dependsFilm exposure depends
on certain factors like:on certain factors like:
1.1. Speed of the film.Speed of the film.
2.2. Speed of the screens.Speed of the screens.
3.3. Tube to film distance.Tube to film distance.
4.4. Size of patient’s head.Size of patient’s head.
5.5. Milli-amperage and kilo-voltage used in generating the X-Milli-amperage and kilo-voltage used in generating the X-
ray beam.ray beam.
6.6. The film-exposure time .The film-exposure time .
More exposure is necessary for postero-anterior cephalogamsMore exposure is necessary for postero-anterior cephalogams
than for lateral viewsthan for lateral views (Enlow 1982) .(Enlow 1982) .www.indiandentalacademy.com

 The tracing of postero-anterior cephalogram is carried out by placingThe tracing of postero-anterior cephalogram is carried out by placing
the cephalogram in front of the examiner so that patient’s rightthe cephalogram in front of the examiner so that patient’s right
should be on the examiner’s left.should be on the examiner’s left.
 The tracing should include most of the important structures of theThe tracing should include most of the important structures of the
upper, middle and lower anterior face and the posterior .upper, middle and lower anterior face and the posterior .
 Assess and compare where the structures have been identified in theAssess and compare where the structures have been identified in the
current lateral cephalogram of the same patient.current lateral cephalogram of the same patient.
The tracing of Postero-anterior Cephalogram begins with the mid-lineThe tracing of Postero-anterior Cephalogram begins with the mid-line
structures seen in the lateral cephalogram and should include thestructures seen in the lateral cephalogram and should include the
occipital, parietal , frontal and nasal bones , the maxilla, the sphenoidoccipital, parietal , frontal and nasal bones , the maxilla, the sphenoid
bone and the symphysis of mandiblebone and the symphysis of mandible (Broadbent, 1975).(Broadbent, 1975).

1. External peripheral cranial
bone surfaces
5. Orbital outline & inferior
surface of the orbital plate
of the frontal bone
4. Nasal septum, crista galli,
and floor of the nose
6. Oblique line formed by the
external surface of the
greater wing of the
sphenoid bone in the area
of the temporal fossa
7. Superior surface of the
petrous portion of the
temporal bone
2. Mastoid processess
3. Occipital condyles

8. Lateral surface of the
frontosphenoid process of
the zygoma and the
zygomatic arch,
including the key ridge
9. Cross section of the
zygomatic arch
10. Infratemporal surface of
the maxilla in the area of
the tuberosity
11. Body and rami, coronoid
process and condyles of
the mandible
12. As many dental units as
possible

 Ag- antegonion- the highest
point in the antegonial notch
 Ans- anterior nasal spine
 Cd- condylar- the most
superior point of the
condylar head
 Cor- coronoid- the most
superior point of the
coronoid process
 Iif- incision inferior frontale-
the midpoint between the
mandibular central incisors
at the level of the incisal
edges
 Isf- incision superior
frontale- the midpoint
between th maxillary central
incisors at the level of incisal
edgeswww.indiandentalacademy.com

 lpa- lateral piriform aperture- the
most lateral aspect of the piriform
aperture
 Lo- latero orbitale- the intersection
of the lateral orbital contour with
the innominate line
 M- mandibular midpoint- located by
projecting the mental spine on the
lower mandibular border,
perpendicular to the line ag-ag
 Lm- mandibular molar- the most
prominent point on the buccal
surace of the mandibular molar
 Um- maxillary molar- the most
prominent point on the buccal
surace of the maxillary molar
 Ma- mastoid- the lowest point of the
mastoid process
 Mx- maxillare- the intersection of
the lateral contour of the maxillary
alveolar process and the lower
contour of the maxillozygomatic
process of the maxilla

 Mo- medioorbitale- the midpoint
on the medial orbital margin that
is closest to the median plane
 Mf- mental foramen- the centre
of the mental foramen
 Om- orbital midpoint- the
projection on the line lo-lo of the
top of the nasal septum at the
base of the crista galli
 Za- point zygomatic arch- point
at the most lateral border of the
centre of the zygomatic arch
 Tns- top nasal septum- the
highest point on the superior
aspect of the nasal septum
 Mzmf- zygomaticofrontal medial
suture point
 Lzmf- zygomaticofrontal lateral
suture point

The postero-anterior cephalometry is useful as a diagnosticThe postero-anterior cephalometry is useful as a diagnostic
tool. It serves to provide:tool. It serves to provide:
Gross Inspection:Gross Inspection: It provides information about morphology, shapeIt provides information about morphology, shape
and size of the skull, bone density, suture morphology.and size of the skull, bone density, suture morphology.
It may help to detect pathology of hard and soft tissuesIt may help to detect pathology of hard and soft tissues
Description and Comparison:Description and Comparison: Postero-anterior cephalograms of twoPostero-anterior cephalograms of two
persons can be compared to describe the skull .persons can be compared to describe the skull .
Diagnosis:Diagnosis: It analyses the nature and origin of the problem,It analyses the nature and origin of the problem,
thereby, providing the possibility of quantification andthereby, providing the possibility of quantification and
classification.classification.

 Treatment Planning:Treatment Planning:
The diagnostic information obtained helps to decideThe diagnostic information obtained helps to decide
comprehensive and precise treatment plan .comprehensive and precise treatment plan .
 Growth assessment and evaluation of treatment
results:
Postero-anterior cephalograms of a patient are taken at variousPostero-anterior cephalograms of a patient are taken at various
time intervals and are compared to each preceeding one .time intervals and are compared to each preceeding one .
The superimpositions are made on the external peripheral cranialThe superimpositions are made on the external peripheral cranial
bone outline or on any of the reference horizontal planes.bone outline or on any of the reference horizontal planes.
Interpretation of characteristics and relationships of variousInterpretation of characteristics and relationships of various
craniofacial structures can also assess growth .craniofacial structures can also assess growth .

Aims:
They evaluate craniofacial skeleton by means of linear absoluteThey evaluate craniofacial skeleton by means of linear absolute
measurements of:measurements of:
 Width or height.Width or height.
 AnglesAngles
 Ratios.Ratios.
 Volumetric Comparison.Volumetric Comparison.

Uses:
 Different structures of cranio-facial complex can also be analysedDifferent structures of cranio-facial complex can also be analysed
using qualitative methods.using qualitative methods.
 A postero-anterior cephalogram evaluates the verical, transverse andA postero-anterior cephalogram evaluates the verical, transverse and
sagittal dimensions of different structures.sagittal dimensions of different structures.
 Different structures can be evaluated w.r.t their vertical dimension,Different structures can be evaluated w.r.t their vertical dimension,
position and proportionality.position and proportionality.
 Vertical asymmetry can be easily detected by connecting bilateralVertical asymmetry can be easily detected by connecting bilateral
structures, drawing transverse planes, and by observing their relativestructures, drawing transverse planes, and by observing their relative
orientationorientation.( Sollar, 1947; Proffit,1991)..( Sollar, 1947; Proffit,1991).
 The use of ratios in postero-anterior cephalogram can help compareThe use of ratios in postero-anterior cephalogram can help compare
different persons or groups whose radiographs have been taken withdifferent persons or groups whose radiographs have been taken with
uncontrolled enlargement of different structures of skull on X-rayuncontrolled enlargement of different structures of skull on X-ray
filmfilm ( Athanasiou et al, 1992).( Athanasiou et al, 1992).www.indiandentalacademy.com

Limitations:
 Precise linear measurements on postero-anterior cephalograms mayPrecise linear measurements on postero-anterior cephalograms may
be misleading. eg. The apparent distance will be affected by a tilt ofbe misleading. eg. The apparent distance will be affected by a tilt of
the head in the head holder.the head in the head holder.
 Angular measurements can also be influenced in an uncontrolledAngular measurements can also be influenced in an uncontrolled
manner.manner.
 Diagnostic interpretation of ratios for clinical applications inDiagnostic interpretation of ratios for clinical applications in
individual cases is difficult.individual cases is difficult.

 Athanasios E Athanasiou and Aart JW Van der Meij :Athanasios E Athanasiou and Aart JW Van der Meij :
Orthodontic Cephalometry , Mosby-Wolfe Publications,1997 , 3Orthodontic Cephalometry , Mosby-Wolfe Publications,1997 , 3rdrd
edn. , 141-161.edn. , 141-161.

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