Postero - Anterior Chphalometry /cosmetic dentistry courses

21-12-06
www.indiandentalacademy.comwww.indiandentalacademy.com

CONTENTSCONTENTS
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.

INTRODUCTIONINTRODUCTION
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 diagnosticrequires comprehensive three- dimensional diagnostic
examination but assessment of postero-anterior and basilarexamination but assessment of postero-anterior and basilar
cephalometric views are particularly important for dento-cephalometric views are particularly important for dento-
alveolar and facial asymmetries; dental and skeletal crossbitesalveolar and facial asymmetries; dental and skeletal crossbites
and functional mandibular displacements.and functional mandibular 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 ofimportant adjunct for qualitative and quantitative evaluation of
the dento-facial region.the dento-facial region.

TECHNICAL ASPECTSTECHNICAL ASPECTS
EquipmentEquipment :: Head-holder or Cephalostat.Head-holder or Cephalostat.
X-ray source.X-ray source.
Cassette holder containing the film.Cassette holder containing the film.
Patient positioning:Patient positioning: Patient is positioned upright facing the film.Patient is positioned upright facing the film.
X-ray source: Connection between the X-ray source andConnection between the X-ray source and
cassette holder containing the film should be rigid.cassette holder containing the film should be rigid.
Distance between X-ray source to patient:Distance between X-ray source to patient: 5 feet ( 152.4cm)5 feet ( 152.4cm)
For the postero-anterior projection, the distance is measuredFor the postero-anterior projection, the distance is measured
to the earpost axis.to the earpost axis. www.indiandentalacademy.comwww.indiandentalacademy.com

Different Head Positions:
Fixed Head Position:Fixed Head Position:
The patient is fixed in the head-holder with the help of two ear-The patient is fixed in the head-holder with the help of two ear-
rods, and the patient’s head rests on the uppermost side of therods, and the patient’s head rests on the uppermost side of the
rods, which are inserted into the ear holes.rods, which are inserted into the ear holes.
The Frankfort horizontal plane is parallel to the floor in order toThe Frankfort horizontal plane is parallel to the floor in order to
maintain all vertical dimensions.maintain all vertical dimensions.
Natural Head Position:Natural Head Position:
It is a standardized orientation of head, which is assumed byIt is a standardized orientation of head, which is assumed by
focusing on a distant point at eye levelfocusing on a distant point at eye level ( Moorrees, 1985)( Moorrees, 1985)..
Reproducibility of the natural head position is approx. 2Reproducibility of the natural head position is approx. 200
, which, which
supports its use in Cephalometry.supports its use in Cephalometry.(( Lundstrom and Lundstrom,Lundstrom and Lundstrom,
1992).1992).
The ear rods are placed directly in front of the tragus so thatThe ear rods are placed directly in front of the tragus so that
they lightly contact the skin, thus support the head bilaterally inthey lightly contact the skin, thus support the head bilaterally in
transverse plane.transverse plane. www.indiandentalacademy.comwww.indiandentalacademy.com

FIXED HEAD POSITION NATURAL HEAD POSITIONFIXED HEAD POSITION NATURAL HEAD POSITION

Other techniques of head positioning:
According to Chierici ( 1981)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 positionforehead lightly touching the cassette holder. This head position
helps evaluate craniofacial anomalies of upper face.helps evaluate craniofacial anomalies of upper face.
According to Faber ( 1985)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 thepostero-anterior cephalogram should be taken with the
patient’s mouth slightly opened.patient’s mouth slightly opened.
This helps differentiate between functional mandibularThis helps differentiate between functional mandibular
displacement and dento-skeletal facial asymmetry.displacement and dento-skeletal facial asymmetry.

CHIERICI HEAD POSITION FABER HEAD POSITIONCHIERICI HEAD POSITION FABER HEAD POSITION

Exposure conditions and Considerations:
According toAccording to Manson- HingManson- Hing, 1985:, 1985: Film exposure depends onFilm exposure depends on
certain factors like:certain factors like:
Speed of the film.Speed of the film.
Speed of the screens.Speed of the screens.
Tube to film distance.Tube to film distance.
Size of patient’s head.Size of patient’s head.
Milli-amperage and kilo-voltage used in generating the X-rayMilli-amperage and kilo-voltage used in generating the X-ray
beam.beam.
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) .( Enlow) .

SKULL ANATOMY: FRONTAL VIEWSKULL ANATOMY: FRONTAL VIEW

SKULL ANATOMY: POSTERIOR VIEWSKULL ANATOMY: POSTERIOR VIEW

RADIOGRAPHIC ANATOMYRADIOGRAPHIC ANATOMY

CEPHALOGRAPH - TRACING PROCEDURECEPHALOGRAPH - TRACING PROCEDURE
The tracing of postero-anterior cephalogram is carried out byThe tracing of postero-anterior cephalogram is carried out by
placing the cephalogram in front of the examiner so thatplacing the cephalogram in front of the examiner so that
patient’s right should be on the examiner’s left.patient’s right should be on the examiner’s left.
The tracing should include most of the important structures ofThe tracing should include most of the important structures of
the upper, middle and lower anterior face and the posterior .the upper, middle and lower anterior face and the posterior .
Assess and compare where the structures have been identifiedAssess and compare where the structures have been identified
in the current lateral cephalogram of the same patient.in the current lateral cephalogram of the same patient.
The tracing of Postero-anterior Cephalogram begins with theThe tracing of Postero-anterior Cephalogram begins with the
mid-line structures seen in the lateral cephalogram and shouldmid-line structures seen in the lateral cephalogram and should
include the occipetal, parietal , frontal and nasal bones , theinclude the occipetal, parietal , frontal and nasal bones , the
maxilla, the sphenoid bone and the symphysis of mandiblemaxilla, the sphenoid bone and the symphysis of mandible
( Broadbent, 1975)( Broadbent, 1975)..

Structures Included in the Postero-AnteriorStructures Included in the Postero-Anterior
CephalogramCephalogram

POSTERO-ANTERIOR CEPHALOMETRIC LANDMARKSPOSTERO-ANTERIOR CEPHALOMETRIC LANDMARKS

PURPOSE OF POSTERO-ANTERIORPURPOSE OF POSTERO-ANTERIOR
CEPHALOMETRYCEPHALOMETRY
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,It provides information about morphology,
shape and size of the skull, bone density, suture morphology.shape 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 cephalogramsPostero-anterior cephalograms
of two persons can be compared to describe the skull .of two 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 obtainedThe diagnostic information obtained
helps to decide comprehensive and precise treatment plan .helps to decide comprehensive and precise treatment plan .www.indiandentalacademy.comwww.indiandentalacademy.com

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 peripheralThe superimpositions are made on the external peripheral
cranial bone outline or on any of the reference horizontalcranial bone outline or on any of the reference horizontal
planes.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 .

POSTERO-ANTERIOR CEPHALOMETRIC USES &POSTERO-ANTERIOR CEPHALOMETRIC USES &
LIMITATIONSLIMITATIONS
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 beDifferent structures of cranio-facial complex can also be
analysed using qualitative methods.analysed using qualitative methods.
A postero-anterior cephalogram evaluates the verical,A postero-anterior cephalogram evaluates the verical,
transverse and sagittal dimensions of different structures.transverse and sagittal dimensions of different structures.
Different structures can be evaluated w.r.t their verticalDifferent structures can be evaluated w.r.t their vertical
dimension, position and proportionality.dimension, position and proportionality.
Vertical asymmetry can be easily detected by connectingVertical asymmetry can be easily detected by connecting
bilateral structures, drawing transverse planes, and bybilateral structures, drawing transverse planes, and by
observing their relative orientationobserving their relative orientation..( Sollar, 1947; Proffit,1991).( Sollar, 1947; Proffit,1991).
The use of ratios in postero-anterior cephalogram can helpThe use of ratios in postero-anterior cephalogram can help
compare different persons or groups whose radiographs havecompare different persons or groups whose radiographs have
been taken with uncontrolled enlargement of different structuresbeen taken with uncontrolled enlargement of different structures
of skull on X-ray filmof skull on X-ray film ( Athanasiou et al, 1992).( Athanasiou et al, 1992).www.indiandentalacademy.comwww.indiandentalacademy.com

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

BIBLIOGRAPHY
Athanasios E Athanasiou and Aart JW Van der Meij :Athanasios E Athanasiou and Aart JW Van der Meij :
Orthodontic Cephalometry , Mosby-Wolfe Publications,1997 ,Orthodontic Cephalometry , Mosby-Wolfe Publications,1997 ,
33rdrd
edn. , 141-161.edn. , 141-161.

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