postero anterior cephalometrics /certified fixed orthodontic courses by indian dental academy

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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.


Mal-occlusions and dento-facial deformities constitute Mal-occlusions and dento-facial deformities constitute three-dimensional conditions or pathologies. three-dimensional conditions or pathologies. Orthodontic treatment requires comprehensive three- Orthodontic treatment requires comprehensive three- dimensional diagnostic examination but assessment of dimensional diagnostic examination but assessment of postero-anterior and basilar cephalometric views are postero-anterior and basilar cephalometric views are particularly important for dento-alveolar and facial particularly important for dento-alveolar and facial asymmetries; dental and skeletal crossbites and asymmetries; dental and skeletal crossbites and functional mandibular displacements. functional mandibular displacements.

With the advent of cephalometric radiography, postero-With the advent of cephalometric radiography, postero-anterior cephalometric projections and relevant anterior cephalometric projections and relevant analyses constitute an important adjunct for qualitative analyses constitute an important adjunct for qualitative and quantitative evaluation of the dento-facial region.and quantitative evaluation of the dento-facial region.


Equipment :: 1.1. Head-holder or Head-holder or

Cephalostat.Cephalostat.2.2. X-ray source.X-ray source.3.3. Cassette holder Cassette holder

containing the film.containing the film.


Patient positioning: Patient is positioned Patient is positioned upright facing the upright facing the film.film.

X-ray source: Connection between Connection between the X-ray source the X-ray source and cassette holder and cassette holder containing the film containing 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, anterior projection, the distance is the distance is measuredmeasured

to the earpost to the earpost axis.axis.


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


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


Other techniques of head positioning:

According to Chierici ( 1981):

Patient’s head should be positioned with the tip of the Patient’s head should be positioned with the tip of the nose and forehead lightly touching the cassette holder. nose and forehead lightly touching the cassette holder. This head position helps evaluate craniofacial This head position helps evaluate craniofacial anomalies of upper face.anomalies of upper face.

According to Faber ( 1985):

In cases of suspected significant mandibular In cases of suspected significant mandibular displacement, the postero-anterior cephalogram should displacement, the postero-anterior cephalogram should be taken with the patient’s mouth slightly opened.be taken with the patient’s mouth slightly opened.

This helps differentiate between functional mandibular This helps differentiate between functional mandibular displacement and dento-skeletal facial asymmetry. displacement and dento-skeletal facial asymmetry.


According to According to Manson- Hing, 1985:Manson- Hing, 1985: Film exposure Film exposure depends on certain factors like:depends 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 Milli-amperage and kilo-voltage used in

generating the X-ray beam.generating the X-ray beam.6.6. The film-exposure time .The film-exposure time .More exposure is necessary for postero-anterior More exposure is necessary for postero-anterior

cephalogams than for lateral views cephalogams than for lateral views (Enlow 1982) (Enlow 1982) .. www.indiandentalacademy.com

The tracing of postero-anterior cephalogram is carried The tracing of postero-anterior cephalogram is carried out by placing the cephalogram in front of the examiner out by placing the cephalogram in front of the examiner so that patient’s right should be on the examiner’s left.so that patient’s right should be on the examiner’s left.

The tracing should include most of the important The tracing should include most of the important structures of the upper, middle and lower anterior face structures of the upper, middle and lower anterior face and the posterior .and the posterior .

Assess and compare where the structures have been Assess and compare where the structures have been identified in the current lateral cephalogram of the same identified in the current lateral cephalogram of the same patient.patient.

The tracing of Postero-anterior Cephalogram begins with The tracing of Postero-anterior Cephalogram begins with the mid-line structures seen in the lateral cephalogram the mid-line structures seen in the lateral cephalogram and should include the occipital, parietal , frontal and and should include the occipital, parietal , frontal and nasal bones , the maxilla, the sphenoid bone and the nasal bones , the maxilla, the sphenoid bone and the symphysis of mandible symphysis of mandible (Broadbent, 1975).(Broadbent, 1975).www.indiandentalacademy.com

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 processess3. 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 The postero-anterior cephalometry is useful as a diagnostic diagnostic tool. It serves to provide:tool. It serves to provide:

Gross Inspection: Gross Inspection: It provides information about It provides information about morphology, shape and size of the skull, bone density, morphology, shape and size of the skull, bone density, suture morphology.suture morphology. It may help to detect pathology of hard and soft It may help to detect pathology of hard and soft tissuestissues

Description and Comparison:Description and Comparison: Postero-anterior Postero-anterior cephalograms of two persons can be compared to cephalograms of two persons can be compared to describe the skull .describe the skull .

Diagnosis: Diagnosis: It analyses the nature and origin of the It analyses the nature and origin of the problem,problem, thereby, providing the possibility of quantification thereby, providing the possibility of quantification and classification.and classification.


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

Aims:

They evaluate craniofacial skeleton by means of linear They evaluate craniofacial skeleton by means of linear absolute measurements of:absolute 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 Different 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 vertical Different structures can be evaluated w.r.t their vertical dimension, position and proportionality.dimension, position and proportionality.

Vertical asymmetry can be easily detected by connecting Vertical asymmetry can be easily detected by connecting bilateral structures, drawing transverse planes, and by bilateral structures, drawing transverse planes, and by observing their relative orientationobserving their relative orientation.( Sollar, 1947; .( Sollar, 1947; Proffit,1991).Proffit,1991).

The use of ratios in postero-anterior cephalogram can help The use of ratios in postero-anterior cephalogram can help compare different persons or groups whose radiographs compare different persons or groups whose radiographs have been taken with uncontrolled enlargement of different have been taken with uncontrolled enlargement of different structures of skull on X-ray film structures of skull on X-ray film ( Athanasiou et al, 1992).( Athanasiou et al, 1992).


Limitations:

Precise linear measurements on postero-anterior Precise linear measurements on postero-anterior cephalograms may be misleading. eg. The apparent cephalograms may be misleading. eg. The apparent distance will be affected by a tilt of the head in the distance will be affected by a tilt of the head in the head holder.head holder.

Angular measurements can also be influenced in an Angular measurements can also be influenced in an uncontrolled manner.uncontrolled manner.

Diagnostic interpretation of ratios for clinical Diagnostic interpretation of ratios for clinical applications in individual cases is difficult.applications in 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 Orthodontic Cephalometry , Mosby-Wolfe

Publications,1997 , 3Publications,1997 , 3rdrd edn. , 141-161. edn. , 141-161.
