• Extraoral radiographs (outside the mouth) are taken when large areas of the skull or jaw must be examined or when patients are unable to open their mouth for film placement.
  • Intensifying screens are used with films for all extraoral radiography.
  • Intensifying screens creates an image receptor system 10 to 60 times more sensitive to x rays than the film alone.
  • Extraoral radiographs do not show the details as well as intraoral films.
  • They are not adequate for detection of subtle changes such as the early stages of dental caries or periodontal disease.
  • Cephalometric and skull view = 20X25cm (8X10 inch )
  • Lateral oblique projection of mandible = 13x18cm (5×7 inch)
  • Lateral oblique projection (ramus and body)
  • PA view (postero anterior)
  • Lateral skull and lateral cephalometric view
  • Waters view (occipital mental view)
  • Reverse towns view
  • Sub mento vertex view (base or full skull view.
  • Panoramic radiographs.
  • TMJ views.

It demonstrates:

  • Premolar, molar region.
  • Inferior body of mandible.
  • Periapical region of teeth.
  • Cassette placed against the patient’s cheeks centered over first molar.
  • Lower border of cassette should be parallel and 2 cm below inferior border of mandible.

Head position

  • Head is tilted towards the side to be examined with protruded mandible

Position of central ray

  • Directed towards first molar region of mandibular body to be examined from a point 2 cm below angle of the mandible on the tube side.
  • Central ray should be as close to perpendicular to the plane of film

Exposure parameter

  • Kvp= 65
  • mA=10.

It demonstrates:

  • Region from mandibular angle to condyle.
  • 3rd molar region of maxilla and mandible.

Film placement

  • Cassette placed over the ramus of mandible in far enough posterior to include condyle.
  • Lower border of cassette should be parallel and 2cm below inferior border of mandible.

Head position

  • Head is tilted towards the side of examined until a line between angle of mandible next to the tube and the condyle on the side away from the tube is parallel to floor.
  • Ask patients to protrude the mandible (prevent the super imposition of cervical spine).

Projection of central beam

  • Directed posteriorly towards the center of ramus on the site of interest from a point 2cm below inferior border of first molar region of the mandible on the tube side

Exposure parameter

  • Kvp=65
  • mA=10.
  • Line connecting the superior border of external auditory meatus with the infra orbital rim.
  • Line joining the central portion of external auditory meatus to the outer canthus of eye.

Examination of the skull for:

  • Presence of disease.
  • Trauma
  • Developmental anomalies.
  • Mediolateral changes of skull.
  • Facial structures.
  • Frontal sinus.
  • Ethmoid sinus.
  • Nasal fossa.
  • Orbits
  • Because the x ray beam passes in the posterior to anterior direction through the skull.

What is the technique for taking PA view?

Film placement

  • Film should be positioned vertically in front of the head.

Patient position

  • Canthomeatal line should be parallel to floor and perpendicular to image receptor for straight PA.
  • For cephalometric application (Caldwell projection) canthomeatal line should be 10 degree above the horizontal plane and Frankfurt plane perpendicular to the film.

Projection of central beam

  • Perpendicular to the plane of film.
  • Parallel to the patients mid sagittal plane.
  • Centered at the level of bridge of the nose
  • Source to object distance should be 90 to 102cm (36 to 40 inches) for skull projection.
  • For cephalometric projection source to object distance should be 212.4cm (60 inches).
  • Kvp – 75 to 80.
  • By placing the back of the patient’s head against the image detector, the AP skull view is of the entire skull and is non angled. It does not highlight any particular area.
  • The name AP is because the x ray beam travels Anterior to Posterior through the skull. This is called Anteroposterior.
  • The AP Skull View has a higher radiation dose to the eyes than the PA view, and it has higher magnification of the bones.

Used for the evaluation of:

  • Skull and facial bones in trauma.
  • Presence of disease.
  • Development anomalies.
  • Nasopharyngeal soft tissues.
  • Paranasal sinuses.
  • Hard palate.
  • Assessment of facial growth (in orthodontics).
  • Pre and post treatment records (in oral surgery and prosthetics).

Patient position

  • The mid sagittal plane should be parallel to plane of film.

Projection of central beam

  • Directed towards the external auditory meatus perpendicular to the plane of film and mid sagittal plane.
  • For cephalometric projection the source to object distance is 212.4cm (60 inches).
  • For skull projection source to object distance should be 91to102cm (36 to 40 inches).

For evaluation of:

  • Maxillary sinuses.
  • Frontal and ethmoid sinuses.
  • Orbits
  • Fronto-zygomatic suture.
  • Nasal cavity.
  • Position of coronoid process of mandible between maxilla and zygomatic arch.

Patient position

  • Image receptor should be placed in front of patient.
  • The mid sagittal plane perpendicular to the plane of film.
  • Raise the chin high so that Canthomeatal line elevated 37˚ above the horizontal plane.
  • If the patients mouth is open the image of sphenoid sinus will be projected on palate.

Position of central beam

  • Projected perpendicular to the film through the mid sagittal plane at the level of maxillary sinus.
  • Kvp=70 – 80.

For evaluation of:

  • Fracture of condylar neck.
  • Displacement of condyle.
  • Postero – lateral wall of maxillary sinus.

Patient position

  • Head is centered in front of the cassette.
  • Canthomeatal line should be oriented downwards 25 -30˚.
  • Ask patients to open the mouth widely (helps in visualization of condyle).

Position of central beam

  • Directed perpendicular to the film in the sagittal plane through the occipital bone.
  • Kvp=75 – 80

For the evaluation of:

  • Base of skull.
  • Position and orientation of condyle.
  • Sphenoid sinus.
  • Curvature of mandible.
  • Lateral wall of maxillary sinuses.
  • Displacement of zygomatic arch.
  • Medial and lateral pterygoid plates.
  • Foramens in the base of the skull.

Patient position

  • Patients head and neck are hyperextended backward as far as possible and the vertex of the skull is placed on the center of cassette.
  • The mid sagittal plane of head is perpendicular to the floor.
  • Canthomeatal line should be extended 10 degrees past vertical so that Frankfurt line is oriented vertically and parallel to the film.

Projection of central beam

  • Directed from below the mandible upward towards the vertex of the skull.
  • It is positioned far enough anterior to pass about 2cm infront of line connecting right and left condylar process.
  • For visualization of zygomatic arches the exposure time should be reduced to one third of that use to visualize the skull (also known as JUG HANDLE view).

1. Goaz PW, White SC Extra oral radiographic examinations. Book of oral radiology, principles and interpretation 2nd edition 1990; 299-313.
2. White SC, Pharaoh MJ Physics of ionizing radiation. Book of oral radiology principles and interpretations 6th edition 2009;210-24.
3. Murphy A, Morgan MA et al. Skull (PA view) Available from: https://radiopaedia.org/articles/skull-pa-view-2.
4. Northwest Radiography, Inc. Prescription dental imaging laboratories. Available from: https://nwrad.com/imagery/ap-skull/.

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