5. Introduction to Panoramic
Radiography
• Commonplace in dental practice
• Considered essential in radiographic
diagnosis
• 30% of dental units sold are
panoramic
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6. Introduction to Panoramic
Radiography
• “Panorama” means unobstructed
view of a region in any direction
• Panoramic radiograph show greater
coverage than periapical and
bitewing radiographs
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7. Introduction to Panoramic
Radiography
• New technique
• Introduced in 1959
• Employs scanography (slit beam) &
curved surface rotational
tomography
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8. Client Dose from Panoramic
Radiography
• 10 times less radiation than a
complete intraoral survey using long,
round PID & E+ film
• 4 time less radiation than a bitewing
survey using long, round PID and E+
film
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13. Disadvantages of Panoramic
Radiography
• Poor image quality due to
– Tomographic process
– Increased object-film distance
– Use of intensifying screens
– Faster film with larger crystals
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14. Disadvantages of Panoramic
Radiography
• Focal Trough (Image Layer)
– Areas outside are not visible
– Size & shape limits imagery to those
structures which “fit” into the image
layer
– Size & shape not adjustable so not all
client’s arches image equally well
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15. Disadvantages of Panoramic
Radiography
• Distortion
– Vertical & horizontal distortion with
variations causes uneven magnification
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16. Disadvantages of Panoramic
Radiography
• Superimposition & Ghost Images
– All objects in the field of the beam, even
those outside of the image layer are
projected onto the film but most are not
seen.
– Objects with the greatest density are
projected in two places on the film
• Intended (useable image)
• Ghost image (reversed, higher, blurred)
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17. Disadvantages of Panoramic
Radiography
• Superimposition & Other Imaging
Quirks
– Ghost images may hide pathosis
– Soft tissue shadows may mimic
pathosis
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19. Focal Trough
• An imaginary, three-dimensional curved area
that is horseshoe shaped.
• This is a very important concept because
many technique errors are caused by
improper positioning of the patient’s jaws
within the focal trough.
• When the jaws are positioned within this area,
the radiograph will be clear.
• When the jaws are positioned outside of this
area, the images on the radiograph will
appear blurred or indistinct.
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23. The Head Positioner
• Each panoramic unit has a head positioner used
to align the patient’s teeth as accurately as
possible.
• Each head positioner consists of a chin rest,
notched bite-block, forehead rest, and lateral
head supports or guides.
• Each panoramic unit is different, and the operator
must follow the manufacturer’s instructions on
how to position the patient in the focal trough.
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27. Positioning of the Teeth
• Posterior to focal trough
• If the patient’s anterior teeth are not positioned in
the groove on the bite-block and are either too far
back on the bite-block or posterior to the focal
trough, the anterior teeth appear “fat” and out of
focus on the radiograph.
• Anterior to focal trough
• If the patient’s anterior teeth are not positioned in
the groove on the bite-block and are either too far
forward or anterior to the focal trough, the teeth
will appear “skinny” and out of focus.
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32. Positioning of the Spine
If the patient’s spine is not straight, the cervical
spine will appear as a radiopaque artifact in the
center of the film and obscure diagnostic
information.
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43. Common Errors
• Patient preparation errors
• Ghost images: A ghost image looks like the real object
except that it appears on the opposite side of the film.
• Lead apron artifact: If the lead apron is placed too
high, or if a lead apron with a thyroid collar is used, a
cone-shaped radiopaque artifact results.
• Patient seating errors
• Chin too high
• Chin too low
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