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Uses of the panoramic x-ray
- evaluate impacted teeth
- evluate eruption patterns
- detect diseases, lesions, and conditions of the jaw
- examine extent of large lesions
- evaluate trauma
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What should the panoramic film not be used to determine?
- diagnos caries
- periodontal disease
- periapical regions
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The x ray tube moves around the patients head in one direction while the film rotates in the____________________.
opposite direction
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allows the imaging of one layer or section of the body while blurring images from structures in other planes
tomography
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The tomography image in dental radiology conforms to what?
the shape of the dental arches
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the pivotal point or axis, around which the cassette carrier and x-ray tubehead rotate is termed what?
rotation center
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What are the 3 rotation centers?
- double-center rotation
- triple-center rotation
- moving=center rotation
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does the center of rotation change as the film and tubehead rotate around the patient? What does this allow?
- yes
- the image layer to conform to the elliptical shape of the dental arches
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the location and number of rotational centers influences what?
the size and shape of the focal troph
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2 rotation centers, one for the right side, one for the left side
double-center rotation
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3 rotational centers, uninterrupted image
triple-center rotation
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continously moving circle, uninterrupted image
moving-center rotation
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a 3 dimensional curved zone in which structures are clearly demonstrated on a panoramic radiograph; used to determine where the dental arches must be positioned to achieve the clearest image
focal trough
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in most panoramic x-ray machines, the focal trough is__________in the anterior, and____________in the posterior
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What do different panoramic x-ray machines differ in?
- number of rotation centers
- size and shape of focal trough
- type of film transport mechanism used
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what are the similar components that each panoramic x ray machine have?
- x-ray tube head
- head positioner
- exposure controls
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describe the collimater used in panoramic radiography.
lead plate with an opening in the shape of a narrow vertical slit
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Where does the x ray beam travel in panoramic radiography?
through the narrow slit in the collimator, emerges as a narrow band and passes through the pt, then through another vertical slit in the cassette carrier
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what is the main purpose of a collimator?
to reduce patient exposure to x radiation
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Does the vertical angulation ever change in panoramic x ray?
no
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the tubehead of the unit always rotates___________the pts head as the film rotates______________of the pts head.
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head positioner consists of
- chin rest
- notched bite block
- forehead rest
- lateral head support or guides
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Which of these is fixed and can't be moved?:
kvP
mA
exposure time
exposure time
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What is the purpose of the screen film?
it converts the x rays to light, and then exposes the film
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What sizes are the film used in panoramic radiology available in?
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what color of light does calcium tungstate screen emit? And rare earth?
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Which type of intensifying screen is recommended and why?
rare earth, because it requires less x-ray exposure and is faster, so less radiation to the pt
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What must you label on the casset of the panoramic film?
- left and right sides
- dentist name
- pt name
- date
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What is the purpose of placing pts teeth in the notch of the biteblock?
to align the teeth in the focal trough
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Where should the pts midsagittal plane be positioned for a pano?
perpendicular to the floor
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where should the pts frankfort plane be positioned for a pano?
parallel to the floor
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What are 2 more common pt preparation errors in panoramic radiography?
- ghost image
- lead apron artifact
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a radioopaque artifact seen on a panoramic film that is produced when a radiodense object is penetrated twice by the x ray beam, such as earings or hearing aids etc.
ghost image
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how does a ghost image appear on a radiograph?
indistinct, larger, and higher than its counter part, and is blurred
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What will appear on the radiograph if the pts lips arent closed on the bite block?
a darke radiolucent shadow that obscures the anterior teeth
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What will appear on the radiograph if the tongue is not positioned on the roof of the mouth?
a dark radiolucent shadow that obscures the apices of the maxillary teeth
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What happens if the pts chin is tipped up and the frankfort plane is not parallel to the floor?
- hard palate and floor of the nasal cavity appear superimposed over the roots of the maxillary teeth
- loss of detail in the maxillary incisor region
- reverse smile line is seen on radiograph
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What happens if the pts chin is tipped down and the frankfort plane is not parallel with the floor?
- mandibular incisors appear blurred
- loss of detailn in the anterior apical regions
- condyles may not be visible
- exagerated smile line
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What happens if the pt is positioned anterior to the focal trough?
anterior teeth appear skinny; image is blurred
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What happens if the pt is positioned posterior to the focal trough?
anterior teeth appear fat; out of focus and blurred
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What happens if the pts head is not centered, midsagittal plane is not perpendicular to the floor?
the ramus and posterior teeth appear unequally magnified on the pano; the side furthest from the film appears magnified, and the side closest appears smaller
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What happens if the pts spine is not strait?
the cervical spine appears on the radiograph as a radiopacity
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What are the advantages of the pano?
- field size
- simplicity
- pt cooperation
- minimal exposure to radiation
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What are the disadvantages of the pano?
- image quality
- focal trough limitations
- distortion
- equipment cost
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