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77 Cards in this Set
- Front
- Back
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Extraoral Images
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taken when large areas of skull or jaw to be examined
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Extraoral
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outside of mouth
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Extraoral are good for evaluating large areas
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but not so good for detecting subtle changes ie dental caries or perio changes
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Digital panoramic unit
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filmless recording of panoramic image
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CBCT
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cone beam computed tomography
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Cone Beam Computed Tomography
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3D digital imaging using a cone shape beam of radiation rotating around pt head
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Panoramic imaging
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was not recommended for diagnostic caries, perioo or lesions
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Bitewings
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had to supplement panoramic images
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New Full Featured digital Panoramic units introduced with
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Special C-arm......producing images showing inter proximal carious lesions
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Two types of Panoramic Units
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*film based imaging
*direct digital imaging |
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Main Difference between film based and direct digital Pan imaging
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image receptor
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INSTEAD of Film Digital Units use a
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sensor array
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After processing, image is immediately produced on computer monitor
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instead of on a film
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To produce a series of individual images, Image receptor & tube head rotate around
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patients head
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over all view of maxi & mandi
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produced when images are combined on a single film
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Focal Trough
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aka image layer
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3D hourse shoe shaped zone
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Focal Trough
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if pt's jaw positioned in focal trough correctly
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result is reasonably clear & well defined radiograph
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Film based pan radiography require
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pan x-ray unit, screen type film, intensifying screen & cassettes
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Main components of Panoramic unit
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tube head, head positioned & exposure controls
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Tube head
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similar to intraoral unit
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Vertical angulation of panoramic tube head
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is NOT adjustable
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Head Positioner
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aligns pt's teeth as accurately as possible
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Head Positioner consists of
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*chin rest
*notched bite-block *forehead rest *lateral support guides |
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Exposure controls
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allow milliamprage & kilovoltage settings to be adjusted to accomodate pt different sizes
**Exposure can not be changed** |
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Film & Intensifying Screen
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extraoral film held in cassette and is sensitive to light from intensifying screen
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Patient Preparation Errors
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*Ghost Images
*Lead Apron Artifact |
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Ghost images happens when
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metallic or radiodense objects are not removed prior to exposure
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Radiodense objects
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glasses, earings, necklaces, tongue rings, peircings, partals, dentures orthodontic retainers, hearing aids
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Ghost images look similair to
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real radiodense object except it appears on opposite side of film
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Solution to ghost images
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have patient remove all radiodense objects before positioning pt for panoramic radiograph
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Lead Apron Artifact happens when
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lead apron is incorrectly placed, or if thyroid collar is used during exposure
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Lead apron artifact
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radiopaque cone shaped artifact results interferes with diagnostic info
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lead apron artifact solution
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use lead apron without a thyroid collar
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Patient Positioning Errors
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*lips & tongue
*chin too high *chin too low *posterior to focal through *anterior to focal through *spine not straight |
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lips & tongue
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LIPS--must be closed on bite block during exposure
TONGUE-- mist be in contact with palate |
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dark radiolucent shadow obscures anterior teeth
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if lips are not closed on bite block during exposure
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dark radiolucent shadow obscures apices of maxi teeth
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if tongue is not in contact with palate during exposure
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Frankfort Plane
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imaginary plane that passes through top of ear canal and bottom of eye socket
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Chin positioned too High
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or tipped forward
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Frankfort plane is incorrect (too high)
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*hard palate & nasal cav floor superimposed over roots of maxi teeth
*detail of maxi incisor lost *maxi incisor will appear blurred & magnified *reverse smile line,(frown) |
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Proper Frankfort Plane
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Position pt with Frankfort plane parallel to floor
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Chin positioned to low
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or tipped down
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Frankfort plane is incorrect ( too low)
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*mandi incisors blurry
*detail in anterior apical regions lost *condyle not visible *exaggerated smile line.....huge smile |
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Posterior to Focal Trough
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anterior teeth too far back on bite block.......anterior teeth look fat & out of focus
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Posterior focal trough SOLUTION
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anterior teeth placed end-
to end in groove on bite block |
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Anterior focal trough
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anterior teeth not in groove of bite block, and are too far forward.....anterior teeth look too skinny & out of focus
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Anterior focal trough SOLUTION
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anterior teeth placed in end to end position in groove of bite block
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Spine not straight
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cervical spine appears as radiopacity in film centre obscuring diagnostic info
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Advantage of Panoramic Imaging
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*field size
*ease of use *patient acceptance *less exposure to radiation |
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Disadvantages of Panoramic Imaging
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*image sharpness
*focal trough limitations *distortion *cost of equipment |
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Technology provides 3D views of mouth, face & jaw from any direction
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CBCT dental imagings
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can be easily manipulated adjusted colourized on computer
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the digital imaging
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Panoramic images are 2 diminutional and
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cannot provide info re buccal or lingual width or locations, nor distinguish between soft tissues
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CBCT Hardware
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is not difficult to learn to use
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Additional training needed to
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interpret CBCT images because of 3D view
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Cephalostat
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(film holder and head positioned)
special devices fitted for panoramic units, allowing operator to easily position both film and patient |
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Film used for jaw or transcranial projections
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occlusal film #4
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Grid
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device used to reduce amount of scatter radiation that reaches extraoral film during exposure
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Scatter Radiation can cause
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film fog & reduce film contrast
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Decreases amount of film fog & Incerases contrast of radiograph image
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Grid
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Grid composed of
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thin led strips embedded in plastic permitting passage of xray beam
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Skull Radiography
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most often used in oral surgery & ortho
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most skull radiography require use of
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extra oral unit & cephalostat
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Due to structures being superimposed over one another
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maany cases require multiple exposures to obtain clear view of area
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Most common Skull Radiographs used in dentistry
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*Lateral Cephalometric Projection
*Posteroanterior Projection *Tempromandibular Joint Projection |
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Lateral Cephalometric Projection (face skull & soft tissue profile)
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*evaluates facial growth & development, trauma, disease, and developmental abnormalities
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Posteroanterior Projection (frontal ethmoid sinuses, orbits & nasal cav)
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projection evaluates facial growth & development, trauma, disease, and developmental abnormalities
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Tempromandibular Joint TMJ
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jaw joint...
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Difficult to examine radiographically
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TMJ---due to multiple adjacent bony structures
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Radiography CANNOT be used to examine
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articular disc & other soft tissues of TMJ
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Special techniques such as orthography & CBCT
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used to examine TJM soft tissues * articular disc
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Magnetic Resonance Imaging (MRI)
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technique for obtaining cross-sectional images w/o exposing patient to X-rays
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Most Important Advantage to MRI
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its ability to distinguish among soft tissues i.e..lesions of nasopharynx, salivary glands, sinuses & other intercranial structures
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Valuable in diagnosis of TMJ Disorders
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MRI
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Computed Tomography (CT)
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*used in dentistry primarily for diagnosing lesions & planning implant cases
*x-radiation is energy source |
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MRI & CT Scanners
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are NOT found in dental offices
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