extraoral imaging Flashcards
Panoramic X-ray
the tubehead rotates behind the patient’s head
machine that captures the entire mouth in a single image
- evaluating large areas of the skull
- detecting impacted teeth, eruption patterns, and TMJ problems
what are the downsides of a panoramic x-ray?
usually not clear and detailed enough to assess caries and periodontal diseases
Focal trough
horseshoe-shaped narrow curved space where the structure is captured
objects inside the focal trough are?
clear
objects outside the focal trough are?
blurred
Collimator
a lead plate with a narrow vertical opening
panoramic x-ray
what can the clinician control?
the milliamperage and kilovoltage from the exposure setting
Can the exposure time be changed?
No
T/F: for x-rays, all objects should be removed from the mouth
including eyewear, earrings, nose rings, and other jewelry
dentures, retainers, tongue ring, etc
True
what should be worn to protect the patient’s back and shoulder?
a lead apron (without a thyroid collar)
to be worn like a poncho
wearing a thyroid collar would result in a shark’s fin artifact
which position of the machine is used to achieve the ideal position?
head position (consists of chin rest, notched bite-block, forehead rest, and lateral head support)
Frankfort plane
line from the bottom of the orbit to the top of the auditory meatus
Frankfort plane should be — to the floor
parallel
the patient should look forward and tip their chin?
slightly down (towards the floor)
this elevates the posterior palate so that it doesn’t overlap with the apices of the maxillary teeth
The midsaggital plane should be — to the floor
perpendicular
right before the exposure, the patient should swallow and — ?
lift the tip of the tongue up to the roof of the mouth
failure in lifting the tip of the tongue up to the roof of the mouth results in?
shadows over the maxillary teeth
shark’s fin error
lead collar above line
fix by lowering collar position
an exaggerated smile means?
patient’s chin is tipped too far down
fix by repositioning the chin
a flat or reversed smile means?
patient’s chin is tipped too far up
fix by repositioning the chin
if the Maxillary incisors’ roots are blurred?
the chin is tipped too far up
if one side of the x-ray shows larger teeth/condyle?
the patient’s head is twisted
reposition the head, midsagittal plane perpendicular to the floor (the larger side is the distant side)
Washington monument error
a white straight opacity in the middle of the image due to slumping caused ghost image of the spine
move patient’s feet forward, straighten the spine and lean backward
Air space error
Airway shadow in an arch shapeover maxillary teeth due to tongue not touching the roof of the mouth
have the patient swallow and reposition the tongue
Thick and wide anterior teeth mean?
chin placed behind the focal trough
reposition the chin forward, bite at the notch of the stick
Skinny anterior teeth mean?
chin placed too far forward
reposition the chin back, bite at the notch of the stick
small incisors
head too foward error
enlarged incisors
head too far back error
a ghose image indicates that?
accessories have not been removed
Ghost image looks similar to the real object but is on the opposite of the image and slightly higher (e.g., an earring on the right side produces a ghost image on the left side)
radiograph anatomical landmarks
Incisive foramen
passageway for nasopalatine nerves. Small radiolucent oval between roots of maxillary central incisors
(should not be confused with periapical disease)
radiograph anatomical landmarks
Median palatal suture
vertical radiolucent thin line in the middle of the palate
(should not be mistaken for a fracture)
Nasal septum
thin wall that divides the nasal cavity into two
radiopaque vertical strip
Nasal spine
projection of bone anteriorly
- radiopaque triangle shape at median palatal suture where nasal septum and fossae meet
Nasal cavity (nasal fossae)
large air-filled space above and behind the nose in the middle of the face
radiolucent oval shapes superior to central incisors
Inverted Y
junction where the nasal fossa and the maxillary sinus meet. Most commonly found superior to the maxillary canine apex
Maxillary sinus
hollow spaces in bone superior to molar and premolar
Maxillary tuberosity
distal portion of the alveolar process. Rounded, radiopaque elevation distal to third molar regions
Hamulus
extension of medial pterygoid plate of sphenoid bone
- radiopaque hook-like protrusion posterior to maxillary tuberosity
Zygomatic process
protruded arch of the zygomatic bone. U-shaped radiopaque band superior to molar apices
Coronoid process
anterior portion of the ramus
Radiopaque triangular projection usually superimposed over maxillary tuberosity
Genial tubercles
4 bony spines used for muscle attachment of the genioglossus and geniohyoid muscles
Circular radiopacities inferior to central incisor apices
Lingual foramen
exit for incisive vessel branches
The radiolucent circle inside the opaque genial tubercles on the mandibular anteriors
Mental foramen
Opening for mental nerve and vessels inferior to mandibular premolar apices.
Round radiolucent area sometimes mistaken for periapical disease
Mental ridge
Ridge of bone located on the anterior surface of the mandible
Bilateral radiopaque lines, starting inferior to premolar apices and extending anteriorly to the midline
External oblique ridge
Linear area of bone on the external surface of the mandible
The radiopaque line running anterior from the ramus across the molars
Internal oblique ridge (mylohyoid)
Elevated long area on the internal surface of the mandible
The radiopaque line running along the premolar and molar apices. It is usually positioned below the external oblique ridge on radiographs
Submandibular fossa
radiolucent band that runs inferior to the mylohyoid line and apices of molars
Nutrient canals
thin vertical radiolucent lines near the teeth, may be mistaken for bone fractures
Mandibular canal
Radiolucent horizontal band outlined with a thin line of cortical bone
Inferior alveolar nerve and arteries pass inside the canal. Stretches from the mandibular foramen to the mental foramen
Cephalometric projection
shows the lateral view of the skull
-Helps in evaluating trauma and facial growth
Lateral jaw exposure
Evaluates the posterior portion of the mandible or lateral areas that are too large to capture for periapical receptors
-Helps in evaluating growth and development, diseases, and trauma
Posteroanterior projection
shows the frontal and ethmoid sinuses, orbits, and nasal cavities
Water’s projection
provides images of the maxillary sinus
MRI (magnetic resonance imaging)
used for images of the soft tissue, TMJ, etc.
NOTE: If the image shows soft structures (not bone), an MRI was used
CT, CAT scan
computer tomography (CT), also called computed axial tomography (CAT) scan, produces a two-dimensional image of a three-dimensional structure
-Helpful for implant planning, soft tissue lesions, and salivary glands inspections
Cone-beam computed tomography (CBCT)
produces a three-dimensional image of a structure
What is a CBCT useful for?
Inplant planning, TMJ issues, and soft tissue lesions
Provides information for the articular joints and soft tissue when detecting issues with TMJ
How does a CBCT operate? (ie. pano/3d machine)
The arm rotates around the patient’s head in 360°
During this process, 200-600 two-dimensional images are formed which are combined to produce a 3D image
Which scan requires lower doses of radiation between CT exposures and CBCT scans?
CBCT; comparable to 3-4 full-mouth series radiographs
Sialography
detects salivary stones and other blockages
