Dentals - Extra-Oral Flashcards
why are panoramic views taken?
to allow a more general assessment of the teeth and jaws
what are 6 reasons why a panoramic view would be taken?
assessment of third molars prior to multiple extractions jaw #s severe periodontal disease orthodontic assessment TMJ problems
give 5 more reasons why a panoramic view would be taken
assessment of large pathological lesions
when intra-oral radiography is impossible due to gagging or trismus
patients with gross decay
assessment for implants
where a bony lesion or an unerupted tooth cannot be demonstrated
how are panoramic views taken?
type of tomography (slice through patient)
tube and film move round head
patient positioning is crucial so the jaws are in the focal trough
what 5 steps are carried out to prep the patient
justify request
check medical history
confirm patients identity
ask patients to remove earrings, glasses, necklaces and dentures
explain machine movement to patient, especially children
what 6 steps are taken to position the patient
position patient upright - not slumped
guide patients head between head clamps
ask patient to bite the bite rod gently
tilt head forward
teeth and jaw positioned with focal trough
ensure patient places their tongue against their palate during the exposure
what can be used to guide positioning?
positioning lights
what are 3 image criteria for a well positioned film
symmetrical
no magnification or diminution of teeth
occlusal plate flat or slight downward curve
what are the 6 common positioning errors
too far in too far out chin up chin down head rotated patient slumped
what will occur on the image if the patient is too far in - 3 points
the anterior teeth will be blurred and narrow in appearance
the premolars will be overlapped
the c spine may be superimposed on the rami
what will occur on the image if the patient is too far out - 2 points
the anterior teeth will be blurred and wide in appearance
the condyles may fall outside the sides of the film
what will occur on the image if the patients is in a chin up position - 3 points
the roots of the upper incisors will be blurred
the condyles may be lost on the side of the film
the hard palate may be projected over the upper roots apices
what will occur on the image if the patient is in the chin down position - 3 points
the lower incisor roots will be blurred
the hyoid bone may be projected over the mandible
the occlusal plane will have characteristic “smile sign”
what will occur on the image if the patients head is rotated - 2 points
the teeth on one side of the midline will have overlapping contacts and will be magnified relative to those on the other side
the width of the mandibular ramus on each side will also be different
what will occur on the image if the patient is slumped - 1 point
this results in an opaque ghost image of the c spine to be projected over the midline of the film
describe a ghost image - 3 points
formed when the object is located between the x-ray source and the centre of rotation
appear on the opposite side from the real image
always higher up and blurred
what is included in the image evaluation - 10 points
ID label should not obscure the image whole of mandible imaged bone levels demonstrated incisors biting edge to edge no artefacts no radiolucent air shadow minimisation of c spine shadow correct anatomical markers all teeth in focus no movement
why are lateral cephalometric view taken - 3 points
as part of an orthodontic assessment
accurately show the position of teeth and their relationship to the skull
orthognathic assessment
how are lateral ceph’s taken
where is x-ray tube and why?
why is a filter used?
pt set up in a cepalosat with rods in ears and against the bridge of the nose - puts patient in known position and allows review radiographs to be taken in the exact same way
at 2m away to get a parallel beam to minimise magnification
so facial soft tissue profile is seen
patient positioning for lateral ceph - 6 points
gently place ear plugs into EAMs Frankfort plane should be parallel to the floor position the nasal support align light to outer canthus of eye ask patient to bite on the back teeth lips should be relaxed
image evaluation for lateral ceph - 6 points
ear plugs should be superimposed facial structures should be superimposed upper occlusal plane parallel to floor molars in occlusion soft tissue outline from forehead to chin no movement
what are 6 clinical indications for lateral oblique mandible
when an OPG is difficult to perform on young children, elderly or special needs
#ed mandible
assessment of large pathologies
when periapical radiography is not possible
salivary glands
TMJs
what does CBCT stand for?
Cone Beam Computed Tomography
what is CBCT
compact, faster, and safer version of regular CT
uses cone-shaped x-ray beam
easily accessible by patients
what 3 things are dramatically reduced
the size of scanner, radiation dose (up to 100x less) and time needed for scanning (about 1 minute)
