radiographic techniques Flashcards
what are the different types of intra-oral radiographs?
peri-apicals, bitewings, occlusal
what are the 5 different types of extra oral radiographs
DPT, lateral cephalogram, postero-anterior mandile, lateral oblique mandible, occipito-mental views of the facial bone (try and look at pictures of each of theses views to familiarise)
why take a DPT?
It shows the teeth and supporting structures
why take a lateral cephalogram?
it is used in ortho to assess the relationship of the teeth and jaws, and the mandible to the rest of the facial skeleton, we can also see the soft tissue pattern of the nose and lips which is useful for surgical planning.
why take a postero-anterior mandible
useful for showing mandible fractures
how are PA mandibles taken?
should be requested in conjunction with a DPT, two views taken at right angles to one another (to show the full extent of a fracture)
why take a lateral oblique mandible?
for children who cannot tolerate bitewings, and adults with mandible fractures if a DPT isnt available
why take an occipito-mental view of the facial bone
first instance when a patient comes to A&E with facial trauma. it also shows fractures of the orbits, maxilla, and zygomatic arches
how are occipito-mental views taken
two views are taken, first with the beam angles at 10 degrees, second with beam angles 30 degrees
the films should be taken erect as this can show fluid levels in the maxillary sinuses (antra)
when would you take peri-apicals
apical (surgery pre and post op, infection, inflammation/pathology, cysts) bone legions, perio status, trauma, root morph pre xla, unerupted teeth, endo, implant post op.
how should you decide which type of radiograph to take?
FDGP (faculty of general dental practice) selection criteria for dental radiography 2018
what techniques are there for taking periapicals? describe each
paralleling - the standard technique, uses a holder to facilitate positioning and keep receptor parallel to the tooth and the x-ray beam.
bisected angle - use this method if the patient cannot tolerate the holder in there mouth, can also ask the patient to hold the film in their mouth with their finger or use a holder that looks like a lollipop stick
what are the advantages and disadvantages for each intra-oral radiographic technique?
paralleling - it allows accurate geometry of image, minimised magnification, accurate and reproducible image, however, it may not be tolerated well by patients.
bisected angle - easily tolerated, patients finger is exposed to radiation and geometry of image is compromised
what are the different types of holders?
blue anterior, yellow posterior (for pa’s)
what type of receptors are used in DDH
DDH uses phosphor plates (processed, ereased, and re-used) - this is called computed radiology.
what impacts the geometry of radiographs
receptor tooth relationship - vertical plane of film should be parallel to long axis of the tooth, horizontal plane of film should be parallel to dental arch under examination. (vertical distortion elongates apices, horizontal distortion causes overlapping)
Xray tube position (vertical angulation) - beam should be at right angles to tooth and receptor (beam angled up - teeth will appear longer, beam angles down - roots look shortened)
xray tube position (horizontal) - if beam is not 90 degrees to the tooth, overlapping of the teeth could occur. (ensure that the collimator has 4 corners fitted properly on aiming ring)
explain magnification
this is impacted by the DISTANCE of the x-ray source (focal spot) to the receptor, and the DISTANCE of the object to the receptor
the further the source to object, and closer the object to receptor is, the less beam diverges and the less the image is magnified
what is cone cutting?
appears white on a radiograph
corners of the collimator are not touching guiding ring which ends up absorbing x rays preventing the receptor from being exposed and forming the image
what are some barriers to good positioning ?
mouth size, gag reflex, film size, digital sensor shape and size
explain the difference between the receptor sizes
0,1,2,3,4
for adult PA’s - 0/1 used anteriorly (2 can be used for bisected angle technique), 2 is used posteriorly
for child PA’s - 0 for anterior and primary posterior, 2 for permanent posterior
bw’s - over age 10 use 2 always, under 10 use 0/1
4 for occlusal
what is the radio-opaque dot on radiographs?
indicated if image is left or right
periapicals should be positioned next to the crown of a tooth, bitewings PIP TO PALATE
what is the controlled area
this is the immediate vicinity around the x ray source which only the patient is allowed to be in
