radiographic techniques

Question 1

what are the different types of intra-oral radiographs?

Answer 1

peri-apicals, bitewings, occlusal

Question 2

what are the 5 different types of extra oral radiographs

Answer 2

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)

Question 3

why take a DPT?

Answer 3

It shows the teeth and supporting structures

Question 4

why take a lateral cephalogram?

Answer 4

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.

Question 5

why take a postero-anterior mandible

Answer 5

useful for showing mandible fractures

Question 6

how are PA mandibles taken?

Answer 6

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)

Question 7

why take a lateral oblique mandible?

Answer 7

for children who cannot tolerate bitewings, and adults with mandible fractures if a DPT isnt available

Question 8

why take an occipito-mental view of the facial bone

Answer 8

first instance when a patient comes to A&E with facial trauma. it also shows fractures of the orbits, maxilla, and zygomatic arches

Question 9

how are occipito-mental views taken

Answer 9

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)

Question 10

when would you take peri-apicals

Answer 10

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.

Question 11

how should you decide which type of radiograph to take?

Answer 11

FDGP (faculty of general dental practice) selection criteria for dental radiography 2018

Question 12

what techniques are there for taking periapicals? describe each

Answer 12

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

Question 13

what are the advantages and disadvantages for each intra-oral radiographic technique?

Answer 13

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

Question 14

what are the different types of holders?

Answer 14

blue anterior, yellow posterior (for pa’s)

Question 15

what type of receptors are used in DDH

Answer 15

DDH uses phosphor plates (processed, ereased, and re-used) - this is called computed radiology.

Question 16

what impacts the geometry of radiographs

Answer 16

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)

Question 17

explain magnification

Answer 17

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

Question 18

what is cone cutting?

Answer 18

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

Question 19

what are some barriers to good positioning ?

Answer 19

mouth size, gag reflex, film size, digital sensor shape and size

Question 20

explain the difference between the receptor sizes

Answer 20

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

Question 21

what is the radio-opaque dot on radiographs?

Answer 21

indicated if image is left or right

periapicals should be positioned next to the crown of a tooth, bitewings PIP TO PALATE

Question 22

what is the controlled area

Answer 22

this is the immediate vicinity around the x ray source which only the patient is allowed to be in