radiographic techniques Flashcards
name 3 types of intra-oral radiographs
-periapical
-bitewing
-occlusal (mandibular and maxillary)
where is the receptor placed for intra oral radiographs?
placed within the mouth of the patient
name 5 examples of extra oral radiographs
-dpt
-lateral celphalogram
-postero-anterior mandible
-lateral oblique mandible
-occipito-mental views of facial bones
where is the receptor found in extra-oral radiographs?
external to the patients body
what can be seen in peri-apical radiographs?
from crown to apex of root and in between teeth
what can be seen in horizontal bitewing radiographs?
4d-8m
bone levels
what can be seen in vertical bitewing radiographs?
more of bone but still NOT entire root
what can be seen in occlusal radiographs?
mandibular- FOM and teeth
maxillary- anterior teeth and anterior part of maxillary
how is a dpt taken?
the X-ray tube moves round the patients head
how long is the exposure of dpt’s?
14 seconds
what can be seen on a dpt?
teeth and supporting structures
what does a lateral cephalogram radiograph show?
skull
what is a lateral cephalogram commonly used for?
orthodontics
what can lateral cephalograms show?
relation of teeth to mandible
relation of mandible to rest of facial skeleton
what are postero-anterior mandible radiographs used for?
to view mandibular fractures
how are posters-anterior mandible radiographs taken?
two images taken at right angles to each other
- as mandibular fractures often occur in more than 1 place
when are lateral oblique mandible radiographs taken?
-for children who cannot tolerate bitewing radiographs
-mandibular fractures
when would occipito-mental views of facial bones be used?
facial trauma fractures
what sort of fractures can be seen on occipito-mental radiographs?
-orbital
-maxillary
-zygomatic arches
why are peri-apical radiographs used?
-apical pathology (inflammation, infection, cysts)
-periodontal status
-endodontics
-pre extraction to view roots
-trauma to teeth/bone
-unerupted teeth position
-implants
-apical surgery
what are the 2 radiographic intra-oral techniques called?
-paralleling technique
-bisected angle technique
describe the paralleling technique?
-accurate geometry of image
-receptor is held in holder
-holder keeps receptor parallel to tooth and beam
-produced accurate and reproducible image
-x-ray beam positioned perpendicular to tooth/receptor
what are the negatives to the paralleling technique?
-holders are bulky and may not be tolerated by the patient
-but paralleling prevents repeats and exposure of radiation to finger
what is the bisected angle technique?
-no holder used
-operator dependent so image is not reproducible
-receptor held in place by patients finger or lollipop holder (finger exposed to radiation)
what is the most commonly used technique for intra-oral radiographs?
the paralleling technique
what are the following coloured holders used for?
blue
yellow
red
green
blue- anterior PA
yellow- posterior PA
red- H and V bitewings
green-endodontics
what type of image receptor is used at DDH?
phosphor plates
what does computed radiology receptors mean?
receptor film is processed, erased and reused
finish the sentence
holders reduce variables in …
geometry
what does the geometry of an image mean?
it means that the image does not change has much when looking at it from a different angle
what are 3 variables that affect the geometry of a radiographic image?
-receptor to tooth relationship
-perpendicular direction of X-ray to receptor
-magnification
how should the receptor be in relation to the tooth?
-vertical axis of receptor must be parallel to long axis of the tooth
-horizontal axis of receptor must be parallel to dental arch
how would wrong position of vertical and horizontal planes of receptor to tooth affect image?
vertical- distort image- elongate or shorten
horizontal-overlapping
what is magnification of an image affected by?
xray beam to receptor distance
tooth to receptor distance
what shape is an xray beam?
divergent cone shaped
what is the ideal positioning for correct magnification?
long xray beam to receptor distance
short receptor to tooth distance
when taking an image of posterior teeth what orientation should the film be?
horizontal
when taking an image of posterior teeth what orientation should the film be?
horizontal
when taking an image of anterior teeth what orientation should the film be?
vertical
what is cone cutting?
seen when corners of collimator are not touched the ring slides and they absorb the radiation
what are the film sizes used in DDH?
0,1,2 and 4
what film size should be used for an adult anterior PA?
0,1
what film size should be used for an adult posterior PA?
2
what film size should be used adult and children over 10 bitewings?
2
what film size should be used for children posterior PA of deciduous teeth and permanent teeth ?
d- 0
p-2
what film size should be used for child anterior PA?
0
what film size should be used for bitewings for children under 10?
0/1
where should the dot on receptor be during PA?
to the crown (bite block)
where should the dot on receptor be during bitewings?
to the palate
what is the controlled area?
the immediate vicinity around the x ray- must be outside this area to keep personal radiation dose to a minimum
