oral radiography Flashcards
what is the focal trough
only a slice of the object is in focus on the x-ray and this is the focal trough
reasons for OPT
8
assessment of third molars
assessment of #mandible
assess bone heights in perio disease
ortho assessment
assess bony lesions in mandible or maxilla
implant planning
assess TMJ
assess antral disease
what are ghost shadows
cast by structures (e.g. cervical vertebrae, mandible, palate) that are outside the focal trough on the OPT
appear on the opposite side of the real image couterpart and slightly higher up than the real image
air shadow appearance on OPT
radiolucent because there is no photon absorption where there is tissue
error that could’ve occured in OPT to cause anterior teeth that are out of focus and magnified
pt positioned too far from the film
error that could’ve occured in OPT to cause molars larger on one side than the other
pt asymmetrically positioned in machine (head to one side or the other)
error that could’ve occured in OPT to cause vertical or horizontal distortion in one part of the imaeg
pt moved whilst radiograph being taken
error that could’ve occured in OPT to cause it to be too dark
overexposure - due to inc exposure time either by operator or faulty equipment
overdevelopment - excessive time in developer solution or too concentraterd
fogging - light leaking onto film during development
pt with v thin tissues
how often must dentist have radiation protection update course
5 hours over 5 years
ways to minimise radiation dose to pt during IO radiograph
high speed film
recatangular collimation
quality control
optimal kV (70)
view for interproximal caries
bitewings
view for internal derangement of TMH
MRI scan
view for impacted lower third molar
OPT
view for blow out # of the orbital floor
CBCT of whole face
view for salivary calculus in the submandibular floor
true mandibular occlusal
view for presence of an impacted permanent canine
maxillary true occlusal
ALARP principle
as low as reasonable practicable
factors to achieve ALARP
- every radiograph needs to be justified
- optimised- keep exposure as low as possible
- should be a limitation of radiation dose
- written guidelines for exposure setting of radiograph
- fastest speed film should be used that will give good quality radiograpah (usually E)
- rectangular collimation
- minimal skin focus distance (>60kV=20cm)
- film holders used rather than pt holding the film
- referrals should be sent with existing relevant radiographs
- reports for all radiographs
- quality assurance programme to optimise results
what is sialograhy
involves introducing a radiopaque medium into ductal system of a major salivary gland and then taking a radiographic image
indications for sialography
obstruction in ductal system e.g. calculi, siaolith
assess structure of teh gland and ductal system and to see if there is any pathology or changes in them
contraindications to sialography
allergy to iodine containing compounds
infection in the gland
ultrasound for salivary gland imaging
adv
no ionising radiation
excellent for superficial masses
can use if to guide FNA
can use to differentiate between solid and cystic masses
ID radiolucent calculi not seen on radiographs
I/O masses can be visualised with small probes
describe odonotogenic keratocyst radiographic appearance
radiolucent lesion
well defined
multilocular although may be unilocular
scalloped margins
adj teeth may be displaced
tooth roots not usually resorbed
describe dentigerous cyst radiographic appearance
radiolucent lesion
well circumscribed
usually unilocular - can be pseudolucular (septa)
rounded
contains crown of tooth/adj to
associated tooth is displaced
adv digital over film
no processing faults
no risk from handling the chemicals involved in processing
lower radiation dose as the image receptors are more sensitive than conventional film
ease storage
ease tranfer
electronic enhancement of images
differental dx for large radiolucent, mutlilocular lesion with smooth, scalloped well defined margins with internal septa
bony expansion of mandible and displacement of IDC
no resorption of tooth roots
6
ameloblastoma
odontogenic keratocyst
calcifying epithelial odontogenic tumour (early stage)
myxoma
ameloblastoma fibroma
haemangioma
7 signs for IDC and impacted wisdom teeth
darkening of the root
deflection of the root
narrowing of the root
dark and bifid apex of root
interruption of white line of canal
diversion of canal
narrowing of canal
