oral radiography

Question 1

what is the focal trough

Answer 1

only a slice of the object is in focus on the x-ray and this is the focal trough

Question 2

reasons for OPT

8

Answer 2

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

Question 3

what are ghost shadows

Answer 3

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

Question 4

air shadow appearance on OPT

Answer 4

radiolucent because there is no photon absorption where there is tissue

Question 5

error that could’ve occured in OPT to cause anterior teeth that are out of focus and magnified

Answer 5

pt positioned too far from the film

Question 6

error that could’ve occured in OPT to cause molars larger on one side than the other

Answer 6

pt asymmetrically positioned in machine (head to one side or the other)

Question 7

error that could’ve occured in OPT to cause vertical or horizontal distortion in one part of the imaeg

Answer 7

pt moved whilst radiograph being taken

Question 8

error that could’ve occured in OPT to cause it to be too dark

Answer 8

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

Question 9

how often must dentist have radiation protection update course

Answer 9

5 hours over 5 years

Question 10

ways to minimise radiation dose to pt during IO radiograph

Answer 10

high speed film
recatangular collimation
quality control
optimal kV (70)

Question 11

view for interproximal caries

Answer 11

bitewings

Question 12

view for internal derangement of TMH

Answer 12

MRI scan

Question 13

view for impacted lower third molar

Answer 13

OPT

Question 14

view for blow out # of the orbital floor

Answer 14

CBCT of whole face

Question 15

view for salivary calculus in the submandibular floor

Answer 15

true mandibular occlusal

Question 16

view for presence of an impacted permanent canine

Answer 16

maxillary true occlusal

Question 17

ALARP principle

Answer 17

as low as reasonable practicable

Question 18

factors to achieve ALARP

Answer 18

• 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

Question 19

what is sialograhy

Answer 19

involves introducing a radiopaque medium into ductal system of a major salivary gland and then taking a radiographic image

Question 20

indications for sialography

Answer 20

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

Question 21

contraindications to sialography

Answer 21

allergy to iodine containing compounds
infection in the gland

Question 22

ultrasound for salivary gland imaging
adv

Answer 22

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

Question 23

describe odonotogenic keratocyst radiographic appearance

Answer 23

radiolucent lesion
well defined
multilocular although may be unilocular
scalloped margins
adj teeth may be displaced
tooth roots not usually resorbed

Question 24

describe dentigerous cyst radiographic appearance

Answer 24

radiolucent lesion
well circumscribed
usually unilocular - can be pseudolucular (septa)
rounded
contains crown of tooth/adj to
associated tooth is displaced

Question 25

adv digital over film

Answer 25

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

Question 26

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

Answer 26

ameloblastoma
odontogenic keratocyst
calcifying epithelial odontogenic tumour (early stage)
myxoma
ameloblastoma fibroma
haemangioma

Question 27

7 signs for IDC and impacted wisdom teeth

Answer 27

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