Radiology Flashcards
where does the frankfort line run from
from superior border of external auditory meatus to inferior orbital
where does orbitomeatal line run from
centre of external auditory meatus to outer canthus of eye
what is the difference between anteroposterior and posteroanterior
anteroposterior - the tube is anterior to the patient with the receptor behind them
posteroanterior - the tube is posterior to the patient and the receptor is infront of them
why is PA always used in external imaging for the face
the structure we want to see are at the front. PA reduces magnification and reduces dose
what should be included in a radiographic report
the type of film
grade - acceptable or not
teeth and structures present
if restorations not already charted note these - RCT - condensed, to length
bone levels
periradicular changes - location, size, margins
caries
what are differential diagnosis in the radiological seive?
normal
developmental
traumatic
inflammatory
cystic
neoplastic
osteodystrophy
metabolic/systemic
idiopathic
iatrogenic
foreign body
artefact
when explaining radiolucencies, what should be included in the description
size
shape
location
margins - well defined, corticated
aetiology
affect on other structures - displacement, expansion, resorption
what are some clinical indications for CBCT
orthognathic surgery
unerupted teeth
implant planning
pathology - cysts, malignancy
cleft palate
dental abnormalities
what are kinds of odontogenic cysts
radicular cyst, dentigerous cyst, orthokeratocyst
what are signs and symptoms of cysts
can be asymptomatic, increase in size, swelling, TTP on teeth, mobility of teeth, drifting of teeth, loss of vitality and change in colour of teeth
what should be included when describing a cyst on radiograph
location, shape, margins - well defined, corticated, locular - uni-locular or multi, teeth involved, effecting any anatomy
where does a radicular cyst develop from
periapical granuloma due to pulpal necrosis, stimulates rest cells of malassez to proliferate, forms epithelial lining around fluid and allows it to grow in size, corticated margins of cyst is continuous with lamina dura
what is the difference between periapical granuloma and a radicular cyst
size - radicular cyst is more than 15mm, if the tooth has been RCT and the granuloma doesnt reduce - then it is a cyst
what is a cyst
pathological cavity or sac, containing fluid, semi-fluid or gas, may or may not be epithelial lined
what is the difference between a radicular cyst and a residual cyst
radicular cyst is when the cause is still present, residual cyst is when the cause has been removed (RCT or XLA) but the cyst persists
what is a dentigerous cyst and where does it come from
cystic change of a dental follicle in unerupted teeth, been there for too long. Develops from reduced enamel epithelium. can be seen extending from ACJ of unerupted tooth
how do you decide if a dentigerous cysts is a cyst or a follicle
measure from cusp to follicle. If less than 4mm - follicle. More than 4mm, consider cyst, if more than 10mm assume cyst
what is the histology of a dentigerous cyst
thin layer of non-keratinised stratified squamous epithelium, coming from reduced enamel epithelium
what is the difference between an eruption cyst and a dentigerous cyst
an eruption cyst is in soft tissue and develops from rest of serres, appears blueish in colour, tooth will erupt through it
what is an odontogenic keratocyst
developmental cyst developing from dental lamina, not one particular tooth
what is characteristic of a OK
multi-locular or pseudolocular - rarely one big balloon
scalloped margins giving view of pseudolocular
expansion through medullary bone - mesio-distal direction, cannot expand through cortical bone
displacement of adjacent teeth but unlikely to cause root resorption (more in ameloblastoma)
what is a pre-surgical diagnostic test done with cyst aspirate for an OK
contains squames and low soluble protein content
what is seen histologically with an OK and what impact does this have on surgery
very thin parakeratinised lining
lining is very friable, if teared during surgery, likely to leave daughter cells and allows for recurrence
how does basal cell naevus syndrome present
multiple odontogenic keratocysts
multiple basal cell carcinomas
clacification of the intra cranial dura mater
name 2 non-odontogenic cysts
naso-palatine duct cyst and solitary cyst
where is the naso-palatine duct cyst and what can it be confused with
anterior between central incisors, can appear heart shaped due to nasal spine. can be confused with incisive follicle. if less than 6mm - follicle. 6-10mm - monitor, larger than 10 - assume cyst
what is a solitary cyst
non-odontigenic developmental cyst, non-epithelial lined, normally asymptomatic, incidental finding, normally just monitor and it resolves on its own
how might cystic material be obtained for tests
aspirate - if suspect fluid
incisional biopsy - remove part of the cystic lining, can be done with marsipulisation
excisional biopsy - remove cyst and send for testing
what are treatment options for cysts
enucleation - complete removal of cyst
marsipulisation - create opening of cyst into oral cavity and allow for slow drainage
what are the benefits are risks of enucleation
benefits - complete removal of cyst in one surgery, less follow up required, whole lining can be examined
risks - if large cyst - risk of fracture, large surgery requiring GA - is patient well enough for this, risk of recurrence if not all removed, damage to adjacent structures, if dentigerous cyst - loss of tooth
when would marsipulisation be indicated and what is the risk of it
indications - large cyst which would leave the mandible at risk of fracture, elderly patient, dentigerous cyst where patient wants to retain tooth, cyst is close to important structures e.g. ID canal
risks - a lot of follow up required for pack change etc, risk of the window closing and the cyst re-growing
