Extra Oral Flashcards
what are the 3 extra oral views related to the mandible?
postero-anterior mandible
lateral oblique of mandible
DPT
what are the 3 extra oral views relating to the maxilla and cranium?
lateral cephalogram
occipito-mental views
sialography
what are the 3 positioning landmarks?
radiographic base line
frankfort plane
maxillary occlusal plane
where is the radiographic base line?
outer canthus of eye to EAM
where is frankfort plane?
IOB to upper border EAM
where is the maxillary occlusal plane?
ala of nose to tragus of ear
what extra oral view uses the frankfort plane?
DPT
what extra oral view uses the maxillary occlusal plane?
cone beam CT
What equipment do you need?
skull unit/ cephalometric unit
image receptor
anti-scatter grid
what is Compton scattering?
when x-rays pass through tissues some are scattered
what is used to stop scattering?
anti-scatter grid
what does scattering result in?
grey image lacking contrast
what does an anti-scatter grid contain?
lead slats alternating with plastic
what is a postero-anterior mandible view used for?
fractures medio-lateral displacement
cysts and malignancy causing medio-lateral expansion/ bone destruction
good visualisation of posterior body and ramus
what position is patient for PA mandible?
facing film
RB horizontal 90 degree to film
centre of beam to mid-line of patient
where is the midline?
between eyes/ external protuberance
how may a PA mandible view look if RB not 90 degrees to receptor?
cant see the head and neck of condyle
what is a lateral oblique jaw view used for?
fracture of body, ramus and condyle
pathology
wisdom teeth
dental assessment for patients with ASN
caries in children who cant tolerate bitewings
what positioning is used with skull unit for LO jaw view when querying a fracture?
isocentric positioning
what is isocentric positioning?
patient supine
position for area to imaged
rotate machine into horizontal plane
angle 25 degrees towards head
tilt top of patients head towards film
what positioning is used with the skull unit for LO jaw view when visualising dental pathology?
vertical angulation
how is vertical angulation for LO jaw view obtained?
patient hold cassette against and parallel to area examined
tube head beneath lower border of body of mandible that ISNT being examined
aim tube towards teeth
angle tube head slightly upwards
what is the most common positioning for LO jaw view?
horizontal angulation
how is horizontal angulation for LO jaw view obtained?
patient hold cassette against and parallel to area under examination
tube head is positioned along occlusal plane just below the ear towards maxillary and mandibular teeth being examined
aims through radiographic keyhole
when is cephalometric radiography used?
orthodontic assessment
pre orthognathic surgery
what is used to take a cephalometric radiograph?
Cephalostat
how is a lateral ceph set up?
mid sagittal plane parallel to film
patient positioned with ear rods
frankfort plane horizontal
centre of beam aimed at EAM
teeth in occlusion
how is magnification reduced?
long focus to patient distance
short patient to film distance
how do you calculate magnification?
magnification rod on image
how are soft tissues seen on a lateral ceph?
aluminium filter positioned over anterior face
how is PA ceph set up?
patient positioned for PA mandible
x-ray beam aimed at midline level with EAM
RB parallel to floor
when would you use occipito-mental views?
facial bone fractures - le fort fractures
pathology
what are the 3 occipito-mental view angulations?
OM 0
OM 10
OM 30
How is OM view set up?
patient face film holder
nose and chin touching holder
RB 45 degree to film
aim centre of x-ray beam to midline of patient
angle beam 10 degree or 30 degree to feet
what does increasing angulation of OM view do?
projects dense bones of skull base down away from facial structures
improves view of zygomatic arch
what is cone beam computed tomography?
3D reconstruction of anatomy
