Extra-Oral Radiography Including Cephalograms Flashcards
what are some purposes of extra-oral radiographs?
- imaging larger sections of dentition
- patient cannot tolerate intra-oral radiographs
- imagine non-dentoalveolar regions
what are common types of extra-oral radiographs?
- panoramic radiographs
- cephalometric radiographs
- oblique lateral radiographs
- skull radiographs
In relation to extra-oral radiograph terminology, what does true mean?
angulation of beam is perpendicular to head
In relation to extra-oral radiograph terminology, what does oblique mean?
angulation of beam is not perpendicular to head
In relation to extra-oral radiograph terminology, what does lateral mean?
beam aimed at side of head
In relation to extra-oral radiograph terminology, what does postero-anterior mean?
beam starts posteriorly & passes anteriorly
what are examples of reference lines/planes used in extra-oral radiography?
- mid-sagittal plane
- interpupillary line
- Frankfort plane
- orbitomeatal line
what is the function of anatomical reference lines/planes?
anatomical landmarks used to aid positioning of extra-oral radiographs
- allows them to be reproduced
what difference in degrees is there between the Frankfort plane & the orbitomeatal line? (roughly)
10 degrees
what is cephalometry?
the measurement & study of the head (using different points, angles & distances to analyse anatomy)
what are the clinical applications of cephalometry?
- orthodontics & orthognathic surgery
- monitor changes in dentition over time
what is the most common type of cephalogram taken?
lateral cephalogram !
what is the main anatomy seen on a lateral cephalogram?
- teeth
- facial bones & soft tissues
- paranasal sinuses
- cervical vertebrae
- pharyngeal soft tissue
why might lateral cephalograms be used in orthodontics?
- assessing skeletal discrepancies before use of orthodontic appliances
- aiding location & assessment on unerupted, malformed or misplaces teeth
- giving an indication of teeth root length (often upper incisors)
at what stages of orthodontic treatment might a lateral cephalogram be taken/used?
- diagnosis
- treatment planning
- monitoring progress
- appraisal of treatment results
what do all cephalogram units have?
a cephalostat
what is the cephalostat?
Part of cephalogram unit that ensures standardised positioning of equipment & patients head
what are the functions of the cephalostat?
- holds head at correct angle
- stabilises head to prevent movement
- establishes correct distances between x-ray focal spot, patient & receptor
what are the different parts of the cephalostat?
- ear rods
- forehead support
at what distance should the receptor lie from the x-ray focal spot in standardised cephalograms?
1.5m to 1.8m distance
- minimises magnification
what problem surrounds imaging soft tissues with a lateral cephalogram?
soft tissues show up poorly when exposure settings are optimised for hard tissues (won’t be able to see)
how can soft tissues be better highlighted on lateral cephalograms?
- aluminium wedge filter in the unit that attenuates the specific area of the beam to expose the facial soft tissues
- use software to enhance soft tissues post-exposure
How can patients be shielded & protected when having a lateral cephalogram taken?
thyroid collar used (as thyroid gland is radiosensitive)
what is CBCT?
Cone Beam Computed Tomography
- provides cross sectional imagining
