BDS4 Seminar radiology Flashcards
why might take an OPT for ortho?
- State of development - presence or absence of permanent teeth
- Presence and position of ectopic or supernumerary teeth
- The stage of development of individual teeth
- The morphology of unerupted teeth
- State of the alveolar bone ( Periodontal disease )
- State of the teeth . Size of restorations, gross caries, periapical infection, other pathology
other indications for opt?
- pathological jaw lesions
- surgery - evaluation and review
- trauma /fractures
how can faults arise in opt?
- Due to the limitations in the width of the focal trough – particularly at the front of the mouth.
- Faults in patient positioning
- Movement of patient during the exposure
problems with focal trough for ortho?
- class II div 1 - Roots of one or both upper and lower incisors may be blurred or not visible
- Class III – roots of upper incisors may be blurred
what happens if pt too far froward in opt?
teeth look narrower
- because the teeth are further from the centre of rotation and the x-ray beam therefore passed more quickly
through these teeth relative to the speed of the image
receptor
if pt too far back in opt machine?
teeth will look wider
- teeth are closer to the centre of rotation and the x-ray beam therefore passed more slowly through
these teeth relative to the speed of the image receptor
what are ghost images?
- Ghost images are shadows created on the opposite side of
the OPT from the object which caused them. - They are caused by the tomographic movement of the xray machine.
- They are always seen at a higher level on the opposite side of the mouth because the x-ray beam of the machine is angled upwards by 8 degrees.
- Ghost images can be caused by metal objects ,
restorations, earrings or by normal anatomic features
cause?
Patient positioned in OPT machine with Frankfort plane
tipped down – This produces a “smiley face” appearance.
cause?
Gross distortion of image due to the patient moving during
the exposure
Why do we request a standard upper occlusal view?
pathology upper anterior region
confirm unerupted teeth
Root resorption – but PA view better for assessment
To aid localisation of unerupted teeth in combination with another radiographic view (parallax)
Why might we request a periapical view?
To assess for root resorption
To look for evidence of periapical infection
To assess if a tooth might be
ankylosed
To aid localisation of unerupted teeth in combination with another radiographic view
(parallax)
Why might we request a bitewing radiograph?
To assess caries status
To provide more information on tooth prognosis
To get more information on alveolar bone levels
localisation of unerupted teeth which radiographic views required?
OPT and AOM
= vertical parallax
Two periapical views
= horizontal parallax
how is principle parallax applied?
There must be a change in position of the X-ray
tube between the two radiographs.
beam- further away - same direct
beam - closer - opposite direction
palatal
buccal
what is ANB discrepancies?
what is vertical discrepancies?
what are dentoalveolar measurement?
what are commonly used soft tissue planes?$
what does this depict
Short facial type with reduced vertical proportions
what does this depict?
Long facial type with increased vertical proportions
what does this depict?
Acromegaly due to pituitary adenoma. Note enlarged sella turcica.
