10 - Radiographic Techniques 3

Question 1

difference between paralleling & bisected techniques?

Answer 1

1. holder: paralleling uses a holder to position the film, bisected doesn’t
2. position: in paralleling: film is parallel to tooth. in bisected, the film orientation depends on the operator
3. reproducible: paralleling allows this, but bisected angle images are not reproducible.

Question 2

why use bisected angle technique? (radiologically and radiographically)

Answer 2

radiologically: change position or shape of tooth.
radiographically: when patients can’t tolerate holders, or when access is difficult

Question 3

bisected angle technique:

• where is the film placed?
• what should the operator observe?
• how does the operator decide where to angle the beam?

Answer 3

• film is placed as close to the tooth as possible
• should observe the angulation of the film relative to the tooth
• operator bisects angle made between tooth & film. angles x-ray tube for beam to be 90degrees to the bisector

Question 4

paralleling: advantages & disadvantages

Answer 4

• accurate
• reproducible
• good for detecting caries & bone levels
• no irradiation of finger
• easy to learn
• can be uncomfortable for patients
• perfect positioning difficult to achieve

Question 5

bisected angle: advantages & disadvantages

Answer 5

• more comfortable for patient
• useful for special needs patients, or those with strong gag reflex
• can be inaccurate (foreshortening/elongation)
• operator dependent: can be difficult to learn
• irradiates finger

Question 6

occlusal radiographs: taken for? demonstrates what?

Answer 6

• taken to show areas larger than possible on periapical

- demonstrates: unerupted teeth, supernumerary teeth, cysts

Question 7

occlusal radiograph techniques: name the angulation for the following:

• anterior oblique occlusal maxilla
• lateral oblique occlusal maxilla
• anterior oblique occlusal mandible
• lateral oblique occlusal mandible
• true occlusal mandible

Answer 7

• 65deg (patient’s brow bone)
• 60-70 deg (patient’s cheekbone area)
• 45deg
• 45deg
• 90deg (directly underneath patient’s chin)

Question 8

what is radiographic localization and what does it help with?

Answer 8

• a technique used to determine the position of teeth or other foreign objects in the jaw by correct positioning and angulation of xray beam
• overcomes the limitation of the 2D image in assessing relationships of structures in a 3D object

Question 9

what are the two systems for localizations?

Answer 9

• utilize two views at 90deg to each other

- parallax shift

Question 10

indications for radiographic localization?

Answer 10

• assess buccal-palatal relationship of unerupted teeth to the dental arch
• position of foreign bodies
• expansion/destruction of bone
• position of salivary calculi
• separate multiple roots of teeth for RCT
• assessing the displacement of fractures

Question 11

parallax shift technique:

• how are the images taken different?
• usually taken for? what does it do?

Answer 11

• 2 views taken of same object, with a change in angulation.
• usually taken to determine buccal/palatal position of non-visible object
• it separates superimposed objects