radiographic techniques 3

Question 1

what are the basics of bisected angle technique?

Answer 1

• film/image receptor is placed as close to tooth as possible - without bending etc
• will usually contact crown but be distance from root apex
• long axis of tooth & film form an angle which is mentally bisected
• x-ray tube head is positioned so that beam is at 90 degrees to bisecting plane
• overall length of image should be equal to length of tooth - law of similar triangles

Question 2

What are reasons for utilising bisected angle technique?

Answer 2

• to separate the roots of teeth
• to overcome superimposition
• when assessing root fractures
• when localising unerupted teeth
• when diagnosing apical pathology & the paralleling technique cannot be used
• when its OK to have a distorted view

Question 3

describe oblique occlusal views

Answer 3

• modified bisecting angle technique
• mandible and maxilla
• anterior and lateral
• show teeth from crown to apex
• distortion often occurs
• superimposition away from central area
• easy technique for patients

Question 4

When should you request oblique occlusal radiographs?

Answer 4

• When a larger area is to be imaged than will fit on periapical film
• some patients who retch
• children who cannot tolerate periapical views
• parallax views - to help assess the relative position of pathology or unerupted teeth

Question 5

mandibular occlusal views

Answer 5

—  Oblique and true occlusal views.
—  Anterior oblique is often called 45⁰
—  Film & long axis of incisors are at 90⁰ to each other
—  Bisected angle is 45⁰
—  Beam is angled at 90⁰ to the bisecting plane & therefore hits the film at 45

Question 6

describe mandibular true occlusal

Answer 6

• not all teeth may be seen in cross section
• often taken to check for submandibular duct calculi
• x-ray beam at 90 degrees to film
• teeth look like buttons

Question 7

What do we mean by localisation?

Answer 7

• Finding the exact position of a structure that cannot be seen clinically
• overcoming the limitations of a 2D picture
• assessing the relationship of one structure to another
• building up a 3D image of a structure

Question 8

What are indications for radiographic localisation?

Answer 8

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

Question 9

What are the relationship of these 2 views?

Answer 9

• Both are parallel to long axis of objects
• views are 90 degrees to each other

Question 10

describe parallax views

Answer 10

• 2 views/radiographs taken of same object with a change in angulation of beam
• relative movement of object being localised to fixed point
• horizontal or vertical plain
• usually taken to determine buccal/palatal position of non-visible object
• separate superimposed objects