Bisecting Angle and Occlusal Radiography

Question 1

What are the basics of bisected angle technique?

Answer 1

• film/receptor is palced as close to tooth as possible without bending
• will usually contact crown but be some distance from root apex
• long axis of tooth and 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

Question 2

Reasons for using bisected angle technique?

Answer 2

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

Question 3

What is an oblique occlusal view?

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 oblique occlusal radiographs be requested?

Answer 4

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

Question 5

Why may a mandibular true occlusal radiograph be taken?

Answer 5

• often taken to check for submandibular duct calculi
• x-ray beam at 90 degrees to film
• teeth look like buttons

Question 6

What is meant by localisation?

Answer 6

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

Question 7

Indications for radiographic localisation?

Answer 7

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

Question 8

What are parallax views?

Answer 8

• 2 views 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