Bisecting angle technique & Occlusal radiography

Question 1

What is the Bisecting angle periapical teachnique?

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 90⁰ to bisecting plane

Overall length of image should be equal to length of tooth – law of similar triangles!

Question 2

What are the 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

What if we want a bigger view?

Answer 3

CONSIDER USING AN OCCLUSAL VIEW

Question 4

When to 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

What is the Mandibular occlusal views?

Answer 5

Question 6

What are 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 90º 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 the 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 Parallax Views?

Answer 9

• 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