Intra-Oral Techniques

Question 1

What is the ideal projection geometry? (3 points)

Answer 1

• image receptor and object in contact and parallel
• parallel beam of x-rays
• X-ray beam perpendicular to object (patient) plane and image receptor

Question 2

If ideal projection geometry was possible with intra-oral radiographs, what would the image outcome be like?

Answer 2

Image size would be identical to object size

Question 3

What are some problems with getting an ideal projection geometry when taking an intra-oral image of a tooth?

Answer 3

• image receptor and object not in contact (tooth in bone so can only contact part of it)
• X-ray beam central ray MAY or MAY NOT be perpendicular to object plane and image receptor

Question 4

Why is the image size not identical to the object size?

Answer 4

Due to magnification because of divergent beams

Question 5

What are the 2 solutions to the probs with projection geometry (two techniques)?

Answer 5

• Paralleling technique
• Bisecting angle technique

Question 6

What is the paralleling technique?

Answer 6

• The image receptor and the object are parallel but not in contact
• The x-ray beam is directed at right angles to the image receptor

Question 7

In the paralleling technique, describe the x-ray beams with regards to being perpendicular to the image receptor/long axis of the tooth.

Answer 7

Only the central beam is truly perpendicular to the long axis of the tooth and image receptor

The outer beams aren’t quite perpendicular due to divergent beams

Question 8

Why do divergent beams happen in paralleling technique?

Answer 8

because of the distance between the image receptor and object being x-rayed (allows potential for undesired magnification)

Question 9

What can be used to help reduce the magnification?

Answer 9

A short focus to skin distance

Question 10

What are the benefits of film holders and beam-aiming devices?

Answer 10

• dose reduction
• improved quality
• fewer rejects/retakes

Question 11

Describe the parts/components of the film holder devices.

Answer 11

have a bite, block, beam aiming device, image receptor support

Question 12

How are film holders sterilised?

Answer 12

They are autoclvaed

Question 13

Incorrect assembly of film holders can result in what?

Answer 13

‘coning off’ - only part of the receptor reached so full image not made

Question 14

What is the extra part found on an endodontic film holder?

Answer 14

A basket to support instrument heads or gutta percha points

Question 15

What is rectangular collimation and why is it used?

Answer 15

It controls shape and size of the x-ray beam and therefore allows dose reduction Rectangular to match the image receptor

Question 16

How do collimators work?

Answer 16

Dark area around edge is lead and very good at absorbing x-rays The x-rays cannot get out from anywhere apart from the silvery section in the middle

Question 17

What is the summary of the paralleling technique?

Answer 17

• Image receptor and object parallel but not in contact
• image receptor and object a distance apart
• use long xray focus
• skin fsd to reduce magnification
• requires use of film holders
• stabilise with cotton roll between bite block and teeth in arch OPPOSITE to that being xrayed

Question 18

How are periapicals/bitewings taken? write down and refer to notes

Answer 18

FOR THE TECHNIQUES ON HOW TO TAKE X-RAYS REFER TO NOTES

Question 19

What is the curve of Spee?

Answer 19

‘happy smile’ Curves up posteriorly (seen from antero-posterior view)

Question 20

What is the curve of Monson/why is it relevant?

Answer 20

A bucco-lingual angulation Influences x-ray technique e.g. bitewings are panoramic