Intro to Dental Radiography

Question 1

Radiology request card

Answer 1

Must be completed comprehensively and completely, otherwise no images will be taken and your px will be returned to clinic

Question 2

Imaging requests

Answer 2

An imaging request form is completed by referrer
Must include:
1. Px identification label on both sides of document
2. Details of clinic and its consultant e.g. RD2/ Dr Dentist
3. Date
4. Clear and precise indication of images required
5. Clinical justification for those images
6. Clinicians signature
Any omissions and images will not be taken; px will be returned to clinic for appropriate corrections to be made

Question 3

Extra-oral images

Answer 3

Dental Panoramic Tomograph (DPT, OPT, OPG)
Lateral & Postero-anterior (PA) Cephalometry
PA Mandible
Oblique Lateral Mandible
Occipitomental (OM) 10 and 30 degrees

Question 4

Intra-oral images

Answer 4

Periapicals - paralleling and bisecting angle techniques
Bitewings
Maxillary occlusals
Mandibular occlusals

Question 5

Which nerve goes through mandibular foramen

Answer 5

Inferior alveolar nerve

Question 6

Positioning requirements

Answer 6

Px’s dental arch must be positioned accurately within zone of sharpness called ‘focal trough’
Series of positioning light beams enable operator to achieve this

Question 7

Positioning technique

Answer 7

Have px remove jewellery, hair ornaments and intra-oral appliances containing metal in order that they do not cause artefactual images
Have pxs approach x-ray unit and hold hand grips for stability
Present bite block and ask them to bite in upper and lower grooves to place teeth in edge to edge occlusion
Activate positioning lights
Encourage px to press shoulders and chest forward to minimise image of cervical spine
Request they ‘suck bite block’ to press tongue into palate thus eliminating air over dorsum of tongue
Finally remind them to keep still for duration of exposure; approx 15-20s

Question 8

Positioning lights

Answer 8

Sagittal light: coincides with px’s midline to ensure no tilt
Frankfort Plane light: demonstrates line connecting infra-orbital margin with upper notch of tragus of ear to ensure hard palate is horizontal
Image layer/ focal trough light: assessed for its position relative to upper 3, appropriate selection made on unit controls thus ensuring dental arch is in focal trough

Question 9

Forming DPT image

Answer 9

DPT is not captured in its entirety as with other images
Image built up oover exposure period of up to 18s
Different part of px imaged at different stages in cycle

Question 10

Paralleling periapicals

Answer 10

Taken using either film or photostimulable phosphor plates, in various sizes (image receptors)
-x-ray unit + image receptor holders with beam aiming arm and locator ring
Image receptor must be parallel with tooth/ teeth
Made possible by using paralleling device
Once exposed receptor is placed in appropriately sized cassette and introduced into image plate reader

Question 11

Advantages of paralleling technique

Answer 11

Accurate image; no elongation, foreshortening overlapping or cone cut
Little superimposition of other anatomical structures
Images are reproducible

Question 12

Disadvantages of paralleling technique

Answer 12

Quite uncomfortable to px, often stimulating gag reflex

Holders need to be sterilized or disposable

Question 13

Elongation and foreshortening

Answer 13

If vertical angle of central beam too steep = foreshortened
If vertical angle of central beam too shallow = elongated
(bisecting angle periapical technique)

Question 14

Maxillary canine

Answer 14

Image receptor is held in place by thumb or index finger of opposite hand
Central x-ray beam directed perpendicular to bisecting line in both horizontal and vertical planes and centred to receptor
(bisecting angle periapical technique)

Question 15

Maxillary premolar

Answer 15

Receptor held in place, long axis horizontally, lower border 2mm beyond and parallel with occlusal surface of premolars
Centre x-ray beam to receptor, perpendicularly in vertical and horizontal planes
(bisecting angle periapical technique)

Question 16

Advantages of bisecting technique (not used)

Answer 16

More comfortable for px

Quicker than having to assemble holders

Question 17

Disadvantages of bisecting technique (not used)

Answer 17

Image often distorted, elongation, overlap etc., due to many variables
Superimposition of zygomatic buttress is problematic in imaging upper posterior molars
Bone levels are not clearly demonstrated
Not reproducible

Question 18

Bitewings

Answer 18

Demonstrates interproximal spaces of teeth in upper and lower arch on one image
Using another type of beam aiming device
Bite platform is central to receptor holder so an equal proportion of upper and lower teeth are demonstrated
Receptor should be placed carefully into sulcus with mesial and distal border equidistant from lingual surface of premolars and molars
-avoids overlapping of crowns and therefore demonstrates interproximal spaces clearly on resulting image

Question 19

Alignment of central beam (bitewing)

Answer 19

Important in all imagine but particularly in horizontal plane when taking bitewings; misalignment results in overlapping and inability to detect caries

Question 20

Maxillary occlusal

Answer 20

To demonstrate anterior maxillary region - possibly unerupted canines

Question 21

Mandibular 45 degrees occlusal

Answer 21

To demonstrate lower apical region, cysts, tumours or fracture displacement of anterior mandible in vertical plane

Question 22

Mandibular 90 degrees occlusal

Answer 22

To detect presence of radiopaque calculi in floor of mouth
To assess bucco-lingual position of unerupted dentition
Evaluate bucco-lingual expansion caused by tumours or lesions in body of mandible
Assessment of fracture displacement in horizontal plane

Question 23

Mandibular posterior oblique occlusal

Answer 23

To detect radiopaque calculi in submandibular salivary gland
Assess bucco-lingual position of unerupted lower third molars
Evaluate extent of bucco-lingual expansion of cysts, tumours and other bony lesions in body and angle of mandible