Extra-Oral

Question 1

What are the purposes of extra-oral x-rays?

Answer 1

Imaging larger sections of the dentition
Alternative when a patient is unable to tolerate intra-oral radiography
Imaging non-dentoalveolar regions

Question 2

What does a lateral view of a radiograph indicate?

Answer 2

It is aimed at the side of the head

Question 3

What does a postero-anterior view of a radiograph indicate?

Answer 3

Starting posteriorly and passing anteriorly

Question 4

What does a true angulation of beam mean?

Answer 4

Perpendicular to the head

Question 5

What does an oblique angulation of beam mean?

Answer 5

It is not perpendicular to the head

Question 6

What is the Mid-Sagittal plane?

Answer 6

Line down the middle of the face

Question 7

What is the Frankfort Plane?

Answer 7

Connects infraorbital margin(eye) & super border of the external auditory meatus (ear)

Question 8

What is the Interpupillary line?

Answer 8

Line that connects both pupils

Question 9

What is Cephalometry?

Answer 9

The measurement & study of the head
Uses many different points, angles & distances to analyse anatomy

Question 10

What are the clinical applications of cephalometry?

Answer 10

Orthodontics & orthognathic surgery
Often used to monitor changes over time

Question 11

What are some uses for Lateral Cephalograms in Orthodontics?

Answer 11

Assessing skeletal discrepancies when functional appliances or fixed appliances are to be used for labio-lingual movement of the incisors
Aiding location & assessment of unerupted, malformed or misplaced teeth
Gives an indication of upper incisor root length

Question 12

What does a Cephalostat do?

Answer 12

Ensures standardised positioning of equipment & patients head
–avoids discrepancies between radiographs taken years apart by different staff
–reduces magnification/distortion of image

Question 13

What are the functions of a Cephalostat?

Answer 13

Holds head at correct angle
Stabilises head to prevent movement
Establishes correct distances between X-ray focal spot, patient and receptor

Question 14

What is the standardised distance for a cephalostat?

Answer 14

Receptor should be 1.5-1.8m away from the X-ray focal spot to minimise magnification

Question 15

What collimation should units that do not use a solid-state sensor also have to reduce exposure to the cranium?

Answer 15

Triangular (removes exposure of the neck)

Question 16

What patient contact shielding should be used when taking Cephalograms?

Answer 16

Thyroid collar, as the thyroid gland is relatively radiosensitive

Question 17

What image does a CBCT provide?

Answer 17

Cross-sectional imaging
But at an increased radiation dose

Question 18

What is an Oblique Lateral Radiograph?

Answer 18

A view of posterior jaws without superimposition of contralateral side
Uncommon now but can be useful if a patient is unable to tolerate intra-oral radiographs and unable to stay still or fit in a panoramic unit