Past paper questions

Question 1

Which external reference plane of the patient should you position horizontally when setting up for a panoramic radiograph?

Answer 1

• Frankfort plane

Question 2

When you look at the panoramic radiograph you have taken, some of the teeth are horizontally distorted. Which positioning error results in the following:

i) The incisor teeth being horizontally magnified
ii) The posterior teeth on one side being wider than on the other

Answer 2

i - Patient too far back in machine
ii - Patient rotated in machine

Question 3

The patient is unable to remove their earrings with the result that there are ghost images of the earrings. Give THREE important features that apply to all ghost images.

Answer 3

• Higher than original image
• Opposite side to original
• Radiopaque

Question 4

What panoramic radiograph would you take i) A pre-extraction radiograph for partially erupted 48, when there is no evidence of 38 in the mouth; 48 is to be extracted under local analgesia?

Answer 4

• Right half pano

Question 5

What radiograph would you take for ii) For a child patient with caries, who cannot tolerate bitewings?

Answer 5

• Orthogonal projection

Question 6

5. The maxillary sinus is depicted in a panoramic radiograph. Which margins or walls are seen in the following locations:

i) Horizontally above the roots of the premolars and molars.
ii) Vertically above the third molar region.

Answer 6

i - Floor wall
ii - Posterior wall

Question 7

When would you use a Oblique lateral radiograph?

Answer 7

• Poorly cooperative children
• Learning difficulties
• Involuntary movements e.g. tremors
• Unconscious

Question 8

How are x-rays used to determine working length?

Question 9

What radiographic view would you use to view a failed to erupt central incisor?

Answer 9

• Periapical

Question 10

How should the planes be set up in a panoramic radiograph?

Answer 10

• Mid sagittal plane perpendicular to the floor , pt bite down on block and align their midline with line on machine
• Horizontal plane aka Frankfort horizontal plane should be parallel to floor and perpendicular to Mid sagittal plane
• Focal trough align with dental arches, horizontal and vertical angles of machine adjusted to align this

Question 11

How should the planes be set up in a OPT radiograph?

Answer 11

• Mid sagittal plane perpendicular to the floor , pt bite down on block and align their midline with line on machine
• Horizontal plane aka Frankfort horizontal plane should be parallel to floor and perpendicular to Mid sagittal plane
• Occlusal plane - bite down on block in natural and relaxed position so occlusal plane properly aligned
• Focal trough align with dental arches, horizontal and vertical angles of machine adjusted to align this

Question 12

Why are incisor teeth horizontally magnified?

Question 13

Why are posterior teeth wider on one side of a radiograph?

Answer 13

• Due to horizontal magnification or elongation
• X-ray beam aimed at teeth from angle that is perpendicular to plane of film
• Curvature of dental arch causes one side to be angled slightly away from film and the other slightly towards
• More pronounced on posterior than anterior because posterior have greater curvature and angled more away from film
• To minimise this use paralleling technique which reduces distortion and magnification

Question 14

What are some features of a ghost image?

Question 15

How can you tell if a tooth is non-vital from an x-ray?

Answer 15

• Periapical radiolucency
• Widened periodontal ligament
• Decreased or absent lamina dura
• Root resorption
• Pulp calcification

Question 16

How do you identify the grade of x-ray?

Answer 16

• Most common classification is the Image Quality Assurance (IQA) system
• Grade A = Highest diagnostic quality with excellent clarity, contrast and detail
• Grade B = Good diagnostic quality with slightly less clarity, contrast and detail than Grade C = Acceptable diagnostic quality but may have some limitations in terms of clarity, contrast or detail
  Grade D = Poor diagnostic quality and only used in emergency situations where no other diagnostic options available

Question 17

What are all the planes?

Question 18

What are some things a patient can do which affects image quality?

Answer 18

• Movement can cause distortion and blurring of image
• Wearing metal jewellery which can cause artifacts and distortions on the image
• Keeping removable dental appliances in their mouth can also distort the image
• Change position from what they have been instructed to do as incorrect positioning can lead to inaccurate or incomplete image that is not diagnostically acceptable

Question 19

What are some oral implications of radiotherapy?

Answer 19

• Xerostomia
• Radiation induced caries
• Oral mucositis
• Taste changes so lead to eating more high sugary snacks which increase risk of caries and periodontal disease
• Caries
• Periodontal disease
• Trismus
• ORN

Question 20

What is the link of radiotherapy in parotid region to formation of ulcers and why enhanced prevention is needed?

Answer 20

• Radiotherapy in the parotid region can cause damage to surrounding tissues including the salivary glands
• Lead to radiation induced Xerostomia
• Makes the mouth more susceptible to formation of ulcers and infection due to less lubrication and traumatic ulceration can occur
• Enhanced prevention like excellent oral hygiene instruction
• Saliva replacement therapy like saliva orthana or BioXtra
• Reg sips of water and chew sugar free chewing gum
• Healthy diet and nutrients
• Avoid tobacco and alcohol