ORE Part 1 Radiology & Radiation Protection 2 — Questions and Answers
Question 1: What is the purpose of a 'dental panoramic tomograph' (DPT/OPG) compared to periapical radiographs?
- DPT provides a broad overview of the dentition, alveolar bone, mandible, and TMJ in a single image but with less detail; periapicals provide superior detail of individual teeth and periapical areas (Correct answer)
- DPT provides higher resolution than periapicals
- Periapicals show more of the mandible than DPT
- DPT is higher dose than a full periapical series always
Correct answer: DPT provides a broad overview of the dentition, alveolar bone, mandible, and TMJ in a single image but with less detail; periapicals provide superior detail of individual teeth and periapical areas
DPT (Panoramic/OPG) provides a single overview image of the full dentition, alveolar bone, sinuses, and TMJ regions — useful for initial assessments, impacted teeth, and pathology screening. Periapicals offer superior detail for individual teeth and periapical regions.
Question 2: What is the 'dead man's handle' (deadman switch) concept in dental radiography?
- The X-ray exposure switch must be actively held by the operator — releasing it automatically stops exposure, preventing accidental prolonged radiation release (Correct answer)
- A safety device on the dental chair
- A mechanism that powers down X-ray equipment when the dentist leaves the room
- A term for the exposure timer in intraoral radiography
Correct answer: The X-ray exposure switch must be actively held by the operator — releasing it automatically stops exposure, preventing accidental prolonged radiation release
The deadman switch (non-latching exposure switch) ensures the operator must actively maintain pressure throughout exposure. Releasing the switch immediately terminates exposure, preventing accidental prolonged irradiation.
Question 3: What is the recommended minimum distance the operator should stand from the X-ray tube head during exposure?
- At least 1.5–2 metres away, outside the primary beam, ideally behind a lead screen or wall (Correct answer)
- 0.5 metres is sufficient
- No minimum distance if wearing a lead apron
- Distance only matters for panoramic equipment
Correct answer: At least 1.5–2 metres away, outside the primary beam, ideally behind a lead screen or wall
Operators should stand at least 1.5–2 metres from the tube head, outside the primary beam (not at 90° to it), and ideally behind a structural barrier during dental X-ray exposures.
Question 4: What is the significance of a 'cone beam CT' (CBCT) scan in dental practice compared to conventional dental X-rays?
- CBCT provides 3D volumetric imaging but delivers significantly higher radiation dose than 2D dental radiographs — use must be justified by need for 3D information unavailable from conventional imaging (Correct answer)
- CBCT has no higher dose than a standard periapical
- CBCT replaces all conventional dental radiography
- CBCT is the first-line radiograph for all new patients
Correct answer: CBCT provides 3D volumetric imaging but delivers significantly higher radiation dose than 2D dental radiographs — use must be justified by need for 3D information unavailable from conventional imaging
CBCT provides three-dimensional imaging crucial for implant planning, surgical anatomy, and complex endodontics. However, the effective dose is significantly higher than conventional dental radiographs (approximately 40–500 µSv), requiring strict justification.
Question 5: What is 'fog' on a dental radiograph and what causes it?
- Overall grey, low-contrast appearance caused by: light leakage in darkroom, expired film, improper processing, or secondary/scatter radiation reaching the film (Correct answer)
- A normal feature of all radiographs
- Only caused by patient movement
- A sign of overexposure to X-rays only
Correct answer: Overall grey, low-contrast appearance caused by: light leakage in darkroom, expired film, improper processing, or secondary/scatter radiation reaching the film
Radiographic fog is a general increase in film density reducing contrast and diagnostic quality. Causes include: secondary/scatter radiation, light leaks, outdated film, improper processing temperatures, or chemical contamination.
Question 6: Which radiographic technique is used to assess the alveolar crest bone level in periodontal disease?
- Horizontal bitewing radiographs (Correct answer)
- Periapical radiographs alone
- Lateral skull radiograph
- Dental panoramic tomograph only
Correct answer: Horizontal bitewing radiographs
Horizontal bitewing radiographs are the gold standard for assessing alveolar bone levels in the premolar and molar regions, clearly showing the interdental crest bone height relative to the cemento-enamel junction.
ORE Part 1 Radiology & Radiation Protection 2
What is the purpose of a 'dental panoramic tomograph' (DPT/OPG) compared to periapical radiographs?