MJDF Radiology & IRMER 3 — Questions and Answers
Question 1: What are the three components of the radiation protection triangle (justification, optimisation, dose limitation)?
- Justification: benefit must outweigh risk; Optimisation (ALARP): minimize dose; Dose limitation: restrict doses to defined limits (Correct answer)
- Justification, documentation, reporting
- Selection, technique, developing
- Cost, time, safety
Correct answer: Justification: benefit must outweigh risk; Optimisation (ALARP): minimize dose; Dose limitation: restrict doses to defined limits
The three pillars of radiation protection are: justification (net benefit over risk), optimisation (ALARP — lowest reasonable dose for adequate image), and dose limitation (adherence to defined dose constraints and limits).
Question 2: What is the appearance of an odontogenic keratocyst on a panoramic radiograph?
- Well-defined uni- or multilocular radiolucency with corticated border, often with scalloped margins, in the posterior mandible (Correct answer)
- Diffuse radiolucency without border
- Radiopaque lesion with calcifications
- Always associated with an unerupted tooth
Correct answer: Well-defined uni- or multilocular radiolucency with corticated border, often with scalloped margins, in the posterior mandible
OKCs appear as well-defined, often elongated radiolucencies with smooth corticated margins, sometimes multilocular ('soap bubble'), most commonly in the posterior mandible/ramus, with or without associated impacted teeth.
Question 3: What radiographic sign is associated with external root resorption?
- Blunting or irregular shortening of the root apex on periapical radiograph (Correct answer)
- Widening of the PDL space without root change
- Radiopaque halo around the root apex
- Hypercementosis (bulbous root)
Correct answer: Blunting or irregular shortening of the root apex on periapical radiograph
External root resorption appears as progressive shortening, blunting, or irregular excavation of the root apex; in orthodontic resorption, blunting of apices is the classic finding.
Question 4: What is the significance of a widened PDL space on a periapical radiograph?
- Indicates occlusal trauma, early periapical inflammation, neoplastic infiltration, or systemic disease — requires clinical correlation (Correct answer)
- A normal variant always
- Indicates healthy periodontium
- Caused only by caries
Correct answer: Indicates occlusal trauma, early periapical inflammation, neoplastic infiltration, or systemic disease — requires clinical correlation
A widened PDL space has multiple causes: occlusal overload/trauma, early periapical inflammatory disease, Langerhans cell histiocytosis, scleroderma, or rare neoplastic infiltration; clinical and systemic assessment is needed.
Question 5: What is a dental panoramic tomograph (OPG) most commonly used for in routine dental practice?
- Overview of the dentition, jaws, and TMJs — assessment of third molars, bone levels, pathology, and developing teeth (Correct answer)
- Detection of early interproximal caries
- Precise measurement of periodontal bone levels
- Diagnosis of periapical pathology in single teeth
Correct answer: Overview of the dentition, jaws, and TMJs — assessment of third molars, bone levels, pathology, and developing teeth
The OPG provides a broad survey image of both dental arches, sinuses, and TMJs, useful for third molar assessment, pathology screening, orthodontic planning, and bone level surveys, but lacks detail for caries or periapical diagnosis.
Question 6: What patient preparation is essential before a panoramic radiograph to avoid artefacts?
- Remove all metallic objects (earrings, necklaces, removable appliances); position correctly with Frankfurt plane horizontal (Correct answer)
- Wear a lead apron only
- Bite down firmly on cotton rolls
- Take the radiograph immediately without preparation
Correct answer: Remove all metallic objects (earrings, necklaces, removable appliances); position correctly with Frankfurt plane horizontal
Metallic objects cause ghost and scatter artefacts; removable appliances create radiopaque artefacts obscuring the dentition; correct positioning (Frankfurt plane horizontal, correct chin position) prevents distortion.
MJDF Radiology & IRMER 3
What are the three components of the radiation protection triangle (justification, optimisation, dose limitation)?