MJDF Radiology & IRMER 4

Question 1

What is the effective dose from a dental bitewing radiograph (digital) compared to background radiation?

Accepted Answer

Approximately 1–8 µSv per image; background radiation is approximately 2,700 µSv/year in UK

Answer

A digital bitewing delivers approximately 1–8 µSv (depending on technique), representing a very small fraction of the average UK background radiation of approximately 2.7 mSv/year; this context aids risk communication with patients.

Question 2

What is the definition of 'radiation weighting factor' (wR)?

Accepted Answer

A factor applied to absorbed dose to account for the biological effectiveness of different radiation types (X-rays: wR=1)

Answer

The radiation weighting factor (wR) converts absorbed dose (Gy) to equivalent dose (Sv), accounting for the biological damage potential of different radiation types; for X-rays and gamma rays, wR = 1 (alpha particles wR = 20).

Question 3

Under IRR 2017, what is the role of the Radiation Protection Supervisor (RPS) in a dental practice?

Accepted Answer

Ensures day-to-day compliance with local radiation protection rules and supervises radiation workers in practice

Answer

The RPS (usually a trained senior team member in the practice) ensures that the local rules for radiation protection are followed in daily practice and acts as the first point of contact for radiation protection matters.

Question 4

What is the clinical significance of a 'J-shaped' root canal on a periapical radiograph?

Accepted Answer

Suggests a lateral canal or missed additional root — important for endodontic planning

Answer

A J-shaped radiolucency at the root apex suggests the possibility of a missed lateral or accessory canal, an untreated additional root, or a strip perforation during endodontic treatment.

Question 5

What is the appearance of hypercementosis on a periapical radiograph?

Accepted Answer

Bulbous enlargement of the root apex surrounded by normal PDL space and lamina dura

Answer

Hypercementosis appears as excessive cementum deposition around the root, giving a club-shaped or bulbous root appearance with an intact (widened) PDL space and lamina dura, distinguishing it from periapical pathology.

MJDF Part 1 Practice Test

MJDF Part 1 Practice Test

MJDF Radiology & IRMER 4