NBDHE Test Dental Radiography and Interpretation 1 — Questions and Answers
Question 1: A 'herringbone' or 'tire track' pattern artifact appears on a processed dental radiograph. This artifact is MOST likely caused by:
- Overdevelopment in the developer solution
- Placing the film in the mouth with the lead foil side facing the x-ray source (Correct answer)
- Excessive bending of the film during placement
- Contamination of the developer with fixer solution
Correct answer: Placing the film in the mouth with the lead foil side facing the x-ray source
When a periapical film is placed backwards (lead foil side toward the tube), the x-ray beam passes through the foil before reaching the emulsion, creating a faint herringbone or tire-track pattern from the embossed lead foil backing. This also results in a significantly underexposed, lighter-than-normal image.
Question 2: A radiopaque, well-defined mass is noted within the pulp chamber of a mandibular first molar on a periapical radiograph. The tooth responds normally to vitality testing. This finding is MOST consistent with:
- Condensing osteitis
- A pulp stone (denticle) (Correct answer)
- Hypercementosis
- Internal root resorption
Correct answer: A pulp stone (denticle)
Pulp stones (denticles) are calcified masses that form within the pulp chamber and appear as discrete radiopaque structures inside the tooth. They are often incidental findings in vital teeth and are not pathological in isolation. Internal resorption would appear as a radiolucent widening of the canal, while condensing osteitis and hypercementosis occur in periapical/root regions, not within the pulp.
Question 3: Which film speed classification requires the LEAST exposure time (lowest radiation dose) to produce a diagnostically acceptable periapical radiograph?
- D-speed (Ultraspeed)
- E-speed (Ektaspeed)
- F-speed (Insight) (Correct answer)
- C-speed
Correct answer: F-speed (Insight)
F-speed film (e.g., Kodak Insight) is the fastest conventional film available and requires approximately 20% less exposure than E-speed and 60% less than D-speed. Faster film requires fewer x-ray photons to produce an image, directly reducing patient dose. The trade-off is a very slight increase in grain, though F-speed images remain diagnostically acceptable.
Question 4: Foreshortening of tooth images on a periapical radiograph taken with the bisecting angle technique is caused by:
- Insufficient vertical angulation (too flat/shallow)
- Excessive vertical angulation (too steep) (Correct answer)
- Incorrect horizontal angulation
- Failure to center the central ray on the film
Correct answer: Excessive vertical angulation (too steep)
In the bisecting angle technique, the central ray should be directed perpendicular to the imaginary bisector of the angle formed by the film and the long axis of the tooth. If the vertical angulation is excessive (too steep), the recorded image of the tooth is shorter than actual length — foreshortening. Insufficient vertical angulation produces the opposite error: elongation.
Question 5: On a periapical radiograph of the maxillary molar region, the radiopaque 'inverted Y' landmark is formed by the junction of:
- The floor of the orbit and the lateral wall of the nasal cavity
- The floor of the nasal cavity and the anterior wall of the maxillary sinus (Correct answer)
- The hard palate and the nasal septum
- The zygomatic arch and the maxillary tuberosity
Correct answer: The floor of the nasal cavity and the anterior wall of the maxillary sinus
The classic 'inverted Y' (or upside-down Y) seen in the maxillary premolar–first molar area on a periapical radiograph is created where the floor of the nasal cavity (appearing as one radiopaque line) intersects with the anterior wall of the maxillary sinus (the other line). Recognizing this landmark helps differentiate normal anatomy from pathological radiolucency in the periapical region.
Question 6: Compared to a round (cylindrical) position-indicating device (PID), the use of a rectangular collimator reduces the patient's radiation exposure by approximately:
- 15–20%
- 30–40%
- 55–70% (Correct answer)
- 85–95%
Correct answer: 55–70%
A round PID exposes a circular field roughly 2.75 inches in diameter, much larger than the film or sensor. A rectangular collimator restricts the beam to just slightly larger than the receptor, reducing the irradiated tissue area and lowering patient dose by approximately 60% (range 55–70%). This makes rectangular collimation one of the most effective dose-reduction strategies in intraoral radiography.
NBDHE Test Dental Radiography and Interpretation 1
A 'herringbone' or 'tire track' pattern artifact appears on a processed dental radiograph.
This artifact is MOST likely caused by: