RDA Radiographic Techniques and Errors 4 — Questions and Answers
Question 1: A radiograph shows the apices of the maxillary molars superimposed over the zygomatic arch. Which error caused this?
- Insufficient vertical angulation (Correct answer)
- Excessive vertical angulation
- Incorrect horizontal angulation
- Patient movement during exposure
Correct answer: Insufficient vertical angulation
Insufficient (flat) vertical angulation causes the zygomatic arch to overlap the apices of the maxillary molars.
Question 2: Which receptor placement error results in a radiograph showing the roots of mandibular teeth appearing foreshortened?
- Receptor tilted toward the tongue (Correct answer)
- Receptor tilted away from the teeth
- Receptor placed too far anteriorly
- Receptor placed too far posteriorly
Correct answer: Receptor tilted toward the tongue
When the receptor tilts toward the tongue (cupped), the effective vertical angulation increases, foreshortening the image.
Question 3: During a bitewing series, the contact areas of posterior teeth are not open. The MOST likely cause is:
- Incorrect vertical angulation
- Incorrect horizontal angulation (Correct answer)
- Insufficient exposure time
- Patient's head tilted
Correct answer: Incorrect horizontal angulation
Overlapping of proximal contacts on bitewings is caused by incorrect horizontal angulation, where the beam does not pass through the embrasures.
Question 4: A periapical radiograph of the mandibular incisors shows a herringbone pattern on the image. What is the cause?
- Double exposure
- Film or receptor placed backward (Correct answer)
- Excessive kVp setting
- Cone-cutting error
Correct answer: Film or receptor placed backward
The herringbone (tire-track) pattern results from X-rays passing through the lead foil backing when the receptor is placed backward in the mouth.
Question 5: Which type of film fault produces a clear (unexposed) area on a processed radiograph shaped like a half-moon?
- Chemical fog
- Crimping artifact (Correct answer)
- Reticulation
- Pressure mark from double packaging
Correct answer: Crimping artifact
A crescent-shaped (half-moon) clear area results from crimping or bending the film sharply before exposure, which blocks X-rays from reaching that area.
Question 6: When using the paralleling technique, the cone (PID) is directed perpendicular to the:
- Long axis of the tooth only
- Receptor only
- Both the long axis of the tooth and the receptor (Correct answer)
- Occlusal plane
Correct answer: Both the long axis of the tooth and the receptor
In the paralleling technique, the receptor is placed parallel to the tooth's long axis and the PID is directed perpendicular to both.
Question 7: A panoramic radiograph shows the anterior teeth appearing blurry and out of focus. The MOST likely cause is:
- Patient positioned too far forward in the focal trough (Correct answer)
- Patient positioned too far backward in the focal trough
- Excessive kVp
- Patient movement of the hands
Correct answer: Patient positioned too far forward in the focal trough
When the patient is positioned too far forward, the anterior teeth are in front of the focal trough, causing them to appear blurry and narrowed.
RDA Radiographic Techniques and Errors 4
A radiograph shows the apices of the maxillary molars superimposed over the zygomatic arch.
Which error caused this?