Free RDA Radiographic Techniques and Errors Questions and Answers 1 — Questions and Answers
Question 1: The radiographic error known as 'elongation,' where teeth appear stretched out, is caused by:
- Excessive vertical angulation
- Incorrect horizontal angulation
- Insufficient vertical angulation (Correct answer)
- Placing the film backwards
Correct answer: Insufficient vertical angulation
Elongation occurs when the vertical angulation of the x-ray beam is too flat or insufficient. This causes the beam to strike the tooth and film at a shallow angle, projecting a longer, distorted image onto the film.
Question 2: Overlapping of the interproximal contacts on a bitewing radiograph is a common error caused by:
- Incorrect horizontal angulation (Correct answer)
- Incorrect vertical angulation
- Patient movement
- Film bending
Correct answer: Incorrect horizontal angulation
To open the contacts between teeth on a radiograph, the central x-ray beam must be directed parallel to the interproximal spaces. Incorrect horizontal angulation causes the beam to pass through the contacts at an angle, superimposing one tooth over the other.
Question 3: A 'cone cut' error on a radiograph appears as a clear, unexposed crescent or straight line and is caused by:
- The patient swallowing during exposure
- The PID not being centered over the film (Correct answer)
- Using exhausted developer solution
- Reversing the film in the mouth
Correct answer: The PID not being centered over the film
A cone cut occurs when the primary x-ray beam is not aimed at the center of the film or sensor. As a result, part of the film is not exposed to radiation, leaving a clear, unexposed area that corresponds to the shape of the PID (Position Indicating Device) opening.
Question 4: In the paralleling technique, the central ray of the x-ray beam is directed:
- Parallel to the long axis of the tooth
- Perpendicular to the bisector of the angle
- Perpendicular to the film and the long axis of the tooth (Correct answer)
- At a +10 degree vertical angulation
Correct answer: Perpendicular to the film and the long axis of the tooth
The paralleling technique is based on the geometric principle of creating an accurate image by having the film parallel to the tooth's long axis. To avoid distortion, the central ray must then be directed perpendicular (at a 90-degree angle) to both the tooth and the film.
Question 5: The radiographic error that results in images appearing shorter and more stout than their actual size is called foreshortening. What is the cause?
- Insufficient vertical angulation
- Excessive vertical angulation (Correct answer)
- Incorrect film placement
- Horizontal angulation being too mesial
Correct answer: Excessive vertical angulation
Foreshortening is the opposite of elongation and is caused by excessive or too-steep vertical angulation. This steep angle causes the image of the tooth to be projected onto a smaller area of the film, making it appear compressed or shorter.
Question 6: A processed radiograph that appears too dark (high in density) is likely the result of:
- Underdevelopment or cool developer
- Insufficient exposure time
- Fixer solution contamination
- Excessive exposure time or overdevelopment (Correct answer)
Correct answer: Excessive exposure time or overdevelopment
An overly dark radiograph indicates that the film's silver halide crystals received too much exposure or were over-processed. This can be caused by excessive exposure time, kVp, or mA, or by leaving the film in the developer solution for too long or at too high a temperature.
Free RDA Radiographic Techniques and Errors Questions and Answers 1
The radiographic error known as 'elongation,' where teeth appear stretched out, is caused by: