Free EFDA Radiology & Dental Imaging Techniques Questions and Answers — Questions and Answers

Question 1: What is the primary purpose of the paralleling technique in dental radiography?

To reduce patient discomfort
To achieve minimal image distortion and accurate tooth length (Correct answer)
To decrease radiation exposure time
To eliminate the need for film holders

Correct answer: To achieve minimal image distortion and accurate tooth length

The paralleling technique, also known as the long-cone technique, positions the film or sensor parallel to the long axis of the tooth and the central ray perpendicular to both. This geometric relationship minimizes magnification and distortion, producing a radiograph that accurately represents the true length and shape of the tooth and surrounding structures. This accuracy is crucial for precise diagnosis and treatment planning.

Question 2: Which anatomical structure appears radiopaque on dental X-rays?

Pulp chamber
Enamel (Correct answer)
Periodontal ligament space
Soft tissue of the gums

Correct answer: Enamel

Radiopaque structures appear white or light gray on dental X-rays because they absorb a significant amount of X-ray radiation. Enamel, being the most highly mineralized tissue in the body, is very dense and absorbs a large amount of radiation, making it appear distinctly radiopaque. Less dense structures like the pulp chamber or soft tissues appear radiolucent (darker).

Question 3: What is the recommended PID (Position-Indicating Device) length to reduce radiation scatter?

4 inches
8 inches (Correct answer)
12 inches
16 inches

Correct answer: 8 inches

A longer PID (Position-Indicating Device), typically 8 or 16 inches, helps reduce radiation scatter and magnification. While 16 inches is often preferred for minimal distortion, an 8-inch PID is a common and effective length for reducing scatter compared to shorter PIDs. The longer the PID, the more parallel the X-ray beams become, leading to a sharper image and less divergence of the beam.

Question 4: Which error occurs when the X-ray beam is not centered over the film/sensor?

Elongation
Foreshortening
Cone-cut (Correct answer)
Overlapping

Correct answer: Cone-cut

A cone-cut error occurs when the central X-ray beam is not properly aligned with the center of the film or sensor. This results in a clear, unexposed (white or black, depending on film/digital) crescent-shaped area on the radiograph where the X-ray beam did not reach the entire image receptor. It indicates improper angulation or positioning of the PID relative to the image receptor.

Question 5: What is the ALARA principle in dental radiography?

As Long As Resolution Allows
As Low As Reasonably Achievable (Correct answer)
Always Leave A Residual Area
Avoid Lateral Angulation Repeatedly Always

Correct answer: As Low As Reasonably Achievable

ALARA is a fundamental principle in radiation protection, standing for 'As Low As Reasonably Achievable.' In dental radiography, this means using the lowest possible dose to achieve diagnostic quality images, employing techniques like lead aprons, thyroid collars, fast films/digital sensors, and proper exposure settings to minimize patient and operator exposure to radiation.

Question 6: Which type of radiograph is best for detecting interproximal caries?

Periapical
Panoramic
Bitewing (Correct answer)
Occlusal

Correct answer: Bitewing

Bitewing radiographs are specifically designed to show the crowns of both maxillary and mandibular teeth in one image, along with the alveolar bone crests. Their angulation and positioning are ideal for detecting interproximal (between teeth) caries, assessing the integrity of existing restorations, and evaluating bone levels in the posterior regions. This makes them the best choice for identifying cavities between teeth.

Question 7: What is the purpose of a lead apron during X-ray exposure?

To improve image clarity
To shield the patient's thyroid and torso (Correct answer)
To stabilize the patient
To reduce exposure time

Correct answer: To shield the patient's thyroid and torso

A lead apron is a critical radiation safety device used during dental X-ray exposure. Its primary purpose is to shield radiosensitive organs, specifically the patient's thyroid gland and torso, including reproductive organs, from unnecessary radiation. This practice adheres to the ALARA principle (As Low As Reasonably Achievable) to minimize radiation exposure and protect patient health.

Question 8: Which factor determines the contrast of a dental radiograph?

mA (milliamperage)
Exposure time
kVp (kilovoltage peak) (Correct answer)
Film size

Correct answer: kVp (kilovoltage peak)

Kilovoltage peak (kVp) is the primary factor that directly controls the contrast of a dental radiograph. Adjusting the kVp setting determines the range of shades of gray in the image; higher kVp produces lower contrast (more shades of gray), while lower kVp yields higher contrast (more black and white). This allows the dental professional to optimize the image for specific diagnostic needs.

Question 9: What is the recommended vertical angulation for maxillary premolar periapicals?

+10 degrees
+20 to +30 degrees (Correct answer)
-15 degrees
0 degrees

Correct answer: +20 to +30 degrees

The recommended vertical angulation for maxillary premolar periapical radiographs is typically +20 to +30 degrees. This positive angulation is necessary to properly project the image of the maxillary premolars onto the film or sensor. It compensates for the curvature of the palate and prevents image distortion such as foreshortening or elongation, ensuring diagnostic accuracy.

Free EFDA Radiology & Dental Imaging Techniques Questions and Answers

What is the primary purpose of the paralleling technique in dental radiography?