Dental Assistant Practice Test
Dental Radiation Health & Safety Practice Questions
Radiation Health & Safety makes up 13 of every 50 questions on a Tigertest Dental practice test. Here are 10 of the 52 questions on it, each with the answer and the reason.
Updated by the Tigertest team. Weighted to the DANB GC, RHS (March 2025) and ICE (March 2025) outlines. Expanded functions vary by state.
1. During staff training on the x-ray tubehead, a new assistant asks where the electrons that produce x-rays come from. The correct answer is the:
- A.Lead collimator at the PID opening
- B.Tungsten filament in the cathode
- C.Aluminum filter disks in the tubehead
- D.Tungsten target in the anode
Answer: B. Heating the tungsten filament in the cathode releases a cloud of electrons (thermionic emission). The anode target is where those electrons strike and x-rays are produced, not where the electrons originate.
2. When electrons strike the tungsten target of the anode, approximately what share of their energy becomes x-rays?
- A.About 10 percent
- B.About 99 percent
- C.About 50 percent
- D.About 1 percent
Answer: D. Only about 1% of the electrons' energy becomes x-rays; about 99% becomes heat, which is why the target sits in a copper stem and oil bath. 99% is the heat figure, a tempting reversal.
3. A state inspector checks the aluminum filtration in the tubehead of the office's intraoral unit. The purpose of this aluminum is to:
- A.Absorb low-energy x-rays that only add dose
- B.Speed up electrons traveling toward the anode
- C.Cool the anode during repeated exposures
- D.Limit the beam to 2.75 inches at the skin
Answer: A. Aluminum filtration removes long-wavelength, low-energy x-rays that cannot reach the receptor and would only be absorbed by the patient. Limiting beam size to 2.75 inches is the job of the lead collimator, not the filter.
4. The office replaces its 8-inch position-indicating device with a 16-inch PID for paralleling technique. Compared with the shorter PID, the longer one:
- A.Removes the need for a receptor holder
- B.Increases the skin dose to the patient
- C.Less magnification and sharper images
- D.Allows a shorter exposure time
Answer: C. A longer target-receptor distance uses more parallel central rays, so images show less magnification and better definition. By the inverse square law the longer PID needs more exposure time, not less.
5. The dentist wants periapical images with many shades of gray (long-scale, low contrast) to evaluate periodontal bone. The assistant should adjust the:
- A.Milliamperage upward
- B.Kilovoltage downward
- C.Kilovoltage upward
- D.Exposure time downward
Answer: C. Higher kVp produces more penetrating x-rays and a long gray scale with lower contrast. Raising mA increases the quantity of x-rays and image density but does not change contrast.
6. Which exposure factor controls the number of electrons produced at the cathode and therefore the quantity of x-rays generated?
- A.Milliamperage (mA)
- B.Aluminum filtration
- C.Kilovoltage peak (kVp)
- D.Target-receptor distance
Answer: A. Milliamperage regulates filament heating and thus the number of electrons and x-rays produced. kVp controls the speed of the electrons and the penetrating quality of the beam, not the quantity.
7. A bitewing image is too light even though processing was correct. The unit has fixed kVp and mA settings. To increase image density, the assistant should:
- A.Switch to a longer PID
- B.Decrease the exposure time
- C.Raise the chair before the exposure
- D.Increase the exposure time
Answer: D. With kVp and mA fixed, increasing exposure time increases total x-rays (mAs) and darkens the image. A longer PID lowers beam intensity at the receptor, which would make the image even lighter.
8. An exposure is correct with an 8-inch target-receptor distance. If the operator changes to a 16-inch distance, the beam intensity at the receptor becomes:
- A.One-half of the original
- B.One-fourth of the original
- C.Four times the original
- D.Twice the original
Answer: B. By the inverse square law, doubling the distance gives (1/2) squared, or 1/4 the intensity, so exposure must be increased about four times to compensate. One-half is the tempting linear answer.
9. A practice still using D-speed film asks whether to switch to F-speed film. Compared with D-speed film, F-speed film:
- A.Is limited to extraoral imaging
- B.Needs about 60 percent less exposure
- C.Needs about twice the exposure of D-speed
- D.Cannot be processed automatically
Answer: B. F-speed film needs roughly 60% less exposure than D-speed film (about 20% less than E-speed), which is why ADA and FDA guidance recommends the fastest receptor. Faster film needs less, not more, radiation.
10. An office comparing image receptors for intraoral radiographs asks which one generally needs the least radiation for a diagnostic image. The assistant answers:
- A.D-speed film
- B.E-speed film
- C.An intensifying screen cassette
- D.A direct digital sensor
Answer: D. Direct digital sensors (CCD or CMOS) generally need less exposure than film; PSP plates fall close to F-speed film. Intensifying screens are used with extraoral film cassettes, not for intraoral images.
Practice all 52 radiation health & safety questions, and the rest of the 200-question bank, in the free Dental training sets. Questions you miss come back until you have mastered them.
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