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DANB RHS Practice Test: Free Radiation Health and Safety Exam Questions (Dental X-Ray)
153 practice questions for the Radiation Health and Safety (RHS) exam, DANB's dental x-ray exam. It is part of the CDA, and many states accept it on its own for dental assistants who take x-rays. The questions follow the RHS outline effective March 12, 2025, weighted like the exam: Purpose and Technique (50%), Radiation Characteristics and Protection (25%) and Infection Prevention and Control (25%). Like the real exam, it is digital only: CCD, CMOS and PSP receptors, no film processing. Expect landmarks and what they look like, which image fits which job, paralleling and bisecting, foreshortening and overlap, panoramic positioning errors, kVp and mA, the inverse square law, gray and sievert, dose limits, the ADA/FDA selection criteria and barriers for sensors. Every question is tagged to its outline area and every answer names its public source.
The real test: 75 multiple-choice questions in 60 minutes, at a Pearson VUE test center or by live remote proctoring, with no eligibility requirements. It is computer adaptive and scored from 100 to 900, with 400 to pass. It tests digital radiography only and follows the RHS outline effective March 2025: Purpose and Technique 50%, Radiation Characteristics and Protection 25% and Infection Prevention and Control 25%. Many states accept it for dental assistants who take x-rays, and it is one of the three CDA exams. Our practice test is full length, 75 questions split by the outline weights, passing at 70% (53 of 75).
Here: 153 questions. Our own practice questions, built on DANB's public Radiation Health and Safety (RHS) exam outline and written from public sources (CDC, OSHA, the ADA/FDA radiography recommendations, FDA, NRC, EPA, NIH StatPearls, open-access dental research and US Army dental specialist courses), with every answer's source named. Topics are the 3 areas of the outline. Not DANB's test questions. Free.
"On the test" is the rough share of a 75-question test for each topic, following the exam's published weights.
10 sample questions
On a dental image, what does 'radiopaque' mean?
A.Doubled, because the sensor was exposed twice
B.Dark or black, because x-rays pass straight through
C.Blurry, because the patient moved during exposure
D.Light or white, because the structure blocks x-rays
Show answer
D. Light or white, because the structure blocks x-rays
RHS-1 · I. Purpose and Technique
Inside the x-ray tube, what part gives off the electrons that make x-rays?
A.The lead lining inside the PID cylinder
B.The aluminum filter at the tube's exit port
C.The heated tungsten filament in the cathode
D.The copper stem behind the anode target
Show answer
C. The heated tungsten filament in the cathode
RHS-78 · II. Radiation Characteristics and Protection
Under CDC's Spaulding categories, how is a digital intraoral sensor classified?
A.Not classified, since it is an electronic device
B.Critical, because it penetrates soft tissue and bone
C.Semicritical, because it touches mucous membranes
D.Noncritical, because it touches only intact skin
Show answer
C. Semicritical, because it touches mucous membranes
RHS-116 · III. Infection Prevention and Control
On a maxillary central incisor periapical image, a dark (radiolucent) oval area sits between and above the roots of the central incisors. What normal landmark is this?
A.The incisive foramen
B.The mental foramen
C.The coronoid process
D.The genial tubercles
Show answer
A. The incisive foramen
RHS-2 · I. Purpose and Technique
When electrons hit the anode target, what happens to most of their energy?
A.It becomes heat; less than 1% becomes x-rays
B.It turns into electricity sent back to the wall
C.It becomes x-rays; less than 1% becomes heat
D.It becomes visible light in the dental operatory
Show answer
A. It becomes heat; less than 1% becomes x-rays
RHS-79 · II. Radiation Characteristics and Protection
A digital sensor can't be heat-sterilized or high-level disinfected. What does CDC say is the minimum between patients?
A.No reprocessing at all as long as the barrier sleeve looked intact
B.A quick rinse under running tap water and a wipe with a dry paper towel
C.An FDA-cleared barrier, then clean and disinfect it after removal
D.Soaking the whole sensor and its cable in bleach overnight
Show answer
C. An FDA-cleared barrier, then clean and disinfect it after removal
RHS-117 · III. Infection Prevention and Control
A small round radiolucency below and between the mandibular premolar roots could be mistaken for an abscess. What normal landmark is often there?
A.The nasal fossa
B.The maxillary sinus
C.The mental foramen
D.The incisive foramen
Show answer
C. The mental foramen
RHS-3 · I. Purpose and Technique
Which statement about x-rays is true?
A.They travel in straight lines at light speed and have no mass or charge
B.They are slowed by air, so they stop about 6 feet from the tubehead
C.They carry a negative charge and bend toward any metal in their path
D.They can be focused with a lens, like visible light, into a smaller beam
Show answer
A. They travel in straight lines at light speed and have no mass or charge
RHS-80 · II. Radiation Characteristics and Protection
Why does CDC still require disinfecting a sensor after its plastic sleeve is removed?
A.The sleeve makes the sensor radioactive, so it must be wiped down after
B.It doesn't; the sleeve fully replaces any cleaning of the sensor itself
C.Barriers tear or leak; one study found sleeves failing 44% of the time
D.Disinfectant is what makes the sensor capture the image the next time
Show answer
C. Barriers tear or leak; one study found sleeves failing 44% of the time
RHS-118 · III. Infection Prevention and Control
On a mandibular incisor periapical, which landmark appears as a small white ring with a dark center below the incisor apices?
A.The external oblique ridge in the incisor region
B.The mylohyoid ridge seen end-on below the apices
C.The zygomatic process sitting over the root tips
D.The genial tubercles around the lingual foramen
Show answer
D. The genial tubercles around the lingual foramen