DANB RHS practice test: 30 dental radiography questions

Which of the following is a deterministic effect of radiation?

Pick the option you would mark on test day. The choice stays fixed, and every option then explains itself.

1. Heritable mutation

   A heritable mutation passed to offspring is a stochastic effect: it has no threshold, and dose changes its probability rather than its severity.
2. Skin erythema

   Skin reddening appears only above a dose threshold and gets worse as dose rises, which defines a deterministic effect.
3. Leukemia

   Leukemia is a radiation-induced cancer, and cancers are stochastic effects whose probability, not severity, rises with dose.
4. Thyroid cancer

   Thyroid cancer is likewise stochastic; this is the reason the thyroid is kept out of the beam, not a threshold effect.

For intraoral periapical and bitewing images, how is the patient's midsagittal plane positioned?

1. Parallel to the floor

   The occlusal plane, not the midsagittal plane, is set parallel to the floor; mixing up the two planes is the usual slip here.
2. Tilted 15° toward the operator

   A head tilted 15° toward the operator changes the angles between beam, teeth and receptor and invites angulation errors.
3. Perpendicular to the floor

   The midsagittal plane is set vertical, perpendicular to the floor, so the angulation of the beam is predictable for every intraoral image.
4. Tilted 15° away from the operator

   A head tilted away from the operator distorts angulation just as much as a tilt toward the operator.

A periapical of tooth #30, treated endodontically two years ago, shows a uniform radiopaque line running from the pulp chamber to the apex. This is most likely:

1. Internal resorption with calcific repair

   Internal resorption shows as a radiolucent widening of the pulp space, not a uniform white line ending at the apex.
2. Condensing osteitis around the apex

   Condensing osteitis is diffuse radiopacity in the bone around the root tip, not a density inside the root.
3. Gutta-percha root canal filling

   After endodontic treatment the canal is obturated with gutta-percha and sealer, which shows as an even radiopaque line from the chamber to the apex.
4. A prefabricated metal post

   A post fills only the coronal part of the canal and is usually more radiopaque, so it would not run evenly to the apex.

For a lateral cephalometric image, how are the patient's teeth usually positioned?

1. Closed together in centric occlusion

   A lateral ceph is taken with the teeth together in centric occlusion so the relationship of the jaws and teeth can be measured.
2. Held apart by a cotton roll on each side

   Teeth held apart by cotton rolls would change the jaw relationship that the ceph is meant to record.
3. Opened wide to separate the arches

   A mouth opened wide is used for some TMJ views, not for a lateral ceph, and it separates the arches being measured.
4. Edge to edge in a notched bite block

   Biting edge to edge in a notched block is the panoramic setup; it would distort the occlusal relationship on a ceph.

When mounting a molar periapical image, which finding identifies it as mandibular rather than maxillary?

1. A U-shaped zygoma above the roots

   The U-shaped zygomatic process lies above the maxillary molar roots, so it identifies a maxillary image.
2. A hook-like hamulus behind the molars

   The hamulus projects behind the maxillary tuberosity, which places the image in the upper arch.
3. A radiolucent sinus above the apices

   The maxillary sinus over the roots is a maxillary landmark; a dark area above the apices does not point to the mandible.
4. A radiolucent canal below the apices

   The mandibular canal is a dark band bordered by thin white lines running below the molar roots, which marks the image as mandibular.

On a panoramic image, which sign suggests a mandibular third molar root is in close contact with the mandibular canal?

1. Loss of the crestal lamina dura around the tooth

   Loss of crestal lamina dura relates to periodontal bone, not to the root's relationship with the canal.
2. A radiopaque band just above the molar crown

   A white band above the crown reflects overlapping structures or bone over the crown, not the root near the canal.
3. Widening of the follicle space around the crown

   A widened follicle concerns the crown and suggests a cyst risk; it says nothing about root contact with the canal.
4. A dark band across the root at the overlap

   Darkening of the root where the mandibular canal crosses it is a classic sign that the root and canal are in close contact.

Enlargement of the entire image while its shape stays the same is called:

1. Foreshortening

   Foreshortening makes the tooth look shorter than it is, which changes shape, not just size.
2. Magnification

   Magnification is size distortion: the whole image is uniformly larger than the object while its shape is preserved.
3. Penumbra

   Penumbra is the blurred edge around image details caused by focal spot size and distances, not enlargement.
4. Shape distortion

   Shape distortion, such as elongation, changes proportions; a uniformly larger image keeps its proportions.

When a beam alignment device is used for paralleling, how is the correct vertical angulation obtained?

1. By lining the PID up with the aiming ring

   With a beam alignment device the holder sets the angle: lining the PID up with the ring places the beam at the correct vertical and horizontal angulation.
2. By aiming the PID parallel to the floor

   A PID parallel to the floor is a fixed setting that ignores the position of the receptor and the tooth.
3. By bisecting the tooth–receptor angle

   Bisecting the angle between tooth and receptor belongs to the bisecting technique, not to paralleling.
4. By adding +10 degrees to the tooth angle

   Adding a fixed number of degrees is a made-up rule; the receptor holder's ring already defines the angle.

Which image is most commonly used to survey an edentulous patient's jaws for retained root tips, impacted teeth, or lesions?

1. Lateral cephalometric image

   A lateral ceph shows skull and jaw relationships in profile, with both sides superimposed, so it is not a ridge survey.
2. Full-field CBCT of both jaws

   A full-field CBCT delivers much more dose than needed for a screening survey and is reserved for specific three-dimensional questions.
3. Four posterior horizontal bitewings

   Bitewings need opposing teeth and show only crowns and crestal bone, so they are useless on edentulous jaws.
4. Panoramic image of both jaws

   A panoramic image shows both edentulous ridges in one exposure at low dose, which suits a survey for root tips, impactions and lesions.

A patient wears an earring in the right ear during a panoramic exposure. Where and how does its ghost image appear?

1. Right side, higher and larger

   The real image of the earring is on the right; the ghost is projected across the midline, to the opposite side.
2. Left side, higher and larger

   A ghost image appears on the side opposite the real object, higher than it, and larger and blurrier.
3. Left side, lower and smaller

   The ghost does appear on the left, but because the beam is angled upward it is higher and larger, not lower and smaller.
4. Right side, lower and smaller

   Right side, lower and smaller describes neither the real earring image nor its ghost, which appears on the left and higher.

On a correctly positioned panoramic image, the occlusal plane should appear as:

1. A perfectly flat horizontal line

   A flat or reverse curve suggests the chin was raised too high during the exposure.
2. A downward curve, like a frown

   A frown-shaped plane also comes from the chin tipped up, not from correct positioning.
3. A slight upward curve, like a smile

   With the chin and occlusal plane positioned correctly, the occlusal plane shows a gentle upward curve toward the posterior, a slight smile.
4. A steep curve with overlapped incisors

   An exaggerated smile curve results from the chin tipped too low, which also crowds the lower incisors.

A patient reports sensitivity between teeth #14 and #15, which have mesial composite restorations. Which image best evaluates recurrent interproximal caries?

1. Limited-field CBCT of the maxillary left quadrant

   CBCT is not a caries tool: metal and composite cause artifacts and the dose is unnecessary for a proximal surface question.
2. Panoramic image of both dental arches

   A panoramic image overlaps proximal surfaces and lacks the detail to judge a restoration margin.
3. Bitewing image of the maxillary left molars

   A bitewing shows the proximal surfaces and restoration margins of #14 and #15 with little overlap, which is what a search for recurrent caries needs.
4. Maxillary topographic occlusal image

   An occlusal view shows the arch from above, so the proximal contacts and margins overlap.

A bitewing image has adequate density but low contrast, making crestal bone hard to see. Which exposure change increases contrast on a retake?

1. Increase the kilovoltage peak (kVp)

   Increasing the kilovoltage peak makes the beam more penetrating and adds shades of gray, which lowers contrast further.
2. Decrease the kilovoltage peak (kVp)

   Decreasing the kilovoltage peak gives a less penetrating beam with sharper differences between tissues, which raises contrast; density is then kept by adjusting the other settings.
3. Increase the exposure time

   Longer exposure makes the whole image darker but leaves the range of grays between bone and soft tissue the same.
4. Decrease the milliamperage (mA)

   Lowering the milliamperage lightens the whole image but does not widen the range of grays.

A sensor shows white pixel dropout in the same area for weeks, despite cleaning and reseating the cable. What is the next step?

1. Remove the sensor from use and contact the manufacturer

   A dropout that stays in the same place after cleaning and reseating points to a hardware failure, so the sensor comes out of service and goes back to the manufacturer.
2. Keep using it and note the defect in each patient record

   Documenting a known defect still produces images with missing data and leads to retakes.
3. Open the sensor housing in the office to repair it

   Opening a sealed sensor housing voids the warranty and can ruin the sensor; the repair belongs to the manufacturer.
4. Apply noise-reduction filters to every image from this sensor

   Software filters can hide the dropout but cannot recover the missing pixels, so diagnostic detail is lost.

On an image of a severely resorbed edentulous mandible, where may the mental foramen appear?

1. Near the ridge crest

   Near the ridge crest is right: heavy resorption lowers the crest to the level of the mental foramen, so the foramen appears at the top of the ridge.
2. In the midline below the incisors

   The midline of the mandible shows the lingual foramen and genial tubercles, not the mental foramen, which lies in the premolar region.
3. Superimposed over the ramus

   The ramus holds the mandibular foramen, a different landmark; the mental foramen stays in the body of the mandible.
4. At the lower border of the mandible

   Resorption removes bone from the top of the ridge, so the foramen moves toward the crest, not down to the lower border.

A molar shows a very tall pulp chamber, short roots, and a furcation located near the apex. What is this anomaly?

1. Hypercementosis

   Hypercementosis is extra cementum that makes the roots look bulbous; the pulp chamber is normal.
2. Taurodontism

   Taurodontism gives a tall, enlarged pulp chamber, short roots and a furcation displaced toward the apex.
3. Dilaceration

   Dilaceration is a sharp bend in the root or crown, not an enlarged chamber.
4. Dens in dente

   Dens in dente is an infolding of enamel into the tooth, seen as a 'tooth within a tooth', usually in maxillary lateral incisors.

Rectangular collimation reduces patient radiation dose mainly by:

1. Lowering the kilovoltage of the primary beam

   Lowering the kilovoltage is done on the control panel; a collimator changes the size and shape of the beam, not its voltage.
2. Limiting the beam to the size of the receptor

   A rectangular collimator shrinks the beam to about the receptor's size, so less tissue is irradiated for each image.
3. Shortening the exposure time for each image

   Exposure time is set on the control panel; a collimator does not change it.
4. Removing the low-energy photons from the beam

   Removing low-energy photons is the job of the aluminum filter, not the collimator.

After leaving the focal spot, in what order does the useful beam pass through the tubehead components?

1. Lead collimator, glass window, aluminum filter, PID

   The collimator cannot come before the window, because the window is the exit from the tube itself.
2. Glass window, lead collimator, PID, aluminum filter

   The filter sits inside the tubehead before the collimator; it is not added at the end of the PID.
3. Glass window, aluminum filter, lead collimator, PID

   The beam leaves the tube through the unleaded glass window, is filtered by aluminum, shaped by the lead collimator and then guided by the PID.
4. Aluminum filter, glass window, PID, lead collimator

   This order puts the filter inside the glass tube and the collimator after the PID, which does not match the tubehead.

Keeping a retake log helps a practice reduce patient exposure because it:

1. Records each patient's lifetime cumulative dose

   A retake log lists repeated images and their causes; it is not a tool for estimating a patient's lifetime dose.
2. Satisfies the patient's informed consent

   Informed consent is obtained from the patient before imaging; a log of retakes cannot stand in for it.
3. Shows which errors keep repeating

   A retake log shows which errors keep repeating, such as a technique or a sensor that keeps failing, so the cause can be fixed and future retakes avoided.
4. Replaces the need for personal dosimeters

   Personal dosimeters measure the operator's occupational exposure; a retake log measures no dose, so it cannot replace them.

Which radiation protection measure is most important for panoramic imaging?

1. Placing a thyroid collar on the patient

   A thyroid collar falls in the panoramic beam path and can block anatomy, causing a retake; the ADA's 2024 recommendations also call for ending routine thyroid collars and lead aprons.
2. Using the shortest possible PID

   The shortest possible PID is not a panoramic choice, since panoramic units have no PID; in intraoral imaging a short PID would even raise skin dose.
3. Higher kVp than intraoral imaging

   Panoramic units do run at higher kVp, but that is a technical setting of the unit, not a protection measure.
4. Careful positioning to avoid retakes

   Most avoidable panoramic dose comes from retakes caused by positioning errors, so getting the position right the first time protects the patient most.

After leaving the focal spot on the target, x-rays travel in which pattern?

1. Diverging straight lines

   X-rays travel in straight lines that spread out from the focal spot, which is why the beam widens with distance.
2. Curved lines running in parallel

   Curved lines running in parallel are wrong twice: x-rays travel in straight lines, and they spread out from a small focal spot instead of running parallel.
3. Waves that bend around teeth

   X-rays do not bend around objects; they pass through, are absorbed or are scattered.
4. Converging straight lines

   Converging lines would come together toward a point; the beam does the opposite and spreads out from the focal spot.

A quarterly dosimeter report shows 150 mrem. What is this dose in millisieverts?

1. 15 mSv

   15 mSv results from dividing by 10 instead of 100, a tenfold overestimate.
2. 150 mSv

   150 mSv simply keeps the number and swaps the unit, a hundredfold error.
3. 0.15 mSv

   0.15 mSv comes from dividing by 1,000, as if 1 mSv were 1,000 mrem.
4. 1.5 mSv

   100 mrem equals 1 mSv, so 150 mrem is 1.5 mSv.

The exposure switch is outside the operatory and is pressed right after sensor placement. How is it protected?

1. It is pressed only while wearing sterile gloves

   Sterile gloves are not needed for an exposure switch; the goal is to keep contamination off it, which a barrier does.
2. It is left uncovered and cleaned weekly

   Leaving the switch uncovered and cleaning it weekly ignores that it is touched with gloves from the mouth, even outside the room.
3. It is wiped with alcohol once at the end of the day

   A single wipe at day's end leaves the switch contaminated between patients, and alcohol alone is not an adequate disinfectant.
4. It is covered with a barrier changed after each patient

   The switch is touched with gloves that just handled the sensor, so it needs a barrier that is replaced for every patient.

A patient removes eyeglasses before a panoramic image. Where should the glasses be kept?

1. Held in the radiographer's gloved hand until the exposure ends

   Gloved hands that touched the bite block would contaminate the glasses, and the radiographer must step away during the exposure.
2. On the uncovered counter beside the exposed receptors

   Placing them beside exposed receptors puts them in the contaminated zone.
3. In a clean container away from contaminated items

   The patient's glasses are personal belongings and should stay in a clean place apart from anything touched with contaminated gloves.
4. On the bracket tray next to the used bite block

   The bracket tray with a used bite block is contaminated, so the glasses would pick up saliva.

Used reusable receptor holders are carried from the operatory to the sterilization area in:

1. A folded paper towel

   A folded paper towel soaks through and is open at the edges, so it does not contain contaminated holders safely.
2. A covered, leak-proof container

   Contaminated reusable items are carried in a closed, leak-proof container so nothing spills on the way to the sterilization area.
3. An open tray under the patient bib

   An open tray under the patient bib is still open underneath and can leak, so it is not a closed container.
4. Gloved hands, held away from the body

   Gloved hands held away from the body can still drop or drip contaminated holders; they are not a container.

In radiation biology, the latent period is the time between exposure and:

1. Complete cellular recovery

   Complete cellular recovery, where it happens, comes after the period of injury, not at the end of the latent period.
2. Arrival of the x-ray photons

   The arrival of the x-ray photons is the exposure itself, the starting point of the latent period rather than its end.
3. The formation of free radicals

   The formation of free radicals happens within fractions of a second of exposure, long before any effect can be seen.
4. The first observable effects

   The latent period runs from exposure until the first observable effects appear; it can be short after a high dose or last years for effects such as cancer.

Why is a glutaraldehyde sterilant not used to wipe down the tubehead and control panel?

1. It is cleared only for sterilizing critical items

   Glutaraldehyde is also used as a high-level disinfectant for semicritical items, so this limitation is false.
2. It is a toxic chemical intended for device immersion

   Glutaraldehyde is a toxic sterilant and high-level disinfectant intended for device immersion; its fumes make it unsuitable for wiping equipment.
3. It stains plastic surfaces and exposure switches

   Staining plastic surfaces or exposure switches is not the reason; toxicity and its design for immersion are.
4. It is too weak to kill TB bacteria

   Glutaraldehyde is not too weak: it kills TB bacteria and is far stronger than surface products.

Immediately after each exposure, a PSP plate in its barrier envelope should be:

1. Returned to the box with the unused plates

   Returning an exposed, contaminated plate to the box with the unused plates contaminates the clean stock and mixes exposed and unexposed plates.
2. Set on the uncovered countertop beside the chair

   An uncovered countertop becomes contaminated by the envelope, and the plate can be mixed up with others.
3. Wiped dry and placed in a disposable cup

   Drying the envelope removes saliva, and a disposable cup keeps exposed plates together and away from clean supplies until the series is done.
4. Carried to the scanner in the gloved hand

   Carrying each plate to the scanner with contaminated gloves spreads saliva to the scanner and the area around it.

By CDC's definition, an EPA-registered 'hospital' disinfectant used on the x-ray unit has proven effective against:

1. Mycobacterium tuberculosis, hepatitis B and HIV

   Mycobacterium tuberculosis, hepatitis B and HIV activity are added label claims (tuberculocidal or bloodborne-virus claims); the hospital designation alone does not establish them.
2. Bacterial spores, prions and mold species

   Bacterial spores, prions and mold species fall outside the hospital designation: spores call for a sterilant, prions resist routine disinfection, and mold activity is a separate fungicidal claim.
3. Influenza, measles and norovirus strains

   Influenza, measles and norovirus strains are viruses, and activity against a virus is a separate virucidal claim rather than part of the hospital designation.
4. Staphylococcus, Pseudomonas and Salmonella

   CDC defines an EPA-registered hospital disinfectant by proven activity against Staphylococcus, Pseudomonas and Salmonella; anything beyond these three has to appear as a separate claim on the label.

A receptor holder came out of the sterilizer without a wrap. How should it be handled?

1. Use it at once rather than store it

   An item sterilized without a wrap stops being sterile once it meets room air and hands, so it is used at once rather than stored.
2. Wrap it after the cycle and label it sterile

   Wrapping an item after the cycle traps whatever reached it on the way out; only items packaged before sterilization can be labeled sterile.
3. Keep it in an open drawer for later use

   An open drawer exposes the holder to dust, aerosols and hands, so a later use would be with a contaminated holder.
4. Wipe it with alcohol before each later use

   Wiping with alcohol before a later use is not sterilization; it cannot restore sterility to an exposed item.