DANB RHS Radiation Health and Safety - Set 3 - Part 2

Correct Answer: paralleling

Paralleling keeps the receptor parallel to the tooth and the beam perpendicular to both, satisfying the geometric conditions for an accurate image, so it is the preferred intraoral technique. Option a is incorrect because bisecting introduces dimensional distortion because the receptor is not parallel to the tooth, so it serves as a fallback rather than the most accurate technique. Option b is incorrect because occlusal imaging surveys a broad arch segment and is a special-purpose view, not the routine technique judged for accuracy and minimal distortion on individual teeth. Option d is incorrect because panoramic imaging is an extraoral survey with inherently lower detail and some distortion, so it is not the technique chosen when geometric accuracy matters most.

Correct Answer: long PID

Paralleling moves the receptor away from the tooth to stay parallel, so a long PID is needed to keep magnification low while a holder maintains that parallel position. Option b is incorrect because a short cone widens the beam and increases magnification and scatter, which works against the accuracy paralleling seeks, so it is not what the technique requires. Option c is incorrect because a thyroid collar is patient shielding used for all intraoral work; while important, it is not the specific equipment that makes the paralleling geometry possible. Option d is incorrect because a faster timer adjusts exposure duration, an exposure factor, not the geometric setup; paralleling depends on the holder and a long PID, not on timing.

Correct Answer: directly against the teeth

Bisecting rests the receptor directly against the teeth, and the beam is aimed perpendicular to the imaginary line that bisects the angle between the tooth and the receptor. Option a is incorrect because placing the receptor parallel to the long axis describes the paralleling technique; bisecting deliberately lets the receptor and tooth meet at an angle instead. Option b is incorrect because a focal trough is a panoramic concept, the curved layer of sharp focus; it has nothing to do with where an intraoral bisecting receptor is positioned. Option c is incorrect because the receptor is set against the teeth in the mouth, not tucked behind the lip; placement behind the lip would miss the teeth being imaged entirely.

Correct Answer: dimensional distortion

Because the receptor angles away from the tooth, the projected lengths can be inaccurate, so dimensional distortion is the chief drawback of bisecting compared with the paralleling technique. Option a is incorrect because bisecting does not inherently double the dose; dose depends on exposure factors and beam limiting, not on the choice between bisecting and paralleling geometry. Option b is incorrect because whether an image appears immediately depends on the receptor type, a sensor versus a plate, not on the bisecting technique, so this is not its defining weakness. Option d is incorrect because needing a scanner is a property of PSP plates, an indirect digital receptor; it is unrelated to bisecting, which can be used with any receptor type.

Correct Answer: shallow or flat palate

A shallow or flat palate, like a small mouth or a young child, leaves no room to position the receptor parallel to the tooth, so the bisecting technique becomes the practical fallback. Option a is incorrect because a very large mouth gives ample room for a holder and parallel placement, so it favors paralleling rather than forcing a switch to the bisecting technique. Option c is incorrect because a tall arch with a deep palatal vault accommodates the receptor away from the teeth, supporting paralleling instead of requiring the bisecting workaround. Option d is incorrect because a fully erupted dentition is simply normal anatomy and does not by itself prevent paralleling, so it is not a reason to choose the bisecting approach.

Correct Answer: anterior teeth

Starting with the anterior teeth eases the patient into the procedure and provokes the least gagging, so the sequence works front to back and saves the gag-prone areas for later. Option b is incorrect because maxillary molars are the most likely to trigger gagging, so they are saved for last in a strong gagger, never used to open the sequence. Option c is incorrect because mandibular molars sit deep in the back of the mouth and are more likely to provoke gagging than the front teeth, so they do not begin the series. Option d is incorrect because premolars fall between the anterior and molar regions and come after the anteriors; beginning with them skips the gentler anterior start that reduces gagging.

Correct Answer: the premolar view

Within a posterior quadrant the premolar view is taken before the molar view, working from front to back, because the more anterior premolar placement provokes less gagging than the molar. Option a is incorrect because the molar view sits farther back and is more gag-prone, so it follows rather than precedes the premolar view in the posterior sequence. Option b is incorrect because the canine is an anterior tooth, not part of the posterior quadrant sequence, so it is not the first posterior view exposed in that region. Option c is incorrect because an occlusal view is a separate broad projection, not one of the ordered posterior periapical placements, so it is not the first view within a quadrant.

Correct Answer: maxillary molars

Maxillary molar placements reach far back along the palate and most readily trigger the gag reflex, so they are exposed last, after the patient has settled into the appointment. Option a is incorrect because mandibular anteriors sit at the front of the lower arch and rarely provoke gagging, so they are taken early rather than held until the end. Option b is incorrect because premolar bitewings are positioned more anteriorly than the molars and are comparatively well tolerated, so they need not be postponed for a gagging patient. Option d is incorrect because lower canines are anterior teeth that cause little gagging, so they belong near the start of the sequence, not among the placements saved for last.

Correct Answer: size two

Size two is the standard receptor for adult posterior periapicals and bitewings, large enough to capture the back teeth while still fitting comfortably in the typical adult mouth. Option b is incorrect because size zero is the smallest receptor, intended for small children and primary teeth, so it is too little coverage for adult posterior work. Option c is incorrect because size four is the large occlusal plate the patient bites; it is far too big for routine posterior periapicals or bitewings in an adult. Option d is incorrect because size three is a long, narrow bitewing receptor for a single elongated view, not the standard size used across adult posterior periapicals and bitewings.

Correct Answer: use a smaller receptor with more placements

A narrow arch leaves little width for a standard receptor, so switching to a smaller size and taking more placements lets the operator cover the teeth without forcing the receptor. Option a is incorrect because the largest receptor needs the most room and would not fit a narrow arch, jamming against the tissues and causing discomfort and placement errors. Option b is incorrect because skipping the holder removes the stability that keeps the beam aligned, inviting cone cuts and angulation errors rather than solving the space problem. Option c is incorrect because raising the kilovoltage changes contrast, not the physical fit of the receptor, so it does nothing to address the limited width of a narrow arch.

Correct Answer: four

The standard adult posterior bitewing set is four images, the right and left premolar and molar views, because arch curvature differs by region and one view cannot open all the contacts. Option a is incorrect because two views would leave half the posterior contacts unopened, since each side needs both a premolar and a molar projection to capture all the back teeth. Option c is incorrect because eight is more than the routine posterior set calls for and overshoots the standard four-view examination of the back teeth in both arches. Option d is incorrect because a single bitewing covers only one small region of contacts, far short of surveying the premolar and molar areas on both sides of the mouth.

Correct Answer: plus ten degrees

Bitewings use roughly a positive ten-degree vertical angulation, which directs the central ray through the contacts and records the crowns of both arches and the crestal bone. Option a is incorrect because a negative ten degrees would aim the beam upward in the wrong direction for a bitewing, distorting the projection rather than opening the posterior contacts. Option b is incorrect because forty-five degrees is far too steep for a bitewing and would foreshorten the image, collapsing the crowns instead of presenting them with open contacts. Option d is incorrect because ninety degrees is the angle used for a mandibular occlusal projection, not for a bitewing, where a slight positive angulation is what the technique requires.

Correct Answer: cleft palate

The broad occlusal view surveys a whole arch segment, so it is indicated for a cleft palate as well as retained roots, impactions, salivary stones, and jaw fractures. Option b is incorrect because a single proximal contact is best opened by a bitewing, which is built to show interproximal surfaces; the occlusal view is too broad for that fine detail. Option c is incorrect because crestal bone level is read on bitewings and periapicals that show the bone between teeth, not on the wide occlusal projection of the arch. Option d is incorrect because a soft-tissue profile is captured on a lateral cephalometric for orthodontics; the occlusal view images hard structures within an arch, not the facial profile.

Correct Answer: beyond the bony growths

Maxillary tori are bony bulges on the palate, so the receptor is positioned beyond them, farther toward the midline floor of the palate, to avoid bending or tenting the receptor. Option a is incorrect because resting the receptor on top of the tori props it at an angle and away from the teeth, distorting the image and making the placement uncomfortable. Option b is incorrect because tucking the receptor tightly against the growths forces it to bend over the bony bulge, which warps the geometry and can hurt the patient. Option c is incorrect because placing the receptor outside the mouth describes an extraoral view; intraoral periapicals still require the receptor inside the mouth, just clear of the tori.

Correct Answer: size four

An adult occlusal uses the large size four receptor, which the patient bites to hold flat so it can capture a broad section of the palate or floor of the mouth. Option a is incorrect because size zero is the smallest receptor, made for primary teeth in small children, and it is far too small to survey an adult arch from the occlusal plane. Option b is incorrect because size one is a narrow anterior intraoral receptor, lacking the breadth needed to image a whole arch segment in a single occlusal projection of the palate. Option d is incorrect because size two is the standard posterior periapical and bitewing receptor; it is smaller than the size four plate used to capture the broad occlusal view.

Correct Answer: rotate around the patient's head

In panoramic imaging the tubehead and receptor rotate around the patient's head in opposite directions, with no receptor in the mouth, sweeping the curved arch onto the image. Option a is incorrect because staying still describes a standard intraoral exposure; the defining feature of a panoramic is the synchronized rotation of the tubehead and receptor around the head. Option c is incorrect because no receptor sits inside the mouth for a panoramic, since it is an extraoral technique; the receptor travels outside the head as the unit rotates. Option d is incorrect because the components rotate around the head rather than dropping toward the floor, so downward movement does not describe how a panoramic image is acquired.

Correct Answer: vertical angulation and exposure time

A panoramic unit fixes the vertical angulation and exposure time as part of its preset rotation, so the operator can usually adjust only milliamperage and kilovoltage, not those two. Option b is incorrect because milliamperage is one of the few settings the operator can adjust on a panoramic unit to control density, so it is not among the fixed, non-adjustable factors. Option c is incorrect because kilovoltage is likewise adjustable to manage contrast on most panoramic machines, so it is not one of the parameters locked by the rotation program. Option d is incorrect because patient position is actively set by the operator and is critical to a good panoramic, so it is the opposite of a fixed, non-adjustable factor.

Correct Answer: less radiation dose

A panoramic exposes the patient to less radiation than a full-mouth intraoral survey, which is one of its advantages, though it trades away the fine detail of intraoral images. Option a is incorrect because the panoramic actually delivers less dose than a full series of intraoral films, so claiming it gives more reverses one of its recognized benefits. Option b is incorrect because the doses are not identical; the single rotational panoramic exposure is lower than the cumulative dose of many separate individual intraoral exposures combined. Option c is incorrect because the panoramic offers broad coverage but lower resolution, so it provides less fine diagnostic detail than focused intraoral imaging, rather than the greater detail this option claims.

Correct Answer: milliampere-seconds

Milliampere-seconds determines the number of photons reaching the receptor, so it is the primary control of density; raising it darkens the image and lowering it lightens it. Option a is incorrect because kilovoltage chiefly governs contrast and beam energy and only affects density secondarily, so it is not the primary control of overall image darkness. Option b is incorrect because PID length changes the source distance and beam intensity through geometry, but it is not the factor named as the primary determinant of image density. Option d is incorrect because collimator shape limits the size of the beam to reduce scatter and dose; it does not set how dark the recorded image becomes.

Correct Answer: reduce the exposure factors

A child's smaller tissue mass needs less radiation to form a diagnostic image, so the operator reduces the exposure factors, keeping the dose as low as reasonably achievable. Option b is incorrect because increasing the factors would overexpose a child's smaller anatomy and add unnecessary dose, the opposite of what protection for a young patient requires. Option c is incorrect because the lead apron stays in place for a child, who is more radiosensitive than an adult; removing it would strip away needed protection rather than help. Option d is incorrect because lengthening the exposure time raises the dose and the risk of motion blur in a child, so it works against the goal of reducing exposure for a small patient.