RAD Module 3 (ch21 & ch5)

What does the term "bite-wing" refer to?

The original technique in which the patient bites on a small paper "wing" (now called a tab) attached to the film packet to stabilize it; the image is still called a bite-wing even when no tab is used.

What structures does a bite-wing image show on the same image?

The crowns of maxillary and mandibular teeth, the interproximal areas, and areas of crestal bone.

What is the primary use of bite-wing images?

Detecting interproximal caries (tooth decay), especially early lesions not clinically evident.

Besides detecting caries, what other uses do bite-wing images have?

Monitoring caries progression, assessing existing restorations, and examining crestal bone levels between teeth.

What does "interproximal" mean?

Between two adjacent surfaces.

What is crestal bone?

The coronal (most top) portion of alveolar bone found between teeth; also called the alveolar crest.

What is a contact area?

The area of a tooth that touches an adjacent tooth.

What do opened contacts look like on an image?

Thin radiolucent lines between adjacent tooth surfaces.

What are overlapped contacts?

Areas where the contact area of one tooth is superimposed over the contact area of an adjacent tooth.

What size receptor is recommended for bite-wings in an adult patient?

Size 2.

What size receptor is used for bite-wings in a child with primary dentition?

Size 0 (always placed horizontally).

What size receptor can include all posterior teeth on one side in one exposure, and is it recommended for adults?

Size 3; it is not recommended because it often causes overlapped contacts and may not show crestal bone adequately.

Why does the arch curvature matter in determining the number of bite-wing images?

Curvature differs between the premolar and molar areas, so one image cannot open all posterior contacts; typically four bite-wings are taken (right/left premolar and right/left molar).

What are the two ways to stabilize a bite-wing receptor?

A beam alignment device (such as the Rinn XCP bite-wing instrument) or a bite-wing tab (or bite loop); the beam alignment device is recommended.

On which side of the receptor is the bite-wing tab attached?

The tube side (the white side of film).

When is a bite-wing tab especially useful?

In children or patients with a small mouth or limited opening, where a beam alignment device may not fit.

What does the aiming ring on the Rinn XCP bite-wing instrument do?

It dictates the proper PID angulation and ensures the entire receptor is covered by the x-ray beam.

How is the patient's head positioned before exposing a bite-wing?

The maxillary arch (occlusal plane) is parallel to the floor and the midsagittal plane is perpendicular to the floor.

What is horizontal angulation?

The side-to-side positioning of the PID/central ray.

What is correct horizontal angulation for a bite-wing?

The central ray is directed perpendicular to the curvature of the arch and through the contact areas, producing opened contacts.

What error results from incorrect horizontal angulation?

Overlapped (unopened) contacts.

What is vertical angulation?

The up-and-down positioning of the PID/central ray, measured in degrees on the tubehead.

What makes vertical angulation positive or negative?

Positive if the PID is above the occlusal plane and the beam is directed downward; negative if the PID is below the occlusal plane and the beam is directed upward.

What vertical angulation is recommended for bite-wings with a tab and film or PSP sensors?

+10 degrees.

Why is +10 degrees of vertical angulation used with a bite-wing tab?

To compensate for the slight bend of the upper portion of the receptor and the slight tilt of maxillary teeth.

What error results from using a negative vertical angulation on a bite-wing?

A distorted image: maxillary occlusal surfaces are visible and the apical regions of mandibular teeth are seen.

What are the five basic rules of the bite-wing technique?

Receptor placement (cover prescribed area), receptor position (parallel to crowns and stabilized), vertical angulation (+10 with tab), horizontal angulation (through contacts), and receptor exposure (beam centered on receptor).

What is a cone-cut?

A clear or white unexposed area on an image caused by the x-ray beam not being centered over the receptor.

How does a cone-cut look with a round PID versus a rectangular PID?

A round PID produces a curved border; a rectangular PID produces a linear border.

How do you check for a cone-cut before exposing a bite-wing?

Stand behind the tubehead and look along the side of the PID; no portion of the receptor should be visible.

In what order should you set up the angulations and receptor placement?

Set exposure factors and both angulations (and position the PID) before placing the receptor in the mouth; do not move the PID afterward.

On which tooth is the premolar bite-wing receptor centered?

The mandibular second premolar.

Where should the front edge of the premolar bite-wing receptor be aligned?

With the midline (middle) of the mandibular canine.

On which tooth is the molar bite-wing receptor centered?

The mandibular second molar.

Where should the front edge of the molar bite-wing receptor be aligned?

With the midline (middle) of the mandibular second premolar.

In a bite-wing-only series, which exposure is taken first and why?

The premolar bite-wing, because it is easier for the patient to tolerate and less likely to evoke the gag reflex.

What is the recommended exposure sequence for a patient needing both periapicals and bite-wings?

Anterior periapicals first, then posterior periapicals, then bite-wings last.

Why are bite-wings taken last in a complete mouth series?

They are easiest for the patient to tolerate, leaving the patient with a more positive feeling.

What is a vertical bite-wing and when is it used?

A bite-wing with the long portion of the receptor placed up and down; used to examine alveolar bone level, often for patients with bone loss from periodontal disease.

How many projections are in a modified CMS using vertical bite-wings alone?

Seven (3 anterior and 4 posterior).

How is the bite-wing technique modified for an edentulous space?

Place a cotton roll in the missing tooth area to support the tab or beam alignment device and prevent a tipped occlusal plane.

How is the bite-wing technique modified for mandibular tori?

Place the receptor between the torus and the tongue (never on top of the torus); a beam alignment device is recommended.

What are mandibular tori?

Bony growths along the lingual aspect (tongue side) of the mandible.

Why should PSP receptors not be creased to accommodate bony growths?

Once bent, they exhibit the crease for the remainder of their use and need to be replaced.

How many bite-wing exposures may be needed per side when premolars and third molars have been extracted?

One per side.

What should you say to a patient instead of the word "hurt"?

That the procedure will be "momentarily uncomfortable."

What should you do if you drop a receptor?

Do not pick it up; leave it on the floor because it is contaminated, and dispose of it when you clean the treatment area.

What are the three types of intraoral imaging examinations?

Periapical, interproximal (bite-wing), and occlusal.

What is the purpose of a periapical examination?

To examine the entire tooth (crown and root) and supporting bone.

Where does the term "periapical" come from?

The Greek prefix peri- (around) and the Latin word apex (the terminal end of a tooth root).

What two techniques are used to obtain periapical images?

The paralleling technique and the bisecting technique.

What is the purpose of an interproximal examination?

To examine the crowns of both maxillary and mandibular teeth on a single image, including adjacent tooth surfaces and crestal bone.

What does the quality of the x-ray beam describe, and what controls it?

The mean energy or penetrating ability of the beam; it is controlled by kilovoltage (kV).

What does the quantity of the x-ray beam describe, and what controls it?

The number of x-rays produced; it is controlled by milliamperage (mA).

What kilovoltage range do current dental x-ray units use?

60 to 70 kV (or a fixed 70 kV).

What milliamperage range do current dental x-ray units use?

6 to 8 mA (or a fixed 7 mA).

How does increasing kV affect the x-ray beam?

Electrons move faster and strike the target with more force, producing a more penetrating beam with shorter wavelengths and higher energy.

What is density?

The overall darkness or blackness of an image.

What is contrast?

How sharply dark and light areas are differentiated or separated on an image.

How does increasing kV affect image density and contrast?

Density increases (darker) and contrast decreases (low contrast, many shades of gray).

How does decreasing kV affect image density and contrast?

Density decreases (lighter) and contrast increases (high contrast, mostly black and white).

Which type of contrast is useful for detecting caries, and which for detecting periodontal or periapical disease?

High contrast (low kV) for caries; low contrast (high kV) for periodontal or periapical disease.

How does increasing mA affect an image?

More x-rays are produced and the image has increased density (darker).

Why does increasing mA increase the number of x-rays?

It raises the temperature of the cathode filament, producing more electrons that strike the anode.

What is the relationship between exposure time and kV or mA?

They are inversely related; if kV or mA increases, exposure time decreases to maintain density, and vice versa.

What is an impulse on older x-ray units?

A unit of exposure time equal to 1/60 of a second (60 impulses = 1 second).

Which exposure factor is recommended for adjusting once an x-ray unit is installed, calibrated, and inspected?

Exposure time only (not kV or mA).

Should exposure time be increased or decreased for small children?

Decreased (and increased for adults with large jaws).

What is intensity of the x-ray beam?

The product of the quantity (number of photons) and quality (energy of each photon) per unit of area per unit of exposure time.

Which factors affect the intensity of the x-ray beam?

Kilovoltage, milliamperage, exposure time, and distance.

What are the three distances to consider when exposing a dental image?

Target-surface distance, target-object distance, and target-receptor distance.

What does the inverse square law state?

The intensity of radiation is inversely proportional to the square of the distance from the source of radiation.

What happens to beam intensity if the target-receptor distance is doubled?

The beam is one-fourth as intense.

What happens to beam intensity if the target-receptor distance is tripled?

The beam is one-ninth as intense.

What happens to beam intensity if the target-receptor distance is cut in half?

The beam is four times as intense.

What is the half-value layer (HVL)?

The thickness of a specified material (e.g., aluminum) that reduces the intensity of the x-ray beam by half.

If the HVL is 4 mm, how much aluminum is needed to cut the beam intensity in half?

4 mm of aluminum.

What does a higher HVL indicate?

A more penetrating x-ray beam.

What is the purpose of aluminum filters in the tubehead?

To remove low-energy, less penetrating, longer-wavelength x-rays, increasing the mean penetrating ability of the beam while reducing intensity.

How can density and contrast be corrected with digital imaging versus film?

Digital: image enhancement software adjusts brightness and contrast; film: the image must be retaken with adjusted exposure factors.

Who made the first dental radiograph?

Otto Walkhoff, a German dentist, in 1895 (he exposed himself for 25 minutes).

Who made the first dental radiograph in the United States?

W. J. Morton, a New York physician, using a skull.

Who is credited with the first practical use of radiographs in dentistry in the United States, and what was the cost to him?

C. Edmund Kells (1896); overexposure caused cancers that cost him his fingers, hands, and then arms.

Who developed the first dental x-ray unit and wrote the first paper on radiation dangers?

William H. Rollins, a Boston dentist.

Who was the first to use film in intraoral radiography?

Frank Van Woert.

Who established the first college radiography course for dental students?

Howard Riley Raper.

Who built the first vacuum tube and in what year?

Heinrich Geissler, a German glassblower, in 1838.

What did Hittorf call the discharges from the negative electrode of the vacuum tube?

Cathode rays.

What did William Crookes discover about cathode rays?

They are streams of charged particles.

What did Philip Lenard discover in 1894?

Cathode rays could penetrate a thin aluminum window in the tube and cause fluorescent screens to glow.

Who developed the hot-cathode x-ray tube, and why was it important?

William D. Coolidge (1913); it contained a tungsten filament and became the prototype for all modern x-ray tubes.

Which company made the first prewrapped intraoral film in 1913?

Eastman Kodak Company.

How much exposure time does modern fast film require compared with 1920?

Less than 2% of the initial exposure time.

What are the three intraoral techniques used in dentistry?

The bisecting technique, the paralleling technique, and the bite-wing technique.

What causes overlapped contacts on a bite-wing?

The central ray was not directed through the interproximal spaces (incorrect horizontal angulation); with a device, also a receptor not parallel to the teeth or a PID not flush with the aiming ring.

If overlapping is more pronounced in the posterior half of the image, what was the PID error?

The PID was pointed too much from the mesial toward the distal.

If overlapping is more pronounced in the anterior half of the image, what was the PID error?

The PID was pointed too much from the distal toward the mesial.

What causes a distorted bite-wing image?

Negative vertical angulation was used instead of +10 degrees.

What does too flat a vertical angulation do on a periapical image?

The image is elongated (longer than the actual tooth).

What causes a cone-cut when using a beam alignment device?

The PID was not properly aligned with the beam alignment device, so the beam did not expose the entire receptor.