Intraoral Techniques & Projections

Which intraoral examination shows the crowns of both maxillary and mandibular teeth on one receptor?

Bite-wing

Which intraoral examination emphasizes the tooth apex and surrounding area?

Periapical (PA)

Which two methods are used to expose periapicals?

Paralleling and bisecting

Which intraoral examination evaluates large areas of the maxilla and mandible?

Occlusal

Bite-wings are ideal for evaluating which two findings?

Alveolar bone changes and interproximal caries

How many images commonly make up a complete mouth series (CMS)?

14–20

A complete mouth series may be composed of which image types?

Periapicals alone, or periapicals plus bite-wings

List four diagnostic uses of a complete mouth series.

Generalized disease, retained roots, foreign objects, extensive treatment needs

What other abbreviations are used for a complete mouth series?

FMS and FMX

How is a CMS mounted for review?

Systematically, to review every tooth-bearing region

What are the coverage criteria for a periapical?

Entire crowns and roots plus 2–3 mm beyond the apices

What are the coverage criteria for a bite-wing?

Crowns, crestal bone, and open interproximal contacts

What are the image quality criteria?

Appropriate density, contrast, definition, and detail with minimal distortion

What is the series coverage criterion?

All required tooth-bearing areas without preventable omissions

Which extraoral examination gives a broad overview of the jaws and dentition?

Panoramic

Which extraoral examination is used for craniofacial relationships and orthodontic assessment?

Cephalometric

Name the skull/jaw projections listed for selected needs.

Lateral jaw, posteroanterior, and Waters

Where are receptors placed in extraoral examinations?

Outside the mouth

Who should prescribe images, and on what basis?

The dentist, based on individual need

Which factors are considered when selecting images?

History, clinical findings, disease risk, symptoms, and prior images

When may a CMS be appropriate?

When generalized disease or extensive prior treatment is evident

Is a CMS automatically indicated for every new patient?

No

When prescribing images, what does SELECT mean?

Choose the number, type, and frequency needed to answer the diagnostic question

Best examination for suspected apical pathology?

Periapical

Best examination for interproximal caries monitoring?

Bitewings

Best examination for evaluation of large areas of the maxilla and mandible?

Occlusal

Define the long axis of the tooth.

An imaginary line running lengthwise through the center of the tooth, crown to root apex

Define the central ray.

The center-most portion of the x-ray beam directed at the image receptor

Define parallel.

Two lines or planes that stay the same distance apart at every point and never meet

Define perpendicular.

Two lines that intersect at a right angle

Define intersecting.

Two lines or planes that cross one another at a single point

Define right angle.

The 90-degree angle formed where two perpendicular lines meet

List the three alternative names for the paralleling technique.

Extension cone paralleling, right-angle, and long-cone technique

What must be used to keep the receptor parallel with the long axis of the tooth?

A beam alignment device

Which technique is most commonly used to produce an image with minimal distortion?

Paralleling

Which receptor types can be exposed with the paralleling technique?

Periapical and bite-wing

Why is the object–receptor distance often increased in paralleling?

Anatomy; it allows the receptor to remain parallel to the tooth

What can result when the object–receptor distance is increased?

Magnification and loss of definition

How is magnification accounted for in paralleling?

A long PID (increased target–receptor distance)

What target–receptor distance is used in paralleling?

16 inches

Why must the target–receptor distance be increased?

So only the most parallel rays are directed at the tooth

What do newer machines with recessed focal spots allow?

A shorter PID while maintaining a 16-inch target–receptor distance

What are the components of the XCP?

Bite-block, indicator arm, and aiming ring

What does XCP stand for?

Extension-cone paralleling

How do receptor holders reduce patient exposure?

Prevent cone cuts (fewer retakes) and avoid finger stabilization in the beam

What is the advantage of the Stabe bite-block?

It is disposable and does not need to be sterilized

What is the purpose of universal sensor holders?

They adjust to different digital sensor dimensions

Besides the XCP, which holders are listed for paralleling?

Flip-Ray, Snap-A-Ray, and disposable bite-blocks

In the paralleling technique, how is the receptor placed?

Parallel to the long axis of the tooth

In the paralleling technique, how is the central x-ray beam directed?

At right angles (perpendicular) to both the receptor and the tooth

What receptor size and orientation are used for anterior paralleling?

Size 1, vertical

What receptor size and orientation are used for posterior paralleling?

Size 2, horizontal

Name the five rules of paralleling.

Placement, parallel, vertical angulation, horizontal angulation, exposure

Paralleling rule: how is vertical angulation directed?

Central ray perpendicular to the receptor and tooth

Paralleling rule: how is horizontal angulation directed?

Through the contact areas to avoid overlap

Paralleling rule: how is the beam centered to avoid cone cut?

Center the beam on the receptor

Which patient preparation steps are part of the shared workflow?

Explain procedure, upright chair and patient, adjust headrest, remove interfering objects, place prescribed protection

What does equipment preparation include?

Infection control, setting exposure factors, assembling holders on a covered surface

Why follow the same organized sequence for every technique?

To reduce omissions and unnecessary movement

In the paralleling exposure sequence, which region is exposed first?

Anterior

How many anterior placements are in the paralleling sequence?

Eight: five maxillary and three mandibular

How many posterior placements are in the paralleling sequence?

Eight: four maxillary and four mandibular

Why are anteriors exposed first?

Size 1 receptor is small, easier to tolerate, and less likely to cause gagging

Within each quadrant, which is exposed first and why?

Premolar before molar, to improve tolerance and reduce gagging

How is a shallow palate modified in paralleling?

Cotton-roll support; a limited 5–15° vertical adjustment may be needed

How is a maxillary torus handled in paralleling?

Place the receptor on the far side of the torus

How are mandibular tori handled in paralleling?

Place the receptor between the tori and tongue

How is a sensitive mandibular premolar region handled?

Position beneath the tongue, cushion sharp receptor edges, wiggle into place if needed

What will show on the radiograph with a maxillary torus?

A radiopacity

Which three adjustments help produce a diagnostic-quality image when anatomy interferes?

Cotton rolls, changing vertical angulation, changing receptor location

List the benefits of paralleling.

Accurate dimensions with minimal distortion, simpler beam alignment, reproducible serial images

What is a limitation of paralleling?

Receptor placement and holders may be difficult or uncomfortable in small mouths or challenging anatomy

When is the bisecting technique used?

When paralleling is difficult to use

List the situations in which bisecting may be needed instead of paralleling.

Shallow palate, edentulous, pediatric, palatal tori, shallow floor of mouth, severe gagger, no holders available

Define isometry.

Equality of measurement

Define bisect.

To divide something into two equal parts

Define a right triangle.

A triangle that contains one 90-degree angle

Define the hypotenuse.

The side opposite the right angle; the longest side of a right triangle

What do the interior angles of a triangle total?

180 degrees

Define congruent triangles.

Triangles identical in size and shape, with equal corresponding sides and angles

Define an equilateral triangle.

A triangle with three equal sides and three equal angles

Define angle.

The space between two intersecting lines or surfaces, measured in degrees

State the rule of isometry.

Two triangles are equal if they have two equal angles and share a common side

How does the bisecting technique apply the rule of isometry?

It forms two imaginary equal triangles

Where is the receptor positioned in the bisecting technique?

Close to the lingual tooth surface

What is visualized in the bisecting technique?

An imaginary bisector dividing the angle in two

How is the central ray directed in the bisecting technique?

Perpendicular to the bisector

What two planes meet to create an angle in the bisecting technique?

The receptor plane and the long axis plane

Why are the image and tooth the same length in bisecting?

The triangles are congruent

What receptor size and orientation are traditionally used for bisecting?

Size 2; vertical anterior and horizontal posterior

How much receptor should appear beyond the incisal edges in bisecting?

Approximately one eighth of an inch

Is finger or hand stabilization recommended in bisecting?

No; it may be necessary but is not recommended

Which devices may stabilize the receptor in the bisecting technique?

BAI alignment systems, Snap-A-Ray, or disposable bite-blocks

How do BAI devices used in bisecting differ from those used in paralleling?

A slight shift in angulation

Where is the receptor centered in bisecting?

Over the area of interest along the lingual surface

Define angulation.

Alignment of the central ray in the horizontal and vertical planes

What is correct horizontal angulation?

Central ray perpendicular to the curvature of the arch and through the contact areas

What does incorrect horizontal angulation produce?

Overlapped contact areas

Define vertical angulation.

Positioning of the PID in a vertical (up-and-down) plane

Define horizontal angulation.

Positioning of the tube head and central ray in a horizontal (side-to-side) plane