Chapters: 15-17 Key Terms

Front 1

Ala

Back 1

The wing of the nose. The depression at which the nostril connects with the cheek. Used as a facial landmark in dental radiography.

Front 2

Bisector

Back 2

The imaginary line that bisects the angle formed by the image receptor and teeth. See bisecting technique.

Front 3

Biteblock

Back 3

A plastic or polystyrene device that functions to hold the image receptor in position while it is being exposed. The patient occludes and holds the image receptor in place by biting on the biteblock.

Front 4

Bite Extension

Back 4

The portion of the biteblock that allows the patient to occlude in such a way that the image receptor will be positioned parallel to the long axis of the teeth.

Front 5

Elongated image

Back 5

Refers to a distortion of the radiographic image in which the tooth structures appear longer than the anatomical size. Often caused by insufficient vertical angulation of the central beam.

Front 6

Embrasure

Back 6

The space between the sloping proximal surfaces of the teeth. The space may diverge facially, lingually, occlusally, or apically. The interdental papillae normally fill most of the apical embrasures.

Front 7

Film holder/ Image Receptor Holder

Back 7

Device used to hold and stabilize an intraoral film packet or digital sensor or phosphor plate in the mouth.

Front 8

Foreshortened image

Back 8

Distortion of the radiographic image in which the tooth structures appear shorter than their actual anatomical size. Most often caused by excessive vertical angulation of the central beam.

Front 9

Horizontal Angulation

Back 9

Direction of the central beam in a horizontal plane. Incorrect horizontal angulation results in overlapping the proximal structures.

Front 10

Image Receptor Holder (Positioner)

Back 10

See film holder

Front 11

Isometric triangle

Back 11

One triangle is isometric to another triangle if it has the same size and shape. This means that it must have the same angles and side lengths as the other triangle.

Front 12

Mean Tangent

Back 12

Average point where several curved surfaces touch if a ruler is held against them. The labial or buccal surfaces of all teeth have their most prominent point toward the lips or the cheeks and curve toward the mesial or distal. A mean tangent would be established by using a small ruler or any straight edge (such as a tongue depressor) and attempting to align as many of the teeth as possible. Occasionally, four or even five of the posterior teeth will touch the ruler at some point. Used to establish correct horizontal angulation, which requires that the central ray of the x-ray beam be directed at right angles to the mean tangent.

Front 13

Symphsis

Back 13

Prominent bone where the right and left sides of the mandibular fuse at the midline.

Front 14

Vertical angulation

Back 14

The direction of the central beam in an up or down direction achieved by directing the tip of the PID upward or downward. See Negative angulation and positive angulation.

Front 15

Bitetab

Back 15

An extension, made out of heavy paper or plastic, that is attached at the center of the image receptor will be positioned parallel to the long axes of the teeth.

Front 16

Bitewing Radiograph

Back 16

An intraoral radiograph that shows the crowns of both the upper and lower teeth.

Front 17

Contact Point

Back 17

The area of the tooth surface that touches another tooth. This generally refers to the mesial surface of one tooth making contact with the distal surface of the tooth adjacent to it in the dental arch. The spot where the teeth actually touch is the contact point, and the area between the contact point and the gingiva (gum) is called the embrasure.

Front 18

External Aiming Device (Indicator Ring)

Back 18

An indicating component of some image receptor holders that is used to aid in aligning the x-ray beam to the image receptor.

Front 19

Film Loop (Bitewing Loop)

Back 19

Cardboard or plastic loop used as an image receptor holder in bitewing radiography. The patient bites on the tab portion to hold the image receptor in position during exposure.

Front 20

Horizontal bitewing radiograph

Back 20

Direction of the central beam in a horizontal plane. Incorrect horizontal angulation results in overlapping the proximal structures.

Front 21

Interproximal radiograph

Back 21

See bitewing radiograph.

Front 22

Mean Tangent

Back 22

Average point where several curved surfaces touch if a ruler is held against them. The labial or buccal surfaces of all teeth have their most prominent point toward the lips or the cheeks and curve toward the mesial or distal. A mean tangent would be established by using a small ruler or any straight edge (such as a tongue depressor) and attempting to align as many of the teeth as possible. Occasionally, four or even five of the posterior teeth will touch the ruler at some point. Used to establish correct horizontal angulation, which requires that the central ray of the x-ray beam be directed at right angles to the mean tangent.

Front 23

Overlap

Back 23

Term used to refer to a distortion of the tooth image in which the structures of one tooth are superimposed over the structures of the adjacent tooth. Caused by incorrect horizontal angulation of the central beam and/or incorrect positioning of the image receptor in relationship to the teeth of interest.

Front 24

Point of entry

Back 24

Spot on the surface of the face toward which the central beam of radiation is directed when aligning the PID for intraoral exposures.

Front 25

Proximal surface

Back 25

Where adjacent teeth contact each other in the arch. The mesial and distal surfaces are proximal surfaces.

Front 26

Vertical Angulation

Back 26

The direction of the central beam in an up or down direction achieved by directing the tip of the PID upward or downward. See negative angulation and positive angulation.

Front 27

Vertical Bitewing Radiograph

Back 27

Bitewing radiograph placed in the oral cavity with the long dimension of the image receptor positioned vertically. Covers an increased area in the vertical dimension, resulting in more information regarding the periodontium being recorded.

Front 28

Cross-sectional technique

Back 28

An occlusal radiographic technique in which the central ray is directed perpendicular to the image receptor.

Front 29

Occlusal Radiograph

Back 29

Radiograph produced by placing the image receptor against the incisal or occlusal plane. The patient stabilizes the image receptor by biting down on it. In addition to the teeth, occlusal radiographs may show surrounding maxillary or mandibular structures. Depending on the placement of the image receptor and angle of exposure, cross-sectional or topographic radiographs are produced. See Cross-sectional technique and Topographical technique.

Front 30

Topographical technique

Back 30

Occlusal radiography technique that follows the rules of bisecting. The central rays of the x-ray beam are directed through the apices of the teeth perpendicularly toward the bisector to produce an image.