Dental Radiography: Bitewing, Occlusal, Panoramic, Extraoral, and 3D Imaging

Comprehensive vocabulary flashcards covering dental bitewing techniques, occlusal and localization methods, panoramic imaging principles and errors, extraoral skull projections, and 3D Cone Beam Computed Tomography (CBCT).

Bitewing Radiograph

An intraoral radiograph that records the crowns and alveolar bone crest of both the maxillary and mandibular teeth on a single image, primarily used to detect interproximal caries and assess periodontal bone levels.

Size 3 Image Receptor

A long, narrow image receptor designed specifically for horizontal bitewings requiring only one exposure per side; disadvantages include being narrower in the vertical dimension than size $2$ (showing less crestal bone) and increased likelihood of overlapping interproximal spaces.

Vertical Bitewing Series

A set of seven to eight vertical bitewing radiographs (including posterior and anterior images) recommended when there is a need to image more of the supporting alveolar bone.

Mesiodistal Horizontal Angulation Error

An error where the PID and x-ray beam are directed obliquely from the mesial (deviating by about $15^\circ$), resulting in severe overlapping of contact areas in the distal or posterior region of the radiograph.

Distomesial Horizontal Angulation Error

An error where the PID and x-ray beam are directed obliquely from the distal (deviating by about $15^\circ$), resulting in severe overlapping of contact areas in the mesial or anterior region of the radiograph.

Bitewing Vertical Angulation

The vertical angle setting of the PID for bitewing exposures, established at $+10^\circ$ ($+5^\circ$ sometimes recommended for children); inadequate angulation images excessive mandible, while excessive angulation images excessive maxilla.

Topographical Occlusal Technique

An occlusal examination technique similar to the bisecting technique that yields an image resembling a large periapical radiograph, providing extensive information on the alveolar crest and apical areas of the maxilla or mandible.

Cross-Sectional Occlusal Technique

An occlusal radiographic technique where teeth appear shortened, elliptical, or circular; almost exclusively used on the mandible to image the sublingual area, locate impacted teeth, and detect soft tissue calcifications.

Maxillary Topographical Occlusal Radiograph (Anterior)

An occlusal exposure where the receptor's long dimension is placed buccal-to-buccal, the central ray is directed through a point near the bridge of the nose toward the center of the receptor, with a vertical angulation of $+65^\circ$.

Maxillary Topographical Occlusal Radiograph (Posterior)

An occlusal exposure where the receptor's long dimension is along the midline, the central ray is directed through a point on the ala–tragus line below the outer canthus of the eye, with a vertical angulation of $+45^\circ$.

Mandibular Topographical Occlusal Radiograph (Anterior)

An occlusal projection where the receptor's long dimension is buccal-to-buccal, the central ray enters through the middle of the chin toward the center of the receptor, with a vertical angulation of $-55^\circ$.

Mandibular Topographical Occlusal Radiograph (Posterior)

An occlusal projection where the receptor's long dimension is along the midline, the central ray enters on the inferior border of the mandible directly below the second premolar, with a vertical angulation of $-45^\circ$.

Mandibular Cross-Sectional Occlusal Radiograph

An occlusal projection exposed with the patient reclined and the occlusal plane perpendicular to the floor; the central ray enters $2\,\text{inches}$ ($5\,\text{cm}$) back from the tip of the chin at a vertical angulation of $0^\circ$.

SLOB Rule

A localization principle (Same on Lingual, Opposite on Buccal) stating that if an object appears to move in the same direction as the tube shift on a second radiograph, it is on the lingual; if it moves in the opposite direction, it is on the buccal.

Tomography

An imaging technique used in panoramic radiography where the x-ray tubehead and receptor rotate around a pivot, blurring structures outside a selected plane while imaging a single layer or section sharply.

Focal Trough

A three-dimensional curved zone in panoramic imaging where structures are imaged clearly and with the greatest sharpness.

Double Image

A panoramic radiographic finding produced when an anatomic structure located behind the moving rotation center is penetrated twice by the x-ray beam.

Ghost Image

An artifact on a panoramic image that occurs when a dense or metallic object located outside the focal plane and close to the tubehead is penetrated twice; it appears indistinct, higher, and larger on the side opposite the true object.

Panoramic Collimator

A lead plate containing an opening shaped like a narrow vertical slit that restricts the beam to a narrow band as it emerges from the panoramic tubehead.

Rare Earth Intensifying Screens

Fluorescent screens that emit green light when struck by x-rays; they are faster and require less radiation exposure than calcium tungstate screens emitting blue light, making them recommended for panoramic imaging.

Lead Apron Artifact

A radiopaque, cone-shaped artifact that obscures diagnostic panoramic structures, occurring when a lead apron is placed too high or when a thyroid collar is improperly used.

Chin Tipped Up Error

A panoramic positioning error occurring when the Frankfort plane is not parallel to the floor (chin too high), producing a 'reverse smile line' and loss of detail in the maxillary incisor region.

Chin Tipped Down Error

A panoramic positioning error occurring when the Frankfort plane is angled downward (chin too low), resulting in an 'exaggerated smile line' with shortened or compromised mandibular incisors.

Teeth Anterior to Focal Trough

A positioning error where the patient bites too far forward on the bite-block, causing the anterior teeth to appear abnormally narrow ('skinny') and out of focus.

Teeth Posterior to Focal Trough

A positioning error where the patient bites too far back on the bite-block, causing the anterior teeth to appear abnormally wide ('fat') and out of focus.

Slumped Posture Error

A panoramic imaging error resulting from the patient's spine not being erect, which creates a triangular or dense radiopacity of the cervical spine in the center of the image.

Cephalostat

A specialized device (also called a craniostat) with ear rods and head holders used in extraoral imaging to precisely stabilize and standardize skull alignment.

Radiographic Grid

A device composed of a series of thin lead strips placed between the patient's head and the film to absorb scattered radiation and prevent film fogging in extraoral radiography.

Lateral Jaw Imaging: Body of Mandible

An extraoral technique to examine impacted teeth, fractures, and lesions in the mandibular body; the head is tipped $15^\circ$ toward the side imaged, and the beam is angled $-15^\circ$ to $-20^\circ$ below the inferior border.

Lateral Jaw Imaging: Ramus of Mandible

An extraoral technique to evaluate impacted third molars, large lesions, and fractures extending into the ramus; the head is tilted $15^\circ$ toward the imaged side with the central ray directed posterior to the third molar area at $-15^\circ$ to $-20^\circ$.

Lateral Cephalometric Projection

An extraoral skull view where the midsagittal plane is perpendicular to the floor and the left side of the head rests against the receptor; primarily used in orthodontics to evaluate facial growth, trauma, and developmental abnormalities.

Waters Projection

An extraoral projection where the patient's chin touches the receptor and the tip of the nose is $\frac{1}{2}$ to $1\,\text{inch}$ away; designed specifically to evaluate the maxillary sinus area.

Submentovertex (SMV) Projection

An extraoral skull view where the head is tipped back so the vertex touches the receptor; used to identify the position of the condyles, demonstrate the base of the skull, and evaluate zygomatic arch fractures.

Reverse Towne Projection

An extraoral view taken with the patient's mouth wide open and the forehead touching the receptor, specifically used to diagnose fractures of the condylar neck and ramus.

Transcranial Projection

An extraoral TMJ projection where the receptor is placed flat over the ear and the central ray is directed $+25^\circ$ vertically and $20^\circ$ forward from $2\,\text{inches}$ above and $0.5\,\text{inch}$ behind the ear canal opening to evaluate the superior condylar surface and articular eminence.

Cone Beam Computed Tomography (CBCT)

A 3D imaging technology utilizing a cone-shaped radiation beam that rotates around the patient's head to acquire raw volumetric data reconstructed into cross-sectional slice images.

Multiplanar Reconstructed Images

The simultaneous visualization of 3D volumetric CBCT data across three orthogonal viewing planes: the axial, coronal, and sagittal planes.

DICOM (Digital Imaging and Communications in Medicine)

The standard file format used for distributing and viewing medical and dental multiplanar reconstructed imaging data across healthcare software systems.