Dental Radiation Health and Safety – Vocabulary Review

A comprehensive set of key vocabulary terms and definitions covering radiation physics, safety, equipment, imaging techniques, processing, errors, and regulatory considerations for dental radiography.

Radiation (General)

Energy capable of producing ions by removing or adding an electron to an atom.

X-ray Photon

Weightless, chargeless bundle of electromagnetic energy that travels at the speed of light and can cause ionization.

Natural Background Radiation

Radiation from cosmic rays, the sun, and terrestrial radioactive materials present in earth and air.

Artificial (Man-Made) Radiation

Radiation produced by human activity; medical imaging is the largest contributor.

Electromagnetic Spectrum

Continuum of all electromagnetic waves; x-rays lie between ultraviolet and gamma rays with very short wavelengths.

Ionization

Process in which an atom gains or loses an electron, creating charged particles.

Primary Radiation

The useful x-ray beam produced at the anode target of the tubehead.

Secondary Radiation

X-radiation created when the primary beam interacts with matter.

Scatter Radiation

Form of secondary radiation that has been deflected from its original path by matter.

Ionizing Radiation (Biological)

Radiation capable of causing harmful biological changes in tissues.

Latent Period

Time between radiation exposure and appearance of observable clinical signs.

Period of Injury

Phase during which cellular damage from radiation becomes apparent.

Recovery Period

Time in which some radiation-induced damage is repaired by the body.

Somatic Effects

Radiation effects seen in the irradiated individual, not in future generations.

Genetic Effects

Radiation effects not seen in the exposed person but passed to offspring via reproductive cells.

Radiosensitive Organs

lymphoid tissue, bone marrow, WBCs, reproductive cells, immature cells.

Radioresistant Tissues

mature bone, muscle, nerve, hair.

Dental Radiation-Exposed Organs

Skin, thyroid gland, lens of the eye, and bone marrow.

Control Panel

Part of x-ray unit housing on–off switch, indicator light, exposure button, and mA/kVp/time controls.

Extension Arm

Hollow arm that positions the tubehead and contains electrical wires.

Tubehead

Metal housing containing the x-ray tube, insulating oil, aluminum discs, lead collimator, and PID.

Milliampere (mA)

Control regulating the quantity of electrons; ↑ mA = ↑ number of x-rays produced.

Exposure Time (ET)

Duration of x-ray production; ↑ ET = ↑ number of x-rays.

Kilovoltage Peak (kVp)

Control of beam quality/penetrating power; ↑ kVp = faster electrons and more penetrating x-rays.

PID (Position-Indicating Device)

Lead-lined cylinder or rectangle that directs the x-ray beam; 16-inch length gives least divergence.

Aluminum Filter/Disc

0.5–3 mm aluminum sheet removing long-wavelength, low-energy x-rays from the beam.

Lead Collimator

Lead plate with round or rectangular opening that restricts size and shape of the x-ray beam.

X-ray Tube

Glass vacuum tube housing cathode and anode where x-rays are generated.

Cathode

Negative electrode with tungsten filament producing electrons when heated.

Anode

Positive electrode with tungsten target that receives electrons and produces x-rays.

Step-Down Transformer

Device that reduces incoming voltage to 3–5 V to heat cathode filament.

High-Voltage Circuit

65,000–100,000 V circuit that accelerates electrons from cathode to anode when exposure button is pressed.

NOMAD

Handheld portable dental x-ray device requiring lead shield and, in Virginia, no badge under 2021 exemption.

OSHA Ionizing Radiation Standard

29 CFR 1910.1096; mandates area surveys, restricted zones, personal monitors, and caution signage.

ALARA Concept

"As Low As Reasonably Achievable"—principle that all radiation doses should be minimized.

Thyroid Collar

Lead-lined shield protecting the thyroid during intraoral exposures.

Lead Apron

Protective garment shielding patient’s trunk from scatter radiation.

F-Speed Film

Fastest intraoral film speed, most effective in reducing patient dose (faster than D-speed).

Film/Sensor Holding Device

Instrument that stabilizes receptor in the mouth, ensuring correct position and reduced retakes.

Maximum Permissible Dose (MPD)

Occupational: 5 rem / 0.05 Sv per year; Non-occupational & pregnant worker: 0.1 rem / 0.001 Sv per year.

Film Packet

Assembly containing x-ray film, paper wrapper, lead foil sheet, and outer moisture-proof cover.

Intraoral Film Sizes

0 pediatric, #1 narrow anterior, #2 standard adult, #3 long bite-wing, #4 occlusal.

Film Storage Conditions

50–70 °F, 30–50 % humidity, away from radiation, and used before expiration date.

Digital Sensor (Direct)

Wired device that captures x-ray image and transmits to computer instantly.

Phosphor Plate (Indirect)

Reusable plate storing x-ray energy; scanned to produce digital image.

Advantages of Digital Imaging

Reduced exposure, instant viewing, image enhancement, no chemicals, easier storage and sharing.

Bite-Wing Image

Intraoral radiograph showing crowns of maxillary and mandibular teeth to detect interproximal caries and bone level.

Periapical Image

Intraoral radiograph showing entire tooth and 2–3 mm beyond apex.

Occlusal Image

Large intraoral film taken perpendicular to occlusal plane to view broad areas or locate objects.

Panoramic Image

Extraoral film giving overall view of both arches; useful for gaggers but less detail than intraoral films.

Cassette

Light-tight holder for extraoral film or phosphor plate and intensifying screens.

Cephalometric Image

Lateral skull radiograph commonly used by orthodontists for growth assessment.

Cone Beam CT (CBCT)

3-D imaging modality used to evaluate bone volume and quality, e.g., for implants.

Bite-Wing Tab

Cardboard or adhesive wing that patient bites on to stabilize film.

Vertical Bite-Wing

Bite-wing taken with receptor placed vertically to better evaluate periodontal bone loss.

Full Mouth Series (FMX)

Set of 14–19 intraoral images covering all tooth-bearing areas; includes periapicals and bite-wings.

Paralleling Technique

Technique in which receptor is parallel to long axis of tooth and central ray is perpendicular to both.

XCP Holder

Color-coded device with bite-block, aiming ring, and indicator rod used in paralleling technique.

Bisecting Technique

Technique where central ray is directed perpendicular to an imaginary bisector between tooth long axis and receptor.

Safelight

7.5–15 W red-orange filtered light at least 4 ft from work surface, safe for film handling.

Automatic Processor

Machine that transports film through developer, fixer, wash, and dry cycles automatically.

Daylight Loader

Light-tight glove box attachment allowing film loading into processor in room light.

Duplicating Film

Single-emulsion film used with a film duplicator to make copies of radiographs.

Cone-Cut Error

Clear, unexposed area on film caused by incorrect PID alignment.

Reversed Film Error

Herringbone pattern and light film produced when film is placed backward.

Overlapping Contacts

Result of incorrect horizontal angulation where interproximal spaces are not open.

Overexposed Film

Radiograph that appears too dark from excessive mA, kVp, or exposure time.

Underexposed Film

Radiograph that is too light due to insufficient exposure factors.

Foreshortening

Roots appear short from excessive vertical angulation.

Elongation

Roots appear long from insufficient vertical angulation.

Film Fog

Overall grayness lacking contrast due to light leaks, outdated film, or high developer temperature.

Ghost Image

Faint duplicate image on panoramic caused by metallic object not removed (e.g., earrings).

Reverse Smile Line

Panoramic error with frown appearance caused by chin tipped too high.

Cervical Spine Shadow

Radiopacity in center of panoramic when patient does not stand straight.

Film Mount

Cardboard or plastic frame used to arrange and label processed radiographs.

Identification Dot

Raised marker on intraoral film used for orientation; placed toward occlusal/incisal edge when mounting.

HIPAA

Federal law requiring protection and privacy of patients’ health information; consent needed before sharing radiographs.