Dental X-Ray Film Study Notes

Dental X-Ray Film: Principles and Techniques

Overview

  • Purpose of Chapter

    • Define film composition.

    • Detail latent image formation.

    • Describe the types of intraoral, extraoral, and duplicating film used in dental radiography.

    • Discuss film storage and protection.

Lesson 9.1: Dental X-Ray Film (1 of 3)

  • Key Learning Outcomes:

    • Define terms associated with dental x-ray film.

    • Discuss the importance of radiographers being familiar with dental x-ray film.

    • Describe film composition and latent image formation.

    • List different types of x-ray films used in dentistry.

Lesson 9.1: Dental X-Ray Film (2 of 3)

  • Intraoral Film

    • Definition: Film placed inside the mouth to examine teeth and supporting structures.

    • Packaging: Designed to protect the film from light and moisture, typically in plastic trays or cardboard boxes containing 25, 100, or 150 films.

    • Film Types and Sizes:

    • Different types available, e.g., periapical, bite-wing, and occlusal.

    • Sizes: 0 (children), 1 (anterior teeth in adults), 2 (standard for adults), 3 (long bite-wing), 4 (large areas).

  • Extraoral Film

    • Definition: Film placed outside the mouth during exposure.

    • Types of Extraoral Film:

    • Panoramic film: Provides a wide view of upper and lower jaws.

    • Cephalometric film: Shows bony and soft tissue areas in profile.

    • Packaging: Boxed in quantities of 50 or 100 films; moisture-proof not required.

Lesson 9.1: Dental X-Ray Film (3 of 3)

  • Screen and Nonscreen Films:

    • Screen Films: Require a screen in a cassette for exposure; sensitive to fluorescent light.

    • Nonscreen Films: Directly exposed to x-rays and not recommended for dental use.

  • Duplicating Film: Used to make copies of x-ray films; exposed to light, not x-rays.

  • Film Storage and Protection:

    • Film deteriorates due to heat, humidity, and radiation; store in a cool, dry place, observing its expiration date.

Detailed Film Composition

  • Constituents of Dental X-Ray Film:

    • Film Base:

    • Made of 0.2 mm-thick polyester plastic.

    • Provides strength and stable support for the emulsion.

    • Adhesive Layer:

    • Attaches the emulsion to the base.

    • Film Emulsion:

    • Coating of gelatin and silver halide crystals on both sides of the base.

    • Gelatin: Suspends millions of microscopic silver halide crystals.

    • Silver Halide Crystals: Absorb radiation and store energy during exposure.

    • Protective Layer:

    • Thin coating over emulsion to protect it from damage.

Latent Image Formation

  • Process Overview:

    • Silver halide crystals store energy based on the density of the exposed objects, forming a latent image, which is invisible until chemically processed.

    • Mechanism:

    • When photons strike the emulsion, some crystals become ionized, separating silver and bromine atoms.

    • Irregularities in the lattice structure attract silver atoms, forming latent image centers.

Types of Dental X-Ray Film

  • Intraoral Films:

    • Periapical Film: Shows the entire tooth and 2 mm of supporting bone.

    • Bite-Wing Film: Captures crowns of both arches and is used to examine interproximal surfaces; can utilize stick-on tabs or loops.

    • Occlusal Film: Larger film used for examining extensive areas of the maxilla or mandible.

  • Film Sizes:

    • Periapical:

    • Size 0: For small children.

    • Size 1: For anterior teeth in adults.

    • Size 2: Standard for anterior and posterior teeth in adults.

    • Bite-Wing:

    • Size 0: For posterior teeth in small children.

    • Size 2: For older children or adults.

    • Size 3: Longer and narrower, used only for bite-wing, not currently recommended if all contacts cannot be opened on one film.

    • Occlusal Film:

    • Size 4: For examining large areas, nearly four times the size of Size 2 film.

Intraoral Film Speed

  • Definition: Amount of radiation required to produce a dental image of standard density.

  • Determining Factors:

    • Size of silver halide crystals.

    • Thickness of the emulsion.

    • Presence of special radiosensitive dyes.

  • Speed Ratings: From A (slowest) to F (fastest); only D, E, E/F, and F are used for intraoral radiography.

Extraoral Films

  • Overview: Placed outside the mouth during exposure to evaluate larger areas.

  • Types:

    • Screen Film: Requires a screen in a cassette for exposure to fluorescent light, corresponds to phosphors.

    • Nonscreen Film: Directly exposed to x-rays; not recommended.

Extraoral Film Equipment

  • Intensifying Screens: Convert x-ray energy into visible light, reducing radiation dose to the patient. Types include:

    • Calcium Tungstate Screens: Emit blue light.

    • Rare Earth Screens: Emit green light and require less radiation.

  • Cassette: Holds the film and screens; must be light-tight to maintain film sharpness.

Duplicating Film

  • Definition: Different from radiographic film; used to make copies. It has emulsion on one side, exposed only to light, and is not meant for x-ray exposure.

Film Storage and Protection

  • Recommendations:

    • Store in a cool, dry environment, monitoring expiration dates to avoid degradation of film quality.

Key Points for Radiographers

  • Understanding film composition, types, speed, and storage is crucial for effective dental imaging and patient safety.