DH120 LO6: Film Composition

What is the function of the Adhesive Layer?

It attaches the emulsion to the base and covers both sides of the film base

What are the four basic components of dental x-ray film?

Film base, adhesive layer, film emulsion, and protective layer

What is the composition of film, and how many components are there?

Dental x-ray film has four basic components: film base, adhesive layer, film emulsion, and protective layer

Describe the Film Base component of dental x-ray film.

A 0.2 mm-thick piece of polyester plastic that is transparent and exhibits a slight blue tint

What is the function of the Film Base?

It provides strength and stable support for the delicate emulsion and is designed to withstand heat, moisture, and chemical exposure

When is the adhesive layer applied to the film?

Before the emulsion is applied

What is the Film Emulsion?

A homogenous coating with a mixture of gelatin and silver halide crystals attached to both sides of the film base by the adhesive layer

What does the film emulsion give the film?

Greater sensitivity to x-radiation

What is the function of the Protective Layer?

It is a thin coating over the emulsion that protects the emulsion from damage, including manipulation, mechanical damage, and processing damage

What happens when silver halide crystals absorb x-radiation during exposure?

They store energy from the radiation

What determines the level of stored energy in silver halide crystals?

The density of the objects in the area exposed

What is the pattern formed by the stored energy in the silver halide crystals called?

The latent image

When can the latent image be seen?

Not until chemical processing to produce a visible image

What occurs to the silver halide crystals positioned behind a dense object like an amalgam filling?

They receive almost no radiation and are not energized because the amalgam filling is dense and absorbs the energy

What occurs to the silver halide crystals corresponding to air space (no density)?

They receive more radiation and are highly energized

What is the name for the invisible image created within the emulsion by the stored energy pattern?

The latent image

What happens to the silver halide crystals that are exposed when photons strike the emulsion?

They are ionized, and the silver and bromine atoms are separated

What are sensitivity specks?

Irregularities in the lattice structure of the exposed crystal that attract the silver atoms

What are latent image centers?

Aggregates of neutral silver atoms formed at the sensitivity specks

What are the three main types of dental x-ray film?

Intraoral film, Extraoral film, and Duplicating film

What is Intraoral film used for?

To examine the teeth and supporting structures, placed inside the mouth

What is Extraoral film used for?

To examine large areas of teeth and jaws, placed outside the mouth during an exposure

What are the four components of intraoral film packets?

X-ray film, Paper film wrapper (a black protective sheet), Lead foil sheet, and Outer package wrapping

What is the function of the black protective paper film wrapper inside the packet?

To cover the film and protect it from light

Why is the X-ray film inside the packet typically a double emulsion film?

It requires less radiation exposure to produce an image

What is the purpose of the identification dot on the intraoral x-ray film?

It is used to distinguish between the left and right sides of the client

Where is the Lead foil sheet located within the intraoral film packet?

Behind the film wrapped in black protective paper

What is the function of the Lead foil sheet?

It shields the film from back scattered radiation that creates film fog

What happens if the intraoral film packet is placed in the mouth backward and exposed?

A pattern embossed on the lead foil sheet is visible on a processed radiograph

Describe the Tube side of the outer package wrapping.

It is solid white with a raised bump corresponding to the identification dot on the x-ray film, and this side should face the tubehead during an exposure

What is the function of the Label side of the outer package wrapping?

It is color coded to identify between one and two film packs and according to film speed, and it has a flap used to open the film packet prior to processing

What is Periapical film used to examine?

The entire tooth and 2 mm. of supporting bone

What is Bite-wing film used to examine?

The crowns of both maxillary and mandibular teeth on one film, specifically used for examining interproximal surfaces

What is Occlusal film used for?

Examination of large areas of the maxilla or mandible

What size periapical film is used for small children?

Size 0

What size periapical film is used for anterior teeth in adults?

Size 1

What size periapical film is the standard film used for anterior and posterior teeth in adults?

Size 2

What size bite-wing film is used for posterior teeth in small children?

Size 0

What size bite-wing film is used horizontally or vertically to examine posterior teeth in adults?

Size 2

What is Bite-wing film size 3 known for?

It shows all posterior teeth on one side of the arch, but it is not recommended because all the contacts cannot be opened on one film

What is film speed defined as?

The amount of radiation required to produce a radiograph of standard density

How do you determine the film speed?

Film speed is determined by the size of silver halide crystals, the thickness of the emulsion, and the presence of special radiosensitive dyes

How does the radiation exposure requirement change with fast film?

A fast film requires less radiation exposure

What are the current intraoral film speeds available?

D, E, and F

How much less exposure time does F speed film require compared to D speed film?

About half the exposure time

Name the two common types of extraoral film.

Panoramic film and Cephalometric film

What type of image does Panoramic film provide?

A wide view of the upper and lower jaws

What type of image does Cephalometric film provide?

Bony and soft tissue areas in profile (from the side)

Are extraoral films typically enclosed in moisture-proof packs?

No

What are the two types of extraoral film packaging regarding exposure method?

Screen film and Non-screen film

What is required for Screen film exposure?

The use of a screen in a cassette with phosphors

To what is screen film sensitive, rather than direct x-radiation exposure?

Fluorescent light

What must match when using screen films?

The film-screen combinations

What are the color sensitivities of screen films?

Some screen films are sensitive to blue light, and some are sensitive to green light

What film type does not require the use of a screen and is exposed directly to x-rays?

Nonscreen Film

Is Nonscreen Film recommended for dental use?

No

What is an intensifying screen?

A device that transfers x-ray energy into visible light

What does the visible light produced by the intensifying screen do?

It exposes the screen film

What is the benefit of using an intensifying screen?

It lowers the radiation dose to the patient

Which type of view is the intensifying screen used in?

Extraoral views (with screen film)

Where is a screen film secured when using intensifying screens?

In a cassette between two intensifying screens of matching size

What minute fluorescent crystals coat the smooth plastic sheet of the intensifying screen?

Phosphors

What are the two types of intensifying screens and the color light they emit?

Calcium tungstate screens (blue light) and Rare earth screens (green light)

Which type of intensifying screen requires less radiation?

Rare earth screens (green light)

What is a cassette used for?

To hold the film and the intensifying screens

Why must a cassette be light tight and hold the intensifying screen in contact with the film?

Otherwise, the lack of contact between the film and cassette will result in a lack of sharpness of the image in that area

Describe the back cover of a rigid cassette.

It is metal to reduce scatter radiation

Describe the front cover of a rigid cassette.

It is plastic to allow the photons to pass through

How is a cassette marked for orientation?

It is marked with an L and an R

What is Duplicating film used for?

To make copies of radiographs

How does the exposure time affect the resulting duplicating film (when used with a duplicator)?

The longer it is exposed, the lighter the film will be

What feature of duplicating film makes it different from radiographic film regarding emulsion?

It has an emulsion on one side only

Why does a duplicating film not contain a lead foil?

It is not exposed to x-rays

What must duplicating film be used with, since it is not exposed to x-rays?

A film duplicator

What three factors negatively affect film storage?

Heat, humidity, and radiation

Where should film be kept?

In a cool, dry place

What material must a cassette be made of in the back to reduce scatter radiation?

Metal

What are two applications for which duplicating film is recommended?

Referrals and the submission of insurance claims

What specific structure of the exposed silver halide crystal attracts the separated silver atoms?

Sensitivity specks

How is a photographic image produced on dental x-ray film?

When it is exposed to x-rays that have passed through teeth and adjacent structures

What stimuli cause images to be recorded on the dental x-ray film?

Energy in the form of x-radiation or light