Gpc 1923 Ch 7 Dental X-Ray Film

Front 1

Describe in detail film composition and latent image formation

Back 1

Dental x-ray film serves as a recording medium or image receptor
-Image: a picture or likeness of an object
-Receptor: something that responds to a stimulus

Film composition (4 components)

1) Film base
-flexible piece of polyester plastic 0.2mm
-provide a stable support for the delicate emulsion

2) Adhesive layer
-attach the emulsion to the base
-allows emulsion to stick to the plastic

3) Film emulsion
-A homogenous coating w/ a mixture of gelatine and silver halide crystals attached to both sides of the film base
-halide: a chemical compound that is sensitive to radiation
-Gelatin: used to suspend and disperse millions of microscopic silver halide crystals over the film base
-Halide crystals: The silver halide crystals absorb radiation during exposure and store the energy

4) Protective layer
-a thin coating over the emulsion to protect the emulsion from damage

Latent image formation
-Silver halide crystals (silver bromide and silver iodine) contain various levels of stored energy, depending on the density of the objects in the are exposed
-the stored energy forms a pattern know as the latent image (a duplicate image of the teeth on film)
-The latent image cannot be seen until chemical processing to produce a visible image
-When photons (x-ray) strike the emulsion, some silver bromide crystals are exposed while others are not
-crystals exposed are ionized, and the silver and the bromine atoms are separated
-Irregularities in the structure of the exposed crystal (sensitivity specks) attract the silver atoms
-Sensitivity speck attracts electrons (-) which then attract silver ions (+). The collection of neutral silver atoms (Ag) create latent image centers

Front 2

List and describe the different types of x-ray film used in dentistry

Back 2

Intraoral film: in the mouth for exposure and need radiation

Extraoral film: outside of person

Duplicating film: does not recieve x-ray

Front 3

Define intraoral film and describe intraoral film packaging

Back 3

-Placed inside the mouth and used to examine the teeth and supporting structures

Packaging:
-used to protect the film from light and moisture
-boxes are labeled with the type of film, film speed, film size, number of films per packet, total number of films enclosed, and expiration date
-4 components: x-ray film, paper film wrapper, lead foil sheet, outer package wrapping

1) X-ray film
-1 or 2 film packet
-id dot used to determined film orientation
-id dot located in corner of film
-id dot will be raised on one side and indented on other
-critical to determine right and left sides of patients mouth
-Double film packet used when duplicate radiographs are indicated

2) Paper film wrapper
-A black protective sheet to cover the film and protect it from light
-looks and feels like construction paper

2) Lead foil sheet
-Located behind the film wrapped in black protective paper
-shields the film from back scattered (secondary) radiation that creates film fog.
-has a pattern that is visible on reversed film

4) Outer Package wrapping
-soft vinyl or paper to seal the contents and protect them from light or moisture
-tube side (front side of film)
=solid white w/ a raised bump corresponding to the identification dot on x-ray film
=solid white side should face the tubehead during the exposure

Label side:
-color coded to identify b/w 1 and 2 film packs and according to film speed
-has a flap used to open the film packet prior to processing

Front 4

Identify the types and sizes of intraoral film available

Back 4

3 types of intraoral film
1) Periapical film
2) Bitewing film
3) Occlusal film

Periapical- used to examine the entire tooth and 2 mm of supporting bone. 2mm for posterior, 4mm for anterior

Bitewing film:
-used to examine the crowns of both maxillary and mandibular teeth on one film
-used for examining interproximal surfaces
-can use stick-on tabs of bitewing loops

Occlusal film:
-larger film used for examination of large areas of the maxilla or mandible

Film sizes:
Periapical film:
-0: used for small children
-1 used for anterior teeth for adults
-2 standard film, used for anterior and posterior teeth in adults

Bitewing film
-0: used for posterior teeth in small children
-1: positioned vertically to examine anterior teeth in adults
-2: used horizontally/vertically to examine posterior teeth in adults
-3: shows all posterior teeth on one side of the arch (not recommended, can't see all open contacts)

Occlusal film:
-4: used to examine large areas of the maxilla or mandible (almost 4x the size of standard #2 film)

Front 5

Discuss film speed

Back 5

-The amount of radiation required to produce a radiograph of standard density
-Determined by:
=the size of silver halide crystals
=the thickness of the emulsion
=the presence of special radiosensitive dyes
-a fast film requires less radiation exposure
=larger crystals with increase silver bromide in emulsion
-the current speeds available are D and F
=E speed is off the market
=F speed film (insight film) requires 60% of the exposure time as D speed film

Front 6

Discuss the differences between intraoral film and extraoral film

Back 6

Extraoral film:
-placed outside the mouth during an exposure
-used to examine large areas of teeth and jaws
-panoramic film
=wide view of upper and lower jaws
-cephalometric film
=bony and soft tissue areas in profile (from the side)

Front 7

Describe the difference between screen and nonscreen films

Back 7

Screen films:
-Requires the use of a screen in a cassette with phosphors for exposure
=the film is sensitive to fluorescent light, rather than direct exposure to x-radiation
-some screen films are sensitive to blue light and some are sensitive to green light
=the film-screen combinations must match

Nonscreen film:
-Doesn't require the use of a screen; it is exposed directly to x-rays
-not used in dentistry

Front 8

Describe the use of intensifying screens and cassettes

Back 8

-screen films are used with intensifying screens and cassettes

Intensifying screens:
-a device that transfers x-ray energy into visible light
=visible light then exposes the screen film
=this lowers the radiation dose to the patient
-Screen film is secured in a cassette b/w 2 intensifying screens of matching size
=intensifying screen is a smooth plastic sheet coated with fluorescent crystals called phosphors
-2 types
1) Calcium tungstate screens-have phosphors that emit BLUE light
2) Rare earth screens (less radiation)-have phosphors that emit GREEN light.

Cassettes:
-Houses the film and the intensifying screens
-flexible or rigid
-light tight and hold the intensifying screen in contact with film
-without contact of film and screen, image will lack sharpness of the image in that area
-a rigid cassette has a plastic front cover to allow the photons to pass thru
=the back cover is metal to reduce scatter radiation
-the cassette is marked with an L and an R for orientation

Front 9

Describe duplicating film

Back 9

-Different type of film than radiographic film
-used to make copies of original
=the longer it is exposed, the lighter the film will be
=used for referrals and for the submission of insurance claims
-Duplicating film has emulsion on one side only
=it is not exposed to x-rays
=must use duplicator equipment and white light

Front 10

Discuss proper film storage and protection

Back 10

-Film is affected by heat, humidity, and radiation
=film should be kept in a cool, dry place
=film has an expiration date