1. Chapter 39 Dental Film and Processing Radiographs
Copyright 2003, Elsevier Science (USA).
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2. Introduction
Film processing procedures have a direct effect on the quality of a radiograph.
The dental assistant must be knowledgeable about the types of dental film and film-holding devices and must also thoroughly understand the processing procedures to produce high-quality diagnostic dental radiographs. B
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3. Terminology
Film is the correct term to use before it has been processed. The film is in the packet, the film is placed in the bite-block, and the film is exposed and processed.
After the film has been processed, it becomes a radiograph. B
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4. Types of Film Holders and Beam Alignment Devices
A wide variety of types of intraoral film holders are available on the market today.
A basic film holder is the disposable styrofoam bite-block with a backing plate and a slot for film retention.
The EEZEE-Grip (formerly the Snap-A-Ray) is a double-ended instrument that holds the film between two serrated plastic grips that can be locked into place.
The Endoray device is used to take radiographs when instruments are in the canal.
Uni-bite devices are made by the Rinn Corporation. B
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5. Fig. 39-1 Styrofoam-type disposable bite-block.
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6. Fig. 39-2 The EEZEE-Grip (formerly the Snap-A-Ray) film holder.B
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7. Fig The Endoray is shown with endodontic instruments placed in wax to demonstrate placement of the film holder when instruments are in the canal.
Fig. 39-3 B
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8. Fig. 39-4 The new Rinn XCP are color-coded for easier assembly
Fig The new Rinn XCP are color-coded for easier assembly. The red instruments are for bitewing placement, the yellow are for posterior placement, and the blue are for anterior placement.
Fig. 39-4 B
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9. Dental X-Ray Film
Film used in dental radiography is photographic film that has been adapted for dental use.
A photographic image is produced on dental x-ray film when it is exposed to x-rays that have passed through teeth and adjacent tissues.
The dental assistant must understand the composition of x-ray film and latent image formation that result in increased patient exposure to x-rays. B
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10. Film Composition
Intraoral dental film is made up of a semiflexible, clear cellulose acetate film base that is coated on both sides with an emulsion of silver bromide, silver halide, and silver iodide that are sensitive to radiation. B
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11. Latent Image Formation
When the radiation interacts with the silver halide crystals in the film emulsion, the image on the film is produced.
The image is not visible before processing and is called the latent image.
An example of another type of latent image is fingerprints. If you touch an item, you leave your fingerprints even though you cannot see them on that item. However, when that item is treated, your fingerprints become visible. B
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12. Film Speed
Film speed refers to the amount of radiation required to produce a radiograph of standard density (darkness). Film speed is determined by the following:
The size of the silver halide crystals.
The thickness of the emulsion.
The presence of special radiosensitive dyes. B
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13. Film Speed- cont’d
The film speed determines how much exposure time is required to produce the image on the film.
A fast film requires less radiation, and the film responds more quickly because the silver halide crystals in the emulsion are larger.
The larger the crystals, the faster the film speed. This is the same principal as film speed on photographic film.
The “F” speed is the newest and fastest film on the market today and will reduce radiation exposure to the patient by 20% to 60% compared to E-speed film and D- speed film. B
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14. Fig. 39-7 “Insight” is the new F-speed film available from Kodak
Fig “Insight” is the new F-speed film available from Kodak. (Courtesy Eastman Kodak Co, Rochester, NY.)
Fig. 39-7 B
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15. Types of Dental Film
There are three types of x-ray film used in dental radiography:
Intraoral film
Extraoral film
Duplicating film B
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16. Intraoral Film
Intraoral film is named because it is placed inside the mouth during x-ray exposure.
The intraoral x-ray film has emulsion on both sides of the film instead of emulsion on only one side because it requires less radiation to produce an image.
To protect the film from light and moisture, the film is packaged and referred to as the film packet. B
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17. Contents of the Film Packet
Intraoral film packets are typically available in boxes of 25, 100, or 150 films.
The film packet may contain one film (one-film packet) or two films (two-film packet).
The boxes of film are labeled with the following information: the type of film, film speed, number of films per individual packet, the total number of films in the box, and the film expiration date.
On one corner of the film packet is a small raised bump known as the identification dot. B
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18. Fig. 39-8 Contents of a dental film packet: lead foil, x-ray film, and black paper.
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19. Fig. 39-5 Cross-sectional diagram of film base and emulsion.
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20. The Film Packet
The black paper film wrapper inside the film packet is a protective sheet that covers the film and shields it from light.
The thin lead foil sheet is positioned behind the film to shield the film from back-scattered (secondary) radiation that results in film fog.
The outer packet wrapping is a soft vinyl or paper wrapper that seals the film packet, protective black paper, and lead foil sheet.
The tube side is solid white and has the raised bump on one corner. When placed in the mouth, the white side (tube side) of the film must face the teeth and tubehead, and the raised dot must be toward the incisal/occlusal surface. B
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21. Fig A, The lead foil insert in this package has a raised diamond pattern across both ends. B, Radiograph showing the raised diamond pattern from the lead foil backing when the film is positioned backwards.
Fig AB B
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22. Fig. 39-10 The white side of the film packet faces the tube
Fig The white side of the film packet faces the tube. A, Size 4 occlusal film. B, Size 2 film; size 1 film.
Fig AB B
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23. Sizes of Film Intraoral film packets come in five basic sizes:
Child (#0)
Narrow anterior (#1)
Adult size (#2)
Preformed bitewing (#3)
Occlusal (#4) B
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24. Extraoral Film
An extraoral film is one that is placed outside of the mouth during x-ray exposure.
Extraoral films are used to examine large areas of the head or jaws.
Examples of common extraoral films include panoramic and cephalometric films.
A panoramic film shows a panoramic (wide) view of the upper and lower jaws on a single radiograph.
A cephalometric film shows the bony and soft tissue areas of the facial profile. B
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25. Fig. 39-11 A panoramic film. (Reprinted courtesy Eastman Kodak Co, Rochester, NY.)B
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26. Fig. 39-12 A cephalometric film
Fig A cephalometric film. (Reprinted courtesy Eastman Kodak Co, Rochester, NY.)
Fig B
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27. Extraoral Film Packaging
Extraoral radiography uses a film-screen system. This means that the film is used in combination with intensifying screens.
Extraoral film is supplied in boxes of 50 or 100 films.
Extraoral film used in dental radiography is available in 5 x 7 inch and 8 x 10 inch size.
Extraoral film is not supplied in film packets.
The film is stacked in the box much like a deck of cards.
Because there is no wrapper to protect the film from exposure to light, the film must be loaded into a cassette in the darkroom. B
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28. Fig. 39-13 Boxes of extraoral radiography film
Fig Boxes of extraoral radiography film. (Courtesy Eastman Kodak Co, Rochester, NY.)
Fig B
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29. Film Cassette
A cassette is a plastic or metal case used in extraoral radiography to hold the film and protect it from exposure to light. Cassettes are available in rigid or flexible styles.
To tell the patient’s left from the right as on intraoral films, the front of the cassettes must be marked with lead letters “L” (left side) or “R” (right side).This is because there is no raised dot on extraoral film.
The front side of the cassette must always face the patient during exposure. B
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30. Fig. 39-14 The dental assistant removes a film from a flexible film cassette.
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31. Intensifying Screen
An intensifying screen intensifies or increases the effect of the radiation and thus decreases the amount of exposure time needed.
The intensifying screen is coated with a material called phosphor that gives off light when struck by x-radiation.
The film inside the cassette is sandwiched between the intensifying screens and is affected by both the light produced by the phosphor and the x-radiation.
However, there is a slight loss of image detail as a result of the intensified x-ray beam because the light produces a halo effect at the edge of the image field. B
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32. Types of Screen Film Used in Extraoral Radiography
Green-sensitive: This type of film is used with cassettes that have rare earth intensifying screens.
Blue-sensitive: This type of film is used with cassettes that have calcium tungstate intensifying screens. B
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33. Fig. 39-15 Rigid film cassette with an intensifying screen.B
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34. Duplicating Radiographs
Special duplicating film and a duplicating machine is necessary to duplicate radiographs.
Duplicating film is used only in a darkroom setting and is never exposed to x-rays.
The duplicating machine produces white light to expose the film. Because the film is light-sensitive, the duplication process is performed in the darkroom with the safelight.
The longer the duplicating film is exposed to light, the lighter it will become. This is the opposite of x-ray film, which becomes darker when exposed to light. B
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35. Fig. 39-16 Example of a film duplicator.B
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36. Dental X-Ray Film Processing
Processing is a series of steps that changes the latent image on the exposed film into a radiograph by producing a visible image on the film.
Proper processing is just as important as the exposure technique in producing diagnostic-quality radiographs.
Radiographs that are nondiagnostic because of poor processing techniques must be retaken, and the patient will be exposed to unnecessary radiation.
In many practices, intraoral films are processed in an automatic processor; however, it is still necessary to know how to process the film manually. B
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37. Five Steps in Processing Dental Radiographs:
Development
Rinsing
Fixation
Washing
Drying B
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38. Developing Developing is the first step in processing films.
A chemical solution called the developer is used.
The purpose of the developer is to chemically reduce the exposed silver halide crystals into black metallic silver.
The developer solution also softens the film emulsion during this process. B
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39. Rinsing
Rinsing the films is necessary to remove the developer from the film so that the development process stops.
Usually, agitating the film rack for 20 seconds is sufficient.
This must be done under safelight conditions. B
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40. Fixing
The acidic fixing solution removes the unexposed silver halide crystals from the film emulsion.
The fixer also hardens the film emulsion during this process.
For permanent fixation, the film is kept in the fixer for a minimum of 10 minutes.
However, films may be removed from the fixing solution after 3 minutes for viewing.
Films that are not properly fixed will fade and turn brown in a short time.
Leaving films in the fixer for a long time (i.e., over a weekend) can remove the image from the film. B
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41. Washing Following fixation, a water bath is used to wash the film.
The washing step requires about 20 minutes to thoroughly remove all excess chemicals from the emulsion. B
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42. Drying The final step in film processing is the drying of the films.
Films may be air-dried at room temperature in a dust-free area or placed in a heated drying cabinet.
Films must be completely dried before they can be handled for mounting and viewing. B
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43. Film Processing Solutions
Film processing solutions are available in the following forms:
Powder
Ready-to-use liquid
Liquid concentrate B
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44. Fig. 39-17 Kodak developer and fixer concentrated solutions
Fig Kodak developer and fixer concentrated solutions. (Courtesy Eastman Kodak Co, Rochester, NY.) B
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45. The Darkroom
The term light-tight is often used to describe the darkroom.
To be light-tight, no light leaks can be present.
When you are in the darkroom with the light turned off, no white light should be seen.
X-ray film is extremely sensitive to visible white light.
Any leaks of white light can cause film fog. A fogged film appears dull gray, lacks contrast, and is nondiagnostic. B
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46. Types of Darkroom Lighting
Room lighting: An overhead white light that provides adequate lighting when performing tasks such as cleaning, restocking materials, and mixing chemicals is required.
Safelighting: A safelight is a low-intensity light in the red-orange spectrum. Safelighting provides enough illumination in the darkroom to process films safely without exposing or damaging the film. B
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47. Types of Darkroom Lighting- cont’d
There must be a safe distance between the light and the working area, and to work quickly to keep the exposure to the safelight as short as possible.
Unwrapped films that are left too close to the safelight or exposed to the safelight for more than 2 to 3 minutes appear fogged.
A safelight must be placed a minimum of 4 feet away from the film and working area. B
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48. Fig. 39-18 A minimum distance of 4 feet must exist between the safelight and the working area.
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49. Processing Tanks
Manual processing is a method that is used to develop, rinse, fix, and wash dental x-ray films.
The essential piece of equipment required for manual processing is a processing tank.
The processing tank is divided into compartments to hold the developer solution, water bath, and fixer solution.
A processing tank has two insert tanks and one master tank. B
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50. Fig. 39-19 Processing tanks showing developing and fixing tanks inserts in bath of running water.
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51. Requirements for a Darkroom
Be kept clean at all times.
Infection control items (i.e. gloves, disinfectant, spray, and paper towels).
Container, labeled with a biohazard label, for contaminated film packets or barriers.
Recycle container for lead foil pieces; lead foil should not be thrown in the trash.
A “light-tight room.”
Processing tanks for the developer and fixer solution and a circulating water bath. B
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52. Requirements for a Darkroom- cont’d
Running water with mixing valves to adjust the temperature.
Both a safelight and a source of white (normal) light.
An accurate timer.
An accurate floating thermometer.
Stirring rods or paddles to mix the chemicals and equalize the temperature of the solutions.
Safe storage space for chemicals.
Film hangers.
A film-drying rack and a film dryer. B
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53. Automatic Processor
Automatic film processing is a fast and simple method used to process dental x-ray films.
Other than opening the film packet, the automatic processor automates all film processing steps. B
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54. Automatic Processor- cont’d
Automatic film processing requires only 4 to 6 minutes to develop, fix, wash, and dry a film, whereas manual processing techniques require approximately 1 hour.
The automatic processor maintains the correct temperature of the solutions and adjusts the processing time.
Providing the automatic processor is maintained properly, there is less chance of errors during film processing.
Many dental offices that have automatic processors still maintain manual processing equipment as a stand-by if the automatic processor malfunctions. B
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55. Components of the Automatic Processor
The processor housing covers all of the component parts.
The film feed slot is the the unwrapped films are inserted into the automatic processor.
The roller film transporter is a system of rollers that rapidly moves the film through the compartments.
The developer and fixer compartments holds the solutions.The film is transported directly from the developer into the fixer without a rinsing step.
The water compartment holds circulating water.
The drying chamber holds heated air and dries the wet film. B
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56. Fig. 39-20 Automatic film processing units provide rapid film processing.B
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57. Advantages of Automatic Film Processing
Less processing time is required.
Time and temperatures are automatically controlled.
Less equipment is used.
Less space is required. B
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58. Processing Errors
Processing errors may occur for a variety of reasons, including:
Time and temperature errors (Table 39-4).
Chemical contamination errors (Table 39-5).
Film handling errors (Table 39-6).
Lighting errors (Table 39-7).
The dental assistant must be able to recognize the appearance of common processing errors and know what to do to prevent the problem from occurring again. B
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