it recommended for duplicating film. Higher-speed film contains a special emulsion of silver halide, making it more sensitive to yellow light. As a result, amber light may affect film clarity. When duplicating film is used, a ruby red safelight is required for developing. With the exception of duplicating film, most types Film baths and processing Most offices use automatic processors to develop dental film. In automatic processors, the film travels first through the developer solution, then the fixer solution, then the water, and finally past the drying elements. Figure 1 shows a schematic for both automatic and manual processing systems. Figure 1: Automatic and Manual Film Processing
of dental x-ray film have emulsion layers on both sides. With duplicating film, the emulsion side (usually pink) faces downward toward the light source in the duplicating box. The film to be duplicated is placed emulsion-side down on the duplicating box.
sulfite in the developer solution, which inhibits the oxidation process. After sufficient developing has taken place, the excess developer is rinsed off the film in a water bath. Next, the image is fixed by placing the film in the fixing solution. Chemicals in the fixing solution completely stop the development process and stabilize the image and the emulsion. The main active chemical in the fixing process is ammonium thiosulfate. Table 2 provides additional details on darkroom chemicals. After all the opened, developed x-rays have been fixed, the operator can safely turn on the white lights. The film is then rinsed again in water and dried. Film should always be handled by the edges. This prevents scratches from fingernails or contamination with skin oil, powder from gloves, or other foreign substances such as saliva. When film is developed manually, a darkroom thermometer and darkroom timer are required to maintain proper temperature of the chemicals and to accurately control processing times. Table 2: Darkroom Film-Processing Chemicals Chemical Ingredient Use
Water Hydroquinone
Catalyzes silver halide.
Sodium sulfite Inhibits oxidation; preservative. Sodium carbonate Maintains alkalinity; softens emulsion to accelerate reaction.
Developer
Water Ammonium thiosulfate
Removes unexposed silver.
When manually developing an x-ray, the operator places the film in the developer until the image clearly appears. Developing solutions are a mixture of several chemicals in water. The water tends to soften the emulsion layer on the x-ray film, allowing the chemicals in the developer to better interact with the chemicals in the emulsion. The emulsion contains silver halide crystals, which are light and radiation sensitive; the silver halide crystals react to x-rays during an exposure, but nothing becomes visible on the emulsion until the main developing agent, hydroquinone, interacts with the silver halide. Unfortunately, hydroquinone also interacts with the oxygen in the air and in the developer solution; it would not last long if not for the presence of sodium Temperature For manual processing, the water and chemicals should be kept between 60°F and 85°F. Chemicals should be changed monthly – more frequently if a high volume of x-rays have been
Sodium sulfite
Prevents decomposition; preservative.
Fixer
Potassium aluminum
Hardens emulsion.
Acetic acid Maintains acidity. Note . Adapted from Frommer, H. H., & Stabulas-Savage, J. J. (2011). Radiology for the dental professional ( 9th ed.). St. Louis, MO: Elsevier Mosby.
processed. In addition, the developer and fixer may need to be replenished periodically. Water can be changed daily. Darkroom temperature should be maintained between 50°F and 70°F.
FILM MOUNTING
Proper film mounting is important for the standardized, consistent interpretation of x-rays. A wide variety of cardboard, plastic, and vinyl intraoral mounts are available for different configurations of bite wing x-rays and full-mouth x-rays. Film should be dry before mounting. In emergency situations (e.g., endodontic emergencies), manually processed film can be dried quickly by gently blowing air on it with an air-water syringe.
When the operator follows standard procedures during x-ray exposures (i.e., uses the dimple-down technique and an orderly scheme for taking radiographs), film mounting can be quick and simple. Depending on his or her training, the supervising dentist may prefer that x-rays be mounted with the dimples facing out or facing in. Whichever dimple direction the dentist prefers, the standard should be consistent in order to prevent improper mounting or interpretation of the x-rays. For identification purposes, the date and the patient’s name should be written on the mount, or the x-rays should be placed in a coin envelope with the same information.
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