Radiographic processing – Three methods are used to process radiographs:Instant or chairside, automatic (machine) processing, and manual processing.
(1) Instant or Chairside Developing
The instant or chair side developing method uses a special chemical formula and apparatus to bring out the latent image. It enables the dentist to perform a wet read—an interpretation of the film made before it is fully fixed or dried (in about one minute). Radiographic processing then is completed in the operatory (chair side). The instant method is used in general dentistry offices for emergencies because it saves time. In most cases, endodontic (root canal treatment) procedures require a “quick read” film during radiographic processing to determine if:
• The canal has been thoroughly cleaned.
• The filling material has completely filled the canal and not exited through the apical foramen.
• Other problems exist that could easily be solved before treatment is completed.
Along with special chemicals, Radiographic processing method requires a special light-tight box (a portable darkroom) which can be placed on a table in the operatory. To process film using this method, merely insert your hands with the film in the light-tight openings of the box. Elasticized rubber at the opening of the box will close tightly around your arms as they enter the box.
The special tinted glass window in the lid won’t allow in any room light, but it will permit you to see how to open the film packet and to view the developing radiographic processing. There are separate containers holding developer solution, water, and fixer solution. The special window will enable you to watch the chemicals act on the latent image. Wash the film well in the water tank next to the developer, and place it in the fixing solution until it becomes transparent.
This is also known as clearing time. Wash the film again and then give it to the dentist for a wet read. After a wet read, the radiographic processing film must always be returned to the fixer before being washed and dried.
However, the instant chair side radiographic processing method does have disadvantages. Because special (stronger) chemicals are used and the temperature of the solutions is greater, usually 85° Fahrenheit (F) (29.2° Celsius (C)), the visual quality of the film deteriorates over time. It also can not be used as part of the permanent record or for comparison with other films in the future because it will have poor density, contrast, or fogging.
(2) Automatic radiographic processing
There are many types of automatic radiographic processing. Some take both intraoral and extraoral films; others will only develop intraoral size films. Some work by moving the films through the processing solutions on rollers; others utilize a wire wheel or rack that looks like a Ferris wheel.
Most have the following features in common:
• Temperature control for solutions.
• A processing cycle which takes the film through the developer, then the fixer, and then is washed and dried.
• A fan area at the end of the radiographic processing cycle which produces a dry film.
• Special solutions (not the same chemicals used in instant or manual radiographic processing).
A darkroom is needed only for opening the film and placing it in the machine. Advantages of this system are the following:
1. The radiographic processing time is reduced to five to seven minutes.
2. The film is dry at the end of the processing.
3. There is less time spent in radiographic processing for the dental assistant.
Disadvantages of the system are the following.
1. Rollers in older machines absorb chemicals from the films and pass them on to succeeding films; leaving marks, streaks, and overdeveloped areas.
2. Films tend to stick and “get lost” in the machine.
3, One patient’s films can get mixed up with another when the films are developed one right after another.
4. The maintenance and cleaning of some machines are difficult and time-consuming.
(3) Manual radiographic processing
The manual radiographic processing method requires a darkroom, a special tank, film-holding racks, a thermometer, and developing and fixing solutions. This method is also known as the time! temperature method of developing.
For best results, follow these rules in the darkroom:
• Keep surfaces dry and clean and free from splashes of solution, dust, and water.
• Keep the room light-tight; no regular light must be able to seep in.
• Lock the door so no one can come in during the developing stage. If the film is exposed to light, it will turn black and no pictures will be seen.
• Use the correct time and temperature. Develop films in solutions that are between 68° and 70°F (20° and 21.5°C). If the solutions are warmer, the films will develop faster. If they are cold, the films will take longer to develop. Developing time is also affected by the age of the solutions. Newly mixed ones will work faster than those that are old and have been used a lot.