Processing Technique and Errors that Lead to Poor Quality Radiographs

Depending upon the equipment in the dental office, developing radiographs is performed either conventionally or automatically. Both methods have inherent advantages and sources of error. There is no argument that, if used properly, conventional wet developing provides higher quality radiographs than automatic methods.

However, the fact is that the use of a conventional darkroom is no longer considered contemporary, for a variety of reasons, and today automatic film development is the more common practice despite some disadvantages. One disadvantage is that errors may cause the patient to be subjected to unnecessary additional irradation when a spoiled radiograph must be retaken. Strict guidelines therefore must be applied for film developing. The following describes in general terms the sources of error that must be acknowledged.

Of the utmost importance is that absolutely no daylight should penetrate the darkroom. The darkroom lamp must be properly installed and checked from time to time because it represents an additional source of unintended film exposure; the filters on darkroom lamps may, with time, weaken or fade. The principle of strict cleanliness must be adhered to; chemicals and water droplets on the tabletop represent sources of error that can render interpretation of the radiograph impossible, therefore leading to the necessity to retake the film, and the attendant unnecessary radiation exposure of the patient.

Precise mixing of the chemicals and checking to see that they are not out of date is also of critical significance, as is proper control of the bath temperatures. If the prescribed temperature has not been achieved, development of radiographs must not be undertaken. Cleaning of the tanks and inspection of all machinery must be performed regularly and according to manufacturers’ specifications; this can often be most expeditiously accomplished through a service contract with the manufacturer or sales representative of the company. Unpacking both exposed or unexposed radiographic film must be done with extreme care. The films should be handled only by the edges whenever possible.

Storage of unexposed radiographic film packets is also significant. Poorly stored films age faster, leading to a film fog that reduces contrast and therefore compromises the clarity of the films. Film packets should be stored in a cool location, in an upright position and not together with chemicals. Whenever a fresh carton of radiographic films is opened, the first film from that package should be developed and fixed without being exposed, as a check for film fog. This can provide information about improper storage or undesired invasion of light. Manually developed radiographs must always be sufficiently rinsed if they are to be stored over the long term. Finished films should be stored completely dry in protective plastic sheets to prevent yellowing.

Finally a word about care and handling of film cassettes and intensifying screens. Check the effectiveness of the cassette-locking device regularly as well as the fit of cassette lids. Intensifying screens should be maintained in a clean condition using special solvents, to preclude radiographic artefacts. The screens should be replaced in a timely manner.

Tips for Error-Free Processing:

- Work in a clean area, with clean hands.
- Remove films (panoramic films) from cassettes slowly, and handle by edges only.
- Examine the light source of the darkroom. Change filters regularly. They fade! Do not use conventional red light lamps, but only special (15 watt) darkroom lamps. Check doors for light-proof closure.
- Do not use high intensity lights near or above automatic developers.
- Do not manipulate exposed films for too long, even in the darkroom.
- Use chemicals according to manufacturers’ directions and at the proper working temperature.
- Аn unexposed film subjected to correct development procedure should be completely transparent. Perform this check regularly! Observe also the expiration dates.

Dirty film. This panoramic film was handled by a technician whose fingers were contaminated with developing solution. Note the "fingerprint" near teeth 43 and 44. If such films are handled with fingers contaminated with water or fixative solution, bright spots will appear due to inhibition of normal development processes

The panoramic radiograph exhibits “flashes” as a result of static electrical discharge. This can occur when humidity is extremely low and a film is unwrapped too quickly.

Water drops. Note the bright spots at the angle of the mandible and in the ascending ramus, caused by water drops falling onto the exposed film before development.

Tips for Error-Free Development. Underdevelopment. The radiograph will appear too bright and lacking in contrast if:
- development time is too short,
- the baths are too cold (check temperature of solutions),
- the development solution is too old (solution should be changed at least every three weeks).

Overdevelopment. The radiograph will be too dark and, with formation of fog, will be lacking in contrast if:
- development time is too long,
- development solutions are too warm,
- the film itself is too old or has been stored in an excessively warm location.