Dental Film Processing FAQs

Dark or Fogged Images

Why does x-ray film come out black?
There are five possible reasons why x-ray film may come out black:

The film is overexposed (exposures are too long or the setting is too high).
The processing times are too long.
The temperature is too warm.
The film has been exposed to another light source.
The safelight lens (filter) is cracked or damaged.

Why does exposed x-ray film occasionally have dark areas?
Intermittent problems suggest process variation. Less than optimum imaging will occur if processing conditions drift out of the ideal range. Processing chemicals must be

Replenished daily,
Mixed correctly, and
Stored at a temperature of 65-72°F (18.5-22°C).

Why are my extraoral x-rays covered with black dots?
A consistent pattern indicates a dirt or artifact problem. Gently clean the surface of the intensifying screen with KODAK Intensifying Screen Cleaner and Antistatic Solution, Catalog No. 1064930. Cleaning instructions are packaged with the product. Another cause is dirty processor rollers. Remove the rollers and clean them thoroughly. If this does not correct the problem, replace the cassette with one that is designed for use with the screen.
Static may cause either extraoral or intraoral films to be covered with black dots or lines that look like tree branches. This is common during the winter months when office conditions are dry. You can minimize static discharge by

Adding a humidifier to the office area, or
Opening the cassette or film packets slowly.

I have two processors. Why is the film from one processor foggy and dark?
If one of the processors generates good images, exposure can probably be eliminated as a cause of the problem. Something is most likely happening to the film during processing. Check the processor cycle time and chemical temperature to make sure they are correct. Chemical cross-contamination can also make film appear foggy and dark. Run a test using a sheet of film that has not been exposed to see if the problem recurs.

How can fogged images be avoided?
If the safelight lens (filter) is scratched, cracked, or damaged, it may leak enough light to fog the film. Try processing a test film with the safelight turned off. See What is Safelighting?.

Panoramic Images Distorted

Why do panoramic images distort the size and shape of the back teeth?
This is often caused by patient movement or improper positioning. Position the patient according to the manufacturer's recommendations. Head positioning devices and chin rests are important for accurate placement. Take the time to position the patient correctly! Ask the patient to remove the following:

Eyeglasses,
All jewelry or other metallic ornaments,
Any devices on or around the head and neck area, and
Full or partial dentures.

Be sure to instruct the patient to bite on the bite block, to close his/her lips, and place his/her tongue against the roof of his/her mouth. The patient's back and shoulders should be covered with a panoramic leaded apron.

Screens

Can blue film be used with a green screen?
No. When dental x-ray film is exposed, radiation from the x-ray unit strikes an intensifying screen. The intensifying screen converts x-ray radiation to visible light, which images the film. Dental x-ray film is sensitized to visible light, but only to light in a specific part of the color spectrum. Some films are sensitized to light in the blue part of the spectrum and others to light in the green part of the spectrum. For this reason, you must use each type of film with the correct screen: blue-sensitive film must be used with a blue screen (which emits blue light), and green-sensitive film must be used with a green screen (which emits green light).

Safelighting

What is safelighting?
Safelights provide sufficient illumination in the darkroom so essential activities can be carried out safely and with a minimum of error, but without exposing the film. Safelight filters are selected to transmit light outside the normal spectral sensitivity range of the photographic materials that are handled in their light. Most film emulsions only have a reduced sensitivity to the light transmitted through the safelight filter; therefore, it is necessary to keep safelight illumination levels and film handling times to a practical, safe minimum. To maintain good image quality, periodically check the safelight for scratches and cracks and replace when any defects are found.