The following slides describe the processing
and duplicating of x-ray films and quality
control in dental radiography.
In navigating through the slides, you should click
on the left mouse button when you see the
mouse holding an x-ray tubehead or you are
done reading a slide. Hitting “Enter” or “Page
Down” will also work. To go back to the previous
slide, hit “backspace” or “page up”.
After the films are exposed to radiation, they need to
be processed in order to see the information on the
film. This processing is done using special
chemicals and takes place in a darkroom. The
darkroom should have the following attributes:
• It must be light-tight. Since the silver halide
crystals are sensitive to both x-rays and light, the
area where films are processed must be completely
dark, except for a safelight (see next slide).
• It must have hot and cold water available; a mixing
valve, which regulates temperature, is
• It should have an adequate size and must be kept
very clean (no spilled chemicals).
Safelights are used in the darkroom to provide
adequate light so that you can see what you are
doing when you unwrap films for processing.
The safelights have special filters that produce
light that does not expose the film.
There are two filters currently available: an orange one
(Morlite) and a red one (GBX-2). The orange one can
only be used for D-speed film. The red one can be used
for all film types (D-speed, F-speed, extraoral, and
duplicating). Since most offices use both intraoral and
extraoral film, it makes sense to always have a red filter.
The new Kodak LED red filter (below right) provides
more light than the older safelights.
The safelight should
have a 15-watt bulb
(older style safelight)
and be mounted to the
wall or ceiling at least 4
feet from the area where
the films are unwrapped
and loaded into the film
15 watt bulb
If you have a light leak or improper safelighting in the
darkroom, the film may be fogged before it is
processed. Film fogging is the exposure of more of the
silver halide crystals than would normally be affected
during the taking of a radiograph. The exposure of
these extra crystals results in the film being darker
than normal and will usually decrease the diagnostic
value of the film. If a film is processed without being
exposed to light or x-rays, it should come out
completely clear (white on the viewbox). A fogged film
will have an overall slight grayness (see below).
clear, unfogged film
In order to check for improper safelighting or light
leaks, you can perform the following test. Unwrap a
film in the darkroom and lay it on the top of the
processor. Place metallic (opaque) objects on the film
(coins below left) and wait for 3-4 minutes. Remove the
objects and process the film. If the film comes out
completely clear, everything is OK (below right). If you
see the clear images of the metallic objects
surrounded by gray, there is a light problem (below
middle). Correct as needed.
When you take a radiograph, x-rays penetrate through
the tissues and interact with the silver halide crystals
on the film, creating exposure centers in the crystals.
There are thousands of these crystals and the number
that are affected is dependent on the number of x-rays
reaching a particular area of the film. Many x-rays will
penetrate through objects that have little density,
such as air and soft tissue. Few, if any, x-rays will
penetrate objects with high density, such as amalgam
and gold restorations. This difference in x-ray
penetration results in the formation of a pattern on the
film known as the latent image. Latent means
“hidden”; the image formed by the pattern can not be
seen until the film is processed (see next slide).
expose many silver
penetrate and not as
many silver halide
crystals are exposed
Few, if any, x-rays
halide crystals not
Air/soft tissue Bone Amalgam/gold
= Exposure centers
Basic Steps of Processing
1. Development: exposed silver halide crystals
converted to black metallic silver.
2. Rinsing: Used with manual processing only;
developer solution removed from film before fixing
3. Fixing: unexposed silver halide crystals removed
4. Washing: all chemicals removed from film
5. Drying: after removing moisture, films can be
handled for mounting
After taking the films on the patient, they are taken
to the darkroom for processing. The steps involved
in processing are:
Air/soft tissue Bone Amalgam/gold
Development centers in crystals struck by
x-rays are converted into black metallic
Air/soft tissue Bone Amalgam/gold
Entire crystal converted to
black metallic silver
The crystals that do not have exposure centers
are not affected by the developer if films are in the
developer for the correct amount of time and the
temperature of the developer is correct. However,
if the films are left in the developer too long, or the
temperature is too high, the developer will start to
act on the crystals that were not exposed by x-
rays (no exposure centers) and these crystals will
also be converted to black metallic silver. This
results in the film being darker than ideal.
After the films are properly developed, they go
into the fixing solution. (The films are rinsed first
if using manual processing).
Air/soft tissue Bone Amalgam/gold
In the fixing solution, the unexposed silver halide
crystals are removed from the film by the fixing
After the films have been in the fixing solution for
the specified time, the films are washed and then
dried so that they can be mounted for viewing.
The next two slides review the components of
the developing and fixing solutions.
Developer: Coverts exposed silver halide
crystals into black metallic silver
Preservative: Helps protect the developer from
being oxidized by the air
Activator: Provides alkaline solution needed by
developer; also softens gelatin, allowing
developer to reach crystals
Restrainer: Reduces effects of developer on
Clearing Agent: dissolves and removes
unexposed silver halide crystals from emulsion
Preservative: Inhibits decomposition
(oxidation) of clearing agent
Acidifier: Neutralizes any contaminating alkali
from the developer
Hardener: Hardens emulsion so film can be
Automatic vs. Manual Processing
Most offices use an automatic processor for film
development. While it will produce a very good film
if done properly, manual processing is very time
and labor intensive, requiring a much longer
processing time than automatic processing and
requiring someone to be available to transfer films
into the various solutions. Drying films also takes
The following slides discuss both types of
waterbath (large tank)
With manual processing, two tanks, one containing developer
and one fixer, are placed in a larger tank filled with water. The
water is maintained at a certain temperature using a mixing
valve. The film is first placed in the developer for a specified
time, rinsed in the water, and then placed in the fixer. After
fixing for the appropriate time, the film is washed in the water.
The overflow tube prevents water from rising high enough to
enter the developer or fixer tanks.
For manual processing, films are clipped to some type of
film hanger (see below). The film should be handled only
by the edges to avoid damage. The film hanger, with
films attached, is then placed in the processing
solutions, developer first. If the film is inadvertently
placed in the fixer first, the film will come out completely
clear (no image); the fixer removes all crystals that have
not been converted to black metallic silver by the
developer, even if they have exposure centers.
Develop 5 minutes at 68 degrees
Rinse 30 seconds (agitate continuously)
Fix 4 minutes (Agitate intermittently;
5 seconds every 30 seconds)
Wash 10 minutes in clean running water
Hang films to dry
Manual Processing Times
Place hanger with films attached into the
developer for 5 minutes. The lid is placed
over the tank if you plan to leave the
darkroom during development. (Click to
complete this action).
The silver halide crystals on the film are
converted to black metallic silver in the
developer. (Click to see the films change
from pink to dark gray).
After removing the lid, place the films in the rinse
water and continuously agitate for 30 seconds.
Next put the films in the fixer for 4 minutes and
agitate for 5 seconds every 30 seconds. (Click to
complete these actions)
Remove the films from the fixer and place in
the water bath for 10 minutes. (Click to place
films in water).
Remove film from the wash water and hang
films to dry. (Click to complete action).
When processing films manually, it is important to
check the solution levels at least once each day. If the
solution level is too low, the films at the top of the film
hanger may not be covered and will not be developed
and/or fixed properly.
The solution should be stirred frequently; the
chemicals tend to settle to the bottom and need to be
recirculated for optimum performance.
You should check the solution temperatures often. The
amount of time needed to develop the films is
dependent on the temperature of the solutions. If the
temperature is too low, more development time is
needed. Too high a temperature requires less time in
the developer. See next slide for the ideal time and
Solutions tend to become depleted as more films are
processed. This leads to inadequate developing
and/or fixing and film quality will be decreased. To
prevent this, it is important to replenish the solutions
by adding 8 ounces of chemical (both developer and
fixer) each day. This will maintain the quality of the
solutions for up to 30 films processed during the day.
If more than 30 films are processed, additional
solution must be added at a rate of 1 ounce for every
4 films over 30.
Automatic processors come in various shapes and sizes, but
they all function the same. The film is inserted in the inlet slot
where it is fed into a series of rollers (see photo next slide).
These rollers transport the film through the developer, fixer,
wash and dryer and the film exits the processor ready to
mount. The rollers “squeegie” the excess chemicals off of the
film as it exits each solution; no rinse is needed between the
developer and fixer. (Click to process film).
The photo below shows the insides of an automatic
processor. The wash section is located below the
drying rack. (See diagram on previous slide).
The manufacturer’s of automatic processors identify
the ideal temperature to be used in processing. You
should follow their recommendations.
As with manual processing, the solutions should be
replenished daily. Add 8 ounces of developer and
fixer for up to 30 films. Add one ounce of chemical
for every four films over 30.
The above information pertains to intraoral films. If
panoramic films are processed, they will deplete the
chemicals more quickly, because of their size, and
more frequent replenishment is needed.
Roller Transport Clean-up Film should be used
each day to clean the rollers before beginning film
The processors should be cleaned at every
solution change, which should be done every 2-4
weeks depending on the number of films taken.
Rollers should be cleaned with warm water using
a soft brush. Follow manufacturer’s instructions
for cleaning the processor. (Refer to the owner’s
A daylight loader may be used if there is not enough
room in the dental office for a darkroom. It can be used
for intraoral films only (pans too large) and should be
located in an area with reduced lighting. The unopened
film packets are placed in the loader through the lid in
the top and, after closing the lid, the operator reaches
through the rubber cuffs, opens the films and puts them
in the processor.
The following slides identify some of the errors
commonly seen in film processing.
too dark correct density too light
The density of the film can be affected by
problems in the darkroom, resulting in a film
that is too light (below right) or too dark
(below left). These changes in film density
are discussed in the following five slides.
• Developer too hot
• Too much time in the developer
• Exposure to light (opening door, turning on
light, light leaks around door, incorrect or
A dark film can result from any of the following:
90°F 95°F68°F 80°F
Developer too hot
5 minutes development time for all films
If the films are kept in the developer for the correct
amount of time but the developer is too hot, the
film will get darker as the temperature increases
All films processed at 68° F
15 min. 20 min.5 min. 10 min.
Too much time in the developer
If the films are kept in the developer too long, even
though the temperature is correct, the film will get
darker as the time increases (see below). Notice
that the effects are less pronounced with changes
in time than they are with a change in temperature
as seen on previous slide.
The completely black area on the right side of the film
below is caused by light exposing the film when the
darkroom light (not safelight) was inadvertently turned
on before the film was completely in the automatic
processor. (The tightness of the rollers against the film
prevented light from reaching the front part of the film).
Opening the door during processing could also create
this problem. Light leaks or faulty safelighting would
result in an overall darkening of the film, similar to too
high a temperature.
Exposure to light
• Developer too cold
• Not enough time in the developer
• Under replenishment (developer gets weak)
• Contaminated developer
• Excessive fixation
A light film can result from any of the following:
Dark spots – developer contamination
If drops of developer accidentally contact the film prior
to processing, the developing action will start to act on
these areas immediately. When the film is then placed
in the developer, the overall time that these areas are
developed is longer than for the rest of the film,
resulting in darker spots.
Light spots – fixer contamination
If drops of fixer accidentally contact the film prior to
processing, the fixing action will start to act on these
areas immediately. When the film is then placed in the
developer, there are fewer crystals to be converted to
black metallic silver, resulting in lighter spots. Usually
the contamination is on one side of the film only so that
the crystals in the emulsion on the opposite side are
processed normally and you can still see part of the
Yellow/brown stain – depleted fixer
If the film is not adequately fixed, the undeveloped
crystals (those without exposure centers) will not be
removed from the film, resulting in a yellowish-brown
stain. This is more apparent in the film below in the
areas that were not exposed to x-rays. The left side of
the film represents a cone cut (dotted lines) and the
areas in the crowns represent amalgam or gold
Films overlapped during processing
If films are fed into the automatic processor too
quickly, the films may overlap each other,
preventing the processing chemicals from acting
on the overlapped emulsions. This results in a dark
area on each film (see below).
If the automatic processor is not cleaned properly,
the rollers may become dirty . This results in black
lines on the film (see below).
If the film is removed too quickly from the packet
(intraoral) or from the film box or cassette
(extraoral), contact with overlying materials may
create friction, resulting in a static discharge. This
may create black dots, lines, “lightning bolts”, or
tree-branch patterns (see below).
It is often necessary to send a copy of films to another
general dentist, a specialist, or to obtain a
preauthorization from the insurance company. In order
to get this copy, the film needs to be duplicated.
A duplicate film is made by directing a light source
through the original film onto special duplicating film.
This is most effectively done using a commercial
duplicator (see below). A red safelight is used (GBX-2,
The original film must be in tight contact with the
duplicating film. This is accomplished by closing the
lid on the duplicator and locking it or pushing down
Duplicating film has a single emulsion layer. The
emulsion side must be in contact with the original film.
Duplicating film is a direct positive film, meaning that
it gives a positive, or duplicate, image of the original
film. If you increase the amount of time the light is on,
the duplicate film will be lighter; less light exposure
creates a darker duplicate film.
If done properly, a duplicate film will provide most
of the diagnostic information needed (see below).
However, duplicate films are never as good as the
If not done properly, duplicate films will be of little
value in trying to make a diagnosis. Films should
always be removed from film mounts before
duplicating in order to insure tight contact
between the original and duplicate films. Lack of
tight contact produced the duplicate film below.
The definition of quality assurance listed in NCRP
Report No. 145 (December, 2003) is:
“The mechanisms to ensure continuously optimal
functioning of both technical and operational
aspects of radiologic procedures to produce
maximal diagnostic information while minimizing
patient radiation exposure.”
Quality Assurance: Components
The technical and operational aspects of radiologic
1. X-ray units: These need to be inspected by a
qualified expert at regular intervals to ensure
2. X-ray Film: The film needs to be used before the
expiration date and stored appropraitely
3. Technique: The operator must use proper
technique in taking films
4. Processing: Optimal performance needs to be
evaluated daily using quality control tests
5. Viewing conditions: Proper viewing conditions
need to be maintained for optimal diagnoses
Quality Assurance: Benefits
The benefits of a good quality assurance program are:
1. Improved diagnosis: if the quality of the
films is optimized, the films will provide the
best diagnostic information
2. Reduced patient exposure: if the x-ray
machine is working properly and no retakes
are needed (due to faulty technique or
processing), patient exposure will be minimized
3. Time and cost savings: If everything is done
properly, and no retakes are necessary, the
operator won’t need to devote excess time to
retaking films and fewer films will be used.
Quality Assurance: Methods
The methods that can be used to provide
quality assurance include:
1. Scheduling an equipment inspection
through the State Radiologic Health
2. Reviewing the technical capabilities of the
personnel taking the radiographs and
providing training as needed, including
continuing education required by the state
3. Daily monitoring of equipment and viewing
4. Quality Control tests (see next slide)
Quality Control Tests
Quality Control Tests are primarily used to identify
problems with the processing of films but may also
identify problems with the x-ray equipment. Quality
Control Tests include:
Reference Radiograph: A properly exposed and
processed film is kept on the viewbox. Each day
a new film is exposed and processed and
compared to the reference radiograph.
Differences in the films may indicate a problem.
This is the least reliable test.
Quality Control Tests (continued)
Step Wedge: an aluminum step wedge (see below)
with varying thicknesses of aluminum (steps) is
placed on a film packet and exposed with standard
exposure settings. It is then processed under ideal
conditions (processor cleaned with new solutions).
Each day a new film is exposed and processed using
the step wedge. These daily films are compared to
the original (ideal) film. (see next slide).
Step Wedge pattern on film
area on film
If the steps on the daily film
line up with the steps on
the original film (same
densities) the test is
considered negative. This
indicates that everything is
satisfactory and no
changes are needed.
Same densities on
If the steps on the daily film
do not line up with the steps
on the original film (different
densities) the test is
considered positive. This
indicates that there is a
problem that needs to be
corrected. The most likely
problem is with processing.
If you clean the processor
and add new solutions and
the steps on a new film still
do not line up, the problem
is probably with the x-ray
Different densities on
This concludes the section on Processing,
Duplicating and Quality Control.
Additional self-study modules are available
If you have any questions, you may e-mail
me at: email@example.com
Robert M. Jaynes, DDS, MS
Director, Radiology Group
College of Dentistry
Ohio State University