INTRODUCTION
Film processing refers to series of steps that produce
a visible permanent image on dental radiograph.
The purpose
-to convert latent (invisible) image on the
film into a visible image.
-to preserve the visible image so that it is
permanent and does not disappear from the
dental radiograph.
What is latent image ??? …
How does latent image form??....
Exposure to x-rays
results in the release
of electrons, from the
bromide ions
Free electrons reach
a sensitivity site and
impart a negative
charge.
Free interstitial
silver ions are
attracted to the
sensitivity site
Silver ions
acquire an
electron and
become silver
atoms
 These silver
atoms constitute
the latent image
Film processing steps
Manual Processing Procedure
Consists of 5 steps :
1.
2.
3.
4.
5.
Developing
Rinsing
Fixing
Washing
Drying
Development
Film is placed in developer solution for a specific
amount of time at specific temperature.
Developer distinguishes between the exposed and
unexposed silver halide crystals
Initiates a chemical reaction that reduces the exposed
silver halide crystals into metallic silver and creates dark
or black areas on a dental radiograph, at the same time
unexposed silver halide remains unaffected .
Rinsing
Film is rinsed in water for 30 seconds with
continuous and gentle agitations
- dilutes the developer present in the emulsion,
slowing the developing process
- removes the alkali activator, preventing
neutralization of the acid fixer .
Fixing
Fixer solution
- removes the unexposed silver halide crystals
and create white or clear areas on the dental
radiograph
- and also helps in hardening and shrinkage of
film emulsion
Washing
Film is washed in running water to remove any remaining
traces of chemical solutions.
Washing efficiency declines rapidly when water
temperature falls below 60 degree F.
Warm water softens the emulsion and film will be easily
damaged.
Any silver or thiosulfate that remains because of
improper rinsing discolors and stains the film due to reaction
of thiosulfate with the silver to form brown
silver sulphide.
Drying & Mounting for viewing
After through rinsing the film is dried - in drying
cabinet or hang up in a well ventilated dust free room.
 Followed by mounting of the radiograph
Film processing solutions
a) Developer solution
4 basic ingredients
1)
2)
3)
4)
Developing agent
Preservative
Activator
Restrainer
Developing agent (reducing agent)
-Phenidone (1 – phenyl – 3 – pyrozolidine )
-Hydroquinone (parahydroxy benzene )
Primary function - to provide electrons to exposed silver
halide crystals and reduce the silver ions into solid
grains of metallic silver
Phenidone serves as first electron donor.
This electron transfer generates the oxidized form of
phenidone
Hydroquinone provides electron to reduce the oxidized
phenidone to its original active state so that it can
continue to reduce silver halide grains
Hydroquinone also produces high contrast in the
radiograph
Activator
The developer is active only at alkaline pH, around
10 – 11
Alkaline compounds (activators ) such as sodium or
potassium hydroxide.
Buffer – sodium bicarbonate – to maintain the state
Cause the gelatin to swell so that the developing agents
can diffuse more rapidly into the emulsion
Preservative
The developing agent contains an antioxidant or
preservative - sodium sulphite.
-inhibits the tendency of the developing agent to
combine with the oxygen dissolved in water or in the
air & preserve the solution in usable condition for
several weeks.
Oxidation of the developing agents forms coloured
substances which will stain the film and add to film
fog.
Restrainer
Bromide usually potassium bromide and benzotriazole
are added to restrain development of unexposed silver
halide crystals .
They depress the reduction of both exposed and
unexposed crystals, but more effective in depressing
the reduction of unexposed crystals.
Act as antifog agents and increase contrast
Solvent / vehicle
Distilled water is used
Developer replenisher
During film processing phenidone and hydroquinone is
consumed, and bromide ions and other by products are
released into solution.
Developer also become inactivated by exposure to oxygen
– “Seasoned” solution
Daily 8 ounces of fresh developer ( Replenisher) per
gallon of developing solutions – for development of an
average of 30 periapical and 5 panoramic films per day.
With regular replenishment , solutions last for 3 to 4
weeks .
b) Fixing solution
- dissolve and remove the under developed silver halide
crystals from the emulsion.
– to harden and shrink the film emulsion
Fixing solution consists of :
1) Clearing agent ( fixing agent)
2) Acidifier
3) Preservative
4) Hardener
- fixer should be replenished daily at the rate of 8 ounces
per gallon.
Clearing agent ( fixing agent)
Ammonium thiosulfate (hypo)
Chemically reacts with the undeveloped silver
bromide and converts it into a stable water soluble
complex which are be washed out of the film.
Preservative
Ammonium sulfite
-prevents the oxidation of thiosulfate clearing agent
Acidifier
Fixing solution contains acetic acid buffer system
(pH 4 to 4.5) to keep the fixer pH constant.
-promotes good diffusion of thiosulfate into the
emulsion and of silver thiosulphate complex out of the
emulsion.
- inactivates any carry over developing agents in the
film emulsion, blocking continued development of any
unexposed crystals while the film is in fixing tank.
Hardener
Hardening agent most often used are aluminum sulfate /
aluminum chloride
- Aluminum complexes with the gelatin ( by chelating
process) and prevents damage to the gelatin during
subsequent handling.
-reduce swelling of the emulsion during final wash. This
lessens mechanical damage to the emulsion and limits
water absorption, thus shortening drying time .
Solvent
Water is used
Different Methods of Chemical
Processing
1. Manual method
-Time temperature method
-Visual method
-Rapid processing method
2. Automatic method
3. Monobath method
4. Day light method
5. Self developing films
1a)Time temperature method
This method is best for processing of radiographs,
keeping all exposure parameters standard (kVp, mA,
exposure time) .
Based on the temperature of the processing solutions
and instructions of the manufacturer, processing time
has to be set .
Processing Temperature & Times
Solution
temperature
Time in
developer
(min)
Rinse time
Time in
fixer (min)
Wash time
(min)
65 0F (18.5 0C)
6.0
0.5
10-12
20
68 0F (20.0 0C)
5.0
0.5
10
20
70 0F (21.0 0C)
4.5
0.5
9-10
20
72 0F (22.0 0C)
4.0
0.5
8-9
20
75 0F (24.0 0C)
3.0
0.5
6-7
20
2.5
0.5
5-6
20
80 0F (26.5 0C)
b) Visual method
This manual method consists of placing the film in
developing solution and viewing them from time to
time in the safe light, thus the degree of developing is at
the operators discretion.
Advantage : Film can be developed to the contrast and
details desired for the particular subject
Disadvantage :Each film has to be processed
individually and is very time consuming
c) Rapid processing chemicals
In recent years manufactures have produced rapid processing
solutions that develop a film in 15 seconds and fix them in 15
seconds at room temperature.
They contain higher concentration of hydroquinone and more
alkaline pH, which causes the emulsion to swell more, thus
providing greater access to the developer.
The resultant images do not have the same degree of contrast
and discolor over a period of time if not fully washed .
After viewing, if these films are kept in the conventional fixing
solution for 4 minutes and washed for 10 minutes , the contrast
is improved and the film become more stable in storage.
2) Automatic method
This method uses equipment that automates all the
processing steps.
They are 2 types
1. Automatic Dunking models that produce a washed
film that still has to be dried
2. Miniature Roller type that produces a dried film.
ADVANTAGES:
-Less processing time is required (less than 4 – 7 mts)
-Less floor space is required and day light loading
capability.
-No wet films to be handled , no film hangers, no film
dryer.
-Density and uniformity of results
DISADVANTAGES :
-Quality is not as high as that of manually developed
radiograph.
-High cost of equipment and maintenance.
Dark Room
Primary function of a dark room is to produce a completely
darkened environment in which x-ray film can be handled
and processed to produce diagnostic radiograph.
Dark room requirements
1. Convenient location
2. Adequate size
3. Correct lighting equipment / Illumination.
4. Ample working space with adequate storage.
5. Temperature and humidity control.
Ideally dark room should be located near the area where
x-ray units are installed.
The size of the dark room will vary depending upon:
- volume of radiographs processed
- number of persons using dark room.
-type of processing equipment used(processing tanks
/automatic processor).
-the place required for duplication of films and
storage.
Size : 3 × 3feet - for an individual dentist.
16 to 20 square feet a group practice/institution.
clean and dry working area( for loading film and
unwrapping the films)
 working area should be at least 3 feet away from
the processing tanks
dark room should be well ventilated, use of air
conditioner is recommended.
 room temperature of 70 degree F and humidity levels
between 50 to 70% is recommended.
Room must be light tight or light proof – no leaks and
should have both white light and safe light
White light illumination is required during preparation
of solutions and cleaning tanks
Safe light should be of low intensity, with a relatively long
wave length of 600 nm and above (orange – red) - which
does not rapidly affect open film , but permit one to see
enough of working area
 Intensity of illumination
- the bulb should be 7 ½ to
15 watts.
-distance of the safe light
above the work area
should be 4 feet.

Time of exposure
- should be limited to about
5 minutes because film
emulsion shows some
sensitivity to safelight
with prolonged exposure
Processing Tank
Essential piece of equipment for manual processing Processing tank.
divided into compartments to hold
the developer solution, water bath, and fixer solution.
A processing tank has two insert tanks and one master tank.
Water inlet
water
inlet
Cold
Hot
Mixing valve
Developer
Developer insert
insert tank
tank
overflow tube
Fixer
insert tank
drain
water bath (large tank)
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