Film processing

DENTAL X-RAY FILM PROCESSING

Film processing refers to a series of steps that produce a visible permanent image on a dental radiograph.

To convert the latent image (invisible) 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.

PROCESSING METHODS

A. Manual Processing.
B. Automatic Processing.
C. Self Developing Films.

MANUAL FILM PROCESSING

Consists of the following five steps:

DEVELOPING SOLUTION:

• Developer
• Activator
• Preservative
• Restrainer
• Developer Replenisher
• FIXER SOLUTION:
• Fixing agent
• Preservative
• Acidifier
• Hardening agent
FILM PROCESSING SOLUTIONS

Silver bromide crystal

Latent image




Emulsion changes during film processing. A, Before exposure, many silver bromide crystals are present in the emulsion. B, After exposure, the exposed crystals containing silver particles at latent image sites constitute the latent image (shaded areas in the crystals).
C, The developing solution converts the exposed crystals containing silver particles at the latent image sites into grains of metallic silver. D, The fixing solution and washing procedure dissolve and wash away the unexposed, undeveloped silver bromide crystals.

When the x-ray is immersed in the developer chemicals, it soaks into the gelatin and reacts with the silver halide crystals. The energized crystals then form metallic silver and bromide. In metallic form, tiny silver particles appear black. The silver is deposited onto the film and causes the darker areas. The crystals that were not energized are simply washed away by the fixer and that area of the film remains white. So the developer reacts with the energized crystals to make the black areas, and the fixer removes the un energized crystals and leaves those areas white. If the film comes out too dark, it is because it is overexposed (too much radiation) or overdeveloped. If the film is too light, it is underexposed, underdeveloped, or over fixed.

DEVELOPMENT

DEVELOPING SOLUTION
• DEVELOPER
• Purpose of developing
Developing solution convert the exposed silver halide crystals into black metallic silver grains.
This process begins at latent image sites.
At latent image site, electrons from the developing agents are conducted into the silver halide crystals and reduces the constitute silver ion to solid grains of metallic silver.
Ag+ + electron  Ag.
(Silver ion in crystal + (electron from  silver atoms.
containing latent image ) developer)
Unexposed silver halide crystals, are unaffected during the time of reduction of exposed crystals into metallic silver.
Softens the film emulsion during the process.


II. ACTIVATOR
Alkaline in nature
Developing agents are active only at alkaline PH values( high PH) .
This causes the gelatin to swell so that developing agents easily diffuse with emulsion.
III. PRESERVATIVE
Prevents oxidation of developing agents

IV.RESTRAINER

Prevents the development of unexposed silver halide crystals.
The restrainer acts as ‘antifog agent’ and increases the contrast.
V .DEVELOPER REPLENISHER
Developer sol must be replenished daily to prolong the life of seasoned solution.

RINSING

A continuous, gentle rinsing for 30 sec in water is necessary after developing:
To dilute the developer and slowing the development process.
To remove alkali activator.

FIXING

A chemical solution fixer is used in the fixing process.


Purpose of Fixer
Remove the unexposed, unenergized silver halide crystals from the film emulsion.
Hardens the film emulsion during the process.

FIXING SOLUTION

I.FIXING AGENT

Dissolves and removes the unexposed silver halide grains.

Ammonium thiosulfate forms a stable, water soluble complexes with silver ions (silver thiosulfate complex), which then diffuses from the emulsion.
Thiosulfate does not have a rapid effect on the metallic silver grains in the film emulsion
But excessive fixation results in loss of film density, because the grains of silver slowly dissolve in the acetic acid of fixing solution.

II. ACIDIFIER

Contains an acetic acid buffer system (PH 4-4.5),which required for:
good diffusion of thiosulfate into the emulsion
silver thiosulfate complex out of the emulsion.
Inactivate any carryover developing agents in the film emulsion, hence blocks the further development of any unexposed crystals.
III. PRESERVATIVE
Sodium sulfite
Prevents oxidation of fixing agents as they are unstable in the acidic environment of fixing solution.
Binds with any colored oxidized developer carried over into the fixing solution, and removed it from the solution.
This prevents oxidized developer from staining the film.


IV. HARDNER
Aluminium sulfate

*This complexes with gelatin and hardens the gelatin during fixing process.

reduces the swelling of emulsion
↓
Lessens mechanical damage to the emulsion

Limits water absorption
↓
shortening drying time.

WASHING

Necessary to thoroughly remove all the excess chemicals from the emulsion.

DRYING

Should be air dried at room temperature in a dust free area.
Must be completely dried before they can be handled for mounting and viewing.

Time-temperature chart

AUTOMATIC PROCESSOR
(Uses a roller transport system)
PROCESSOR HOUSING:
-Encases all the the component parts of the automatic processor.
FILM FEED SLOT:
-Opening on the outside of the processor housing used to insert unwrapped films into the automatic processor.
ROLLER FILM TRANSPORTER:
System of rollers ( propelled by motor driven gears and belts) used to move the film rapidly through the developer, fixer, water, and drying compartments.
Rollers produces wrining action that removes the excess solution from the emulsion.

DEVELOPER COMPARTMENT:

Holds the developer solution.
Developing solution is specially formulated for automatic processor and different from developing solution used in manual processing.
A hardening chemical ‘glutaraldehyde’ is added to the conventional manual processing developing solution, to prevent the emulsion from softening and sticking to the solution.
Sulfate compounds are also added to the manual processing developer, to minimize the swelling of the emulsion, so that the films can be transported by the roller uniformly.
Because the total processing time is reduced in automatic processing, the chemical concentration and temperature of the developing solutions must be increased.


FIXING COMPARTMENT:
-Holds fixer solution
-Film directly transfer to fixer from developer without rinsing step.
-In fixer solution, the film is rapidly fixed and then hardened.
-Fixing solution is specially formulated for automatic processor and different from fixing solution used in manual processing.
-Fixing solution for automatic processor is highly concentrated chemical solution, that contains additional hardening agents.

WATER COMPARTMENT:

Holds circulating water, used to wash the films after fixation.
DRYING CHAMBERS:
Holds heated air, used to dry wet film.
FILM RECOVERY SLOT:
Opening on the outside of the processor housing, where the dry, processed radiograph emerges from the automatic processor.

ADVANTAGES

Time saving 4-6 minute.
Constant film quality is achieved, due to fixed processing cycles.
Need for dark room is eliminated.
Less floor space is required.
Chemicals can be replenished automatically by machine.
Large number of films can be processed continuously.


DISADVANTAGES
Equipment is relatively expensive.
Strict maintenance and regular change is required, dirty rollers produce marked films.
Films may get lost in the tank.

SELF DEVELOPING FILMS

-Self-developing films are an alternative.
-The x-ray film is presented in a special sachet, containing developer and fixer.
-Following exposure the developer tab is pulled, unveiling developer solution, which is milked down towards the film and massaged around it gently.
After about 15 seconds, the fixer tab is pulled to release fixer solution, which is similarly milked down to the film.
-After fixing the used chemicals are discarded and the film is rinsed thoroughly under running water about 10 minutes.

Advantages :

No dark room or processing facilities are needed.
Time saving.
Disadvantages :
Poor over all image quality.
Image detoriates rapidly over time.
No lead foil inside the film hence less flexible and can be easily bent .
These films are difficult to use in position holders.
Relatively expensive


MOUNTING RADIOGRAPHS
Radiographs must be preserved and maintained in the most satisfactory and useful condition.
Periapical, interproximal, and occlusal films are best handled and stored in a film mount.
Mounts are made of plastic or cardboard and may have a clear plastic window that covers and protects the film.
However, the window may have scratches or imperfections that interfere with radiographic interpretation
The operator can arrange several films from the same individual in a film mount in the proper anatomic relationship.

The preferred method of positioning periapical and occlusal films in the film mount is to arrange them so that the images of the teeth are in the anatomic position and have the same relationship to the viewer as when the viewer faces the patient.

The radiographs of the teeth in the right quadrants should be placed in the left side of the mount and those of the left quadrants in the right side.

THANK YOU