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processing

processing. 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

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processing

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  1. processing

  2. 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.

  3. What is latent image ??? …

  4. How does latent image form??....

  5. 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

  6. Silver ions acquire an electron and become silver atoms • These silver atoms constitute the latent image

  7. Film processing steps

  8. Manual Processing Procedure 0 Consists of 5 steps : Developing Rinsing Fixing Washing Drying

  9. 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 .

  10. 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 .

  11. 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

  12. 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.

  13. 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

  14. Film processing solutions a) Developer solution 4 basic ingredients Developing agent Preservative Activator Restrainer

  15. 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

  16. 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

  17. 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

  18. 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.

  19. Restrainer Bromide usually potassium bromide and benzotriazoleare 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

  20. 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 .

  21. 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 : Clearing agent ( fixing agent) Acidifier Preservative Hardener - fixer should be replenished daily at the rate of 8 ounces per gallon.

  22. 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

  23. 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.

  24. 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

  25. 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

  26. 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 .

  27. Processing Temperature & Times

  28. 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

  29. 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.

  30. 2) Automatic method This method uses equipment that automates all the processing steps. They are 2 types Automatic Dunking models that produce a washed film that still has to be dried Miniature Roller type that produces a dried film.

  31. 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.

  32. 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.

  33. 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.

  34. 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.

  35. 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

  36. 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

  37. Processing Tank 0 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. Cold water inlet Water inlet Hot Mixing valve Developer insert tank Fixer insert tank Developer insert tank overflow tube water bath (large tank) drain

  38. THANK YOU

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