 Hello everyone, welcome back to another session on Dental Streamer. So today we have extra fill-in processing session. So fill-in processing which refers to a series of steps that produce visible permanent image on Dental radiograph. So our ultimate intention is to create a visible permanent image, it should be visible and it should be permanent. And the basic purpose of processing is to convert latent image on the fill-in into a visible image. We will go into detail about the latent image in next slides. So the purpose is to create a permanent image from the invisible image and also to preserve the visible image so that it is permanent and does not disappear from the Dental radiograph. So what is a latent image? Okay, so this is the basic picture of X-ray radiation. We are taking a X-ray of these teeth from the X-ray tube. The photons are ejected and it passes through the tooth and it reaches here in the fill-in the chemical reaction happens and there is a latent image formation. So how does this latent image form? So we need to understand a dental fill-in or an X-ray fill-in. It has protective coating on either side with emulsion and adhesive subcoating. In between these layers we have a base. So this fill-in emulsion is made up of silver bromide crystals and silver iodide crystals which is precipitated in gelatin and laid on a thin sheet of transparent base. So these silver iodide and silver bromide are present on the emulsion. So this picture explains the structure of an X-ray fill-in and its finer details. So it is a three dimensional structure which has various ions and atoms within it such as iodide ion, bromide ion, bromine atom, silver ion, interstitial silver ion and sensitive site. So hope you can make out all these. This is iodide ion. This is bromide ion whereas this is interstitial silver ions and this is a sensitive site. So why it is important because if it is a perfectly arranged structure with perfectly balanced ions and atoms it will not create a latent image or invisible. Silver halide crystals are imperfect in various aspects because it has interstitial silver ions. These are the interstitial silver ions. These are free ions in the spaces between the crystalline lattice. So this I told you the film emulsion is made up of silver bromide crystals and silver iodide crystals which are precipitated in gelatin and which is laid on a thin sheet of transparent base. So this is a base. So emulsion has all these silver bromide crystals and silver iodide crystals. So silver iodide crystals, so this is a picture of the crystal, the details of crystal where the industrial silver ion is present between the crystalline lattice. So it has arranged in a symmetrical fashion but there is irregularities and physical distortion. Then only it will become a capturable x-ray otherwise it will be a perfect site which will not produce any x-ray or any latent image. So physical distortions are present in regular rectangular array of silver and bromide ion crystals due to the presence of iodine atom. So due to the presence of iodine atom and which is occupying at some of the bromide sites. And silver iodide crystals are chemically sensitized by the presence of sulfur compounds. So sulfur compounds will be present at some point which is known as the latent image sites which will ultimately give rise to the latent image and after that to produce a visible permanent image. So what are the functions of these latent image sites? So the function is to begin the process of image formation by dropping the electrons generated when the emulsion is irradiated. That will see step by step in next slides. So this is nothing but the details of an x-ray film and its minor details how the lattice is structured, how the ions and other atoms are dispersed and what is a sensitive site or latent image site which has sulfur impurities. So there should be always impurities and physical irregularities within the site then only it will capture and it will produce a latent image if it is a perfectly arranged atoms and ions there will not be any image production. So it should be photosensitive. So how it is become photosensitive by the help of these physical irregularities and physical distortion and presence of interstitial silver ions. Now let's see the basic process of x-ray. So when an x-ray tube produces a photon it goes to the x-ray film and it creates some chemical reactions. So what is happening when a photon is hitting an x-ray film particularly that silver halide crystals when x-ray hit that particular bromide ion it releases an electron. Okay so when photon hits a film on a minute level it hits the silver halide crystals and we can say precisely the bromide ions. So when it hits the bromide ions okay bromide ions it is not atom it is ions it releases an electron okay so it releases an electron. So what happens is these free electrons reach a sensitive site or latent image site and it impart the latent image site a negative charge. Before it was not charged it is neutral it has just sulfur impurities and it can capture electron but it is still a neutral site. So when this photon hits this bromide ion it releases electron it reaches a sensitive site and it imparts a negative charge. So now it is negative so it will search for a positive ion. So what happens the free interstitial silver ions that is ag plus it get attracted to this sensitive site. Okay so this is a interstitial silver ion which is ag plus okay. So the silver ions acquire an electron and becomes silver atom at this site. Okay that is the process happening bromide release electron it goes to sensitive site it becomes negative it will attract ag plus ion and it become silver atoms. So these silver atoms constitute the latent image. So this is the latent image. Now it is the image is produced but it is not in a visible state it is invisible but the image is produced the chemical reaction is happened. Now we need to make the latent image to a visible or permanent image. So that process has basically five steps. The first one is developing then rinsing fixing washing and drying. So developing as film is placed in a developer solution for a specific amount of time at specific temperature. So this developer it can distinguish between the exposed and unexposed silver halide crystals. See not all the silver halide crystals are sensitized. Okay some are non-sensitized because some are not able to capture the electrons. Only few or some of the silver halide crystals which are sensitized and it acquired ag plus ions and it become silver atoms not all the sides. So some are exposed some are not exposed. So this developer can distinguish which are exposed and which are not exposed. So it initiates a chemical reaction which reduces exposed only exposed which reduces the exposed silver halide crystals into metallic silver okay. So that metallic silver shows as a dark or black areas on the dental radiograph. At the same time the unexposed silver halide remains unaffected. Okay so unaffected means it is not getting exposed it is not changing to not exposed it is not changing to black or dark areas because these are unexposed silver halides. Now after developing we go to the rinsing process film is rinsed in water for 30 seconds to remove all the developing solution by a continuous and gentle agitation which dilutes the developer present in the emulsion which slows the developing process and it removes alkali activator preventing neutralization of acid fixer because the developer is basically alkaline and next we are putting into acidic solution that is acidic fixer. So if we don't clean up this solution this will get neutralized that the acid fixer will get neutralized. So to avoid that we are rinsing it with water after that we put it in fixer solution what is fixer doing it removes the unexposed silver halide crystals if it is not removed we will not be able to differentiate which are exposed which are not exposed because the exposed are now become dark okay. Now we need to visualize it and we need to differentiate it we need to see the structures in the x-ray. So in order to get that differentiation we need to remove the unexposed silver halide crystals so that is what fixing doing okay. So it removes the unexposed and shows the differentiation of that structures. So these silver halide crystals create when we are removing unexposed silver halide crystals it create a white or clear areas so that we can differentiate the black or dark areas which was developed or which was exposed to silver halide crystals. In addition to that it also helps in hardening and shrinkage of film emulsion. Then again we wash the film in running water to remove any remaining traces of chemical solution and washing efficiency declined rapidly when water temperature falls below 60 degree. So warm water softens emulsion on film will be easily damaged so any silver or tassel fate which remains because of improper rinsing will result in discoloration and staining of the film okay. After that we put it for drying and mounting for viewing so that is a process so we have this many process developing rinsing fixing washing and drying. Now let's say one by one the developer solution has four basic ingredients developing agent preservative activator and restrainer. The developing agent or reducing agent is pinnidon which is one phenyl three pyros already and hydroquinone which is para hydroxybenzene. So the basic function is to provide electrons to the exposed silver halide crystal and reduces silver ions to solid grains of metallic silver. So the silver halide crystals which has sensitive sites which equate the ag plus ions and becomes and becomes the ag atom okay. Those silver halide crystals will be reduced and to make it to metallic silver. So this metallic silver will be shown as dark or black areas okay. So pinnidon which serves as a first electron donor this electron transfer which generates oxidized form of pinnidon whereas a hydroquinone which provides electron to reduce the oxidized pinnidon to its original active state so that it can continue to reduce the silver halide crystal. So this is the first electron donor pinnidon whereas a hydroquinone provides electron to reduce the oxidized pinnidon okay and hydroquinone which also produces high contrast in the radiograph. And the second component of developer is activator. So the developer is active only at alkaline pH which is around 10 to 11. So this alkaline compounds are sodium or potassium hydroxide and we have a sodium bicarbonate buffer to maintain the state because gelatin to swell so that the developing agents can diffuse more rapidly into the emulsion. Next we have preservative. So the developing agent contains an antioxidant of preservative which is sodium sulfide which inhibits the tendency of the developing agent to combine with the oxygen dissolved in the water or in the air and preserve the solution in usable condition for several weeks. So oxidation of the developing agents forms colored substances which will stain the film and add to the film fork. And restrainer usually bromide usually like compounds such as potassium bromide and benzo triazole are added to restrain the development of unexposed silver halide crystals. So they depress the reduction of both exposed and unexposed crystals but more effective in depressing the reduction of unexposed crystals. So it acts as an anti-fog agent and increase the contrast because it is not exposing the unexposed crystals and distilled water is a solvent or vehicle. So developer replenisher during the film processing finidone and hydroquinone is consumed and bromide ions and other byproducts are released into solution. So developer also become inactivated by exposure to oxygen season solution. Okay so we need to replenish this daily eight ounce of fresh developer per gallon of developing solution for development of an average 30 IOPA and 5 OPG per day. So it can last up to three to four weeks. Now we move on to the fixing solution. So fixing the purpose is to dissolve and remove the underdeveloped silver halide crystals from the emulsion and also to harden and shrink the film emulsion. So it is removing the unexposed silver halide crystals or underdeveloped silver halide crystals because in developing solution we know that in restrainer depress both the exposed and unexposed but more effective in repressing the unexposed crystals. So these unexposed crystals will be removed and creating a white area. So the compounds are solution consists of clearing agent that is fixing agent acidifier, preservative and hardener and it should be replenished daily at rate of eight ounces per gallon. So clearing or fixing agent is ammonium thiosulfite which chemically reacts with the underdeveloped or undeveloped silver bromide and converts it into a stable water soluble complex which are we washed out of the film. So it will remove the undeveloped silver bromide and it is converting to a stable water soluble complex which will be removed from the film. So preservative is ammonium sulfite which prevents the oxidation of thiosulfite clearing agent. Acidifier is acetic acid buffer system with a range of 4 to 4.5 which keeps a fixed pH constant which promotes good diffusion of thiosulfate into the emulsion and of silver thiosulfate complex out of the emulsion and also it inactivates any carrier of a developing agent in the film emulsion blocking the continued development of any unexposed crystals while the film is fixing tank. Film is in the fixing tank and hardener is like hardening agent most often used are aluminum sulfate or aluminum chloride. So these aluminum complexes with gelatin by chelating process and also it prevents damage to the gelatin during subsequent handling which reduces swelling of the emulsion during final wash this lessens the mechanical damage to the emulsion and limits the water absorption. Solvent is water. So there are various methods of processing the manual method like time from time temperature method, visual method, rapid processing method and also we have automatic monobot method, daylight method and self-developing films okay. So these are the various methods. So the first method is time temperature method. This method is best for processing of radiographs keeping all exposure parameters standards that is kilovolt milliampere exposure time all keeping standard and based on the temperature of the processing solution and instruction of the manufacturer processing has to be set. So these are the time duration, rinsing time and time in fixer and washing time at different temperature. The next method is visual method. This manual method consists of placing the filament developing solution and viewing them. This is what we commonly use and viewing them from time to time in safe light this degree of developing is at the operator discretion. So we are deciding how much it is developed whether it is properly developed or not. So advantages film can be developed to the contrast and details desired with the for the particular subject. But the disadvantages each film has to be processed individually and is very time consuming. Rapid processing chemicals in recent times manufacturers they produce rapid processing solution that develops a film in 15 seconds and fix them in 15 seconds at room temperature. So second method is automatic method. This method uses equipments that automates all the process. There are like two types automatic dunking models which produces a washed film that still has to be dried and miniature roller type that produces a dry film. So we put the film here it goes to developing solution and then it goes to fixing solution and washing and drying and coming out. Okay. So advantage is less processing time usually four to seven minutes less flow space is required and no wet films to be handled no film hangers no film dryers density and uniformity. Disadvantage is quality is not as high as manually developed ones high cost of equipment and maintenance. So regarding the dark room so dark room is the area where this X-ray film process is happening. So primary function of dark room is to produce a completely darkened environment in which X-ray film can be handled and processed to produce a diagnostic radiograph. Requirements it should be a convenient location size and adequate illumination ample working space temperature and humidity control. So ideally dark room should be located near the area where X-ray units are installed. Size of the dark room will vary depending upon the volume of radiographs processed and number of persons using this room and type of processing equipments usually three by three feet for individual endist and 16 to 20 square feet for a group practice. So it should be clean and dry working area working area should be at least three feet away from the processing tanks dark room should be well ventilated use of air conditioner is recommended room temperature is 70 degree Fahrenheit and humidity level 52 70 percentage. So room must be a light light or light proof no leaks should have both white light and safe light. Now white light illumination is required during preparation of solution and cleaning tanks. Safe light should be of low intensity with a relatively low wavelength of 600 nanometer and above in the orange region of the spectrum which does not rapidly affect the open feeling but permit one to see enough of the working area. So intensity of illumination the bulb should be seven half to 15 watts distance of safe light above the working area should be at four feet from the film or the working area. The time of exposure should be limited to about five minutes because the film emulsion shows some sensitivity to safe light with prolonged exposure so within five minutes all the work should be done. So processing tank essential piece of equipment for manual processing. So this is a processing tank which is divided into compartments to hold the developer solution the water bath and fixed solution. So processing tank has two insert tank and one master tank. Okay so this is a developing solution which will be replenished frequently and will be kept here and this is a fixer tank which will be kept here after frequent replenishment and there will be water bath. Okay so there will be a cover and outflow pipe. So that's all about processing of extra film. So we were discussing in detail about the latent image formation how the latent image is formed which is an invisible one and how it is processed and details about the developer and fixed solution and the various components of the developer and fixed solution. Okay so the developer has all these four developing agent preservatives activator and restrainer whereas the fixing solution also has clearing agent or fixing agent as a different preservative and compartment. Okay so that's all about processing and latent image formation. So I'll come up with a new topic in the industry more. Thank you.