CH. 7
SCREEN FILM
(indirect exposure film) is exposed primarily by a fluorescent type of light given off by special emulsion-coated intensifying screens that are positioned between the film and the x-ray source.
what are some factors that determine film speed?
- size of the silver halide crystals (*****most important in increasing film speed****) - thickness of the emulsion - addition of special radio sensitive dyes
what are the 5 sizes of intraoral film?
0, 1, 2, 3, 4
how many films does a film packet have?
1 or 2
the 5 film sizes are used to expose 3 types of intraoral film projections:
1. bitewing 2. periapical (PA) 3. occlusal
the basic steps of processing dental x-ray films are:
1. developing 2. rinsing (automatic processors often omit this step) 3. fixing 4. washing 5. drying
all intraoral film packets are assembled similarly and consist of:
1. film 2. black paper wrapping 3. lead foil 4. moisture-resistant outer wrapping
what equipment is needed for manual processing?
1. processing tank 2. thermometer and timer 3. film hangers
what are the advantages of manual processing?
1. reliable and not subject to equipment malfunction 2. clinician has more control over the processing procedure, including the ability to adjust the time-temperature 3. ability to read the radiograph prior to the end of the processing procedure
what does the fixing step do?
1. stops further film development---- the permanent image is produced during this step 2. removes the unexposed/undeveloped silver halide crystals ( those that were not exposed to xrays) 3. hardens (fixes) the emulsion
what 4 forms of illumination are desirable in the well-equipped dark room?
1. white ceiling light 2. safelight -- safelight filter 3. viewbox 4. in-use light
what are the 2 most common sizes of extraoral films used
8 x 10 inch 5 or 6 inch x 12 inch
time-temperature chart: 60 degrees F ------ min? 65 degrees F ------ min? 68 degrees F ------ min? 70 degrees F ------- min? 75 degrees F ------ min? 80 degrees F ------ min?
9 min 7 min 5 min 4.5 min 4 min 3 min
which speed group is the slowest
A
which speed group is the fastest
F
True or False All of the radiation penetrating the patient's tissues will reach the film emulsion
FALSE not all of it will reach film emulsion
TRUE OR FALSE faster speed films are less diagnostic
FALSE there are no studies to prove it
sensitivity of a dental radiogrpahic film to radiation exposure.
FILM SPEED
the chemical solution used in film processing that removes all unexposed and any remaining undeveloped silver halide crystals from film emulsion to make an image permanently visible.
FIXER
what are the two types of drying methods?
air-dried at room temp. heated cabinet especially made for this purpose
VIEWBOX
aka an illuminator is a light source (generally a lamp behind an opaque glass) used for viewing radiographs. It allows a clinician the opportunity for a quick reading, viewing the radiograph without leaving the darkroom.
FILM HANGER
aka film rack. a stainless stell frame to which the films can be attached. it allows the radiographer to transport the films between each of the processing solutions.
SELECTIVE REDUCTION
only the nonmetallic elements, the halides, are removed and the exposed silver remains
what does the moisture-resistant outer wrapping consist of?
paper or soft vinyl plastic and holds the packet contents and protects the film from light and moisture
the faster the film speed, the less _______________ required
radiation
what is a size 2 film designed for?
referred to as a standard film or periapical film (PA). this film size is used to take both PA and bitewing radiogrpahs in adults and children whose oral cavities are large enough. this is the most selected size used in all intraoral radiography
the film used in dental radiography is photographic film that has been especially adapted in ___________, ______________, _________, and ____________ for dental uses
size emulsion speed packaging
IDENTIFICATION DOT
small raised dot located in the corner of the film. it is used to determine film orientation and to distinguish between radiographs of the patients right and left sides
the American National Standards Institute (ANSI) groups film speed using letters of the alphabet __ -__.
speed group A to speed group F
speed refers to...
the amount of radiation required to produce a radiograph of acceptable density
if there is any white light in the darkroom what can happen to the film?
the darkroom can blacken the film or cause film fog. therefore the darkroom should be LIGHT-TIGHT
enamel and bone will absorb, or stop, more x-rays from reaching the film than the less dense structures such as...
the dentin or pulp chambers of the teeth
EMULSION
the gelatinous coating on radiographic film containing silver halide crystals
the larger the number on the intraoral film .....
the larger the size of the film
MANUAL PROCESSING
the method used to process films by hand in a series of steps
what happens when radiation does reach the emulsion? (refer to page 80 for a good example of emulsion)
the silver halide crystals are separated into silver and bromide and iodide ions that store this energy as a latent image. these energy centers store the invisible image pattern until the processing procedure produces a visual image.
what do the developing agents do?
they reduce the exposed silver halide crystals to metallic silver but have o effect on the unexposed crystals at recommended TIME-TEMPERATURES
what is the biggest disadvantage of manual processing?
time required to produce a finished radiograph
why is a thermometer and timer useful for manual processing?
to achieve selective reduction at recommended time-temp. and eliminate guesswork, a thermometer and timer are necessary
what is the main function of gelatin?
to keep the silver halide crystals evenly suspended over the base
what is the role of the developer?
to reduce the exposed silver halide crystals within the film emulsion to black metallic silver the developer is responsible for creating the film's radiolucent appearance.
what is the purpose of washing?
to remove any remaining traces of the chemicals
what is the purpose of rinsing?
to remove as much of the alkaline developer as possible before placing the film in the fixer solution. it preserves the acidity of the fixer and prolongs its useful life
what is the 5 or 6 x 12 in used for
used for panoramic radiographs of the entire dentition
FILM PACKETS
what small films suitable for intraoral radiogrphy are made into
currently which speed films are only available
D, E, and F
orange or yellow filters allow for safe handling of what speed film?
D-speed
provides an area where x-ray films can be safely handled and processed. It is a well equiped room with adequate safelighting aids in producing high-quality radiographic images
DARKROOM
what speed films require a red filter
E and F speed and most extraoral films
______________ transforms the latent image, which is produced when the x-ray photons are absorbed by the siler halide crystals in the emulsion, into a visible, stable image by means of chemicals
PROCESSING
stainless steel receptacle used to process dental radiographs; divided into compartments containing chemical solutions of developer and fixer, and water for rinsing and washing
PROCESSING TANK
principle of dental radiographic film processing where the length of time a film stays in the developer solution depends on the temperature of the developer solution. A low temp. requires an increased developing time; a high temperature requires a decreased developing time to produce an acceptable radiographic image.
TIME-TEMPERATURE
true or false x-ray film is sensitive to white light
TRUE
if the radiograph is needed immediatley for a quick reading of the image, the film may e read under white light conditions after 2 or 3 minutes of fixing. this is called a _____ _______________
WET READING
what does elon do?
a developing agent that reduces (converts) expose silver halide crystals to black metallic silver; quickly builds up to gray tones
what is the action of hydroquinone?
a developing agent that reduces (converts) exposed silver halide crystals to black metallic silver; slowly builds up black tones and contrast
what happens when a packet contains 2 radiographic films that have been exposed?
a duplicate radiograph results at no additional radiation exposure to the patient
ANTIHALATION COATING
a dye added to the nonemulsion side of duplicating film to prevent backscattered UV light from coming through the films and creating an unsharp image
what does ammonium thiosulfate or sodium thiosulfate do ?
a fixing agent (clearing agent) that removes unexposed and any remaining undeveloped silver halide crystals
DAYLIGHT LOADER
a light shielded compartment attached to an automatic processor allowing films to e unwrapped in a room with white light
DUPLICATING FILM
a photographic film used in conjunction with a film duplicator that uses infrared and ultraviolet light to make copies of intra- and extraoral film-based radiographs
what does sodium sulfite do?
a preservative that slows rate of oxidation and prevents deterioration of fixing agent
what happens to gelatin when it dries after being placed in developing solution?
a supercoat layer of gelatin shrinks to protect the emulsion from handling, leaving a smooth surface that becomes the radiograph
IN-USE LIGHT
a warning light outside the darkroom which indicates that it is not safe to open the door
each emulsion layer is attached to the base by a thin layer of what?
adhesive
is the sheet of lead foil located in the front or the back of the film?
back of them film packet, behind the film
this is what the film is wrapped in that adds additional protection from light exposure
black paper wrapping
what is a size 4 film designed for?
generally referred to as occlusal films used for taking occlusal radiographs
what happens if the film is not washed?
chemicals will continue to react within the dried emulsion and ruin the image over time
EXTRAORAL FILM
classified as screen film, is larger in size and designed for use outside the mouth
what is a size 3 film designed for?
comes with a preattached bite tab and is used exclusively to take bitewing radiographs. Its loger horizontal dimension will record more teeth than a size 2 allowing for the exposure of two size 3 films compared to four size 2 films in a set of bitewing radiographs
GELATIN
component of film emulsion in which halide crystals are suspended
SILVER HALIDE CRYSTALS
compounds that are sensitive to radiation. they are 90-99% of bromine and 1-10% silver iodide that make up dental radiographic film emulsion. When exposed to x-rays silber halide crystals retain the LATENT image
films used in dental radiography have a thin, flexible, clear, or blue-tinted polyester base. what does the blue tint enhance?
contrast and image quality
the chemical ingredients in the developer solution are....
develping agents (aka reducing agents)---- HYDROQUINONE and ELON preservative ----- SODIUM SULFITE activator (aka alkalizer) ---- SODIUM CARBONATE restrainer---- POTASSIUM BROMIDE
what is the last step in film processing ?
drying
the rigid but flexible film base is coated on both sides with what?
emulsion consisting of silver halide (bromide and iodide) crystals embedded in gelatin.
this part of the film provides support for the fragile emulsion and strength for handling
film base
the larger the crystals the faster the ________ ___________
film speed
INTRAORAL FILM
films designed for use inside the oral cavity
what are the chemical ingredients in the fixer solution ?
fixing agent (aka clearing agent)--- AMMONIUM/ SODIUM THIOSULFATE preservative ---- SODIUM SULFITE hardening agent--- POTASSIUM ALUM acidifier--- ACEDIC ACID
what is the 8 x 10 inch used for
for lateral views of the jaw, cephalometric profiles, and posteroanterior views of the skull
what is a size 0 film designed for?
for small children and is often called pedo or pedodontic film
the emulsion layers are covered by a supercoating of ________ to protect the emulsion from scratching and handling
gelatin
LATENT (INVISIBLE) IMAGE
invisible image produced when a radiographic film is exposed to x-ray photons. Image remains stored by the silver halide crystals within the film emulsion until the film is processed.
what is the purpose of a lead foil in the film packet?
it absorbs scattered radiation that strikes the film emulsion from the back side of the film (the side away from the tube), fogging or reducing the clarity of the image.
what does potassium alum do?
it is a hardening agent that shrinks and hardens gelatin emulsion
what does the acetic acid do?
it is an acidifier that stops further development by neutralizing alkali of developer
why is a white ceiling light useful in the darkroom?
it provides illumination for the size of the room will allow the clinician to perform equipment maintenance and other tasks requiring visibility
why is a safelight filter useful in a darkroom?
it removes the short wavelengthsin the blue-green region of the visible light spectrum. the longer wavelength red-orange light is allowed to pass through the filter to illuminate the darkroom.
what happens to gelatin when placed in a liquid
it swells, exposing the silver halide crysals to the chemicals in the developing solution.
why is a safelight useful in the darkroom?
its a filtered white lightbulb or a special light-emitting diode (LED) bulb that provides enough light int he darkroom to allow the clinician to perform activities without exposing or fogging the film
what does sodium sulfite do?
its a preservative that prevents rapid oxidation of developing agents
what does potassium bromide do?
its a restrainer that restrains developing agents from developing unexposed silver halide crystals, which produce film fog
what does sodium carbonate do?
its an activator that activates developing agents by providing required alkalinity
what is the one disadvatnage of larger crystals
larger crystals tend to produce an image that is more grainy. smaller crystals produce a sharper image. however, practice still prefer large crystals for more acceptable exposure.
what is a size 1 film designed for?
may also be used for children in adults, the use of the narrow 1 film is normally limited to exposing radiographs of the anterior teeth. although it images only 2 or 3 teeth, this film is ideal for areas where the oral cavity is narrow
how many sides of the duplicating film is coated with emulsion?
one
SOLARIZED EMULSION
one side of duplicating film that responds to infrared and ultraviolet light by getting lighter with longer exposure time, and darker with shorter exposure time
what is a LIGHT TIGHT room?
one that is completely dark and excludes all light
