DENTAL FILM
Introduction
I- THE SILVER FILM
I.1. Definition
I.2. Components
I.3. Different film formats
I.4. Properties
1.5. Formation of the latent image
1.6. Film processing
1.7. Reading a snapshot
1.8. Storage:
II- THE DIGITAL SENSOR
II.1. Definition and General Principle
II.2. Digital sensor technologies
II.2.1. Direct digital imaging:
a- The charge-coupled device (CCD) sensor or Charge Transfer Device (DTC) b- The CMOS (Complementary metal-oxyd silicon) sensor
c- Different formats
II.2.2. Indirect digitization
a- ERLM (Radio-Luminescent Memory Screen) sensors or photo-stimulable phosphorus plates
b- Different formats of ERLM sensors
II.3. Properties of digital sensors
II.4. Digital image processing
II.5. Reading and Storage
III- Summary of the advantages and disadvantages of different dental films
Conclusion
Introduction :
Radiography is an essential tool for diagnosis in endodontics. The radiographic examination is so rich in information that the temptation is sometimes great to establish a treatment plan based solely on reading a retro-alveolar image.
Silver film has long remained the benchmark in dental imaging, thanks to the precision of the image that can be obtained and the amount of information available. This quality is however directly linked to the way of using and especially processing these images.
Intraoral digital imaging was born in France in 1987 with the development of Radio-Visio-Graphie (RVG) by Francis Mouyen.
Since the 1990s, digital technology has evolved enormously and is now on the way to becoming the benchmark
I- THE SILVER FILM:
I.1. Definition: This is a very high definition, screenless, plastic film on which the emulsion sensitive to X-rays and light exposure is deposited, recording the radiographic image. It is contained in a light- and environment-tight pouch.
I.2. Components: X-ray film has two main components: – The film, which is sensitive to X-rays and light exposure, records the X-ray image.
– The packaging helps contain the film and protect it.
I.2.1. The film itself: (Fig 1)
-The silver film consists of a plastic support on which is deposited the emulsion of silver bromide grains (AgBr) sensitive to X-rays and daylight, which are embedded in a matrix.;
– the support is made of 0.18 mm thick polyester. It is therefore flexible, which allows it to easily adapt to anatomical structures without causing deformation or destruction of the image.
-It is coated on both sides with a thin adhesive layer composed of gelatin on which the photosensitive emulsion is deposited.
Fig 1. Section of a silver film
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Dr. B. GASMI / HCA THE DENTAL FILM 2023/2024
I.2.2. Packaging: consists of three elements:
Black paper, lead sheet, plastic envelope (Fig.2)
Black paper:
It surrounds the X-ray film and protects it from light exposure. The lead sheet:
It is located between the black paper and the plastic sleeve on the side opposite the source of the radiation. This lead sheet has a dual role:
-it reduces the irradiation of tissues located behind the film,
-it protects the film from secondary radiation diffused in the opposite direction by the structures located behind the film, which eliminates the blurring that would result. The plastic envelope:
It contains all the elements mentioned above.
It is a heat-sealed pouch that is light and watertight, thus preventing contamination of the film by the patient’s saliva and/or blood.
The two sides of the envelope are different (Fig3), allowing easy positioning when taking the photo:
The face to be exposed to X-rays. This face has a raised point in one of its corners called a boss. The film and the lead sheet also have this point. It makes it easier to position the films in the mouth: it is a rule to orient the boss at the level of the occlusal surface of the teeth.
The side not to be exposed: generally two-tone and does not have a bossage
Fig.3: a-side of the film
expose to X-ray, note the
bossage (arrow)
b- face not to expose
usually two-tone
Dr. B. GASMI / HCA THE DENTAL FILM 2023/2024
1.3. Different film formats:
There are different formats of intraoral films, allowing them to address all clinical situations. Of course, there are films of different dimensions adapted to the area to be X-rayed (anterior, posterior, occlusal, etc.) as well as to the patient (adult or child).
Here are the different formats that can be found commercially (Fig 4): Size: 22/35 mm, periapical in children (Fig. 4.a)
Size: 24/40 mm, periapical in children and adults (Fig. 4.b)
Size: 31/41 mm, periapical in adults (Fig. 4.c)
Size: 57/76 mm, Occlusal (occlusal bite) (Fig. 4.d)
Size: 27/54 retro-coronal (bite wing) (Fig. 4.e)
Fig.4: Different formats of silver film
I.4. Properties: When describing the properties of X-ray film, numerous and complex physical concepts must be taken into account. Image resolution: The finer the silver bromide grains, the better the definition of the image produced. It is expressed in pairs of lines per millimeter pl/mm. The human eye can discern about 10 pl/mm.
The resolution of silver film is more than 20 pl/mm.
The sensitivity of the film:
A sensitive or “fast” film is exposed to a small amount of radiation. This sensitivity is a function of the size of the silver bromide grains: the finer the grains, the less sensitive the film. ISO E and F films are the most widely used today. Example: Exposure time in seconds for a premolar
ISO E 🡪 0.32 sec ISO F 🡪 0.25 sec
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Dr. B. GASMI / HCA THE DENTAL FILM 2023/2024
Irradiation dose:
Intraoral film of sensitivity group F would allow, with comparable image quality, a dose reduction of 15 to 25% compared to E films. Replacing the films with digital receptors would result in a 34% reduction in exposure compared to F sensitivity films.
1.5. Formation of the latent image:
– The exposed Br-Ag crystals will undergo a transformation with each absorbed X-ray photon to result in the formation of silver ions (Ag+) in each crystal concerned. – All of these points will form the latent image.
– Unexposed Br-Ag crystals remain unchanged.
1.6. Film processing:
-The darkroom: allows the film to be processed and quality images to be obtained. It must be light-tight.
-It can be either:
∙ Commercially available darkroom for manual processing with dimensions of approximately 445 x 302 x 311 mm (Fig.5)
∙ Automatic developing machine to save time (Fig.6). -In both cases, the darkroom consists of four baths, placed from left to right: -developer, -rinsing water, -fixer, -rinsing water.
-There is also the possibility of carrying out a single-bath treatment: a single bath for the developer and the fixer.
-For the image to be visible, the film must be processed.
-Processing a film consists of: developing it, rinsing it, fixing it, washing it and finally drying it.
Fig.5 Dark room for manual processing Fig.6 Automatic developing machine
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Dr. B. GASMI / HCA THE DENTAL FILM 2023/2024
1- Development:
The film is removed from its packaging and processed away from light. It is immersed in a developer solution (hydroquinone, genol) and developed for 4 minutes.
Development is a physicochemical process where:
– exposed areas undergo a reduction reaction of Ag+ ions into Ag atoms. – unexposed areas (residual Br-Ag) remain unchanged (no reaction)
2- Rinsing: The film is rinsed in running water for 15 to 30 seconds to get rid of excess developer.
3- Fixation: (sodium thiosulfate)
It allows the dissolution of unsensitized (unexposed) silver bromide (Br-Ag). The film can be read wet after 1 to 2 minutes of soaking but must then be placed back in the fixing bath for a total of 10 minutes. 4- Final wash: is done in running water for 10 to 20 minutes.
5- drying: in the open air for a period of between 10 and 30 minutes.
Note: Self-developing silver X-ray film (Fig.7): The film processing product is presented in the envelope isolated from the film itself (single bath).
Fig.7: Self-developing silver X-ray film
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Dr. B. GASMI / HCA THE DENTAL FILM 2023/2024
1.7. Reading a snapshot:
To be able to detail a film precisely, the following conditions must be respected: – the reading of the image is done by transillumination; the transmitted light must be as homogeneous as possible (negatoscope);
– magnifying glasses must be used to better observe the structures specific to each case.
1.8. Storage:
The photos are stored using single storage pockets (for a single photo) or multiple storage pockets (for several photos).
It must be precisely annotated on the covers:
The patient’s name, first name,
The date the photo was taken as well as
The number of the X-rayed tooth.
This administrative process allows for easy identification and archiving of X-rays in the patient’s medical file.
Conservation and sustainability:
X-ray film must be stored in accordance with certain rules in order to preserve all its qualities. The storage conditions are:
-Film stored in a pocket in the folder
-the temperature must be room temperature
– the film must be kept away from a radiation zone and protected from humidity.
II- The digital sensor:
II.1. Definition and General Principle: (Fig.8)
The digital sensor, unlike silver film, undergoes a physical and not chemical process to obtain the image (computer processing)
It is an electronic structure that transforms the energy of the received X-ray into an electric current, allowing the visualization of the radiographic image on a screen. In the digital image we speak of a pixel which is the digital equivalent of the silver bromide crystal in conventional radiography. A pixel is of a gray level depending on the quantity of energy generated. All of these pixels provide an image that can be interpreted on a screen.
DENTAL FILM
II.2. Digital sensor technologies:
Two main types of digital imaging coexist: direct and indirect digital imaging.
II.2.1. Direct digital imaging:
As the name suggests, it gives an instant image on the monitor (screen), upon receipt of the X-rays on the sensor; the sensor is connected to the central unit by a cable.
a- The charge-coupled device (CCD) or Charge Transfer Device (DTC) type sensor:
It is the oldest in digital radiology,
It comes in the form of a small box containing:
– a scintillator which transforms the Rx into a photonic (luminescent) image – a plate of optical fibers which ensures the transfer of the luminescent image to the CCD – a CCD which transforms the photonic image into an electrical signal.
b- The CMOS (Complementary metal-oxide silicon) sensor
-It has the same components of the CCD except that it does not have charge transfer (CCD plate)
-Uses microprocessor and memory technology
-Scanning is done on the same chip as the sensor itself. -cheaper
c- Different formats: (Fig.9)
The direct sensor is usually connected to the rest of the equipment by a cable. Nowadays, there are wireless sensors, making them more practical. There are sensors of different formats that are rigid and suitable for children and adults.
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Dr. B. GASMI / HCA THE DENTAL FILM 2023/2024
Fig.9: Different formats of direct digital imaging sensors
II.2.2. Indirect digitization:
a- ERLM (Radio-Luminescent Memory Screen) sensors or photo-stimulable phosphor plates:
– indirect digital imaging requires additional processing of the detector; once subjected to X-rays,
The radio-luminescent memory display (ERLM) used here is wireless and is read by laser scanning in a reading unit (scanner) (Fig. 10), visualization on the monitor (screen) can be envisaged after 7 to 90 seconds.
– this sensor is capable of conserving photonic energy during irradiation, hence the memory option, the stored energy constitutes a latent image.
-the image will be developed in a scanner with a laser beam that restores the image in a few seconds, so the image is not obtained instantly (indirect) -The plates are initialized by exposure to intense light in order to eliminate the images and reset it, so they are reusable
b- Different formats of ERLM sensors:
These sensors have the same dimensions as the classic retro-alveolar film (but are less flexible), and are used in the same way: they are therefore cable-free and exist in different formats. (Fig.11)
Fig.11: different formats of ERLM plates
II.3. Properties of digital sensors:
Image resolution:
ERLM sensors: up to 12 pl/mm,
CCD/CMOS sensors between 7 and 14 pl/mm for older models. Film sensitivity:
Digital sensors are more sensitive than conventional film, and it is possible to obtain an image with 25% of the X-ray dose used for silver film.
Irradiation dose:
The most sensitive digital sensor in the series results in an 87.5% dose reduction compared to the most sensitive film (ISO F).
II.4. Digital image processing :
The processing and analysis of information is done using suitable software from digital data stored in the computer.
Image processing can be divided into 3 parts:
Image enhancement, Image compression, Image analysis Image enhancement (Fig.12)
Image compression :
The goal of image compression is to reduce the size of files to make them easier to store and transmit.
Image analysis:
This involves extracting information from the image that is not necessarily visible to the observer.
Measurement: very useful in endodontics to measure the working length (Fig.13) Zoom: enlargement of the image
Fig.13: Measuring the working length in endodontics.
DENTAL FILM
II.5. Reading and Storage:
Once the digital X-ray has been taken, it will be read on the computer screen.
Reading necessarily requires the computerization of the dental office (computer, printer, backup systems) as well as software adapted to the digital radiology system used. At that time, the image can be stored in the computer’s memory (or peripheral).
The archiving of X-rays is therefore computer-based and can be done directly on the hard drive.
III- Summary of the advantages and disadvantages of the different dental films: table.1
| Benefits | |
| Silver film | The digital sensor |
| -High spatial resolution (more than 20 pl/mm), -Easy handling of the film in the mouth (flexible, thin), -Satisfactory hygiene (watertight protective envelope), -Access in several formats (retroalveolar, occlusal and pedo), | – No more use of chemicals – Optimized ergonomics, – Reduced irradiation dose, – High sensitivity: possibility of reducing doses, – Speed of obtaining the image – Possibility of working on the image (brightness, contrast, measurements, enlargement, etc.), – Easy storage, – Communication encouraged both with the patient and with colleagues. |
DENTAL FILM
| Disadvantages | |
| Silver film | The digital sensor |
| -Development: darkroom, long time, cost of films and products, stocks to be constantly renewed, storage of chemical products, etc. -Waste: (lead sheets, development products, etc.) disposal by a specialized organization, -Image processing: Impossible to retouch the image: definitive and static image, Quality depends on development (respect for the durations of each stage, frequency of renewal of products, etc.), -Storage: Need to mark and archive films (risk of loss of films, problem of film aging), -Irradiation: significant but tending to reduce (type E and F films faster and more sensitive, more efficient generators), | Cost: investment (computer hardware, sensor, etc.) and maintenance of this equipment, -Hygiene: non-sterilizable sensors, therefore need to use single-use protections -Spatial resolution: lower than conventional films. -Possibility of computer failures -Temptation to multiply the shots, which leads to an increase in the patient’s irradiation. |
Conclusion
Silver film comes in several sensitivities and its processing requires baths or a developing machine. Observation must be done on a negatoscope. Storage and archiving must be perfectly controlled so that the monitoring of a pathology is possible.
Intraoral electronic sensors and technical progress now make it possible to obtain, with digital radiology , images of good quality than with film, but above all easier to use clinically. The X-rays will be automatically stored and archived in the patient’s digital file.
DENTAL FILM
Wisdom teeth can cause infections if not removed.
Dental crowns restore the function and appearance of damaged teeth.
Swollen gums are often a sign of periodontal disease.
Orthodontic treatments can be performed at any age.
Composite fillings are discreet and durable.
Composite fillings are discreet and durable.
Interdental brushes effectively clean tight spaces.
Visiting the dentist every six months prevents dental problems.