As previously mentioned in my blog post “Types of Radiographs” intra-oral films are placed inside a patients’ mouth when a radiograph is being taken, therefore they must be reasonably small in order to fit comfortably inside the mouth. There are several sizes available;
- 31 x 41 mm
- 22 x 35 mm
These sizes are used for bitewing and Periapical radiographs.
- 57 x 76 mm (This less common sized film is used for occlusal radiographs.)
Because radiographic films are fairly flexible and the intra-oral films are so small they are quite comfortable for the patient when a radiograph needs to be taken, but this can also mean that this type of image receptor is the most vulnerable one to damage from the patient during use. Using a film holder can significantly reduce the risk of damage and it is good practice to use one anyway for intra-oral films.
Another factor to consider with intra-oral radiographs is that they are placed in a wet environment – inside a patients’ mouth, therefore the film must be be kept inside a waterproof covering. Intra-oral radiographic films are provided already inside a protective covering which can remain in place during the exposure and will not affect the resultant image, but these coverings, or film packets, provide protection to more than just light and saliva.
Intra-oral film packets consist of a number of layers;
- The exterior of the film packet is waterproof – usually plastic, to protect the film from saliva.
The plastic packet is either coloured or marked in some way in order to show the user which is the front and which is the back of the film and to indicate the film speed.
Film speed basically determines the speed at which the film will react to x-rays. The higher the film speed the less exposure and therefore the lower the radiation dose required to produce a quality image. Most dentists use ‘E’ or ‘F’ speed films, which are the fastest films which will still produce good quality radiographic images. Different manufacturers use different colours to show the speed of the film enclosed.
- The radiographic film found inside the plastic packet is covered with black protective paper. This paper is primarily used to protect the film from light, but it also acts as barrier to prevent damage to the film from the person handling it during processing, it is also an added layer of protection in case the waterproof covering is ineffective.
- At the back of the film is a thin layer of lead foil. Lead foil is used to protect the patients’ tissues from any residual radiation which would continue through the film to the surrounding tissues if the lead foil were not present. This foil also prevents any scattered secondary radiation scattering back onto the film and degrading the image.
Although radiographic intra-oral films are comfortable for the patient and are provided in a protective plastic packet they do have one drawback in particular, which is that the film must be manually processed, this not only gives rise to potential problems with the final image but is also time consuming, the dentist and patient will have to wait for several minutes before the image can be viewed and assessed. They also require a slightly higher dose of radiation to be used than digital image receptors do, in order for a quality radiographic image to be produced.