![]() One corner of each dental film has a small, raised dot that is used for film orientation ( Fig. Some diagnostic tasks, such as detection of incipient caries or early periapical disease, require this higher resolution. Direct exposure film is used for intraoral examinations because it provides higher resolution images than screen-film combinations. With a double layer of emulsion, less radiation is required to produce an image. Intraoral dental x-ray film is made as a double-emulsion film-that is, both sides of the base are coated with an emulsion. The base is uniformly translucent and casts no pattern on the resultant radiograph. The film base must also withstand exposure to processing solutions without becoming distorted. The base for dental x-ray film is made of polyester polyethylene terephthalate, which provides the proper degree of flexibility to allow easy handling of the film. The function of the film base is to support the emulsion. Screen film and intensifying screens are used for extraoral projections, such as panoramic and cephalometric radiographs. Screen film is used with intensifying screens (described later in this chapter) that emit visible light. All intraoral dental film is direct exposure film. Film intended to be exposed by x rays is called direct exposure film. This barrier helps protect the film from damage by scratching, contamination, or pressure from rollers when an automatic processor is used.įilm emulsions are sensitive to both x-ray photons and visible light. An additional layer of vehicle is added to the film emulsion as an overcoat. During film processing (described later in this chapter) the vehicle absorbs processing solutions, allowing the chemicals to reach and react with the silver halide grains. The silver halide grains are suspended in a surrounding vehicle that is applied to both sides of the supporting base. ![]() (Courtesy Carestream Dental, a division of Carestream Health, Inc.) The orientation of the tabular crystals in the emulsion is essentially parallel to the film surface to increase the exposure surface of the crystals to the incident x-ray beam. INSIGHT film has about twice the number of silver grains so that it requires only half the exposure of Ultra-speed film.įIGURE 5-3 Cross-sectional electron microscope image of emulsion of INSIGHT film. The tabular grains are oriented parallel with the film surface to offer a large cross-sectional area to the x-ray beam ( Fig. The silver halide grains in INSIGHT film and Ultra-speed film (Carestream Dental, a division of Carestream Health, Inc.) are flat, tabular crystals with a mean diameter of about 1.8 µm ( Fig. The composition of a dental film emulsion is shown in Table 5-1. The silver halide grains are composed primarily of crystals of silver bromide. The two principal components of emulsion are silver halide grains, which are sensitive to x radiation and visible light, and a vehicle matrix in which the crystals are suspended. (Courtesy Carestream Dental, a division of Carestream Health, Inc.) Emulsion Note the overcoat, emulsion, and base on this double-emulsion film. 5-1).įIGURE 5-1 Scanning electron micrograph of INSIGHT dental x-ray film (original magnification 300×). The base is a plastic supporting material onto which the emulsion is coated ( Fig. The emulsion, which is sensitive to x rays and visible light, records the radiographic image. X-ray film has two principal components: (1) emulsion and (2) base. Digital radiographic systems, which also may be used to make radiographs, are described in Chapter 4. This chapter describes x-ray film and film processing and the use of intensifying screens. The image receptor most often used in dental radiography is x-ray film. ![]() For this information to be useful diagnostically, the remnant beam must be recorded on an image receptor. The pattern of the photons that exits the patient, the remnant beam, conveys information about the patient’s anatomy. ![]() A beam of x-ray photons that passes through the dental arches is reduced in intensity (attenuated) by absorption and scattering of photons out of the primary beam. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |