A radiograph is considered ideal when it is dimensionally accurate, covers the area of interest completely and has optimum density and contrast. When the above criteria are not met the radiograph is termed faulty. A faulty radiograph is non-diagnostic and necessitates retaking the radiograph which leads to unnecessary patient exposure.
The overall appearance of the radiograph is dark. The radiographic image will show decreased image contrast and detail and as some authors believe they appear as though the radiographs are being viewed through a fog thereby obscuring the image (Figure 1).
Ideal film storage temperature is between 50°F and 70°F (10–20°C) and between 30% and 50% relative humidity. Any increase is known to cause increased sensitization of the film emulsion. The expiry date of the film packets have to be checked and it is also recommended that the radiology unit stocks only sufficient number of film packets that can be used within 2 months’ time.
Emulsion is coated onto the plastic supportive base of the film and it adheres to the base via a coat of adhesive agent. However, during the developing process, the emulsion is rendered soft to aid in the rapid diffusion of the developing agents into the emulsion and reacts with the silver halide grains. However, the hardeners in the fixing solution shrink and harden the gelatin to prevent its damage. White lines appear when the soft film emulsion is removed from the film base by sharp objects.
Static electricity artifacts are formed due to the build-up of electrons in the emulsion. They are frequently caused by low humidity/dry weather or static producing objects such as synthetic materials used in uniforms. Moreover, when films are removed from the film packet or the cassette too rapidly in a dry atmosphere, a small charge of electricity can be released producing these artifacts.
Static artifacts have two common appearances: tree like and smudges. Tree like artifacts (Figure 3) are produced when films are unwrapped rapidly and appear as black lines running across the film and smudge static electricity is produced by polyester clothing and appear as black smudges on the film.
A lead foil is placed within every intraoral radiographic film packet to prevent unnecessary exposure to surrounding structures from the residual X-ray beam and also protects the film from back scatter or secondary radiation that may result in film fog.
Though the term ‘herring bone pattern’ is widely used, many of the new film packets do not display this pattern on the lead foil, rather the tyre mark (Figure 5A) or knurled pattern (Figure 5B) are common.