It is in these cases that radiographs play such an important role in the identification of dental caries. Demineralization and destruction of hard tooth structures result in a loss of tooth density in the area of the lesion. The decreased density allows a greater penetration of x-rays in the carious area, and as a result, the carious lesion appears as a radiolucency on a dental radiograph. Radiolucent structures permit the passage of the x-ray beam and appear dark or black on a dental radiograph. The degree of radiolucency seen on a dental radiograph is determined by the extent and severity of the destruction seen as a result of the caries process.
Caries is always farther advanced clinically than what is seen on a dental radiograph.
The early changes associated with demineralization do not affect the density of the tooth, and consequently, an increased penetration of the x-ray beam is not seen. The bite-wing radiograph, a radiograph that shows the crowns of both the upper and lower teeth on the same film, is the radiograph of choice for the evaluation of dental caries. A periapical radiograph utilizing the paralleling technique can also be used to detect interproximal caries. The premolar bite-wing should demonstrate the distal contact areas of both the maxillary and mandibular canines.