What appears dark gray or black on a radiograph indicating where x-rays passed through tissue?

Radiolucent areas on a radiograph appear dark gray or black, indicating where x-rays have passed through the tissue without being significantly absorbed. This occurs in areas where there is less density, such as cavities, soft tissues, or surrounding tissues that do not contain high concentrations of minerals, like bone. The x-rays that traverse these less dense areas expose the film or digital sensor to a greater extent, resulting in those regions appearing darker on the resulting image.

In contrast, radiopaque areas are where x-rays are absorbed more strongly, typically found in dense structures like teeth and bone, resulting in lighter areas on the radiograph. Understanding the distinction between radiolucent and radiopaque areas is crucial for accurately diagnosing conditions in dental radiography, as it helps in interpreting the presence of decay, lesions, or other pathological changes.