Radiolucency

Radiolucency refers to the property of a material or tissue to transmit X-rays with relatively little attenuation, producing dark or gray areas on radiographic images. It is the opposite of radiopacity, where substances absorb more X-ray energy and appear light. Radiolucent areas can reflect air, soft tissue, or less-dense substances within a structure or region imaged by radiography, computed tomography, or other radiologic modalities.

In dentistry, radiolucencies are commonly evaluated on dental radiographs. They indicate regions of lower density than surrounding tissues. Examples include dental caries, which appear as dark lesions in enamel or dentin; the pulp chamber and root canal are radiolucent relative to dentin; and the periodontal ligament space is a thin radiolucent line around the tooth root. More extensive radiolucencies may signal pathology such as inflammatory periapical lesions, cysts, or bone loss from periodontal disease. Radiolucency can also arise from anatomical features, artifacts, or imaging technique.

Interpretation and limitations: Radiolucent findings are not diagnostic on their own and require correlation with clinical examination and, when needed, additional imaging such as cone-beam computed tomography (CBCT) or conventional tomography. Two-dimensional radiographs can obscure or exaggerate lesions due to overlapping structures; radiolucency may represent tissue composition (air, fluid) rather than disease in some contexts.

See also: Radiopacity, radiodensity.