What anatomical structures appear radiolucent in a dental radiograph?

Radiolucent structures on a dental radiograph are typically those that permit X-rays to pass through more easily, resulting in darker areas on the image. The correct answer identifies air spaces and soft tissues as radiolucent. In dental radiography, air spaces (such as the maxillary sinus or the oral cavity) and soft tissues (like periodontal ligaments, muscles, and mucosa) appear dark because they absorb fewer X-rays compared to denser structures like bone and metal.

The other options consist of materials that are denser and hence appear radiopaque on radiographs, meaning they block X-rays and appear lighter. Bone, for instance, contains minerals that absorb a significant amount of X-rays, making it appear bright. Similarly, enamel and dentin, which are the hard structures of the tooth, also have high densities due to their mineral content. Metal, such as dental restorations, is extremely radiopaque, appearing very light or white on a radiograph because it blocks almost all X-rays.

Understanding these distinctions is crucial for interpreting dental radiographs accurately and for assessing the health of oral structures.