Final answer:
Radiolucent structures on dental x-ray files appear dark or black, while radiopaque structures appear white or light-toned. Fillings are radiopaque and block the passage of X-rays, so they will not appear radiolucent on dental x-ray files.
Step-by-step explanation:
On a dental x-ray file, structures that are radiolucent appear dark or black, indicating that X-rays can pass through them easily. Some examples of radiolucent structures in dental x-rays include tooth decay, cavities, and spaces between teeth. However, fillings, crowns, and other restorative materials are radiopaque and appear white or light-toned on the x-ray, as they block the passage of X-rays. Therefore, the correct answer is that fillings will not appear radiolucent on dental x-ray files.