Which statement correctly describes radiopaque areas on dental radiographs?

• A. Pulp and PDL absorb more x-rays.
• B. Dentin absorbs and transmits x-rays somewhere in between.
• C. Enamel and lamina dura absorb more x-rays.
• D. Cortical bone absorbs less.

Answer: (C)

Radiopaque areas on dental radiographs are structures that attenuate a lot of the X-ray beam, so they appear lighter. Enamel is the most mineralized tissue in a tooth, so it blocks X-rays strongly and shows up as very bright. The lamina dura, the dense bone lining around the tooth root, also attenuates X-rays significantly and appears as a thin, bright border. Dentin is less mineralized than enamel, so it’s radiopaque but not as bright; the pulp and periodontal ligament space are soft tissues and appear radiolucent (darker). Cortical bone is dense and radiopaque as well, but saying it absorbs less contradicts its density. Therefore, enamel and lamina dura correctly describe radiopaque areas.