Which feature distinguishes recurrent caries near a restoration from a primary caries lesion radiographically?

• A. A radiolucent area with diffuse margins beneath or adjacent to a restoration
• B. A narrow radiolucent line along the enamel
• C. A radiopaque area within dentin
• D. A circular radiolucent spot within the crown

Answer: (A)

Recurrent caries near a restoration tend to show a radiolucent area at or just beneath the tooth-restoration interface, often with diffuse, ill-defined margins. This pattern reflects decay that undermines and spreads under the edge of the restoration, indicating the problem is adjacent to, not away from, the preserved tooth structure.

Primary caries, in contrast, usually appear on unrestored surfaces and show a radiolucency beginning in enamel or dentin with more defined margins as it progresses away from restorations. The other patterns described—such as a narrow line along enamel, a radiopaque area in dentin, or a circular radiolucent spot within the crown—do not typify recurrent caries at the restoration margin.