Recurrent caries around a restoration on a radiograph is most accurately described as what?

• A. A radiolucent area with diffuse margins beneath or adjacent to a restoration
• B. A radiopaque area within the restoration
• C. A radiolucent line at the tooth apex
• D. A radiopaque halo around the restoration

Answer: (A)

Recurrent caries around a restoration shows up on radiographs as a radiolucent area along the tooth–restoration interface, typically beneath or adjacent to the restoration, with diffuse, poorly defined margins. This pattern reflects demineralization happening at the margin due to microleakage and bacterial activity under the restoration, not within the restorative material itself. The radiolucent change extends from the margin into the dentin, distinguishing it from decay that starts away from the restoration or from internal flaws in the filling.

The other patterns don’t fit recurrent caries: a radiopaque area within the restoration would indicate the restorative material or another radiopaque component, not decay; a radiolucent line at the tooth apex suggests a periapical lesion, not caries at the margin; a radiopaque halo around the restoration isn’t the appearance of decay.