Radiographic detection of recurrent carious lesions associated with composite restorations. The greatest potential problem associated with posterior composite restoration is secondary caries detection. It is essential that secondary caries is detected as early as possible to enhance the prognosis for a successful treatment outcome. This laboratory study evaluated the optimum level of radiopacity of composite materials for radiographic detection of secondary carious lesions associated with composite materials. Results indicated that for the radiologic detection of secondary caries, it is sufficient for composite materials to have the same level of radiopacity as enamel. 