Influence of Sunscreen Composition on the Apparent Radiopacity of Restorative Materials on Digital Dental Radiography: An In Vitro Study

Background and Objectives: The radiographic interpretation of restorative materials may be influenced not only by their intrinsic composition but also by external substances positioned within the X-ray beam path. Mineral-containing sunscreens (MSs) include metal oxides such as zinc oxide, which may attenuate X-rays and alter radiographic image intensity. This in vitro study evaluated the effects of MS and non-mineral sunscreen (NMS) on the mean gray values (MGVs) and aluminum-equivalent radiopacity of restorative materials. Materials and Methods: Specimens of glass ionomer cement (GIC), flowable composite resin (FC), and resin composite (RC) were covered with a 5 mm polymethyl methacrylate block for soft-tissue simulation. Sunscreens were applied as standardized 1 mm layers, and each material was radiographed under control, NMS, and MS conditions using identical parameters. An 11-step aluminum wedge was used for calibration. MGVs were measured using ImageJ and converted to millimeters of aluminum (mm Al). Results: Restorative material, sunscreen condition, and their interaction significantly affected MGVs (all p < 0.05). NMS produced no significant change compared with control. MS significantly increased the MGVs of GIC, FC, and RC from 67.56, 63.89, and 83.56 to 97.56, 90.00, and 104.11, respectively. Corresponding radiopacity values increased from 2.02, 1.78, and 2.79 mm Al to 3.58, 3.12, and 3.98 mm Al. Conclusions: Under the conditions of this in vitro study, the tested MS significantly increased the apparent radiopacity of all restorative materials, whereas the tested NMS had no significant effect. These findings indicate that the tested mineral-containing formulation, when positioned within the X-ray beam path, can alter the radiographic appearance of dental restorations. Awareness of this potential superimposition effect may help reduce the risk of misinterpretation during radiographic evaluation.