Evaluation of the radiopacity of different universal composite resins aged by thermocycling.

The aim of this study is to evaluate the effects of thermocycling and material thickness on the radiopacity values of various universal composite resins. A total of 18 different composite resin materials were tested, including 7 single-shade, 6 polyshade, and 5 simply-shade composites. Disk-shaped specimens with a diameter of 5 mm and thicknesses of 1 mm and 2 mm were prepared from each material. Radiographic images of all specimens were taken alongside an aluminium step-wedge and tooth sections (enamel and dentin) of corresponding thickness. Using the ImageJ software, the mean gray values (MGV) of each specimen, the 15 steps of the aluminium wedge, and the enamel and dentin sections were measured. These values were converted into aluminium equivalents (mm Al). Differences among materials were analyzed using one-way ANOVA and Tukey's multiple comparison test, while differences related to thickness and aging were evaluated with two-way ANOVA and Tukey's test. The level of statistical significance was set at p < 0.05. All composite resin samples exhibited significantly higher radiopacity values than dentin (p < 0.05). The 2 mm thick samples showed greater radiopacity than those with 1 mm thickness (p = 0.000). The material with the highest radiopacity was Charisma Diamond. Among the 1 mm thick specimens before thermocycling, the lowest radiopacity was observed in Omnichroma. In other parameters, Clearfil Majesty ES-2 exhibited the lowest radiopacity values. All tested composite resins demonstrated higher radiopacity values compared to dentin and met the criteria set by the International Organization for Standardization (ISO). Material thickness significantly affected radiopacity. However, radiopacity values varied among materials after thermocycling through thermocycling.