Radiopacity of Universal Flowable Composite Resins: A Comparative Evaluation

This study evaluates the radiopacity of eight universal flowable composite resins and one condensable universal composite resin using digital radiography, comparing their values with enamel and dentin in terms of equivalent aluminum thickness. Twenty-seven disc-shaped specimens (8 mm diameter and 2 mm thickness) were prepared, including one condensable universal composite resin (Filtek Z250) and eight universal flowable resins (Vittra Unique Flow, Neo Spectra ST-Flow, Omnichroma Flow, G-aenial Universal Flo, G-aenial Universal Injectable, Estelite Universal Flow Superlow, Estelite Universal Flow Medium, Estelite Universal Flow High). ImageJ software was used to calculate the mean gray values (MGV) of the specimens and enamel and dentin. EDS and SEM images (×10,000) were obtained. Statistical analysis included the Shapiro-Wilk test and Welch's ANOVA (p = 0.05). Results showed that all universal resins exhibited significantly higher MGV and mm Al values than dentin. Filtek Z250 and Neo Spectra ST-Flow had significantly higher values than enamel, whereas Vittra Unique Flow and G-aenial Universal Injectable displayed values similar to enamel. Other tested composites had MGV and mm Al values between those of enamel and dentin. EDS confirmed that the composites contained at least two radiopaque elements. Despite differences in radiopacity among the universal resins, all tested materials met the radiopacity criteria established by the International Organization for Standardization (ISO).