Radiopacity of contemporary flowable resin composites with different material formulations

To evaluate and compare the radiopacity of contemporary flowable resin composites representing different material types using a digital radiographic system and aluminum-equivalent measurements.

Six flowable resin composites, including universal injectable, bulk-fill, ormocer-based, and short-fiber-reinforced formulations, were investigated. Disc-shaped specimens (5 mm × 2 mm) were prepared and radiographed using a photostimulable phosphor (PSP) system together with a 21-step aluminum step wedge and tooth sections containing enamel and dentin. Mean gray values were measured using ImageJ software and converted to millimeter aluminum equivalent (mm Al) values. Data were analyzed using one-way ANOVA and Tukey's HSD test (α = 0.05).

Significant differences were observed among the tested composite materials (p < 0.001). GC G-ænial Universal Injectable exhibited the highest radiopacity (5.54 ± 0.09 mm Al), whereas Omnichroma Flow Bulk showed the lowest value (2.77 ± 0.09 mm Al). All tested composites exhibited mean radiopacity values above the dentin reference and met the minimum radiopacity requirement specified by ISO 4049.

Radiopacity varied significantly among the tested flowable resin composites, demonstrating that materials with similar clinical indications may differ considerably in their radiographic visibility. These findings suggest that radiopacity should be considered alongside other material properties when selecting restorative materials, particularly in clinical situations where accurate radiographic interpretation during follow-up is important.