Wear resistance, microhardness and compressive strength of high filled flowable composite resins

This in vitro study evaluated microhardness, compressive strength, and wear resistance of seven composite resins: six high-filled flowable and one conventional resin. A total of 140 specimens were prepared from seven composite resins (n = 20). The materials tested included Omnichroma Flow (OCF), Vittra Unique Flow (VUF), Estelite Universal Flow High (EUFH), Medium (EUFM), Superlow (EUFS), Genial Injectable (GUIN), and Filtek Z250 (FZ250). Wear resistance was measured on cylindrical specimens (12 mm × 2 mm ) using a reciprocating tribometer with a Al₂O₃ antagonist, 20 N load, 1 mm stroke, 2.5 mm/s speed, and 1500 cycles. Compressive strength was tested on cylindrical specimens (4 mm × 6 mm) with a universal testing machine at 0.5 mm/min crosshead speed. Vickers microhardness was measured on disc specimens (2 mm × 8 mm) with a 100 g load for 10 s. One-way ANOVA and Tukey HSD tests (p < 0.05) were used for statistical analysis. EUFH, VUF, and OCF had significantly higher wear volumes than FZ250. FZ250 had greater microhardness than all high-filled flowable composites. Although the compressive strength values of the tested high-filled flowable composites were similar to that of the conventional composite resin, variations were observed among the flowable composites themselves. Under the conditions of this in vitro study, high-filled flowable composites showed comparable compressive strength to a conventional composite resin but tended to exhibit higher wear and lower surface hardness, which should be considered when selecting materials for stress-bearing restorations.