Flexural Properties, Wear Resistance, and Microstructural Analysis of Highly Filled Flowable Resin Composites

This study aimed to evaluate the flexural properties and two-body wear resistance of nine highly filled flowable resin composites relative to those of viscous and conventional low-filled flowable composites. In addition, scanning electron microscopy (SEM) analysis of the microstructures was performed.

For each resin composite group (n=12), 12 specimen bars (25 mm × 2 mm × 2 mm) were fabricated using a silicon mold for performing flexural strength (FS), flexural modulus (E), flexural toughness (FT), Weibull modulus (m) tests, and SEM microstructural analysis. For each group, ten bars were tested using a three-point flexural test on a universal testing machine, while the other two were embedded in acrylic resin before being observed by SEM for structural analysis. During the two-body wear test with a chewing simulator, 8 specimens (12 groups, n=8) of each resin composite group were manufactured in a specific mold and subjected to 120,000 cycles of wear against a steatite ball, and the depth loss was measured. Three one-way ANOVA tests followed by Tukey's post hoc tests were conducted to compare the flexural and wear properties among the different groups.

The majority of highly filled composites tested in this study exhibited similar flexural strengths (between 105.68 MPa and 135.49 MPa) and superior wear resistance to those of viscous composites. The flexural moduli (between 5.12 GPa and 9.62 GPa) of these composites were in between those of the viscous and low-filled composites tested in this study.

The highly filled flowable composites tested in this study exhibited different in vitro properties but were often superior to those of viscous resin composite suggesting their possible use for posterior restorations.