Comparison of physical and biological properties of a flowable fiber reinforced and bulk filling composites

Objective: To evaluate in vitro the mechanical, biological, and polymerization behavior of a flowable bulk-fill composite with fibers as a dispersed phase. Methods: EverX FlowTM (GC Corporation) (EXF), one conventional bulk-fill composite (FiltekTM Bulk Fill Posterior Restorative, 3 M (FBF)), and one flowable bulk composite without fibers (SDR (R) flow+, Dentsply (SDR)) were tested. Samples were characterized in terms of flexural strength (ISO 4049), fracture toughness (ISO 20795-1), and Vickers hardness. Polymerization stress and volumetric shrinkage were evaluated. The in vitro biological assessment was achieved on cultured primary Human Gingival Fibroblast cells (HGF). The cell metabolic activity was evaluated using Alamar Blue assay at 1, 3, and 5 days of contact to the 3 tested composite extracts (ISO 10993) and cell morphology was evaluated by confocal microscopy. Data were submitted to One-Way analysis of variance (ANOVA) and independent t-test (alpha = 0.05). Results: FBF showed statistically higher Vickers hardness and flexural modulus than EXF and SDR. However, EXF showed statistically higher KIC than FBF and SDR. EXF had the statistically highest shrinkage stress values and FBF the lowest. Archimedes volumetric shrinkage showed significantly lower values for FBF as compared to the other two composites. Slight cytotoxic effect was observed for the three composites at day one. An enhancement of metabolic activity at day 5 was observed in cells treated with EXF extracts. Significance: EXF had a significantly higher fracture toughness validating its potential use as a restorative material in stress bearing areas. EXF showed higher shrinkage stress values, and less cytotoxic effect. Fiber reinforced flowable composite is mainly indicated for deep and large cavities, signifying the importance for assessing its shrinkage stress and biological behavior. (c) 2021 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Automated summary

The study evaluated the mechanical, biological, and polymerization behavior of a flowable bulk-fill composite with fibers as a dispersed phase in vitro. EXF showed superior fracture toughness, shrinkage stress, and less cytotoxic effect compared to FBF and SDR. All three composites exhibited slight cytotoxic effects on day one but an increase in metabolic activity was observed in cells treated with EXF extracts on day 5.