An Evaluation of the Biaxial-Flexural Strength of Flowable Composites

Objective. The purpose of this paper is to determine the best of five flowable composites regarding flexural strength: Filtek Supreme Flowable, Venus Flow, Gradia Flow, Heliomolar flowable, and Esthet-X Flow. Methods. All materials were from the same shade (A2): Filtek Supreme Flowable, Venus Flow, Gradia Flow, Heliomolar flowable, and Esthet-X Flow. Cylindrical discs with the diameter of 9mm and thickness of 1.2mm were made using a custom-made stainless steel mold. 21 specimens were prepared for each material. Specimens were immersed in distilled water for 72 hours. After 72 hours, specimens were dried and their dimensions measured using a digital caliper (Mutitoyo Corporation, Tokyo, Japan). The strength test was carried out using a universal mechanical testing system (Instron 8841, Instron Corporation, Canton, MA). In the biaxial fixture, the specimens were supported by three stainless steel ball bearings with the diameter of 1.6 mm equally spaced inside the fixture. A mylar strip was placed on top of each specimen to more uniformly distribute the load from the piston. The specimen was loaded at a crosshead speed of 0.5mm/minute until fracture. Results. A 1-way ANOVA was used to look for differences between samples groups, with Tukey’s HSD test for the post-hoc analysis. Gradia Flow (167.35 MPa) and Filtek Supreme Flowable (163.28 MPa) are significantly stronger than Esthet-X Flow (130.43 MPa), Heliomolar Flow (120.82 MPa) and Venus Flow (103.92 MPa), P < 0.05. Conclusions. The flexural strength of some flowable composites may exceed, or at least be statistically similar to packable composites. Grants. Research supported by Nova Southeastern University.