Effect of the incorporation of silica blow spun nanofibers containing silver nanoparticles (SiO2/Ag) on the mechanical, physicochemical, and biological properties of a low-viscosity bulk-fill composite resin

•SiO2/Ag nanofibers were successfully produced by Solution Blow Spinning (SBS).•The incorporation of SiO2/Ag nanofibers improved the microhardness of the composite.•The flexural strength was maintained after simulated ageing for 30 days in water.•Silanization of the nanofibers affected the final properties of the composite. This work aimed at producing silica-blow-spun nanofibers containing silver nanoparticles (SiO2/Ag) and investigating the effect of their incorporation in different proportions, with or without pre-treatment with a silane coupling agent, on the mechanical, physicochemical, and biological properties of a commercial composite low-viscosity bulk-fill resin. The production of SiO2/Ag nanofibers was confirmed by transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). A portion of the produced nanofibers was silanized. Scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), contact angle measurements, and agar diffusion tests against Streptococcus mutans were used to verify the differences between silanized and non-silanized nanofibers. Different proportions (0.5 wt% and 1 wt%) of silanized (SiO2/Ag-0.5S and SiO2/Ag-1S) and non-silanized (SiO2/Ag-0.5NS and SiO2/Ag-1NS) nanofibers were incorporated into the bulk-fill composite (Opus Bulk Fill Flow, FGM). A commercial composite was used as the control. Evaluation of the color parameters (L*, a*, and b*), radiopacity, contact angle, antimicrobial activity, Vickers microhardness, surface roughness (Sa and Sq), flexural strength, and SEM of the fractured surfaces were performed. The data were analyzed using the Mann–Whitney U test (fiber morphology), Kruskal-Wallis tests, with Dunn's post hoc test (antimicrobial activity of the specimen against S. mutans), Student’s t-test (disk diffusion), one-way ANOVA and Tukey (color, radiopacity, and contact angle), and two-way ANOVA and Tukey (microhardness, surface roughness, and flexural strength) tests. All statistical analyses were performed at a significance level of 1% (α = 0.01). Porous nanometric SiO2/Ag fibers were successfully produced. The silanization process, confirmed by FTIR, increased the diameter and contact angle and reduced the growth inhibition halos of the nanofibers (p < 0.01). After the incorporation of nanofibers into the dental composite, all color parameters were altered in all the experimental groups (p < 0.01). All the groups presented adequate radiopacity values. No statisti