Influence of zinc-modified niobium nanoparticles incorporation in resinous monomers on mechanical properties

This in vitro study evaluated the influence of the incorporation of different concentrations of zinc-modified niobium nanoparticles (Nb/Zn) on the mechanical properties of a flowable resin composite (OptiFlow II, LC/Pac-Dent) by surface hardness (SH), depth of cure (DoC), flexural strength (FS), and modulus of elasticity (E). The morphology and composition of Nb/Zn nanoparticles were evaluated by Scanning Electron Microscopy and energy-dispersive X-ray spectroscopy (EDX). The Nb/Zn nanoparticles were incorporated at 3 different concentrations (0.3%; 0.6% e 0.9%), resulting in four groups: OptiFlowII, OptiFlow II+0.3%Nb/Zn, OptiFlow II+0.6%Nb/Zn, and OptiFlow II+0.9%Nb/Zn. SH was measured at the top and bottom of the specimens (n=6/group). FS and E were conducted using a Universal Testing Machine (Instron, 50N) (n=14/group). For SH, DoC, and FS, ANOVA followed by Tukey's test was used for statistical analyses, and for E, pairwise comparisons were conducted using a sandwich covariance matrix (p<0.05). The results showed that OptiFlow II+0.6%Nb/Zn exhibited the lowest top-SH values in all comparisons (p=0.003). Regarding DoC, the data indicated a significant difference between the groups with 0.3% and 0.6% Nb/Zn (p=0.04). For E, OptiFlow II+0.3%Nb/Zn presented higher values (E=3.48±0.15)a compared to OptiFlow II+0.6%Nb/Zn (E=3.3±0.18; p=0.02)b, OptiFlowII presented higher values (E=3.56±0.27)a than OptiFlow II+0.6%Nb/Zn (p=0.01) and OptiFlow II+0.9%Nb/Zn (E=3.3±0.27; p=0.02)b. Thus, the incorporation of Nb/Zn nanoparticles at different concentrations into the OptiFlow II affects its mechanical properties, without altering the depth of cure, but reducing flexural strength. The group with the lowest nanoparticle concentration showed E similar to that of the control group and higher than that of the higher-concentration groups. Overall, the incorporation of Nb/Zn nanoparticles influenced the mechanical behavior of the flowable resin composite. Lower concentrations performed similarly to the control, while higher levels impaired properties, highlighting the need for optimized nanoparticle loading.