Microbiological evaluation and bioactivity of an experimental high viscosity bulk-fill resin composite reinforced by niobium and niobium-fluoridated nanoparticles.

Abstract

In the absence of resin composites that have bioactive potential and antimicrobial effects, recurrence of carious lesions adjacent to the material may occur. Therefore, the objective of the present project is to promote the incorporation of different mass concentrations (0.5% and 1%) of Niobium (Nb) and Niobium-fluorinated (Nb-F) nanoparticles in high-viscosity experimental bulk-fill resin, evaluating its bioactive capacity and antimicrobial effect. A total of 6 study groups will be developed: G1: experimental high viscosity bulk-fill resin (RBF - negative control); G2: RBF + Nb 0.5%, G3: RBF + Nb-F 0.5%, G4: RBF with bioactive capacity (Beautiful Restorative, Shofu), G5: RBF + Nb 1% and G6: RBF + Nb-F1 %. An in vitro simulated body fluid test will be carried out, which involves immersing the resin composites in a solution of ionic concentration, composition and pH similar to blood plasma to verify the formation of apatite on the surface of the composites, predicting its bioactive effect in vivo. Therefore, three specimens per group will be immersed in 5 mL of this solution and kept at 37ºC for a total of 21 days. To assess whether there was surface formation of calcium phosphate, Fourier Transform Infrared Spectroscopy (FTIR) analysis will be conducted on the composites at the initial time (t0), after 14 days (t14) and after 21 days (t21) of immersion. The evaluation of the antimicrobial effect will be carried out using the ATCC 25175 strain of Streptococcus mutans, through the induction of biofilm formation in 24-well plates and six composite resin specimens from each group will be immersed in these wells. Media in all wells will be replaced every 48 hours to prevent nutrient depletion for bacteria. After the biofilm growth period, the specimens will be washed, the biofilm will be disaggregated and the quantitative evaluation will be carried out by counting Colony Forming Units (CFU), which will provide data that will be tabulated, with the number of FUc for each ml and per mm2 of the specimens. Analysis by Confocal Laser Microscopy will have the function of differentiating viable bacteria from non-viable ones through pigment staining that identifies damaged membranes (red) and nucleic acids (green). Finally, a statistical analysis will be carried out in the UFC to verify possible significant differences in relation to the control groups, using ANOVA and Tukey's test. Bioactivity and confocal tests will be qualitatively evaluated.