Aqueous processes yielding hybrid or composite materials are widespread in natural environments and their control is fundamental for a multiplicity of living organisms. Their design and in vitro engineering require knowledge about the spatiotemporal evolution of the interactions between the involved liquid and solid phases and, especially, the interphases governing the development of adhesion during solidification. The present study illustrates the effects of distinct proteins on the precipitation of sodium chloride encompassing the size, shape and distribution of halite crystals formed during the drying of droplets containing equally concentrated saline protein solutions. The precipitates obtained from aqueous sodium chloride formulations buffered with tris(hydroxymethyl)aminomethane (Tris) contained either bovine serum albumin (BSA), fibrinogen or collagen and were characterized with respect to their structure and composition using optical and electron microscopy as well as x-ray analysis. The acquired findings highlight that depending on the protein type present during droplet drying the halite deposits predominantly exhibit cubic or polycrystalline dendritic structures. Based on the phenomenological findings, it is suggested that the formation of the interphase between the growing salt phase and the highly viscous saline aqueous jelly phase containing protein governs not only the material transport in the liquid but also the material exchange between the solid and liquid phases.
Mimosa tenuiflora (Willd.) Poir. (MT) is an underutilized plant specie since its wood is mostly used for energy production. Nonetheless, the bark from this forest plant has a high amount of tannins and other valuable compounds. Tannins have high worldwide importance and, because of that, there is an increasing number of researches on biorefinery systems aiming at maximizing their exploitation. The present study evaluated tannins extracted from the MT bark and their use for producing wood adhesives. Three types of powdered tannins were extracted using different solvents: a pure aqueous solution, a 5% sodium hydroxide (NaOH) aqueous solution, and a 5% sodium bisulfite (NaHSO3) aqueous solution. Distilled water, wheat flour, and formaldehyde were also used as a solvent, a glue extender, and a catalyst, respectively. These adhesives were applied for bonding pine wood joints and their shear strengths were determined. All the MT-based adhesives showed high viscosities and, yielded glue lines with similar shear strengths and similar shear deformations if compared to each other. That tannin-based glue incorporated with the tannin extracted using NaOH or NaHSO3 stood out and yielded similar bonding performances if compared to a commercial adhesive applied as a positive control.
Introduction Bacterial adherence to restorative materials such as composite resin is one of the aetiology of secondary caries. This study evaluated the antibacterial efficacy of fifth generation bonding agent (BA) modified with nisin, against Streptococcus mutans based on its growth, adherence and membrane integrity. Methods Adhesive eluents of the experimental bonding agents were obtained using 250 μl Brain Heart Infusion (BHI) broth and the groups were control (BA with 0% Nisin), bonding agent with 1 wt% (NBA 1) and 5 wt% nisin (NBA 5). To this, 10 μl S. mutans culture was added and incubated at 37 °C. Bacterial growth was estimated by changes in optical density using spectrophotometer every 20 min for 2 h. The results were statistically analysed using one way ANOVA followed by Tukey Post Hoc test. For adherence and membrane integrity test, 10 μl of BHI supplemented with 1% sucrose and 50 μl of bacterial suspension were inoculated onto the cured specimens, and incubated for 4 h. After rinsing, 1 ml of Live/Dead BacLight bacterial viability stain was added and incubated in the dark for 15 min and observed under confocal laser scanning microscope (CLSM) for intact (green/live) and damaged (red/dead) bacterial membranes. Results Mean optical density was significantly higher in control group at all time intervals with maximum value at 2 h (0.83 ± 0.008), while there was a concentration dependant reduction in bacterial growth with the NBA groups (0.50 ± 0.007). Correspondingly, the NBA groups showed higher amount of dead than live bacteria, while live bacteria were predominant in the control group. Significance Addition of an antibacterial agent nisin in dentin bonding agent may render the resin dentin interface more resistant to bacterial penetration, and adherence of cariogenic bacteria like S. mutans .
The aim of the article was to determine the compressive strength and compressive strain of an unmodified and a modified epoxy compounds containing a montmorillonite filler, as well as to determine the effect of temperature and an aging time on the mechanical parameters of the considered epoxy compounds. The subject of the research was both the unmodified and the modified adhesive compounds. The unmodified epoxy compounds were made in four variants, which included the epoxy resins based on a bisphenol A as well as the curing agents: a triethylenetetramine and a polyamide curing agent. The modified compounds containing the montmorillonite filler, were also made in four variants. The samples were subjected in a thermal chamber at 80 °C for 1 and 2 months and in a thermal shock chamber in the temperature range from − 40 °C to 80 °C for 1 and 2 months. The reference samples were seasoned at room temperature 20–25 °C. The epoxy compounds samples were subjected to the compression strength tests in accordance with ISO 604 standard. The compressive strength is influenced by the environment and temperature, the aging time and the presence of the modifying agent. The epoxy compounds subjected at elevated or variable temperatures have higher compressive strength than the reference epoxy compounds. The operation of the climatic chamber or the thermal shock chamber makes the samples more deformable than the reference samples.
The aim was to evaluate the effect of different antioxidant agents on the improvement of bond strength to enamel subjected to a whitening procedure. Samples were divided into six groups (n = 10): control; whitening immediately followed by restorative treatment (WHT); whitening and restoration after a 7-day period (WHT_7D); whitening and application of 10% sodium ascorbate (WHT_SA); application of 5% grape seed extract (WHT_GS); and application of 5% green tea (WHT_GT). All groups except for control fwere whitened (Opalescence PF Regular 16%) for 7 days (4 h/day). All samples were restored (Optibond™ FL, Kerr and Filtek™ Z250 composite, 3M ESPE). In antioxidant groups these were applied for 15 min and immediately restored. Specimens were sectioned in microspecimens (1.0 ± 0.2 mm2 area) for microtensile bond strength (μTBS) testing (0.5 mm/min) on a universal testing machine. ANOVA test with Brown-Forsythe correction and Games-Howell post-hoc test was used (significance level of 5%). Antioxidant groups presented significant higher mean μTBS values than group WHT (p < 0.001). The non-whitened control group was not significantly different to antioxidant experimental groups. Group WHT_7D exhibited a significantly higher mean μTBS value when compared to group WHT (p = 0.022). The different antioxidants significantly influenced microtensile bond strength of restored teeth after whitening.
