Applied Adhesion Science最新文献

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.

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.

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.

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 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.

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.

The use of composite materials in structural applications has significantly expanded in recent years. The transport industry accounts for an increasingly larger share of the final structural weight of vehicles, as manufacturers pursue improvements in fuel economy, lighter more efficient designs, and reduction of emissions. However, the delamination of adhesively bonded composite joints causes premature failure of the bond, inhibiting the use of its full potential and leading to inefficient and over-designed components. A hybrid composite metallic material technology is studied in this work, a method inspired in the fibre metal laminate concept, and which combines the best properties of FRPs and metal alloys. The hybrid composite-metallic adherends aims to increase the joint strength in the through thickness direction, minimise peel stresses and limit delamination. The objective of this work was to evaluate the performance of hybrid joints, bonded with different adhesives by comparing them against a reference joint using a conventional Carbon fibre reinforced polymer (CFRP) adherend. The joints were experimentally tested using a universal testing machine for a crosshead speed of 1?mm/min. Numerical models were developed, using the ABAQUS software, to study the behaviour of all joints studied. The numerical predictions of failure loads and modes were compared to the experimentally obtained results.

Natural fibre-reinforced composites have attracted a great deal of attention by the automotive industry mainly due to their sustainable characteristics and low cost. The use of sustainable composites is expected to continuously increase in this area as the cost and weight of vehicles could be partially reduced by replacing glass fibre composites and aluminium with natural fibre composites. Adhesive bonding is the preferred joining method for composites and is increasingly used in the automotive industry. However, the literature on natural fibre reinforced polymer composite adhesive joints is scarce and needs further investigation. The main objective of this study was to investigate experimentally adhesively bonded joints made of natural, synthetic and interlaminar hybrid fibre-reinforced polymer composites. The effect of the number of the interlaminar synthetic layers required in order to match the bonded joint efficiency of a fully synthetic GFRP bonded joint was studied. It was found that the failure load of the hybrid jute/glass adherend joints increased by increasing the number of external synthetic layers (i.e. the failure load of hybrid 3-layer joint increased by 28.6% compared to hybrid 2-layer joint) and reached the pure synthetic adherends joints efficiency due to the optimum compromise between the adherend material property (i.e. stiffness and strength) and a diminished bondline peel stress state.

The adhesion of coatings on a given substrate has fundamental importance on a coating/substrate system's functionality. The current paper presents the adhesion strength results of FeCr and CoCr-based deposits produced by the electric arc thermal spray process on carbon steel, with an intermediate layer of 95Ni5Al. Three chemical compositions were tested for coating deposition and were characterized using plate and tube specimens made of carbon steel UNS?G10200 to result in a screening of performance. Microstructural evaluation by optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were performed. Coating strength was measured using the standard pull-off test method. The corrosion resistance was analyzed with salt spray exposure, electrochemical polarization, and impedance spectroscopy (EIS) tests. The adhesion strength of FeCr and CoCr alloy coatings shows an overall average tensile strength of 27.2?MPa. All sealed conditions presented low corrosion and the samples with epoxy sealant exhibited a high resistance against corrosion. The X-ray diffraction results have revealed alpha and gamma FeCr alloys and chromite as deposited phases after the coating process.

The objective of this study was to analyze morphologically the all-etching bonding system and self-etching bonding system for enamel with different degrees of fluorosis and evaluate the bond strength of each system. Teeth that were indicated for extraction owing to orthodontic or periodontal problems were selected. According to Dean’s index and the Thylstrup-Fejerskov index, 180 extracted teeth were divided into three groups of mild, moderate, and severe dental fluorosis (DF), with 60 teeth in each group. The teeth in each group were randomly divided into two subgroups (n?=?30), which were then subjected to the all-etching bonding system (Prime & Bond NT) and self-etching bonding system (SE-Bond). Each group of adhesives was used to bond Z350 universal resin (3?M) to the etched dental enamel. Tensile and shear tests were conducted to determine the bond strength. Subsequently, the fractured specimens were investigated using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The Prime & Bond NT was statistically significant for the tensile and shear strength of enamel with mild fluorosis (P?<?0.05) but did not exhibit a significant difference for moderate and severe DF (P?>?0.05). The SE-Bond was not statistically significant for the tensile and shear strength of mild, moderate, or severe DF (P?>?0.05). The SEM and CLSM results reveal that the mild fluorosis enamel crystals were relatively dense, and a small amount of resin remained. The moderate fluorosis enamel crystals were loosely arranged, and the gaps were widened. The severe fluorosis enamel crystals were irregularly arranged. The disorder was aggravated, and the dentinal orifice was exposed by partial enamel exfoliation. The bonding strength of mild fluorosis enamel with the Prime & Bond NT was better than that with the SE-Bond, and cohesive failure was the most common mode of failure. Because there was no difference in the bonding strength of the SE-Bond for different degrees of DF, we recommend the use of the all-etching adhesive system in the clinical treatment of teeth with mild fluorosis.