Effect of ethyl cellulose coating as an evaluation agent against contamination on the bond strength of zirconia restorations: An in vitro study.

STATEMENT OF PROBLEM: During the trial placement of zirconia restorations, contamination of the bonding surface is inevitable. Although cleaning methods for contaminated surfaces have been described, a method of preventing saliva contamination of the bonding surface of zirconia restorations is lacking. PURPOSE: The purpose of this in vitro study was to investigate an ethyl cellulose coating as an evaluation agent to mitigate the effects of saliva contamination on the bond strength of zirconia restorations. MATERIAL AND METHODS: Experimental groups representing different cleaning methods of tetragonal yttria-stabilized tetragonal zirconia polycrystal (4Y-TZP) surfaces were investigated for shear bond strength with a resin luting agent, and the failure mode was analyzed. The 9.0×7.0×5.0-mm zirconia blocks (n=72) were assigned as follows: Group N: uncontaminated control; Group CU: contaminated with saliva, followed by ultrasonic cleaning with ethanol; Group CI: contaminated with saliva, followed by application of a zirconia cleaner; Group PCW: preapplication of a zirconia primer, contaminated with saliva, followed by cleaning with water spray; Group ECU: precoating with the ethyl cellulose agent, contaminated with saliva, followed by removal of the agent in an ultrasonic bath with ethanol. Each group was divided into 3 subgroups (immediate, short-term aging, and long-term aging), and the shear bond strength was measured (n=24). To analyze the bonding surface characteristics, the contact angle was measured (n=5). The surfaces of the zirconia specimens in each experimental group were evaluated by using a field emission scanning electron microscope (n=5). Time-of-flight secondary ion mass spectroscopy was used for the chemical analysis of the conditioned surfaces (n=3). A 2-way analysis of variance (ANOVA) with main effect model for shear bond strength results and a 1-way ANOVA for contact angle data were performed as statistical analysis, followed by the Bonferroni post hoc test (α=.05). RESULTS: The shear bond strength was significantly higher in the ECU group than in the groups with the other cleaning methods (P<.05). After the removal of ethyl cellulose with ethanol, the contact angle and surface topography were found to be similar to those of the control group, and no saliva contaminants were identified in the spectroscopy analysis. CONCLUSIONS: Coating with ethyl cellulose may protect the bonding surface of zirconia restorations from salivary contamination better than cleaning a contaminated surface.

Characterization of a Novel CaCO3-Forming Alkali-Tolerant Rhodococcus erythreus S26 as a Filling Agent for Repairing Concrete Cracks.

Biomineralization, a well-known natural phenomenon associated with various microbial species, is being studied to protect and strengthen building materials such as concrete. We characterized Rhodococcus erythreus S26, a novel urease-producing bacterium exhibiting CaCO3-forming activity, and investigated its ability in repairing concrete cracks for the development of environment-friendly sealants. Strain S26 grown in solid medium formed spherical and polygonal CaCO3 crystals. The S26 cells grown in a urea-containing liquid medium caused culture fluid alkalinization and increased CaCO3 levels, indicating that ureolysis was responsible for CaCO3 formation. Urease activity and CaCO3 formation increased with incubation time, reaching a maximum of 2054 U/min/mL and 3.83 g/L, respectively, at day four. The maximum CaCO3 formation was achieved when calcium lactate was used as the calcium source, followed by calcium gluconate. Although cell growth was observed after the induction period at pH 10.5, strain S26 could grow at a wide range of pH 4-10.5, showing its high alkali tolerance. FESEM showed rhombohedral crystals of 20-60 µm in size. EDX analysis indicated the presence of calcium, carbon, and oxygen in the crystals. XRD confirmed these crystals as CaCO3 containing calcite and vaterite. Furthermore, R. erythreus S26 successfully repaired the artificially induced large cracks of 0.4-0.6 mm width.

Enzyme-mediated biocalcification by a novel alkaliphilic Bacillus psychrodurans LC40 and its eco-friendly application as a biosealant for crack healing.

Biocalcification is a natural biochemical process, which has been regarded as a promising method for sequestering heavy metals or carbon dioxide in the environment, healing cracks in concrete structures, and stabilizing soil. One of the key factors in this process is calcium carbonate-producing bacteria. The purpose of this study was to maximize the production of calcium carbonate by alkaliphilic Bacillus psychrodurans LC40 isolated from a limestone cave, by manipulating the medium composition for fast and non-detrimental crack healing, and to investigate the mechanism of its production. Strain LC40 could grow well in the strongly alkaline region (pH 9.5-11), indicating its alkaliphilic nature. The optimal medium for calcium carbonate production contained 2% tryptone, 1.5% urea, 0.15% NaHCO3, and 150 mM calcium formate (pH 6). Using this medium, the yield of calcium carbonate at 72 h was approximately 8.6-fold higher than that obtained through Urea-CaCl2 medium. In this culture, the urease and carbonic anhydrase activities were observed simultaneously, and the pH of the medium was found to have increased to 9.4, leading to maximum calcium carbonate production. This suggests that this pH value is achieved by the synergistic action of the two enzymes, resulting in a high calcium carbonate yield. The crystals were characterized by FESEM, EDS and XRD, which confirmed the production of rhombohedral and spherical calcium carbonate crystals containing vaterite and calcite. Strain LC40 completely healed a 0.75 mm wide crack in a very short time of 3 days using the optimized medium as a cementation solution. Our findings indicate that B. psychrodurans LC40 could be a promising candidate for the development of eco-friendly biosealant applicable to environmentally stressed concrete structures.

Effect of various agitation methods on adhesive layer formation of HEMA-free universal dentin adhesive.

This study evaluates the effects of various agitation methods on the adhesive layer formation of a new HEMA-free universal dentin adhesive. The µTBS of the universal adhesive, G-Premio BOND in the self-etch mode was evaluated using three agitation methods [passive agitation (PA), active agitation (AA), ultrasonic agitation (UA)], with and without aging treatment. Two-way analysis of variance revealed that aging treatment was not a statistically significant factor. Tukey's HSD test showed significant differences based on the application method, UA>AA>PA. TEM images of the PA group revealed multiple water blisters in the adhesive layers; AA and UA groups presented significantly less or no blisters within the adhesive layers; thus, AA and UA groups exhibited better bonding performance for the HEMA-free universal adhesive. It is assumed that the entrap ped blisters can be reduced with the active application of dentin adhesive, and thus improving the bonding performance.

Membrane trafficking of AQP5 and cAMP dependent phosphorylation in bronchial epithelium.

Phosphorylation pathway has been identified as an important step in membrane trafficking for AQP5. We generated stably transfected BEAS-2B human bronchial epithelial cells with various over-expression constructs on permeable support. In stable cells with wild-type AQP5 and S156A (AQP5 mutant targeting PKA consensus sequence), AQP5 expression was predominantly polarized to the apical membrane, whereas stable cells with N185D (AQP5 mutant targeting second NPA motif), mainly localized to the cytoplasm. Treatment with H89 and/or chlorophenylthio-cAMP (cpt-cAMP) did not affect membrane expression of AQP5 in any of three stable cells. In cells with wild-type AQP5 and N185D, AQP5s were phosphorylated by PKA, while phosphorylation of AQP5 was not detected in cells with S156A. These results indicate that, in AQP5, serine156 may be phosphorylated by PKA, but membrane expression of AQP5 may not be regulated by PKA phosphorylation. We conclude that AQP5 membrane targeting can include more than one mechanism besides cAMP dependent phosphorylation.

Development of a quantitative method for active epidermal growth factor extracted from dissolving microneedle by solid phase extraction and liquid chromatography electrospray ionization mass spectrometry.

Dissolving microneedle (DMN), a transdermal drug delivery in which biological drugs are encapsulated in biodegradable and biocompatible polymers, was fabricated using epidermal growth factor (EGF) as a model drug and hyaluronic acid (HA) as a backbone polymeric matrix. After mixing calibration and DMN samples with insulin, an internal standard, solid phase extraction (SPE) was performed to separate EGF and insulin from HA, and then liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS) was conducted for microgram-scale quantitation. The method showed good linearity (R2=0.997) within a specified range (1-4µg). Additionally, the decrease in EGF levels during DMN fabrication was compared using the SPE/LC-ESI-MS and enzyme-linked immunosorbent assay (ELISA), a traditional analytical method. The ELISA method detected an EGF loss of only 3.88±4.67%, whereas SPE/LC-ESI-MS detected a loss of 16.75±4.39%. Qualitative analysis by circular dichroism showed wavelength shift and splitting after DMN fabrication indicating that EGF was denatured during DMN fabrication and cell viability test showed SPE/LC-ESI-MS is more accurate and reliable for detecting the amount of active EGF loaded into the DMN than ELISA.