Storage In Water Research Articles

Investigation on the effect of interlaced yarn structures on bending properties of textile reinforced cement composite with cold plasma treated polypropylene fabric

The aim of this study is to investigate the effects of yarn intermingling parameters on the bending properties of cement-based composites reinforced with polypropylene fabric treated under cold plasma. In this research, FDY (Fully drawn yarn) polypropylene yarn by three types of Heberlein intermingle jet inserts (P212, P412, S16), was subjected to entanglement process. Then, meshes were woven in plain weave design. The meshes were subjected to cold plasma jet treatment with argon and nitrogen at different exposure time. The fabric surface roughness was studied by friction test. Reinforced cement composite beams were made which after 28 days of storage in water, were subjected to 4-point bending test. The results show that the jet insert change with changing the degree of entanglement affects the toughness and bending properties. The max toughness is related to the plasma untreated fabric reinforced cement composite containing raw yarn (FDY) which is equal to 2388.875 (N.mm). Also, the max bending force is related to the fabric-reinforced sample consisting of interlaced yarn by P412 jet insert and plasma untreated fabric (1249.567 (N)).

USE OF DEAD OAK WOOD IN FURNITURE PRODUCTS

Today, furniture made of wood, on which the openings of insect passageways are visible, is popular. Artificially creating such holes on healthy wood does not meet the aesthetic needs of consumers. Considering the annual increase of 8-10 thousand hectares in drying oak stands in Ukraine and, accordingly, the cost of deadwood reduced by almost 50%, it is proposed to use it after proper treatment to destroy pests for the manufacture of furniture products. An analysis of wood disinfection methods was carried out, which transformed over time from non-toxic substances and processing methods – oil, tar, resin, storage in salt water, charring to modern ones using harmful chemical compounds – pentachlorophenol, alkaline chloride, sodium fluorosilicates, tars, DDT, etc. Analysis of available methods for exterminating timber pests allowed distinguishing antiseptics, fumigation, ultra-high frequency current treatment and thermal modification. The purpose of this study was to determine the method of disinfection of sawn goods made from deadwood oak for further use in furniture products. Theoretical and experimental methods were used to achieve this purpose. The scientific originality of this study lies in the application of the fuzzy logic method to select the priority method of wood disinfection, which lies in decomposition of the problem into simpler components and step-by-step prioritisation of the evaluated components using paired comparisons. For alternative options to achieve the purpose, the following criteria were applied: efficiency, environmental friendliness, industrial manufacturability, durability of the result. The corresponding calculations performed, confirmed by the required consistency index, showed the priority of the method of thermal modification of wood. Experimental studies of heat treatment with the proposed modes of deadwood oak with existing pests, namely Xyleborus dispar (Xyleborus dispar), were carried out. The study determined the possibility of using the action of hot temperatures (t>110 °C) for complete sterilisation of deadwood oak. The result of practical application of this eco-safe method for the manufacture of tabletops has shown its effectiveness and can be useful for furniture makers

Surface milled by CAD-CAM system Vs laboratorial methods to simulate the milled surface: Effect on the resin bond strength to lithium disilicate glass-ceramic

The aim of this study was to assess the resin microshear bond strength (μSBS) and the surface topography of lithium disilicate ceramic milled by CAD/CAM and to compare it with in-lab methods that simulate the topography of milled surfaces; thus, assessing the feasibility of those in-lab methods for in vitro microshear studies. The study was composed of 2 control groups (CAD/CAM group – discs were milled by a CAD/CAM system; POL – polished ceramics surface) and 4 testing groups (SiC – manual grinding simulation with #60 silicon carbide paper; WS – manual grinding with #60 wood-sandpaper; DB – grinding with a fine cylindrical diamond bur; MANDREL – grinding with a CAD/CAM bur coupled to a mandrel). After production, the ceramic samples were crystallized. Surface treatment with hydrofluoric acid (HF) and silane was performed on the bonding surface, then the starch matrices were filled by the resin cement and light-activated. The specimens (n= 45) were submitted to μSBS after 24 h of storage in water (37° C) and the failure pattern was analyzed. Topographic analysis, surface roughness, contact angle, and fractal dimension were performed. One-way ANOVA and Tukey's post-hoc tests were run for roughness, while Bonferroni’ post hoc was used for μSBS data. Fractal dimension data was qualitatively assessed. No difference was found in the μSBS between in-lab simulation methods and the milled group, while the polished group presented the lowest μSBS values. The CAD/CAM milled specimens presented the highest roughness values, while the POL the lowest ones. In regards to surface complexity, no difference was found among all simulated groups and the CAD/CAM group, with an exception for the POL group. All conditions presented an increase in surface complexity after HF etching. Therefore, the resin bond strength to lithium disilicate glass-ceramic is not influenced by the in-lab simulation method, meaning they are predictable approaches when evaluating the resin bonding to the tested ceramic; the surface polishing underestimates the bond results in ∼40%.

Effect of Gravel Content on Mechanical Performance and Porous Structure of Concrete

Concrete is the most widely used material in the field of civil engineering. In order to obtain a strong and durable concrete, it is necessary to study the various parameters entering into its formulation. Mainly the elements forming the concrete skeleton, in particular the gravel content. The transfer of water into concrete directly affects its durability. This transfer is linked to the porous structure and to the continuity of the pores in the concrete. This research studies the effect of gravel content on compressive strength, porosity accessible to water, depth of water penetration and ultrasonic velocity of concrete samples. The study includes 15 types of concrete made by varying the gravel-sand ratio (G/S), 0, 1, 1.5, 2 and 2.5. The cement dosage is taken equal to 150, 250 and 350 Kg/m3. The tests are carried out on cubic samples 10x10x10 cm3 and 15x15x15 cm3 after storage in water for 28 days. The experimental results obtained show that the gravel-sand ratio (G/S) affects the mechanical strength and the porous structure of concrete. Increasing the gravel content in concrete leads to an increase in mechanical strength and ultrasonic speed. However, a high gravel content results in a reduction in the porosity accessible to water and the depth of water penetration.

Effect of C-factor on Micro-tensile Bond Strength of Bulk fill V/S Micro-hybrid Composite in Class II Restorations - An In-Vitro Study.

High Configuration factor (C-factor) results into increased polymerization shrinkage causing stress at resin-dentin interface leading to failure of the restoration. The purpose of this study was to evaluate the effect of C-factor on micro-tensile bond strength (μTBS) of bulk fill composites in class-II cavities when restored in 4mm of bulk as compared to conventional composite. A total of 90 carious, crack free extracted human mandibular permanent molars were selected and randomly divided into 3 groups (n=30). On all samples, class II cavities (3.5X 3.5cm) were made by single operator and divided as Gp1 (2.5mm), Gp2 (4mm), and Gp3 (6mm) on the basis of depth of cavities. Sampling units of 30 in each group were further randomly subdivided into 3 subgroups (n=10 each subgroup), according to the type of composite resin systems to be used for restoration. Experimental Subgroup includes SubGp1 restored with SDR Surefil (Dentsply, caulk, USA) and SubGp2 restored with Sonic fill (kerr, orange, CA, USA), whereas SubGp3 restored with FILTEK Z250 served as control. After storage in water at 37◦C, the teeth were sectioned perpendicular to the restorative tooth interface as 1×1 mm non-trimmed rectangular micro-specimens for micro-tensile bond strength (μTBS) testing. Beams (n=30 max) from each SubGp were fixed to a metal jig and subjected to micro-tensile bond strength testing. The data collected for micro-tensile bond strength (expressed in Mpa) were statistically analysed using one way ANOVA and Tukey's post hoc test. In class II cavities with high C-factor, SDR Surefil showed better μTBS than SonicFill and micro-filled composite when filled in bulk of 4mm, as compared to micro-hybrid composite filled incrementally. There is no effect of high C-factor on μTBS of tooth restored with both SDR Surefil and Sonic Fill in class II cavities as compared to microhybrid composites.

Influence of pH Cycling on Erosive Wear and Color Stability of High-Viscosity Glass Ionomer Cements.

The purpose of this in vitro study was to evaluate erosive wear and change in color of high-viscosity glass ionomer cements after pH cycling in two erosive media. There were 3 experimental groups with 22 samples each, (I) EQUIA Forte HT without coat, (II) Fuji IX and (III) Ketac Universal Aplicap. Each group was randomly divided into three subgroups (n = 6–8) further exposed to different environments, (1) distilled water, (2) green tea (pH 3.78) and (3) Aceto balsamico vinegar (pH 3.0). Mass and L* a* b* values were recorded before and after pH cycling. The samples in subgroups 2 and 3 were exposed to the acidic media two times a day for 10 min, over a period of 14 days. The differences among materials and erosive effects of the three media were tested using three-way analyses of variance with post hoc LSD test at the significance level p < 0.05. The effect of pH cycling in Aceto balsamico and green tea was degrading for all three materials. pH cycling in Aceto balsamico caused significantly higher erosive wear than pH cycling in Fuzetea and storage in distilled water, in all materials (p < 0.05). pH cycling in both acidic media and in the control group resulted in a significant change in L* a* and b* (p < 0.05). The L* value decreased significantly and the a* and b* values increased significantly (p < 0.05).

Triacrylamide-Based Adhesives Stabilize Bonds in Physiologic Conditions

In this study, an acrylamide-based adhesive was combined with a thiourethane-based composite to improve bond stability and reduce polymerization stress, respectively, of simulated composite restorations. The stability testing was conducted under physiologic conditions, combining mechanical and bacterial challenges. Urethane dimethacrylate was combined with a newly synthesized triacrylamide (TMAAEA) or HEMA (2-hydroxyethyl-methacrylate; control) to produce a 2-step total-etch adhesive system. Methacrylate-based composites (70 wt% silanized filler) were formulated, containing thiourethane oligomers at 0 (control) or 20 wt%. Standardized preparations in human third molars were restored; then, epoxy replicas were obtained from the occlusal surfaces before and after 7-d storage in water or with Streptococcus mutans biofilm, which was tested after storage in an incubator (static) or the bioreactor (mechanical challenge). Images were obtained from the replicas (scanning electron microscopy) and cross sections of the samples (confocal laser scanning microscopy) and then analyzed to obtain measurements of gap, bacterial infiltration, and demineralization. Microtensile bond strength of specimens stored in water or biofilm was assessed in 1-mm2 stick specimens. Data were analyzed with analysis of variance and Tukey’s test (α = 0.05). HEMA-based materials had greater initial gap measurements, indicating more efficient bonding for the acrylamide materials. When tested in water, the triacrylamide-based adhesive had smaller gaps in the incubator or bioreactor. In the presence of biofilm, there was less difference among materials, but the acrylamide/thiourethane combination led to statistically lower gap formation in the bioreactor. HEMA and TMAAEA-based adhesives produced statistically similar microtensile bond strengths after being stored in water for 7 d, but after the same period with biofilm-challenged specimens, the TMAAEA-based adhesives were the only ones to retain the initial bond strength values. The use of a stable multiacrylamide-based adhesive led to the preservation of the resin-dentin bonded interface after a physiologically relevant challenge. Future studies will include a multispecies biofilm model.

Exploring the use of a Ruthenium complex incorporated into a methacrylate-based dental material for antimicrobial photodynamic therapy.

To evaluate the effects of a blue light photosensitizer (PS), Ruthenium II complex (Ru), on the chemical, physical, mechanical, and antimicrobial properties of experimental dental resin blends. The experimental resin (BisEMA, TEEGDMA, HPMA, ethanol, and photoinitiator) was loaded with Ru at 0.00%, 0.07%, 0.14%, 0.28%, 0.56%, 1.12%, 1.2%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% w/w. Samples were evaluated for the degree of conversion (DC) after 30 and 60 s curing-time (n = 6). Selected formulations (0.00%, 0.28%, 0.56%, 1.12%) were further tested for shear bond strength (SBS) (n = 15); flexural strength (FS) (n = 12); and antimicrobial properties (CFUs), in dark and light conditions. These latter tests were performed on specimens stored for 24-h or 2-month in 37°C water. Water sorption (WS) and solubility (SL) tests were also performed (n = 12). Data were analyzed either by a one- or two-factor general linear model (α = 0.05). Overall, Ru concentration above 1.2% resulted in reduced DC. In SBS results, only the 1.12%Ru resin blend samples had statistically lower values compared to the 0.00%Ru resin blend at 24-h storage (p = 0.004). In addition, no differences in SBS were detected among the experimental groups after 2-month storage in water. Meanwhile, FS increased for all experimental groups under similar aging conditions (p < 0.001). Antimicrobial properties were improved upon inclusion of Ru and application of light (p < 0.001 for both) at 24-h and 2-month storage. Lastly, no detectable changes in WS or SL were observed for the Ru-added resins compared to the 0.00%Ru resin blend. However, the 0.28% Ru blend presented significantly higher WS compared to the 0.56% Ru blend (p = 0.007). Stable SBS, improved FS, and sustained antimicrobial properties after aging gives significant credence to our approach of adding the Ruthenium II complex into dental adhesive resin blends intended for an aPDT approach.

Effect of conditioning and 3-year aging on the bond strength and interfacial morphology of glass-ionomer cement bonded to dentin

Background/purposeGlass-ionomer cement (GIC) is bioactive and independent. Bioactivity, which is a big trend in restorative dentistry. When they actively stimulate with microbiological species besides their primary function of restoring tooth structure then restorative materials should called “bioactive” materials. The purpose of this study was to determine the bond stability and the change in interfacial ultra-structure of a conventional glass-ionomer cement bonded to dentin, with and without pre-treatment using a polyalkenoic acid conditioner. Material and methodsThe occlusal dentin surfaces of six teeth were ground flat. Glass-ionomer cement was bonded to the surfaces either with or without polyalkenoic acid conditioning. The teeth were sectioned into 1-mm2 stick-shaped specimens. The specimens obtained were randomly assigned to two groups with different periods of storage in water: 1-week and 3-year. The micro-tensile bond strength (μTBS) was determined for each storage time. Additional specimens were prepared for interfacial analysis by using Scanning Electron Microscopy (SEM); they were produced with or without prior polyalkenoic acid conditioning in the same way as in the μTBS test. ResultsThere was no significant difference in μTBS to conditioned dentin and non-conditioned dentin (p > 0.05). The failures appeared to be of a mixed nature, although aging caused more areas of cohesive than adhesive failure in both groups. ConclusionAging did not reduce the bond strength of the conventional glass-ionomer cement to dentin with or without the use of a polyalkenoic acid conditioner. Remineralized dentin layer were observed in both conditioned and unconditioned 3-years specimens.

A Comparison of Solubility Among Zinc Oxide Eucalyptus and Zinc Oxide Eugenol: An In Vitro Study

Introduction: We aimed to compare solubility between zinc oxide eugenol and zinc oxide eucalyptus. Methods: One hundred and twenty standardized plastic ring molds were constructed and filled with zinc oxide eugenol and zinc oxide eucalyptus. The specimens were allowed to dry for 24 hours and then weighed to the nearest 0.0001 g. Then divided randomly into three groups and immersed in distilled water for 1, 7, and 21 days. Then samples were removed from the solution and allowed to dry for 24 hours. Then they were weighed again, the percentage of weight loss was then determined as solubility. Data analyzed by two-way repeated measures ANOVA and the Tukey’s post-hoc test using MedCalc 20.104. Results: Zinc oxide eucalyptus solubility is more than zinc oxide eugenol. All tests of between-subjects effects and within-subjects effects showed statistically significant differences (P < 0.001). Conclusion: The 1st day results showed solubility of not more than 3% following storage in distilled water which meet the requirements of ISO 6876, where both zinc oxide-eugenol (ZOE) (0.05%) and zinc oxide eucalyptus (0.15%) satisfied these criteria.

Comparative efficacy of three deproteinizing agents on the shear bond strength of pit and fissure sealant: An in vitro study

Objective: The objective of this study was to evaluate and compare the shear bond strength (SBS) of pit and fissure sealant with and without deproteinization with agents such as 5% NaOCl, papain gel, and bromelain gel.Materials and Methods: In this in vitro study, 60 premolar teeth were divided into four groups of 15 teeth each. In control Group 1, enamel was etched for 60 s with 37% phosphoric acid and rinsed with water. In Group 2, deproteinizing agent 5% sodium hypochlorite was applied for 60 s before acid etching. In Group 3, deproteinizing agent papain gel was applied for 60 s before acid etching. In Group 4, deproteinizing agent bromelain gel was applied for 60 s before acid etching. Following this, Clinpro™ 3M™ ESPE™ pit and fissure sealant disc was built on the enamel buccal surface of each tooth. Samples were then tested for SBS using Universal Testing Machine after storage in distilled water for 24 h.Results: The mean SBS was highest for Group 4 and lowest for Group 1. SBS was significantly higher in the bromelain gel group, followed by the papain gel group (P < 0.001), 5% NaOCl group (P < 0.001), and control group (P < 0.001).Conclusion: Among deproteinizing agents, deproteinization when carried out with bromelain gel showed effective bond strength and lowest for the control group.

Release characterization and biological effect of Glass Ionomer Functionalized with two different chlorohexidine derivatives: an in vitro study

Objective: To evaluate the effect of adding two different chlorohexidine derivatives; chlorhexidine hexametaphosphate and chlorhexidine digluconate to glass ionomer at three different concentrations (0.25%, 0.75%and 1.5%) regarding the antibacterial effect, chlorhexidine release and fluoride release. Methods: A total of 405 specimens were prepared and tested after 7 days, 3 months and 6 months of storage in distilled water (n=5).For testing antibacterial effect, chlorhexidine release and fluoride release, the mix was packed in a ready-made Split Teflon molds to obtain disc-shaped specimen with dimensions 10 mm in diameter and 2 mm thickness according to ISO standardizations. One-way ANOVA and One-way repeated measure ANOVA test were used for statistical analysis of data. Results: The incorporation of chlorhexidine into ChemFil Superior glass ionomer cement in both derivatives has high significance ability to provide a long-term antimicrobial effect on Streptococcus mutans and Lactobacillius acidophilus. The chlorhexidine release was increased by adding chlorhexidine in both derivatives to GIC than the unmodified Glass-ionomer cement for study duration. However, the fluoride release was decreased in the modified specimens than the original one. Conclusion: Addition of chlorhexidine enhanced the antibacterial effect of the glass ionomer and chlorhexidine release. However, fluoride release was reduced than original

Effects of 3 different light-curing units on the physico-mechanical properties of bleach-shade resin composites.

ObjectivesThis study investigated the microhardness, flexural strength, and color stability of bleach-shade resin composites cured with 3 different light-curing units.Materials and MethodsIn this in vitro experimental study, 270 samples were fabricated of bleach and A2 shades of 3 commercial resin composites (Point 4, G-aenial Anterior, and Estelite Sigma Quick). Samples (n = 5 for each trial) were cured with Bluephase N, Woodpecker LED.D, and Optilux 501 units and underwent Vickers microhardness and flexural strength tests. The samples were tested after 24 hours of storage in distilled water. Color was assessed using a spectrophotometer immediately after preparation and 24 hours after curing. Data were analyzed using 3-way analysis of variance and the Tukey test (p ≤ 0.001).ResultsSamples cured with Optilux exhibited the highest and those cured with LED.D exhibited the lowest microhardness (p = 0.023). The bleach shade of Point 4 composite cured with Optilux displayed the highest flexural strength, while the same composite and shade cured with Sigma Quick exhibited the lowest (p ≤ 0.001). The color change after 24 hours was greatest for the bleach shade of G-aenial cured with Bluephase N and least for the A2 shade of Sigma Quick cured with Optilux (p ≤ 0.001).ConclusionsLight curing with polywave light-emitting diode (LED) yielded results between or statistically similar to those of quartz-tungsten-halogen and monowave LED in the microhardness and flexural strength of both A2 and bleach shades of resin composites. However, the brands of light-curing devices showed significant differences in color stability.

Effect of oral irrigation device and its solution type on the surface roughness and topography of Bulk-fill composite resins.

BackgroundSurface roughness and topography of composite resin materials have a significant role in biofilm aggregation, periodontitis, and recurrent caries. The present study evaluated the effect of the Waterpik oral irrigation device (OID) with different solution [water/ chlorhexidine (CHX)] on the surface roughness and topography of microhybrid (x-tra fil) and nanohybrid (Tetric N-Ceram Bulk) bulk-fill composite resins. Material and MethodsDisk-shaped samples were prepared from each composite resin, measuring 5 mm in diameter and 3 mm in height, and assigned to three groups in terms of treatment (n=19): group A, control (storage in distilled water); group B, OID with water; group C, OID with 0.5% CHX. The samples were treated for eight weeks, simulating one-year use of OID. Profilometry and scanning electron microscopy (SEM) were used to evaluate and compare quantitatively surface roughness (Ra) and qualitative topography of composite resin surfaces before and after treatment. The data were analyzed with paired-samples, Wilcoxon, and generalized estimating equations tests (α=0.05). ResultsThe application of OID increased the Ra of composite resin compared to the control group (P<0.001). No significant difference was detected between the two solutions (water and CHX) (P=0.615). The effect of composite resin type and the cumulative effect of composite resin type and OID solution were not significant on the surface roughness changes of the samples (P=0.243 and P=0.464, respectively). ConclusionsOID with water and CHX solutions increased the surface roughness and topographic changes of microhybrid and nanohybrid bulk-fill composite resins. Key words:Composite resins, irrigation, mouthrinse, surface roughness, topography.

Photothermal sensor based on water-soluble CsPbBr3@sulfobutylether-β-cyclodextrins nanocomposite using a thermometer as readout

All-inorganic perovskite quantum dots (CsPbX3 QDs) with bright photoluminescence are suitable for application in optoelectronic field, but their extreme instability and insolubility in aqueous solution limit their development in other fields. Herein, for the first time, we encapsulated CsPbBr3 QDs using sulfobutylether-β-cyclodextrins to form nanocomposite (CsPbBr3@SBE-β-CD nanocomposite) with high water solubility and stability via a host-guest interaction strategy, in which the PL intensity remained above 100% of the initial value after 3 h storage in water. Hydrogen sulfide (H2S) is known to be an important mediator of diverse cellular functions in health and in disease, which is important to develop a selective and portable detection method for H2S. The obtained CsPbBr3@SBE-β-CD nanocomposite was employed to develop a photothermal sensor for quantitative detection of H2S using a thermometer as signal readout. Specifically, the obtained CsPbBr3@SBE-β-CD nanocomposite was used as the photothermal probe while H2S acted as a switch of the photothermal probe, and the photothermal sensor was triggered by the reaction between H2S and CsPbBr3@SBE-β-CD nanocomposite. Notably, the naked eye and fluorescence spectrophotometer could also be the signal readout for this strategy, and their detection range and limit of detection were not better than those of the proposed photothermal sensor. On the basis of this H2S-triggered photothermal sensor, H2S was successfully detected at a concentration as low as 5.0 µM in organs of adult zebrafish at room temperature for 10 min. Such innovative strategy enables new opportunity for the development of affordable assays, especially as point-of-care testing in low-resource settings.

Effect of different cleaning methods after surface treatment of dental ceramics on the surface characteristics and adhesion to resin-based luting agents

The aim of this study was to assess the efficacy of cleaning methods after the surface treatment of dental ceramics. Ceramic slabs (zirconia – Yz; lithium disilicate-reinforced glass – Ld; and porcelain – Pc), were submitted to different surface treatments (air abrasion for Yz and hydrofluoric acid etching for Ld and Pc), and after, six cleaning methods were tested: DW – distilled water for 60 s; AL – 70% alcohol for 60 s + DW; UDW – ultrasonic bath with distilled water for 60 s; UAL – ultrasonic bath with 70% alcohol for 60 s + DW; IVC – ivoclean for 20 s + DW; PAC – 37% phosphoric acid for 20 s + DW. Microshear bond strength to luting agent was tested after 24 h (baseline) or 6 months storage (aged) in water at 37 °C. Complementary analysis of failure pattern, surface topography and composition, and contact angle measurements were executed. The cleaning methods promoted similar bond strength for Ld and Pc, regardless of the condition (baseline and aged) and for Yz after aging. DW, AL, and PAC decreased the contact angle for Yz, while UAL decreased for Ld. Pc presented a higher wettability with UDW, UAL, and PAC. The use of IVC and PAC resulted in precipitates in the Pc surface. For Yz, more air-abrasion remnants were observed using DW; for both Ld and Pc, a higher presence of fluorine was observed in groups treated with IVC. Despite differences in surface composition, topography and contact angle measurements, after aging the bond strength to the tested ceramic materials was similar regardless of the different cleaning methods.

Long-term hydrolytic stability of CAD/CAM composite blocks.

This study aimed to assess water sorption and solubility of CAD/CAM composite blocks compared to CAD/CAM ceramic after 8 months storage in water and artificial saliva. Eight CAD/CAM blocks were investigated: Five resin-composite blocks (RCBs), one polymer-infiltrated ceramic network (PICN) block, one ceramic-filled polyetheretherketone (PEEK) block, and one feldspathic ceramic block. One hundred and twelve specimens were prepared comprising 14 specimens of each of the eight materials. From each group of specimens, seven randomly selected specimens were immersed in 10mL of water, while the other seven specimens were immersed in artificial saliva. All specimens were stored at 37°C and weighed at various time intervals. The data were analysed via repeat measures ANOVA, one-way ANOVA and Tukey's post hoc test (α=0.05 for all tests). Sorption values (mean [SD]) in water were within the range -1.21 (0.4) to 39.3 (2.1) μg/mm3 and in artificial saliva between -0.7 (0.2) and 41.6 (1.3) μg/mm3 . Solubility values in water were between -0.43 (0.08) and 0.34 (0.18) μg/mm3 and in artificial saliva between -0.53 (0.07) μg/mm3 and 0.33 (0.2) μg/mm3 . CAD/CAM composite blocks were hydrolytically stable under long-term storage (according to ISO 4949:2009), although not as stable as ceramic. Water sorption of CAD/CAM composite blocks was dependent on the resin-matrix and was influenced by the filler weight %.

Interannual Variability of Methane Storage and Emission During Autumn Overturn in a Small Lake

AbstractMethane emissions from freshwater systems, and especially from small lakes, source a significant proportion of naturally produced atmospheric methane. In small temperate lakes, storage flux, that is, the diffusive emission of methane that was stored in anoxic waters during the seasonal overturn of the water column, can contribute a large fraction of annual methane emissions. Here, we use an extensive field data set to quantify methane storage in anoxic deep water and identify as well as quantify the sources and losses of this methane. The comparison of measurements from 4 years in a small temperate lake (Illmensee) shows that methane storage can differ substantially between years. In 2012 and 2018, the annual maximum of the methane stored in the entire water column was around twice as high (5,350 and 5,822 kg) as in 2013 and 2017 (2,722 and 2,295 kg). A methane mass balance approach suggests that the variability of methane storage in the anoxic water between the years was not caused by the methane flux at the anoxic–oxic water interface, but rather was related to changes in the methane source from the anoxic sediments. The interannual differences in sediment flux could not be explained by sediment temperature, but rather by the differing supply of organic matter. Our findings suggest that phytoplankton blooms promote methane storage within the same year and thus cause interannual variability in emissions during autumn overturn.

Fracture strength of teeth with coronal destruction after core build-up restoration with bulk fill materials.

This study aimed to evaluate the fracture strength and failure modes of different core techniques in teeth with simulated coronal destruction. Forty teeth were endodontically prepared and the specimens were divided into four experimental groups (n= 10) according to the core composition: Filtek One Bulk Fill-FOBF, Filtek Z350 XT-FZ350 (standard group), Filtek Bulk Fill Flow-FBFF, and LuxaCore Z-LCZ. CAD/CAM Monolithic zirconia crowns were obtained and cemented with RelyX U200. After storage in distilled water at 37°C for 48 h, the specimens were subjected to thermal cycling and to compressive strength mechanical tests. Statistical analyses (α= 0.05) were performed by non-parametric Kruskal-Wallis, Dunn post hoc, and Fisher's exact tests. No significant differences (p> 0.05) were observed among FOBF, FZ350, and FBFF (mean ranks=20.30, 12.20, and 23.20, respectively). LCZ (mean rank=26.30) produced results similar to those of FOBF and FBFF (p> 0.05) and higher than those of FZ350 (p= 0.042). The most frequent type of failure was irreparable, regardless of the experimental condition. The lowest percentages of reparable fractures were produced by FOBF group (10%). The use of bulk fill materials, including the "core-and-post" LCZ dual-cure resin composite, did not impair the fracture strength of endodontically treated teeth with coronal destruction. Resin composite bulk fill materials that can be used as a core-and-post cementation in an only stage are interesting, since they enable clinicians to work with one only material, and avoid several materials interfaces, technical sensitivity, and longer chair-time due to multistep procedures.

Evaluation of CO2 storage of water alternating gas flooding using experimental and numerical simulation methods

The potential of water alternating gas (WAG) flooding in CO2 storage was exploited using experimental and numerical simulation methods in this study. Through comparing experiments results of WAG flooding and continuous CO2 flooding, WAG flooding after water flooding enhanced oil recovery by 39.0%, 2.2% higher than that of continuous CO2 flooding. However, the water slugs in WAG displaced part of the previously stored CO2 out the core. Only 13.1% of the injected CO2 was stored through WAG, 13.4% lower than that of continuous CO2 flooding. Then, numerical simulations of WAG and continuous CO2 flooding were conducted at a water flooded oil reservoir. The field-scale case study showed that the number of rounds of alteration from CO2 slug to water slug in WAG, the duration time of each round, and the CO2 injection time in each round were the main factors influencing CO2 storage. Improper design of influencing parameters led to 118,986 tons lower CO2 storage through WAG than continuous CO2 flooding. Finally, to obtain the maximum CO2 storage, surrogate optimization was applied to adjust the proposed influencing factors. The optimization results showed less rounds of alteration and a pure CO2 slug size at the end improved the CO2 swept area in the reservoir for CO2 storage and inhibited the displacement of CO2 by water slug. After optimization of the proposed factors, 391,000 tons of CO2 were stored in the water flooded oil reservoir through WAG flooding, 65,764 tons more than continuous CO2 flooding. This study provides valuable experimental data and theoretical guidance for CO2 storage in water flooded oil reservoirs.