Improving Interfacial and Compressive Properties of Polyimide Fiber by Constructing Inorganic Layers on Fiber Surface.

The compressive performance of organic fiber has always been a key problem, limiting its development. In this paper, silicon oxide, alumina, and titanium oxide particles were separately deposited on the surface of high-strength and high-modulus polyimide (PI) fibers to form a structural supporting shell by using a magnetron sputtering method. The theoretical thickness was calculated by thermogravimetric analysis in good agreement with the actual thickness determined from scanning electron microscopy. The mechanics, surface, and interface properties of the measured fibers were analyzed mainly from the aspects of surface energy, interfacial shear strength (IFSS), and compression strength. The results showed that after magnetron sputtering, the inorganic shells were uniformly deposited on the surface of PI fiber, resulting in an increase in the content of inorganic elements as well as the roughness. As a result, the surface energy and IFSS of silica-coated fiber was increased by 174 and 85.6%, respectively, and compression strength was increased by 45.7%. This study provides a new approach for improving the interface property and compression strength of high-strength and high-modulus PI-fiber-reinforced composites.

Advance Analysis of the Obtained Recycled Materials from Used Disposable Surgical Masks.

The production of personal protective equipment (PPE) has increased dramatically in recent years, not only because of the pandemic, but also because of stricter legislation in the field of Employee Protection. The increasing use of PPE, including disposable surgical masks (DSMs), is putting additional pressure on waste collectors. For this reason, it is necessary to find high-quality solutions for this type of waste. Mechanical recycling is still the most common type of recycling, but the recyclates are often classified as low-grade materials. For this reason, a detailed analysis of the recyclates is necessary. These data will help us to improve the properties and find the right end application that will increase the value of the materials. This work represents an extended analysis of the recyclates obtained from DSMs, manufactured from different polymers. Using surface and morphology tests, we have gained insights into the distribution of different polymers in polymer blends and their effects on mechanical and surface properties. It was found that the addition of ear loop material to the PP melt makes the material tougher. In the polymer blends obtained, PP and PA 6 form the surface (affects surface properties), while PU and PET are distributed mainly inside the injection-molded samples.

Strategies for Improving Impaired Osseointegration in Compromised Animal Models.

Implant osseointegration is reduced in patients with systemic conditions that compromise bone quality, such as osteoporosis, disuse syndrome, and type 2 diabetes. Studies using rodent models designed to mimic these compromised conditions demonstrated reduced bone-to-implant contact (BIC) or a decline in bone mineral density. These adverse effects are a consequence of disrupted intercellular communication. A variety of approaches have been developed to compensate for the altered microenvironment inherent in compromised conditions, including the use of biologics and implant surface modification. Chemical and physical modification of surface properties at the microscale, mesoscale, and nanoscale levels to closely resemble the surface topography of osteoclast resorption pits found in bone has proven to be a highly effective strategy for improving implant osseointegration. The addition of hydrophilicity to the surface further enhances osteoblast response at the bone-implant interface. These surface modifications, applied either alone or in combination, improve osseointegration by increasing proliferation and osteoblastic differentiation of osteoprogenitor cells and enhancing angiogenesis while modulating osteoclast activity to achieve net new bone formation, although the specific effects vary with surface treatment. In addition to direct effects on surface-attached cells, the communication between bone marrow stromal cells and immunomodulatory cells is sensitive to these surface properties. This article reports on the advances in titanium surface modifications, alone and in combination with novel therapeutics in animal models of human disease affecting bone quality. It offers clinically translatable perspectives for clinicians to consider when using different surface modification strategies to improve long-term implant performance in compromised patients. This review supports the use of surface modifications, bioactive coatings, and localized therapeutics as pragmatic approaches to improve BIC and enhance osteogenic activity from both structural and molecular standpoints.

Removal of multiple pesticides from water by different types of membranes.

Pesticides are used in agriculture to protect crops from pathogens, insects, fungi and weeds, but the release of pesticides into surface/groundwater by agriculture runoff and rain has raised serious concerns not only for the environment but also for human health. This study aimed to investigate the impact of surface properties on the performance of seven distinct membrane types utilized in nanofiltration (NF), reverse osmosis (RO) and forward osmosis (FO) processes in eliminating multiple pesticides from spiked water. Out of the membranes tested, two are self-fabricated RO membranes while the rest are commercially available membranes. Our results revealed that the self-fabricated RO membranes performed better than other commercial membranes (e.g., SW30XLE, NF270, Duracid and FO) in rejecting the targeted pesticides by achieving at least 99% rejections regardless of the size of pesticides and their log Kow value. Despite the marginally lower water flux exhibited by the self-fabricated membrane compared to the commercial BW30 membrane, its exceptional ability to reject both mono- and divalent salts renders it more apt for treating water sources containing not only pesticides but also various dissolved ions. The enhanced performance of the self-fabricated RO membrane is mainly attributed to the presence of a hydrophilic interlayer (between the polyamide layer and substrate) and the incorporation of hydrophilic nanosheets in tuning its surface characteristics. The findings of the work provide insight into the importance of membrane surface modification for the application of not only the desalination process but also for the removal of contaminants of emerging concern.

Metabolomic reveals the responses of sludge properties and microbial communities to high nitrite stress in denitrifying phosphorus removal systems.

Nitrite, as an electron acceptor, plays a good role in denitrifying phosphorus removal (DPR); however, high nitrite concentration has adverse affects on sludge performance. We investigated the precise mechanisms of responses of sludge to high nitrite stress, including surface characteristics, intracellular and extracellular components, microbial and metabolic responses. When the nitrite stress reached 90 mg/L, the sludge settling performance was improved, but the activated sludge was aging. FTIR and XPS analysis revealed a significant increase in the hydrophobicity of the sludge, resulting in improve settling performance. However, the intracellular carbon sources synthesis was inhibited. In addition, the components in the tightly bound extracellular polymeric substances (TB-EPS) of sludge were significantly reduced and indicated the disturb of metabolism. Notably, Exiguobacterium emerged as a new genus when face high nitrite stress that could maintaining survival in hostile environments. Moreover, metabolomic analysis demonstrated strong biological response to nitrite stress further supported above results that include the inhibited of carbohydrate and amino acid metabolism. More importantly, some lipids (PS, PA, LysoPA, LysoPC and LysoPE) were significantly upregulated that related enhanced membrane lipid remodeling. The comprehensive analyses provide novel insights into the high nitrite stress responses mechanisms in activated sludge systems.

Wnt16 Increases Bone-to-Implant Contact in an Osteopenic Rat Model by Increasing Proliferation and Regulating the Differentiation of Bone Marrow Stromal Cells.

Osseointegration is a complex biological cascade that regulates bone regeneration after implant placement. Implants possessing complex multiscale surface topographies augment this regenerative process through the regulation of bone marrow stromal cells (MSCs) that are in contact with the implant surface. One pathway regulating osteoblastic differentiation is Wnt signaling, and upregulation of non-canonical Wnts increases differentiation of MSCs on these titanium substrates. Wnt16 is a non-canonical Wnt shown to regulate bone morphology in mouse models. This study evaluated the role of Wnt16 during surface-mediated osteoblastic differentiation of MSCs in vitro and osseointegration in vivo. MSCs were cultured on Ti substrates with different surface properties and non-canonical Wnt expression was determined. Subsequently, MSCs were cultured on Ti substrates +/-Wnt16 (100 ng/mL) and anti-Wnt16 antibodies (2 µg/mL). Wnt16 expression was increased in cells grown on microrough surfaces that were processed to be hydrophilic and have nanoscale roughness. However, treatment MSCs on these surfaces with exogenous rhWnt16b increased total DNA content and osteoprotegerin production, but reduced osteoblastic differentiation and production of local factors necessary for osteogenesis. Addition of anti-Wnt16 antibodies blocked the inhibitor effects of Wnt16. The response to Wnt16 was likely independent of other osteogenic pathways like Wnt11-Wnt5a signaling and semaphorin 3a signaling. We used an established rat model of cortical and trabecular femoral bone impairment following botox injections (2 injections of 8 units/leg each, starting and maintenance doses) to assess Wnt16 effects on whole bone morphology and implant osseointegration. Wnt16 injections did not alter whole bone morphology significantly (BV/TV, cortical thickness, restoration of trabecular bone) but were effective at increasing cortical bone-to-implant contact during impaired osseointegration in the botox model. The mechanical quality of the increased bone was not sufficient to rescue the deleterious effects of botox. Clinically, these results are important to understand the interaction of cortical and trabecular bone during implant integration. They suggest a role for Wnt16 in modulating bone remodeling by reducing osteoclastic activity. Targeted strategies to temporally regulate Wnt16 after implant placement could be used to improve osseointegration by increasing the net pool of osteoprogenitor cells.

Surface Treatment of Dental Mini-Sized Implants and Screws: A Systematic Review with Meta-Analysis.

Miniscrews are devices that allow for absolute skeletal anchorage. However, their use has a higher failure rate (10-30%) than dental implants (10%). To overcome these flaws, chemical and/or mechanical treatment of the surface of miniscrews has been suggested. There is no consensus in the current literature about which of these methods is the gold standard; thus, our objective was to carry out a systematic review and meta-analysis of the literature on surface treatments of miniscrews. The review protocol was registered (PROSPERO CRD42023408011) and is in accordance with the PRISMA guidelines. A bibliographic search was carried out on PubMed via MEDLINE, Cochrane Library, Embase and Web of Science. The initial search of the databases yielded 1684 results, with 98 studies included in the review, with one article originating from the search in the bibliographic references of the included studies. The results of this systematic review show that the protocols of miniscrew surface treatments, such as acid-etching; sandblasting, large-grit and acid-etching; photofunctionalization with ultraviolet light; and photobiomodulation, can increase stability and the success of orthodontic treatment. The meta-analysis revealed that the treatment with the highest removal torque is SLA, followed by acid-etching. On the other hand, techniques such as oxidative anodization, anodization with pre-calcification and heat treatment, as well as deposition of chemical compounds, require further investigation to confirm their effectiveness.

Effect of sintering programs and surface treatments on monolithic zirconia.

PURPOSE: To investigate the effect of sintering programs and surface treatments on surface properties, phase transformation and flexural strength of monolithic zirconia. MATERIALS AND METHODS: Zirconia specimens were sintered using three distinct sintering programs [classic (C), speed (S), and superspeed (SS)] (n = 56, each). One sample from each group underwent scanning electron microscopy (SEM) and grain size analysis following sintering. Remaining samples were divided into five subgroups (n = 11) based on the surface treatments: control (CL), polish (P), glaze (G), grind + polish (GP), and grind + glaze (GG). One sample from each subgroup underwent SEM analysis. Remaining samples were thermally aged. Monoclinic phase volume, surface roughness, and three-point flexural strength were measured. Monoclinic phase volume and surface roughness were analyzed by Kruskal-Wallis and Dunn tests. Flexural strength was analyzed by two-way ANOVA and Weibull analysis. The relationships among the groups were analyzed using Spearman's correlation analysis. RESULTS: Sintering program, surface treatment, and sintering × surface treatment (P ≤ .010) affected the monoclinic phase volume, whereas the type of surface treatment and sintering × surface treatment affected the surface roughness (P < .001). Type of sintering program or surface treatment did not affect the flexural strength. Weibull analysis revealed no significant differences between the m and σo values. Monoclinic phase volume was positively correlated with surface roughness in the SGG and SSP groups. CONCLUSION: After sintering monolithic zirconia in each of the three sintering programs, each of the surface treatments can be used. However, for surface quality and aging resistance, G or GG can be recommended as a surface finishing method.

Effect of Non-Thermal Sulfur Hexafluoride Cold Plasma Modification on Surface Properties of Polyoxymethylene.

X-ray photoelectron spectroscopy was employed to reveal the differences in the chemical structure of the topmost layer after plasma modification. It was found out that changes in the surface properties of the polymer could be observed even after 20 seconds of treatment. The surface becomes hydrophobic or superhydrophobic, with the water contact angles up to 160 degrees. Morphological changes and increased roughness can be observed only in the nanoscale, whereas the structure seems to be unaffected in the microscale. As a result of plasma modification a permanent hydrophobic effect was obtained on the polyoxymethylene surface.

In situ retention of lignin-rich bamboo green effectively improves the surface properties of flattened bamboo.

Bamboo has tremendous carbon sequestration potential, and bamboo green is underutilized. This work devised a green-keeping technique in bamboo flattening that preserved natural bamboo green in-situ. The impacts of flattening and green-keeping on bamboo morphology, chemical composition, physical qualities, and composite applications were examined. Bamboo cells were wrinkled after flattening, while bamboo green exhibited a more homogenous surface. Bamboo cellulose crystallinity increased after flattening, hemicellulose deteriorated little, and relative lignin content increased. The hydrophobicity and mildew resistance of the surface of G-FB (green-kept flattened bamboo board) were improved. Compared to untreated bamboo, FB and G-FB had 61.1 % and 49.5 % higher tensile strength and 8.0 % and 33.2 % higher MOR. G-FB-made flooring exhibited a MOR of 134.7 MPa and upgraded surface properties. Bamboo green preservation boosted utilization of materials and improved flattened bamboo's exterior surface without affecting lamination bonding. Simple bamboo green preservation multifunctionalizes flattened bamboo composites.

Aesthetic impact of resin infiltration and its mechanical effect on ceramic bonding for white spot lesions.

BACKGROUND: Treating white spot lesions (WSLs) with resin infiltration alone may not be sufficient, raising questions about its compatibility with other treatments amid controversial or incomplete data. Therefore, this study aimed to assess the aesthetic feasibility of resin infiltration combined with bleaching, as well as its potential mechanical effect on ceramic bonding to WSLs. METHODS: One hundred and fifty flat enamel surfaces of bovine incisors were prepared. Ninety specimens were deminerailized and randomly assigned to three groups(n = 30): post-bleaching resin infiltration (Bl-R), pre-bleaching resin infiltration (R-Bl), and only resin infiltration (R). Color, surface roughness and microhardness were assessed in immediate, thermocycling and pigmentation tests. The remaining sixty samples were randomly assigned to three groups (n = 20): control (Ctrl), bonding (Bo), pre-bonding resin infiltration (R-Bo). Shear bonding strength, failure mode, micro-leakage depth and interface morphology were evaluated after ceramic bonding. The Tukey test and analysis of variance (ANOVA) were used for statistical analysis. RESULTS: For the effect of resin infiltration and bleaching on WSLs, the R-Bl group showed the worst chromic masking ability, with the highest |ΔL|, |Δa|, |Δb|, and ΔE values after treatment. Compared with those in the Bl-R group, the R-Bl and R groups showed significant time-dependent staining, which is possibly attributed to their surface roughness. For the effect of resin infiltration on the adhesive properties of WSLs, resin infiltration reduced the staining penetration depth of WSLs from 2393.54 ± 1118.86 µm to 188.46 ± 89.96 µm (P < 0.05) while reducing WSLs porosity in SEM observation. CONCLUSIONS: Post-bleaching resin infiltration proved to be advantageous in the aesthetic treatment of WSLs. Resin infiltration did not compromise bonding strength but it did reduce microleakage and enhance marginal sealing. Overall, resin infiltration can effectively enhance the chromatic results of treated WSLs and prevent long-term bonding failure between ceramics and enamel. Based on these findings, the use of post-bleaching resin infiltration is recommended, and resin infiltration before ceramic bonding is deemed viable in clinical practice.

Effect of toothbrushing on surface roughness, gloss, and topography of polished and glazed ultra-translucent zirconia.

PURPOSE: This study evaluated the effect of toothbrushing cycles on surface roughness (Ra), gloss (GU), and morphology of two zirconia finishing and polishing protocols. MATERIALS AND METHODS: An ultra-translucent zirconia disc was sectioned into rectangular plates (12 mm × 7 mm × 3 mm) and divided into two groups according to the polishing and finishing system used (diamond rubber abrasive/DRA or glazing/GLA). Bovine enamel (BEN) plates with the same dimensions were used as a Control. Specimens of zirconia and enamel were analyzed for Ra and GU (n = 11) and surface morphology by scanning electron microscopy (n = 3) before toothbrushing (baseline) and after 15,000 and 30,000 toothbrushing cycles. Ra and GU data were analyzed by ANOVA two-way and post-hoc Tukey's test (α = 0.05), while the surface morphology was analyzed qualitatively. RESULTS: The Ra decreased significantly after 30,000 toothbrushing cycles for DRA and GLA zirconia ceramics. DRA showed a higher GU at the baseline, after 15,000 and 30,000 toothbrushing cycles than GLA and BEN. Toothbrushing polished the zirconia, creating a smooth surface, while no changes were observed for BEN. CONCLUSIONS: The increase in toothbrushing cycles (30,000) changed the surface roughness of DRA and GLA zirconia ceramics. DRA zirconia presented the highest GU, which did not change with toothbrushing.

Evaluation of surface energy and surface stability and adherence of Candida albicans to octa fluoro pentyl (meth) acrylate-coated PEEK using plasma spray.

Background: Polyetheretherketone (PEEK) has favorable properties that make it able to be used as a denture base material, but it is also susceptible to the adhesion of microorganisms. In this study, we applied Octafluoropentyl (meth) acrylate (OFPA) coating on the PEEK polymer surface by using plasma spray and investigated the functional groups present on the surface, changes in the surface energy and Candida albicans adhesion. Materials and Methods: In this experimental study, the samples were placed in a control group without surface preparation and three experimental groups that were subjected to plasma spray for 10, 30, and 60 s and then impregnated with degassed Octa fluoropentyl (meth) acrylate (Sigma-Aldrich, USA) monomer. Fourier transform infrared spectroscopy (FTIR) was used to identify the functional groups and new chemical bonds between PEEK and OFPA, and Sessile Drop Method was used to evaluate the surface's wettability. The surface morphology was checked using a LEXT OLS4000 (Olympus®-Japan) microscope, and the inhibition of C. albicans adhesion was also checked by counting the colonies in terms of colony forming unit/mL (CFU/mL). Kurskal-Wallis analysis was conducted to assess Candida adhesion, while wettability was evaluated using analysis of variance and post hoc analyses. The level of statistical significance was set at P < 0.05. Results: FTIR analysis confirmed that a chemical between OFPA and PEEK was established. The samples showed a significant increase in the contact angle after 30 s of plasma application (CA = 88.2 ± 7.3). The contact angle decreased again by increasing the surface modification to 60 s (CA = 64.33 ± 5.5). Examining the surface morphology of the samples shows an increase in surface roughness with increasing plasma time up to 60 s. The number of adherent colonies was the lowest in 30 s group, but it was not statistically significant (P = 0.658). Conclusion: No statistically significant difference in C. albicans CFU/mL count was found between groups. The contact angle of the 30 s group was significantly higher than the control group.

Preparation and Characterization of Quartz-Reinforced Hybrid Composites Based on Unsaturated Polyester Resin from Post-Consumer PET Recyclate.

The paper presents the results of research on hybrid composites made of unsaturated polyester resin based on post-consumer recycled poly(ethylene terephthalate). The polymeric materials were reinforced with quartz flour, which is a common inorganic mineral filler. An environmentally friendly cobalt polymer solution was used to cure the polyester matrix. The results showed the quantitative influence of the quartz filler on the thermal, mechanical and morphological properties of the quartz-polyester composites. A change in the surface wettability and the polarity of the polymeric materials was also noticed, with some deterioration of their gloss.

Investigation of Physicochemical Characteristics of Aspergillus niger Biomass and Examination of Its Ability to Separate Butyl Acetate Isomers.

Aspergillus niger is a species of fungus that is widely found in natural ecosystems and has an important role in various industrial fields and is readily available. To study the adhesion of microbial cells to solid substrates and to improve their properties, physicochemical characterization of microorganisms is extremely important. For this purpose, in this study, the surface properties of A. niger biomass were determined at low cost and with high accuracy by inverse gas chromatography (IGC), a physicochemical characterization technique. IGC experiments were conducted between 303.2 and 328.2 K at infinite dilution. Among these temperatures, various organic solvent vapors were passed over the A. niger biomass considered as stationary phase and their retention behavior was studied. Using the raw data, net retention volumes were calculated and retention diagrams were drawn. From the linear retention diagrams, the dispersive surface energy was calculated according to Dorris-Gray (48.73-46.09 mJ/m2), Donnet-Park (47.12-44.50 mJ/m2), Schultz (46.88-42.45 mJ/m2), and Hamieh (76.42-64.06 mJ/m2) methods. With the IGC method, the acidity-basicity parameters of A. niger biomass were determined and it was found that the surface was basic ( K D / K A = 4.871 ). In the second part of this study, the butyl acetate isomer series, which are difficult to be separated by conventional methods, were effectively separated by the IGC method using A. niger stationary phase.

The Modification of Useful Injection-Molded Parts' Properties Induced Using High-Energy Radiation.

The modification of polymer materials' useful properties can be applicable in many industrial areas due to the ability to make commodity and technical plastics (plastics that offer many benefits, such as processability, by injection molding) useful in more demanding applications. In the case of injection-molded parts, one of the most suitable methods for modification appears to be high-energy irradiation, which is currently used primarily for the modification of mechanical and thermal properties. However, well-chosen doses can effectively modify the properties of the surface layer as well. The purpose of this study is to provide a complex description of high-energy radiation's (ß radiation) influence on the useful properties of injection-molded parts made from common polymers. The results indicate that ß radiation initiates the cross-linking process in material and leads to improved mechanical properties. Besides the cross-linking process, the material also experiences oxidation, which influences the properties of the surface layer. Based on the measured results, the main outputs of this study are appropriately designed regression models that determine the optimal dose of radiation.

Oil addition increases the heat resistance of Clostridium sporogenes spores in braised sauce beef: Perspectives from spore surface characteristics and microstructure.

During thermal processing of braised sauce beef, the lipid content of circularly used sauce increased accordingly because of lipid migration from beef to sauce, which may impact the bacterial heat resistance in the products. This study aims to characterize the heat resistance of Clostridium sporogenes spores in braised sauce beef, and investigate the effects of oil on the spore surface characteristics and microstructure. The results indicated that the heat resistance of C. sporogenes spores in beef was significantly higher than that in sauce. Oil addition remarkably enhanced the spore heat resistance in sauce, with D95°C value three times more than that without oil added, and even higher than that in beef. The results of spore surface characteristics indicated that oil addition led to an increase of hydrophobicity and a decrease of zeta potential, which ultimately increased spore heat resistance. Microstructure analysis indicated that exosporium maintenance and cortex expansion induced by oil addition might contribute to the increase of spore heat resistance. This study has sufficiently verified the importance of oil content on the heat resistance of C. sporogenes spores, which should be taken into consideration when developing thermal processes for controlling the spores in food matrices.

Fibroblasts and osteoblasts behavior after contact with different titanium surfaces used as implant abutment: An in vitro experimental study.

Background: The goal of this in vitro study was to compare three different surfaces: two types of implant surfaces commercially available ([a] smooth/machined and [b] acid-treated surface) versus (c) anodized surface. Discs were manufactured with commercially pure titanium (CP) grade IV, which were subsequently analyzed by scanning microscopy and fibroblastic and osteoblastic cell cultures. Methods: Ninety-nine discs (5 × 2 mm) were manufactured in titanium grade IV and received different surface treatments: (i) Mach group: machined; (ii) AA group: double acid etch; and (iii) AN group: anodizing treatment. Three discs from each group were analyzed by Scanning Electron Microscopy (SEM) to obtain surface topography images and qualitatively analyzed by EDS. Balb/c 3T3 fibroblasts and pre-osteoblastic cells (MC3T3-E1 lineage) were used to investigate each group's biological response (n = 10/cellular type). The data were compared statistically using the ANOVA one-way test, considered as a statistically significant difference p < 0.05. Results: The AA group had numerous micropores with diameters between 5 and 10 µm, while nanopores between 1 and 5 nm were measured in the AN group. The EDX spectrum showed a high titanium concentration in all the analyzed samples. The contact angle and wetting tension were higher in the AA, whereas similar results were observed for the other groups. A lower result was observed for base width in the AA, which was higher in the other two groups. The AN showed the best values in the fibroblast cells, followed by Mach and AA; whereas, in the culture of the MC3T3 cells, the result was precisely the opposite (AA > Mach > AN). There was similar behavior for cell adhesion for the test groups (Mach and AN), with greater adhesion of Balb/c 3T3 fibroblasts compared to MC3T3 cells; in the AA group, there was greater adherence for MC3T3 cells compared to Balb/c 3T3 fibroblasts. Conclusions: The findings suggest that different surface characteristics can produce different biological responses, possibly cell-line dependent. These findings have important implications for the design of implantable medical devices, where the surface characteristics can significantly impact its biocompatibility.

Effect of various surface treatments on relining bond strength of CAD-CAM denture base materials.

PURPOSE: The aim of this study was to analyze the impact of various surface treatments and production methods on the shear bond strength (SBS) between reline material and denture base resins. MATERIALS AND METHODS: One-hundred-twenty specimens were produced using conventional heat-polymerization, subtractive, and additive techniques. Each group consisted of 40 specimens. The specimens were divided into four subgroups, each with 10 samples, for surface treatments. These subgroups were: (1) Control-only monomer application, (2) 50 µm airborne-particle abrasion, (3) 110 µm airborne-particle abrasion, and (4) Roughening with tungsten carbide bur. Representative specimens from each subgroup were examined under SEM. Then, auto-polymerized resin was condensed in the center of the specimens. Specimens were subjected to thermal aging (5000 cycles at 5-55°C). The SBS test was conducted and failure loads were recorded. The data were evaluated by two-way ANOVA and Tukey pairwise multiple comparisons method (p < 0.05). RESULTS: The additively produced group showed significantly lower SBS than conventional and subtractive groups (p < 0.001), with no significant differences between the subtractive and conventional groups. Specimens that underwent monomer application only showed the lowest SBS among surface treatments, while 50 µm airborne-particle abrasion showed the highest SBS. Based on the partial eta-squared analysis results, the surface treatment mainly impacted SBS. CONCLUSIONS: Among the surface treatment methods, treating denture bases with 50 µm airborne-particle abrasion is more effective for maintaining adhesion, especially in the additive technique.

The effect of sulphur supplementation on cadmium phytotoxicity in wheat and lettuce: changes in physiochemical properties of roots and accumulation of phytochelatins.

Intensive sulphur fertilisation has been reported to improve the nutrient balance and growth of Cd-exposed plants, but the reasons of this phenomenon and the role of sulphur compounds in the resistance to cadmium are unclear. We investigated sulphur supplementation-induced changes in the surface properties of roots and the level of thiol peptides (PCs) in Cd-stressed Triticum aestivum L. (monocots clade) and Lactuca sativa L. (dicots clade) grown in nutrient solution. The combination of three sulphur (2 mM S-basic level, 6 or 9 mM S-elevated levels) and four cadmium (0, 0.0002, 0.02 or 0.04 mM Cd) concentrations was used. The physicochemical parameters of the roots were determined based on the apparent surface area (Sr), total variable surface charge (Q), cation exchange capacity (CEC) and surface charge density (SCD). In Cd-exposed plants supplied with sulphur, a different character and trend in the physicochemical changes (adsorption and ion exchange) of roots were noted. At the increased sulphur levels, as a rule, the Sr, CEC, Q and SCD values clearly increased in the lettuce but decreased in the wheat in the entire range of the Cd concentrations, except the enhanced Sr of wheat supplied with 6 mM S together with elevated (0.0002 mM) and unchanged (0.02, 0.04 mM Cd) value of this parameter at 9 mM S. This indicates a clade-specific and/or species-specific plant reaction. The 6 mM S appears to be more effective than 9 mM S in alleviation of the cadmium's toxic effects on roots. It was found that at 0.02 and 0.04 mM Cd, the use of 6 mM S limits the Cd accumulation in the roots of both species in comparison with the basic S fertilisation. Moreover, PC accumulation was much more efficient in wheat than in lettuce, and intensive sulphur nutrition generally induced biosynthesis of these chelating compounds. Physicochemical parameters together with quantitative and qualitative assessment of thiol peptides can be important indicators of the efficiency of root system functioning under cadmium stress. The differences between the species and the multidirectional character of the changes are a result of the involvement of a number of multi-level mechanisms engaged in the defence against metal toxicity.