Months Of Water Storage Research Articles

How Universal Adhesive Systems With Nanoencapsulated Flavonoids Improve Long-Term Bonding to Caries-Affected Dentin.

To determine the presence of nano-encapsulated flavonoids and their effect in universal adhesives on resin-dentin bond-strength (μTBS) and nanoleakage (NL) on artificial caries-affected dentin (CAD) after 24-h and 6 months of water storage (WS). Artificial CAD was created on the occlusal dentin surfaces of 60 human third molars by a microbiological assay. Nanoencapsulated quercetin (Q) and naringin (N) were incorporated into Prime&Bond Universal (PBU; Dentsply-Sirona) and Single Bond Universal (SBU, 3M ESPE). The adhesive systems with and without (control) flavonoids were applied to the CAD surface, and a 4-mm resin composite block (TPH Spectrum, Dentsply Sirona) was built up and light-cured. Specimens were sectioned into resin-dentin beams (0.8 mm2). The hybrid layer (HL) was subjected to micro-Raman analysis to detect N and Q. The specimens were tested in tension in a universal testing machine at 0.5 mm/min. μTBS and NL tests were performed after 24-h and WS. μTBS and NL data were analyzed using a nonparametric three-way ANOVA test followed by Bonferroni's test (α = 5%). Q and N were detected within the HL. N and Q nanocapsules increased μTBS and reduced NL values after WS. At 24 h, the PBU group showed higher NL values than the SBU group, and the values decreased after WS. Incorporating nanoencapsulated flavonoids may improve the longevity of universal bonding systems applied to CAD. Adhesive restorations incorporating nanoencapsulated quercetin or naringin might be a promising alternative for achieving long-term bonding stability.

Long-Term Dentin Bonding Performance of Universal Adhesives: The Effect of HEMA Content and Bioactive Resin Composite.

This study investigated the effects of resin composites (RCs) containing surface pre-reacted glass ionomer (S-PRG) filler on the dentin microtensile bond strength (μTBS) of HEMA-free and HEMA-containing universal adhesives (UAs). Water sorption (WS) and solubility (SL), degree of conversion (DC), and ion release were measured. The UAs BeautiBond Xtreme (BBX; 0% HEMA), Modified Adhesive-1 (E-BBX1; 5% HEMA), Modified Adhesive-2 (E-BBX2; 10% HEMA), and two 2-step self-etch adhesives (2-SEAs): FL-BOND II (FBII; with S-PRG filler) and silica-containing adhesive (E-FBII) were used. Teeth were restored with Beautifil Flow Plus F00 with S-PRG filler (BFP) and flowable resin composite with silica filler (E-BFP). μTBS was evaluated after 24 h and 6 months of water storage. WS and SL measurement followed ISO 4049:2019; spectroscopy measured DC; ICP-MS evaluated ion release. BBX and FBII presented the highest DC. The adhesives did not comply with the WS ISO requirements, but the bonding resin of 2-SEAs complied with the SL threshold. BFP released more ions than E-BFP. BFP positively affected the μTBS of UAs, regardless of HEMA concentration after 24 h, comparable to the 2-SEAs. The 6 months μTBS decrease depended on the adhesive and RC combination. HEMA did not affect the μTBS of UAs, while bioactive resins had a positive impact.

Evaluation of Color Stability of a Composite Resin Using Different Instrument Lubricants After One Month of Water Storage

Background: Clinicians use several lubricants to reduce composite sticking to instruments and facilitate composite modeling. This study evaluated the effect of instrument lubricants on the color stability of a resin composite after one month of water storage. Methods: 60 disc-shaped specimens (2×10 mm) of Tetric N-Ceram composite were prepared using four lubricants, isopropyl alcohol 70%, Adper single bond adhesive (SB), margin bond (MB) and composite wetting resin (CW) (12 samples for each group). No lubricant was used in the control group. Color measurement was done twice, 24 hours after sample preparation and after one month of water storage. Color differences were calculated, and the data were analyzed using ANOVA and Tukey’s post hoc tests. Results: The use of single bond as instrument lubricant caused the most color change (ΔE=4.26), and the control group (no lubricant) showed the least color change (ΔE=1.77). Using composite wetting resin as an instrument lubricant resulted in lower color changes than other instrument lubricants (P<0.05). Conclusion: Composite Wetting Resin used as instrument lubricant had better color stability than other lubricants. Bonding agents are not recommended for composite restorations as instrument lubricants due to the higher risk of affecting color stability. Clinicians should be aware that using instrument lubricants might influence the color properties of dental composites.

Is additional silane application necessary for a new silane-containing universal adhesive to bond to glass ceramics?

To evaluate the in vitro influence of prior silane application on the microshear bond strength (μSBS) of Scotchbond Universal Plus to glass ceramic. Thirty blocks of lithium disilicate ceramic were etched with hydrofluoric acid for 20 s and distributed into Group 1 (no silane and no adhesive), Group 2 (adhesive), Group 3 (silane + adhesive). Three cylinders of resin cement were made on each ceramic block. Five blocks (n = 15 cylinders) were subjected to the μSBS test after 24 h, and the other five blocks (n = 15 cylinders) were tested after 6 months of water storage. According to two-way ANOVA, followed by Tukey's test, the means of μSBS (MPa), denoted by different letters, show significant differences (p < 0.05): after 24 h-Group 1 (31.7)B, Group 2 (43.3)A, and Group 3 (31.3)B; after 6 months-Group 1 (14.8)B, Group 2 (33.6)A, and Group 3 (30.3)A. After 6 months of storage, there was a significant decrease in μSBS for Groups 1 and 2, along with an increase in adhesive failures across all groups. Prior application of silane did not increase the μSBS between Scotchbond Universal Plus and ceramic, and there was degradation at the bond interface over time. Prior application of a silane agent is not necessary when using Scotchbond Universal Plus for bonding to glass ceramics. Regardless of the prior application of silane, there is degradation at the bond interface over time.

Ionic Liquid-Based Silane for SiO2 Nanoparticles: A Versatile Coupling Agent for Dental Resins.

The current longevity of dental resins intraorally is limited by susceptibility to acidic attacks from bacterial metabolic byproducts and vulnerability to enzymatic or hydrolytic degradation. Here, we demonstrate synthesizing an ionic liquid-based antibiofilm silane effective against Streptococcus mutans, a major caries pathogen. Furthermore, we incorporate this silane into dental resins, creating antibiofilm- and degradation-resistant materials applicable across resin types. FTIR, UV-vis, and NMR spectroscopy confirmed the synthesis of the expected ionic liquid-based silane. The characterization of SiO2 after the silanization indicated the presence of the silane and how it interacted with the oxide. All groups achieved a degree of conversion similar to that found for commercial resin composites immediately and after two months of storage in water. The minimum of 2.5 wt % of silane led to lower softening in solvent than the control group (GCTRL) (p < 0.05). While the flexural strength indicated a lower value from 1 wt % of silane compared to GCTRL (p < 0.05), the ultimate tensile strength did not indicate differences among groups (p > 0.05). There was no difference within groups between the immediate and long-term tests of flexural strength (p > 0.05) or ultimate tensile strength (p > 0.05). The addition of at least 5 wt % of silane reduced the viability of S. mutans compared to GCTRL (p < 0.05). The fluorescence microscopy analysis suggested that the higher the silane concentration, the higher the amount of bacteria with membrane defects. There was no difference among groups in the cytotoxicity test (p > 0.05). Therefore, the developed dental resins displayed biocompatibility, proper degree of conversion, improved resistance against softening in solvent, and stability after 6 months of storage in water. This material could be further developed to produce polymeric antimicrobial layers for different surfaces, supporting various potential avenues in developing novel biomaterials with enhanced therapeutic characteristics using ionic liquid-based materials.

Longer light-curing time decreases the effect of ageing on composite resin hardness used in root reinforcement.

This study evaluated the hardness of a composite resin used for root reinforcement, considering the light-curing time, root canal region and ageing due to long-term storage. Twenty incisor roots were reinforced using composite resin, varying the photopolymerisation time (40 or 120 s). Following fibre post cementation, the roots were transversely sectioned into coronal, middle and apical regions. Composite hardness was measured initially and after 18 months of water storage. Data underwent repeated measures analysis of variance and Tukey's post hoc tests. The factors 'light-curing time', 'root region' and 'ageing' affected the hardness. Significant interactions were observed between 'light-curing time × root region' and 'ageing × light-curing time'. Regardless of time, resin hardness in the apical region was lower. After ageing, hardness in the coronal and middle regions decreased when the light-curing time was 40 s, while no significant effect on hardness was noted with a light-curing time of 120 s.

Marginal Leakage in Interfaces Formed by Bovine Dentin and Adhesive Cements Applied with Different Bonding Techniques

Objectives: The aim of this in vitro study was to evaluate the marginal microleakage in interfaces formed by bovine dentin and adhesive cements applied with different bonding techniques. Materials and Methods: Thirty bovine teeth dentin blocks measuring 5 mm x 5 mm x 1 mm were made with one side completely in dentin substract (20 mm2). The dentin blocks were randomly divided into three groups according to the cementation technique used: CTS+RX (conventional 3-step adhesive + dual-activation resin cement), SBS+RX (single-bottle self-etching adhesive + dual-activation resin cement), and SAC (self-adhesive cement). A photopolymerizable composite resin block with the same dimensions was fixed on the dentin block according to the instructions for each adhesive technique. The dentin-composite resin blocks made with each adhesive technique were separated into subgroups (n = 5) for 7 days (control) and for 6 months of water storage. After each period, the blocks were individually immersed in test tubes containing neutral methylene blue dye for 2 hours. The samples were washed, dried, and evaluated with a stereoscopic magnifying glass, and the amount of infiltrated pigment was analyzed using spectrophotometry (Beckman DU 65). The data were submitted to two-way ANOVA and Tukey’s test (5%). Results: Microleakage level for the conventional 3-step or self-etching technique remained similar for 7 days (18 ± 25 and 43 ± 45 μm, respectively) or 6 months (42 ± 55 and 52 ± 87 μm, respectively). The self-adhesive technique showed higher microleakage levels for 7-day (263 ± 98 μm) and 6-month periods (441 ± 226 μm) compared to other adhesive techniques. There was a statistically significant difference between evaluation times only for the self-adhesive technique. Conclusions: Higher microleakage levels by storage in water occurred with the self-adhesive technique in both evaluation periods. Clinical Relevance: The different microleakage levels promoted at the dentin-composite resin interface should be considered in adhesive clinical procedures in relation to long-term use.

Biomechanical Behavior of a 3D-Printed Denture Base Material.

To evaluate relevant material properties (flexural strength [σf], elastic modulus [E], water sorption [Wsp] and solubility [Wsl], and biocompatibility) of an additive manufacturing (AM) polymer vs a heat-curing acrylic resin (AR; control) for the manufacture of complete dentures, testing the hypothesis that fabrications from both materials would present acceptable material properties for clinical use. The σf, E, Wsp, and Wsl were evaluated according to the ISO 20795-1:2013 standard, and the biocompatibility was evaluated using MTT and SRB assays. Disk-shaped specimens were fabricated and used for Wsp (n = 5), Wsl (n = 5), and biocompatibility (n = 3) testing. For assessment of σf and E, bar-shaped specimens (n = 30) were fabricated and stored in 37°C distilled water for 48 hours or 6 months before flexural testing in a universal testing machine with a constant displacement rate (5 ± 1 mm/minute). Data from σf, E, Wsp, Wsl, and biocompatibility tests were statistically analyzed using Student t test (α = .05). Weibull analysis was also used for σf and E data. Significant differences between the two materials were found for the evaluated material properties. Water storage for 6 months did not affect the flexural strength of the AM polymer, but this material showed inadequate σf and Wsl values. Despite adequate biocompatibility and strength stability after 6 months of water storage, the AM polymer recommended for complete dentures needs further development to improve the material properties evaluated in this study.

Prediction Study on the Impact of Engineering Waste Rocks on Water Quality During Reservoir Construction

The impact of dammed reservoirs on the local ecological environment during the operational phases has garnered significant attention. However, there is limited research on the ecological risks posed by reservoirs during the construction period, particularly regarding the waste rock at the bottom of the reservoir. Based on the results of release experiment, the water quality risks of engineering waste rocks to reservoirs were analyzed by a three-dimensional model using the MIKE 3 FM HD and ECO Lab module. The calculation results showed that as the waste rock yards are inundated, SO42− and Fe3+ in the reservoir are released and gradually affecting the water quality in the area in front of the dam. During the process of water storage, the release of pollutants from the waste rocks at the bottom of the reservoir had a significant impact on the underlying water body after two months and then spread from the bottom to the upper layer of water. After three months of water storage, when the water level of the reservoir reached 867 meters, the pollutants released by the waste rock had an impact on the surface water quality. After four months, the release of pollutants from the waste rock yards essentially ceased, and the pollutants gradually accumulated in the bottom water body in front of the dam after dilution and diffusion. In the future, special attention should still be given to the risk assessment of pollutants in the bottom sediments during long-term operation and management of the reservoir.

Effect of filler contents on the bond strength of CAD/CAM resin crowns: New resin primer versus conventional silane agents

Purpose This study aims to evaluate the effects of resin primers containing methyl methacrylate (MMA) and silane agent on the bonding effectiveness of indirect resin composite blocks with three different filler contents.Methods A commercially available computer-aided design/computer-aided manufacturing (CAD/CAM) resin composite block and two experimental resin composite blocks with different filler contents were alumina-blasted and two surface treatments (primer and silane agent) were applied. The resin cement was built up, and the micro-tensile bond strength (μTBS) was measured after 24 hours, 1 month or 3 months of water storage (n = 24 per group). The fracture surfaces after μTBS measurements and resin block/cement interface were observed by scanning electron microscopy (SEM).Results The primer treatment group showed a significantly higher bond strength than the silane group only in F0 (filler content 0 wt%) group (P < 0.001). In the primer group, F0 and F41 (filler content 41 wt%) groups showed significantly higher bond strengths than F82 (filler content 82 wt%) group (P < 0.001). In contrast, in the silane group, F41 group showed significantly higher bond strength than F0 and F82 groups (P < 0.001), and F82 group showed significantly higher bond strength than F0 group (P < 0.001). SEM revealed that the matrix resin was partially destroyed on the fracture surface of the primer group, and an uneven interface surface was observed compared with that of the silane group.Conclusions MMA-containing primers showed higher bonding effectiveness to CAD/CAM resin composite blocks than the silane treatment.

Bond strength to dentin of a Polymer-infiltrate ceramic-network material cemented with dual resin cements submitted to different adhesive strategies

The purpose of the present in vitro study is to assess the immediate and long-term bond strength of a self-adhesive and conventional resin luting agents with a new hybrid restorative material to dentin. Blocks of a polymer-infiltrated ceramic-network (PICN) material (VITA Enamic) were cemented to a flat exposed dentin surface through different protocols. The groups were divided considering the combination of resin luting agent and ceramic surface treatment (U200 – Relyx U200 with silane; Ult + Sil – Relyx Ultimate with silane; Ult + SBU – Relyx Ultimate with Scotchbond Universal) and dentin treatment (NT – no dentin treatment; ER – etch-and-rinse with 35 % phosphoric acid) (n = 6). Beam-shaped specimens were obtained by cutting the cemented restorations. Specimens were submitted to microtensile bond strength in a universal testing machine (EMIC). Half of the specimens were tested 24 h after cementation, and the other half were tested after 12 months of water storage. ANOVA revealed one significant interaction between “time” and “dentin treatment” factors, as ER strategy was associated with bond strength decreases after 12 months. All resin luting agents (u200, Ult + Sil, and Ult + SBU) presented higher immediate μTBS with ER adhesive strategy. As the groups Ult + Sil, with both ER and SE adhesive strategies, and (Ult + SBU), with ER adhesive strategy, showed higher μTBS values after 12 months. It was concluded that conventional dual resin cement, combined with ER strategy produced better bond strength to dentin when cementing indirect PICN restoration.

The effect of different enamel surface preparations on microleakage under orthodontic brackets

Microleakage is caused by many factors, including polymerization shrinkage of the resin, thermal expansion differences between the enamel and the adhesive, and inadequate adherence. This study aims to assess the microleakage value under orthodontic brackets after three distinct enamel surface preparations and compare the results to the traditional procedure. Fifty-four intact upper premolars were randomly distributed into three groups. First group 18 teeth etched with 36% phosphoric acid Dentsply. Second group 18 teeth etched with %1.23 acidulated phosphate fluoride (APF) incorporated phosphoric acid 25%APF 75%phosphoric acid Dentsply. Third group 18 teeth etched with Trans Bond TM Plus Self-Etching prime 3M Unitek, Monrovia, USA. Then, according to the manufacturer's instructions, all groups bonded to stainless steel brackets RAZOR, IOS, USA, using light-cured composite 3M Unitek/ Monrovia, USA. Then, each subgroup was divided into 3 subgroups, 6 teeth each. The first subgroup thermocycled 500 cycles between 5 C and 55 UC in deionized water and tested after 24 hours of water storage. The second subgroup was also thermocycled and tested after 2 months of water storage. The third subgroup was subjected to cyclic acid attack for 2 months by an acidic solution pH=2.5. Microleakage was evaluated using a dye penetration technique. All samples are sectioned and evaluated under a stereomicroscope. For statistical analysis, the Kruskal-Wallis test was employed. P=0.05 was the level of significance. A significant difference was between etching groups following a thermocycler and a twenty-four-hour water storage, no significant difference after thermocycling and two months of water storage, and significant difference at the occlusal side and between overall means of compared etching groups. This study revealed that the highest microleakage values were in the SEP self-etch prime group, then EF 1.23% APF incorporated phosphoric acid group and the ER 36% phosphoric acid group. The gingival side had more microleakage than the occlusal side. Adding around 20-25 percent of 1.23 percent of phosphoric acid for enamel preparation before orthodontic bonding increases microleakage values, but SEP remains the highest. Keywords: Microleakage, Self-etch prime, Acidulated phosphate fluoride, Stainless steel brackets

The Depth of Cure, Sorption and Solubility of Dual-Cured Bulk-Fill Restorative Materials.

This study aimed to examine depth of cure (DoC), mass change, water sorption and solubility of dual-cured bulk-fill restorative materials (Surfil One and Activa) in comparison with a light-cured bulk-fill composite (Filtek One Bulk-Fill) and a resin-modified glass ionomer (Fuji II LC). Twenty specimens were prepared of each material using stainless steel molds designed with a slot (8 × 4 × 2 mm) and irradiated for either 20 or 40 s. The Vickers hardness (VHN) was measured at every 0.5 mm to assess the DoC after 24 h of storage at 37 °C. The depth of cure was reported as the depth corresponding to 80% of the maximum Vickers hardness. Disc-shaped specimens were prepared of each material (n = 5) to investigate mass change, sorption and solubility after 4 months of water storage. The data were analyzed using a two-way and one-way analysis of variance (ANOVA) followed by the Tukey post hoc test (p ≤ 0.05). Fuji II LC had the greatest DoC while Activa had the lowest. The two different irradiation times did not demonstrate a significant difference in DoC for all dual-cured materials (p > 0.05). Fuji II LC had the highest sorption while Filtek One showed the lowest. Surefil One and Fuji II LC had a negative solubility. This study concluded that dual-cured materials showed different depth of cure values despite having the same setting reaction. Both materials exhibited a high water sorption, which might jeopardize their dimensional stability and effect their clinical performance.

Investigation of aging resistance for dental resin composites with and without glass flakes.

Outstanding physical-mechanical properties and aging resistance are key requirements for dental resin composite since it will be placed in the oral environment for a long time. In this work, a new dental resin composite mainly modified by glass flakes was fabricated, and the aging resistance was evaluated by comparing with commercial composites without glass flakes. The new dental resin composite was produced through hand blending of inorganic glass flakes/Si-Al-borosilicate glass (58wt%:7wt% of dental resin composite), POSS-MA (5wt% of resin matrix), Bis-GMA/TEGDMA(64.4wt%:27.6wt% of resin matrix), and CQ/EDMAB (0.9wt%:2.1wt% of resin matrix) together. The flexural strength, elasticity modulus, and hardness, as well as wear were tested for evaluating the aging resistance of different dental resin composite. Among 6 kinds of commercial composites in this study, after 6-month water storage, the maximum percentage of performance degradation is that the flexural strength decreased 39.96%, elasticity modulus decreased 51.53% and hardness decreased 12.52%. In contrast, the new synthesized material decreased 14.53%, 20.88%, and 0.61%, respectively, and performed lesser wear depth compared to some other groups (P < 0.05). It was observed that the new dental resin composite performed better performance stability and wear resistance when compared with commercial dimethacrylate-based or low shrinkage dental resin composite tested in this study. This possibly paves a path for designing tailored dental composite for practical application. Since the aging resistance of dental resin composite modified by glass flakes is superior, it has the potential to be used for promoting the durability of dental resin composite.

Enhancing bond stability: impact of adhesive thinning on resin-dentin bonded interfaces.

This study aimed to investigate the effect of adhesive thinning on resin-dentin-bonded interfaces created by two simplified adhesives. Micro-tensile bond strengths and interfacial nanoleakage were evaluated within bonded dentin interfaces formed by Adper Single Bond 2 and Single Bond Universal after 24 hours and 6 months of water storage. The adhesives were subjected to three different techniques: air-thinning, brush-thinning, or application without thinning. Statistical analysis was performed using a multi-level analysis of variance followed by Bonferroni's post-hoc test, at a significance level of 0.05. Adper Single Bond 2 demonstrated the highest immediate microtensile bond strengths (43.5 ± 1.3 MPa) and the lowest immediate nanoleakage (49.8 ± 2.8%) when air-thinning was employed. Single Bond Universal exhibited the lowest nanoleakage (36.4 ± 1.8%) when air-thinning was used, although there was no significant difference in immediate bond strengths between air-thinning and brush-thinning approaches, which both showed higher values compared to the no-thinning approach. After 6 months of storage, a significant decrease in bond strengths and a significant increase in nanoleakage were observed across most groups (p < 0.001). While all groups displayed varying degrees of instability over a 6-month storage period, air-thinning of simplified etch-and-rinse and self-etch adhesives proved to provide clinically acceptable bonded interfaces. The findings suggest that adhesive thinning techniques can play a vital role in enhancing bond stability and longevity in resin-dentin-bonded interfaces.

Controlled drug delivery from metronidazole-containing bioactive endodontic cements.

This study aims to formulate metronidazole liquid nanocapsules (MTZLNC) and evaluate their effect on the physicochemical and biological properties of calcium silicate-based bioactive endodontic cements, in vitro. A MTZLNC suspension was formulated by deposition of the preformed polymer and characterized by laser diffraction and high-performance liquid chromatography (HPLC). Calcium silicate (CS) was mixed with a radiopaque agent (calcium tungstate - CaWO4), at 10wt%, to produce the cement powder. Cements liquids were used with two concentrations of MTZLNC suspension: 0.3mg/ml and 0.15mg/ml. Cements prepared with distilled water were used as the control. The radiopacity, setting time, and flow were evaluated following ISO 6876:2012. The compressive strength analysis was conducted according to ISO 9917:2007. pH and mineral deposition were evaluated after immersion in simulated body fluid (SBF). Cell behavior was evaluated by the viability of pre-osteoblastic cells and pulp fibroblasts by SRB and MTT and the antibacterial activity against Enterococcus faecalis was analyzed immediately and after nine months of water storage. MTZLNCs were formulated with a median diameter of 148nm and 83.44 % load efficiency. Increased flow and reduced strength were observed for both MTZLNCs concentrations. The incorporation of MTZLNCs maintained the ability of cements to increase pH media and promote mineral deposition over the samples, without promoting cytotoxicity. A 2log10 reduction in E. faecalis CFU was observed immediately and after nine months in water storage. The formulation of MTZLNCs allowed the development of antibacterial calcium silicate-based-cements with suitable physicochemical properties and bioactivity, with a reduction in mechanical strength. The 0.3mg/ml concentration in cements liquid promoted effective and sustainable antibacterial activity.

Dentin Bonding Performance of Universal Adhesives in Primary Teeth In Vitro.

(1) Background: The aim of this in vitro study was to evaluate the micro-tensile bond strength (µ-TBS) of universal adhesives to primary tooth dentin after different storage periods. (2) Methods: Dentin of 100 extracted primary molars was exposed. Dentin surfaces were bonded with six universal adhesives (Adhese®Universal [AU], All-Bond Universal® [ABU], G-Premio Bond [GPB], iBond®Universal [IBU], Prime&Bond active™ [PBa], and Prime&Bond®NT as control [PBN]) and restored with a resin composite build-up (Filtek™ Z250). After 24 h, 6 months, and 12 months of water storage, specimens were cut into sticks, and µ-TBS was measured and analyzed using one-way ANOVA (p < 0.05) for normal distributions and the Mann-Whitney U-test (p < 0.05) for non-normal distribution. Pretesting failures were recorded as 0 MPa. Fracture modes were analyzed under a fluorescence microscope; interfaces were visualized with SEM/TEM. (3) Results: Compared with the reference group (PBN: 32.5/31.2 MPa after 6/12 months), two adhesives showed a significantly higher bond strength after 6 months (AU: 44.1 MPa, ABU: 40.9 MPa; p < 0.05) and one adhesive after 12 months (AU: 42.9 MPa, p < 0.05). GPB revealed significantly lower bond strengths in all storage groups (16.9/15.5/10.9 MPa after 24 h/6 months/12 months; p < 0.05). AU and IBU did not suffer pre-test-failures [PTF]. (4) Conclusions: After 12 months, PBN, IBU, AU, and GPB showed significantly lower results compared ithw initial µ-TBS, whereas AU revealed the highest µ-TBS and no PTF.

The effect of water storage on nanoindentation creep of various CAD-CAM composite blocks

BackgroundTo study the effect of water storage (3 months) on the creep deformation of various CAD-CAM composite structures at the nanoscale and compare it to that at the macroscale.MethodsSeven CAD-CAM blocks were investigated: five resin-composite blocks (RCB), one polymer-infiltrated ceramic network (PICN) block, and one ceramic-filled polyetheretherketone (PEEK) block. Specimens of each material (n = 6) were separated into two groups (n = 3) according to their storage conditions (24 h dry storage at 23˚C and 3 months storage in 37˚C distilled water). Nano-indentation creep measurements were undertaken (creep depth measured in µm) using a nanoindenter (Nanovea) equipped with Berkovich three-sided pyramidal diamond tip. The machine was set for the chosen parameters: a load of 20 gf, a pause of 20 s, and the material type. Thirty indentations on 3 samples were made for each material for each test. Data were analysed using two-way ANOVA followed by one-way ANOVA and Bonferroni post hoc tests and independent t-test (< 0.05) for comparisons between the materials.ResultsThe nanoindentation creep depth after 24 h storage ranged from 0.09 to 0.33 μm and increased after 3 months storage in distilled water to between 0.28 and 3.46 μm. There was a statistically significant difference in nanoindentation creep behaviour between the two storage conditions for each investigated material (independent t-test) and between all materials (Bonferroni post hoc). There was a non-significant negative correlation between nanoindentation creep (µm) and filler weight% at 24 h dry storage but a significant correlation at 3 months of water storage. A further non-significant positive correlation between nanoindentation creep (µm) and bulk compressive creep (%) was found.ConclusionThe PICN material showed superior dimensional stability in terms of nanoindentation creep depth in both storage conditions. Other composite blocks showed comparable performance at 24 h dry condition, but an increased nanoindentation creep upon water storage.

Simultaneous removal of natural organic matters and copper (II) with ultrafiltration for drinking water treatment

Membrane technology plays important roles in drinking water treatment in last decades; ultrafiltration (UF) is typically used to separate natural organic matters (NOM) and nanofiltration (NF) is used primarily to reject divalent ions, due to the different pore sizes of the used membranes. However, high water production rate at low energy consumption will be achieved if NOM and heavy metals can be simultaneously removed via UF-based water treatment process, which is necessary nowadays due to the carbon neutrality target worldwide. Here, a polyethersulfone (PES)-based UF membrane, modified chemically by grafting and crosslinking polyethylenimine (PEI, 25,000 Da) in two steps, was used to simultaneously remove humic acid (HA) and copper (Cu) from water. The molecular weight cut-off of the PEI-modified membrane was ∼110 kDa, and results showed that the efficiencies of HA and Cu2+ removal substantially increased because of the smaller pore size and additional adsorption effects compared to pristine PES membrane. Although the flux of the PEI-modified membrane was reduced, the membrane fouling was significantly alleviated compared with the pristine UF membrane. In comparison with Fe-based coagulants, Al-based coagulants as pretreatment performed better on removing HA and Cu2+, and the membrane flux greatly improved compared to only UF. The higher the coagulant dosage, the better the membrane performance was, particularly the pollutants removal efficiency. In addition, the PEI-modified UF membranes presented excellent pollutants removal after 4 months of storage in water. Besides, the as-modified UF membrane has only limited influence on removing mineral substances (e.g., Ca2+, Mg2+), indicating a potential application in actual water treatment. Furthermore, the PEI-modified membrane can be easily chemically cleaned; the removal efficiencies for hybrid Al-coagulation and UF process were as high as 88.2% ± 0.8% (HA) and 82.8% ± 0.1% (Cu2+) even after 4 cycles of filtration and subsequent chemical cleaning.

Shear Bond Strength and Color Stability of Novel Antibacterial Nanofilled Dental Adhesive Resins.

Experimental adhesives containing co-doped metaloxide nanoparticles were demonstrated to display strong and long-term antibacterial properties against Streptococcus mutans biofilms. The present study represents an effort to characterize the shear-bond strength (SBS) and color stability (CS) of these novel biomaterials. Experimental adhesives were obtained by dispersing nitrogen and fluorine co-doped titanium dioxide nanoparticles (NF_TiO2, 10%, 20% or 30%, v/v%) into OptiBond Solo Plus (OPTB). Dentin surfaces were wet-polished (600-Grit). Specimens (n = 5/group) of Tetric EvoCeram were fabricated and bonded using either OPTB or experimental (OPTB + NF_TiO2) adhesives. Specimens were stored in water (37 °C) for twenty-four hours (T1), three months (T2), and six months (T3). At T1, T2, or T3, specimens were removed from water storage and were tested for SBS. Disc-shaped specimens (n = 10/group; d = 6.0 mm, t = 0.5 mm) of adhesives investigated were fabricated and subjected to thermocycling (10,000 cycles, 5−55 °C, 15 s dwell time). Specimens’ colors were determined with a VITA Easyshade® V spectrophotometer (after every 1000 cycles). SBS data was analyzed using two-way ANOVA and post-hoc Tukey tests, while CS data was analyzed using one-way ANOVA and post-hoc Tukey tests (α = 0.05). Mean values of SBS ranged from 16.39 ± 4.20 MPa (OPTB + 30%NF_TiO2) to 19.11 ± 1.11 MPa (OPTB), from 12.99 ± 2.53 MPa (OPTB + 30% NF_TiO2) to 14.87 ± 2.02 (OPTB) and from 11.37 ± 1.89 (OPTB + 20% NF_TiO2) to 14.19 ± 2.24 (OPTB) after twenty-four hours, three months, and six months of water storage, respectively. Experimental materials had SBS values that were comparable (p > 0.05) to those from OPTB independently of nanoparticle concentration or time-point considered. Experimental materials with higher NF_TiO2 concentrations had less intense color variations and were more color stable than OPTB even after 10,000 thermocycles. In combination, the results reported have demonstrated that experimental adhesives can establish strong and durable bonds to human dentin while displaying colors that are more stable, thereby suggesting that the antibacterial nanotechnology investigated can withstand the harsh conditions within the oral cavity without compromising the esthetic component of dental restorations.