Effect of Different Surface Treatment Methods on Bond Strength of Dental Ceramics to Dental Hard Tissues: A Systematic Review

For long-term successful use of ceramic materials in dental procedures, it is necessary to ensure reliable bonding of restorations to dental substrates. This can be achieved by the application of a proper luting cement and through additional surface conditioning. The present systematic review summarizes the most up-to-date evidence on the use of different surface modification methods to enhance the bond strength of dental ceramics to the hard tissues of the teeth. The authors of the review searched the Web of Science, Scopus, and MEDLINE databases to identify relevant articles published between 1 January 2010 and 1 January 2020. A total of 4892 records were identified, and after screening, the full text of 159 articles was evaluated, which finally resulted in the inclusion of 19 studies. The available reports were found to be heterogeneous in terms of materials and methodology, and therefore, only within-studies comparison was performed instead of comparison between studies. A statistically significant difference in the bond strength between the samples treated with different methods of surface conditioning, or between conditioned and nonconditioned samples, was revealed by most of the studies. Predominantly, the studies showed that a combination of mechanical and chemical methods was the most effective way of enhancing bond strength. Artificial aging and luting cement were also identified as the factors significantly influencing bond strength.     

黑膜厚度与膜表面张力关系的研究

用微干涉测量技术直接测定楔压等温线,研究了电解质浓度对阳离子表面活性剂TTAB在浓度大于cmc时形成黑膜厚度的影响及膜表面张力与溶液表面张力之间的差别.结果显示,黑膜厚度取决于楔压和电解质浓度,随着楔压的增加,液膜厚度减少至一定程度后几乎保持不变,表明黑膜类型的转化是阶跃式的,而电解质屏蔽了液膜两个表面电荷层间的排斥作用,故电解质浓度增加,液膜厚度变小.由楔压等温线得出的膜表面张力的结果说明一般黑膜的表面张力与溶液的表面张力并无明显差别.     

取代基对1-甲基尿嘧啶与N-甲基乙酰胺氢键复合物中氢键强度的影响

使用密度泛函理论B3LYP方法和二阶微扰理论MP2方法对由1-甲基尿嘧啶与N-甲基乙酰胺所形成的氢键复合物中的氢键强度进行了理论研究, 探讨了不同取代基取代氢键受体分子1-甲基尿嘧啶中的氢原子对氢键强度的影响和氢键的协同性. 研究表明: 供电子取代基使N－H…O＝C氢键键长r(H…O)缩短, 氢键强度增强; 吸电子取代基使N－H…O＝C氢键键长r(H…O)伸长, 氢键强度减弱. 自然键轨道(NBO)分析表明: 供电子基团使参与形成氢键的氢原子的正电荷增加, 使氧原子的负电荷增加, 使质子供体和受体分子间的电荷转移量增多; 吸电子基团则相反. 供电子基团使N－H…O＝C氢键中氧原子的孤对电子轨道n(O)对N－H的反键轨道σ^*(N－H)的二阶相互作用稳定化能增强, 吸电子基团使这种二阶相互作用稳定化能减弱. 取代基对与其相近的N－H…O＝C氢键影响更大.     

CO_2加氢活性与担载铁催化剂表面Fe-O键强度的关系

采用浸渍 -还原法 ,制备了 Al2 O3、 Ti O2 、 Zr O2 担载铁催化剂 ,并在温度 6 2 3K、压力 1.5 MPa、空速80 0～ 10 0 0 h- 1、原料气组成 CO2 /H2 为 1∶ 2等实验条件下 ,考察了不同还原温度的催化剂在 CO2 加氢制低碳(C2 ～ C5 )烃中的反应活性 .结果表明 ,以 CO2 转化率计 ,各催化剂均存在最佳还原温度 (Fe/Al2 O3:873K;Fe/Ti O2 :773K;Fe/Zr O2 :72 3K) .将此温度与催化剂表面 Fe- O键强度相关联 ,发现在相同条件下 ,与载体 M-O键长有关的 Fe- O键越强 ,催化剂越容易被还原 ,最佳还原温度越低 ,反应活性越好 .     

低信膜比条件下金膜电极电位溶出分析法研究

推导并验证了信号与金膜厚度的比值较小（即低信膜比）时金膜电极电位溶出分析法的过渡时间方程式和电位时间方程式。实验确定的理论式的应用条件为τ／ｌ２≤５８×１０１０ｓ／ｃｍ２，并发现当扩散路径约为扩散层厚度的３倍时，便可按半无限扩散条件处理扩散问题。从而解决了利用小信号进行金膜电极电位溶出基本问题，即信号与浓度的定量关系。     

The Distance between Minima of Electron Density and Electrostatic Potential as a Measure of Halogen Bond Strength

In this study, we present results of a detailed topological analysis of electron density (ED) of 145 halogen-bonded complexes formed by various fluorine-, chlorine-, bromine-, and iodine-containing compounds with trimethylphosphine oxide, Me₃PO. To characterize the halogen bond (XB) strength, we used the complexation enthalpy, the interatomic distance between oxygen and halogen, as well as the typical set of electron density properties at the bond critical points calculated at B3LYP/jorge-ATZP level of theory. We show for the first time that it is possible to predict the XB strength based on the distance between the minima of ED and molecular electrostatic potential (ESP) along the XB path. The gap between ED and ESP minima exponentially depends on local electronic kinetic energy density at the bond critical point and tends to be a common limiting value for the strongest halogen bond.     

Preparation and Characteristics of Porous Silica Films by a Modified Base-Catalyzed Sol-Gel Process Containing PVA: II. Film Preparation

Porous SiO₂ films were successfully deposited on silicon substrates by a modified base-catalyzed Sol-Gel process (MBCP) containing polyvinyl alcohol (PVA). The process conditions, such as the gelation time, the synthesis temperature, the stabilizing agent of the precursor solution and the spin coating speed, the heat-treatment, the annealing temperature of the film on the microstructure and porosity of porous SiO₂ films were systematically investigated by SEM, XRD and ellipsometry techniques. This study provides a novel preparation technique for the porous SiO₂ film. Using this process, the resultant film can reach a thickness of 3.6 m for one layer, a porosity of 25–50%, a low thermal conductivity of 0.11 W/m·K. This film will be used as a low dielectric layer, an thermal-insulating layer and a low refractive index layer.     

Synthesis and Structure of PEDOT Prepared through a Modified LB Film Method

Adopting LB film method, an arachidic acid (AA)/PEDOT multilayer LB film and polymerized EDOT monomers in hydrophilic group of LB were chosen to prepare the arachidic acid (AA)/PEDOT multilayer LB film. UV-Vis, FT-IR and XPS analyses implied that EDOT was effectively polymerized in film, and thus PEDOT conducting polymer was produced. Analyses of XRR and SIMS indicated that the film had a well-arranged lamella structure, and further research showed that polymerization of EDOT in AA film destroyed the orderliness of the original LB film. This phenomenon could be related to the destructive effect of polymerization on the layered structure. We used four-point probe and semiconductor instrument to study the conductivity property of the film, and observed that the conductivity of AA/PEDOT film had sudden changes with the changes of processing time in an effective conduction network, which was caused by "permeability" in conducting channel of multilayer film. The test results also indicated that the conductivity of AA/PEDOT film was obviously better than that of spin-coating PEDOT/PSS or ODA-SA/PEDOT-PSS film due to the higher π structure of PEDOT structure and ordered film structure.     

Antioxidant,Antimicrobial, and Insecticidal Properties of a Chemically Characterized Essential Oil from the Leaves of Dittrichia viscosa L.

Since some synthetic insecticides cause damage to human health, compounds in plants can be viable alternatives to conventional synthetic pesticides. Dittrichia viscosa L. is a perennial Mediterranean plant known to possess biological activities, including insecticidal properties. The chemical composition of an essential oil (EOD) from D. viscosa, as well as its antioxidant, antimicrobial, and insecticidal effects on the cowpea weevil (Callosobruchus maculatus) were determined. Forty-one volatile compounds were identified in EOD, which accounted for 97.5% of its constituents. Bornyl acetate (41%) was a major compound, followed by borneol (9.3%), α-amorphene (6.6%), and caryophyllene oxide (5.7%). EOD exhibited significant antioxidant activity in all tests performed, with an IC₅₀ of 1.30 ± 0.05 mg/mL in the DPPH test and an EC₅₀ equal to 36.0 ± 2.5 mg/mL in the FRAP assay. In the phosphor-molybdenum test, EOD results ranged from 39.81 ± 0.7 to 192.1 ± 0.8 mg AAE/g E. EOD was active on E. coli (9.5 ± 0.5 mm), S. aureus (31.0 ± 1.5 mm), C. albicans (20.4 ± 0.5 mm), and S. cerevisiae (28.0 ± 1.0 mm), with MICs ranging from 0.1 mg/mL to 3.3 mg/mL. We found that 1 µL of EOD caused 97.5 ± 5.0% insect mortality after 96 h in the inhalation test and 60.0 ± 8.3% in the ingestion assay. The median lethal concentration (LC₅₀) was 7.8 ± 0.3 μL EO/L, while the effective concentration in the ingestion test (LC₅₀) was 15.0 ± 2.1 μL EO/L. We found that 20 µL of EOD caused a reduction of more than 91% of C. maculatus laid eggs.     

Strength of the [Z–I···Hal]− and [Z–Hal···I]− Halogen Bonds: Electron Density Properties and Halogen Bond Length as Estimators of Interaction Energy

Bond energy is the main characteristic of chemical bonds in general and of non-covalent interactions in particular. Simple methods of express estimates of the interaction energy, E_int, using relationships between E_int and a property which is easily accessible from experiment is of great importance for the characterization of non-covalent interactions. In this work, practically important relationships between E_int and electron density, its Laplacian, curvature, potential, kinetic, and total energy densities at the bond critical point as well as bond length were derived for the structures of the [Z–I···Hal]⁻ and [Z–Hal···I]⁻ types bearing halogen bonds and involving iodine as interacting atom(s) (totally 412 structures). The mean absolute deviations for the correlations found were 2.06–4.76 kcal/mol.     

AP-GOD Biosensor Based on a Modified Poly(PHENOL) Film Electrode and Its Application in the Determination of Low Levels of Phosphate

Abstract

The features of a biosensor based on a platinum electrode modified with a poly(phenol) film coupled with two enzymes, alkaline phosphatase(AP) and glucose oxidase(GOD), were studied. The modification of the surface of the working electrode decreases interference from ascorbic acid, uric acid and some oxidizable organic materials (e.g. glycine), and decreases the noise of the current. The concentration of substrate, the activity ratio of the two enzymes, the applied potential, and the assembling of biosensor are important for the determination of low levels of phosphate.

The two enzymes have been immobilized on an Immobilon^(R) membrane. The linearity range appears in two sections with different sensitivity: one from 8-110 μmol I^?1 and another one from 0.1-1.0 mmol I^?1, with 1.2 μA/mmol/cm² and 0.4 μA/mmol/cm², respectively. Except for some heavy metal ions, ascorbic acid and some oxidizable organic materials, common anions and cations don't interfere with the determination of phosphate.

The biosensor has been used to determine phosphate in some synthetic and real samples with a detection limit of 4 μmol I^?1 of phosphate. The results were compared with a standard spectrophotometric method. The accuracy and recovery of phosphate with the biosensor procedure are ±2% and 96 to 103%, respectively.

     

石墨烯/铋复合膜修饰玻碳电极检测板蓝根中的铅和镉

采用滴涂法制备石墨烯(GR)修饰的玻碳电极(GCE),通过电化学富集Bi沉积在GR表面,得到GR/Bi-GCE修饰电极.用方波溶出伏安法研究了Cd2+和Pb2+在GR/Bi-GCE上的电化学行为.在0.1 mol/LpH 4.5的醋酸缓冲溶液中,在-1.1 V富集0.5 mg/L Bi(NO3)3溶液210 s后,溶出峰电流与Cd2+和Pb2+的浓度在0.01～85.0 μmol/L范围内呈良好的线性关系,检出限均为0.003 μmol/L.实验结果表明,此修饰电极对Cd2+和Pb2+均有较好的电化学活性,可对两种物质实现同时测定,具有较高的灵敏度和稳定性.将此电极用于板蓝根中Cd2+和Pb2+的含量测定,结果令人满意.     

High Sensitivity and Reproducibility of a Bismuth/Poly(bromocresol purple) Film Modified Glassy Carbon Electrode for Determination of Trace Amount of Cadmium by Differential Pulse Anodic Stripping Voltammetry

This work described a novel type of bismuth/poly(bromocresol purple) film modified glassy carbon electrode (denoted as Bi/Poly(BCP)/GCE) for anodic stripping analysis of trace Cd²⁺. The Bi/Poly(BCP)/GCE was fabricated in situ by depositing simultaneously bismuth and cadmium by reduction at ?1.20 V on the poly(BCP) film using a differential pulse voltammetry. Under the optimum conditions, the anodic stripping peak current response increased linearly with the Cd²⁺ concentrations in a range of 2.0×10^?8–1.0×10^?7 M and 1.0×10^?7–6.0×10^?6 M in 0.1 M NaAc‐HAc buffer solution (pH 5.0) with the detection limit of 6.5×10^?9 M (S/N=3). The Bi/poly(BCP)/GCE performed good reproducibility and high sensitivity. Finally, this proposed method was successfully applied to determine the concentration of Cd²⁺ in water samples.