1,720,975 research outputs found
Development of di-methacrylate quaternary ammonium monomers with antibacterial activity
Full text linkNine antibacterial di-methacrylate monomers based on bis-quaternary ammonium salts (bis-QAMs) were synthesized and structurally characterized. The biological activity of the bis-QAMs was tested in terms of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) on different bacterial strains achieving promising results and, in most cases, a complete bactericidal effect using a bis-QAM concentration lower than 1 mg/mL. Two of the structures showed comparable and superior activity against S. mutans than the commercial monomer 12-methacryloyloxydodecyl pyridinium bromide (MDBP). All the bis-QAMs here described were able to inhibit S. mutans biofilm formation at a concentration equal to the MIC value. From the analysis of the obtained data, some correlation regarding the structure and the antibacterial activity of the bis-QAMs could be drawn: a flexible alkyl C12 spacer between the two quaternary ammonium moieties increased the monomer antibacterial effect in comparison to the aromatic ones; the equilibrium between hydrophobic and hydrophilic moieties was directly correlated to the bactericidal range of action; the increase of the steric hindrance of the ammonium side groups might be both advantageous or disadvantageous to the antibacterial efficacy depending on the whole monomer chemical structure. Even though the possible correlation between the monomer structures and their bacteriostatic or bactericidal effect is under investigation, the monomers exhibited low cytotoxicity on human dental pulp stem cells, confirming their promising potential in the dental materials' field
Chemoenzymatic synthesis of optically active alpha-methylene-gamma-carboxy-gamma-lactams and gamma-lactones
No full textEfficient synthesis of new fluorinated building blocks by means of hydroformylation
Full text linkHydroformylation of fluorinated alkenes is an efficient method for the preparation of fluorinated functionalized building blocks for the synthesis of biologically active target structures. In this article we summarize known hydroformylation reactions of fluorinated olefins and we add new results from our research groups. Particular attention is paid to the remarkable influence of organofluorine substituents on catalyst activity, regio-and stereoselectivity of the hydroformylation reaction
In vitro study on conditioned dental root surfaces: evaluation of wettability, smear layer, and blood clot adhesion
No full textObjectives: The aim was to investigate the efficacy of citric acid and ethylenediaminetetraacetic acid (EDTA)-based treatments on smear layer removal and blood clot formation and stabilization.
Method and materials: After scaling and root planing, 126 root samples were divided into seven groups treated with: deionized water; saline; citric acid solution; Ultradent Citric Acid gel; EDTA solution; EDTA-based PrefGel; or untreated. Each group was divided into three subgroups: I for the evaluation of smear layer removal and surface wettability, II and III for the evaluation of blood clot formation and stabilization in static or dynamic rinsing conditions.
Results: Conditioning agent treatments increased surface wettability with respect to untreated samples (Ultradent: 45 ± 1 degrees, P = 6.2 × 10-3; EDTA: 36 ± 5 degrees, P = 8.9 × 10-7; PrefGel: 47 ± 7 degrees, P = 3.2 × 10-2). Smear layer removal (30% to 60% with respect to untreated samples) was observed for all the conditioning agents. Clot was absent on untreated samples and samples treated with deionized water. Clot quality was significantly higher for samples treated with conditioning agents (P .05). A statistically significant difference (P = .027) was observed for clot coverage of the saline group, comparing static and dynamic rinsing, confirming the positive effect of treatments on clot stabilization.
Conclusions: The use of conditioning agents improves smear layer removal and clot formation and stabilization with respect to scaling and root planing procedure only, which is, however, considered an essential procedure to promote wound healing in periodontal surgery
New hybrid P-N ligands: coordination chemistry to palladium and catalytic activity in alkene dimerization
No full textEvaluation of the degree of conversion and rate of cure of a new BIS-GMA-free nanohybrid composite
No full textAim: The polymerization efficiency of the newintroduced Bis-GMA-free nanohybrid composite containing pre-polymerized spherical filler Ceram. X®Duo-D3 (CXDD3, Dentsply) was investigated in terms of degree of conversion (DC) and rate of cure (RC). The obtained results were compared with those of two commonly used composites of equivalent dentin shade: the nanohybrid Tetric EvoCeram®-A3.5 (TECA3.5, Ivoclar Vivadent) and the nanofilled FiltekTMSupreme XTE-D3 (FSAD3, 3M ESPE).
Methods: DC was evaluated using a Fourier Transform Infra-Red Attenuated Total Reflectance equipment (FTIR-ATR, Nicolet 6700-ThermoFisher) recording the photopolymerization kinetic (1 spectrum/s). Each composite (N=10) was placed on the FTIRATR diamond stage in a 2-mm thick silicon mold and photopolymerized for 40s with the LED curing-light SmartLite Focus®(Dentsply). Infrared (IR) spectra were obtained between 4000cm−1 and 500cm−1 at a resolution of 16cm−1. DC was calculated as: DC = [1 - (R40)/(R0)] * 100. Where R0 represents the ratio between the intensity of the reactive group signal (C=C, 1635cm-1) and the internal reference (C=O, 715cm-1) of the unpolymerized material and R40 the same ratio after 40s of photopolymerization. The kinetic trend was obtained plotting DC vs. time for all the materials. The kinetic curves were fitted with a second-grade polynomial expression, from the first derivative of the fitting, the RC at selected times (5, 10s) was calculated. RC≤0.5 between two consecutive times was considered as arbitrary value for the curve plateau.All data were subjected to statistical analysis with dedicated software (Statistical Package for Social Sciences Software v.15.0, SPSS Inc.) and tested for the assumptions for the use of parametrical tests: the normality of the distribution and the equality of variances were verified with a Shapiro-Wilk test and a Levene test, respectively. The influence of the materials’ composition on the DC and RC values was evaluated by one-way multivariate analysis of variance (ANOVA), pairwise comparison between groups were performed with a Scheffé post hoc test at a preset α=0.05. Separately, RC values registered for each material after 5 and 10s of curing time were compared with a paired-samples t-test.
Results: For all tested materials, the obtained DC after 40s of photopolymerization was lower than 50%. Among the tested composites, CXDD3 showed the highest DC (p 0.05). Within each composite, RC at 10s resulted significantly lower than that at 5s (pTECA3.5>FSAD3. CXDD3 showed the faster kinetic reaching the plateau (RC≤0.5) after 25s. Differently, FSA3D and TECA3.5 showed a significantly slower kinetic (p<0.05): TECA3.5 kinetic trend reached the plateau after 30s of photopolymerization while the RC of FSA3D slightly decreased with time with a pseudo-linear trend never reaching the RC value set as plateau.
Conclusions: Within the limitation of the present in vitro study, it is possible to assess that DC and RC of the studied composites were materialdependent: CXDD3, characterized by a Bis-GMA-free composition, achieved higher DC thanks to a faster kinetic. However, considering that for all the tested composites the average DC remained below 50% after 40s of photopolymerization, an increase of the curing-time or a reduction of the layer thickness may be suggested in the clinical setting of the dentine shaded composites
Effect of 6-alkyl substituted 2,2'-bipyridines in the Pd-catalyzed styrene carbonylation: shifting the selectivity from polyketones to oligoketones
No full textThe role of polymerization in adhesive dentistry
No full textAdhesive systems are resin-based materials that reach their final mechanical properties through a polymerization process. Previous literature correlated the failure of the adhesive interface to low polymer setting. Adhesives systems are elaborate mixtures of different molecules of both hydrophilic and hydrophobic nature, included in the formulation to adequately infiltrate the complex dental substrate or added to prolong the stability of the adhesive layer over time. Each adhesive component may influence the polymerization reaction of the material. Photopolymerization is a complex reaction that has several clinical implications, and besides the material composition, it is influenced by multiple factors, including the substrate characteristics, the operator technique, and the light cure unit properties. This review is focused on the analysis of factors that have a potential role in the setting of adhesive materials and thus the ultimate characteristics of the adhesive layer and the stability of the resin-dentin interface
Impact of Stereochemistry on Ligand Binding: X-ray Crystallographic Analysis of an Epoxide-Based HIV Protease Inhibitor
No full textA new pseudopeptide epoxide inhibitor, designed for irreversible binding to HIV protease (HIV-PR), has been synthesized and characterized in solution and in the solid state. However, the crystal structure of the complex obtained by inhibitor–enzyme cocrystallization revealed that a minor isomer, with inverted configuration of the epoxide carbons, has been selected by HIV-PR during crystallization. The structural characterization of the well-ordered pseudopeptide, inserted in the catalytic channel with its epoxide group intact, provides deeper insights into inhibitor binding and HIV-PR stereoselectivity, which aids development of future epoxide-based HIV inhibitors
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