Precision Synthesis of a Long-Chain Silane Coupling Agent Using Micro Flow Reactors and Its Application in Dentistry

Silane coupling agents containing a fluorocarbon chain were prepared in high yields. It was found that silanes can be useful modifiers of the surfaces of glass, metals, and resin composites for dental use. The silane coupling agent CF3(CF2)9CH2CH2Si(OCH3)3 was the best modifier of these surfaces in terms of water and oil repellency. Colorants and experimental bacterial plaque detached much more easily from, and adhered less well to, surfaces modified with this silane coupling agent compared with unmodified surfaces. The surfaces of four teeth of a denture were modified with this silane coupling agent by spreading the agent on the surfaces with a small brush followed by brief drying with a hair drier. The modified tooth surfaces of the denture, which was worn for four months in a heavy smoker's oral cavity, were more stain-resistant than the unmodified tooth surfaces. It is expected that silane coupling agents containing a fluorocarbon chain will be useful surface modifiers for enhancement of oral health.

Immediate effects of chlorpromazine and perphenazine following neuroleptic washout on word association of schizophrenic patients

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Background/Objectives: Motor imagery (MI) is the mental practice of motor actions with temporal dynamics and neural features in common with motor execution (ME). Although MI can improve motor performance, it remains unclear how closely performance-related signatures of MI resemble those of ME during learning, particularly in tasks with intrinsic variability. This study investigated similarities and differences between MI and ME during a probabilistic sequence-learning task. Methods: Participants performed a finger-tapping serial reaction time task in either a motor execution (ME; n = 10) or motor imagery (MI; n = 10) condition. The task consisted of 750 auditory stimuli mapped to right-hand finger movements and generated by a probabilistic sequence with deterministic and variable events. Reaction times were analyzed using ANOVA designs to assess the effects of Group, Block, Event Type, and the Last Variable event. Results: The MI group showed a significant reduction in reaction times across blocks (p < 0.001), indicating learning-related performance improvement, whereas no block-wise improvement was observed in the ME group. Both groups were sensitive to the probabilistic structure of the sequence, with reaction times differing across event types. A significant Group × Event interaction (p < 0.01) indicated distinct performance signatures for MI and ME. In both groups, reaction times were modulated by the last variable event. Conclusions: Motor imagery supported learning in a probabilistic sequence task but was influenced by factors distinct from those governing motor execution, suggesting partially different underlying mechanisms.

Chronic administration of low doses of the neurotoxin MPTP to nonhuman primates induces cognitive deficits similar to those seen in early Parkinson's disease (PD) patients, without the confounding effect of significant motor impairment. The present study assessed the extent to which specific attentional and central executive deficits in chronic low dose (CLD) MPTP-treated monkeys could be modified by nicotinic therapies. Four adult male rhesus monkeys were trained to perform attention and executive function tasks and were then administered low doses of MPTP (dose range: 0.025-0.1 mg/kg, i.v.) over 98-158 days until stable cognitive deficits appeared. Results showed that both nicotine and the alpha4beta4 subtype-selective nAChR agonist SIB-1553A could improve certain aspects of attentional and central executive functioning in this model of early Parkinsonism. Nicotine failed to improve performance of CLD-MPTP-treated animals on an attention set-shifting task while SIB-1553A significantly improved at least some aspects of performance, suggesting that the compound increased the animals' ability to maintain a previously formed response set and restored cognitive flexibility. Both nicotine and SIB-1553A caused a dose-dependent enhancement of performance on the focused attention (cued reaction time) task, decreasing reaction times on both cued and noncued trials. Nicotine caused a significant reduction in reaction times but did not alter the error profile on an impulse (motor readiness) task. SIB-1553A reduced reaction times but caused an increase in bar release (i.e. impulsivity) errors. These data suggest that nicotinic drugs may have therapeutic potential for treating cognitive dysfunction in PD.

Exploring task-set reconfiguration with random task sequences

This study investigated the immediate effect of slow yoga breathing (SYB) at 6 breaths per minute (bpm) simultaneously on working memory performance and heart rate variability (HRV) in yoga practitioners. A total of 40 healthy male volunteers performed a working memory task, ‘n-back’, consisting of three levels of difficulty, 0-back, 1-back, and 2-back, separately, before and after three SYB sessions on different days. The SYB sessions included alternate nostril breathing (ANB), right nostril breathing (RNB), and breath awareness (BAW). Repeated measures analysis of variance showed a significant reduction in reaction time (ms) in 2-back condition immediately after ANB (−8%), RNB (−8%) and BAW (−5%) practices. Similarly, the accuracy was improved in the 0-back condition after RNB (4%), and in the 2-back condition after ANB (6%) and RNB (6%) practices. These results suggest that SYB practice enhances cognitive abilities (8–9%) related to memory load and improves the functioning of cardiac autonomic activity, which is required for the successful completion of mental tasks.Trial registered in the Clinical Trials Registry of India (CTRI/2018/01/011132).

The low aqueous solubility of drug-like compounds has been described as one of the main problems causing the failure of new chemical entities in medicinal chemistry programmes. This paper describes our efforts to overcome lack of solubility and to produce a novel template protocol for forming salts of poorly soluble compounds. We prepared a series of 4-hydroxy-6-methyl-3-nitropyridin-2(1H)-one amine salts by using ultrasound irradiation. The poorly water-soluble molecule 4-hydroxy-6-methyl-3-nitropyridin-2(1H)-one was recently described as an inhibitor of the Mycobacterium tuberculosis orotate phosphoribosyltransferase enzyme. Salts of this molecule were prepared in 88–98 % yield from a mixture of 4-hydroxy-6-methyl-3-nitropyridin-2(1H)-one with primary and secondary amines (dimethylamine, diethylamine, dipropylamine, ethanolamine, 2-amino-2-methyl-1,3-propanediol, d-threoninol, pyrrolidine and piperidine) after ultrasound irradiation. The main advantages of this method are a significant reduction in reaction times and the use of a renewable solvent as a reaction medium. Thus the compounds are obtained after irradiation for 8 min in ethanol.

Microemulsion-mediated hydrothermal synthesis of photocatalytic TiO 2 powders

An experimental study was carried out to investigate the effects of coupling agents on the rheological properties, processability, and mechanical properties of highly filed polypropylenes (PP). Inorganic fillers used were CaCO3 and glass beads, and coupling agents used were two silane coupling agents, N‐octyl triethoxy silane and γ‐aminopropyl triethoxy silane, and one titanate coupling agent, isopropyl triisostearoyl titanate. It was found that the addition of the coupling agents to the PP‐CaCO3 (50 wt percent) decreased the melt viscosity and increased the melt elasticity (first normal stress difference). However, the addition of the silane coupling agents to the PP‐glass beads (50 wt percent) affected the rheological properties of the melts quite differently. The N‐octyl triethoxy silane had relatively little effect on either the melt viscosity or the melt elasticity, whereas the γ‐aminopropyl triethoxy silane increased the melt viscosity and decreased the melt elasticity. The CaCO3‐ or glass bead‐filled polypropylenes, with and without coupling agents, were injection‐molded and the mechanical properties of the molded specimens were measured by the use of an Instron testing machine. It was found that the effect on the tensile strength and percent elongation of the filled polypropylenes depended upon the specific coupling agent utilized. A melt‐spinning study was also carried out to investigate the effect of coupling agents on the spinnability (defined as the maximum draw‐down ratio) of the PP‐CaCO3 system, and on the mechanical properties of the melt‐spun fibers. It was found that the spinnability of the PP‐CaCO3 was enhanced considerably by the addition of the coupling agents, and that the tensile strength of the melt‐spun fibers was also improved by their addition. Scanning electron micrographs were taken of the fracture surface of injection‐molded specimens and an attempt was made, with the aid of photomicrographs, to explain the mechanical properties of molded specimens observed experimentally.

Reason for withdrawal from publication This review is now out of date and is being superseded. The new protocol for the update is Weldon JC, Yengopal V, Siegfried N, Gostemeyer G, Schwendicke F, Worthington HV. Dental filling materials for managing carious lesions in the primary dentition. Cochrane Database of Systematic Reviews 2016, Issue 9 . Art. No.: CD012338. DOI: 10.1002/14651858.CD012338, which is available at http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD012338/full

A review study on coupling agents used as ceramic fillers modifiers for dental applications

Objectives: The aim of this study was to assess and compare quantitatively and qualitatively the artifacts induced by various commonly used dental restorative materials in different sections of CBCT image and to characterize the pattern of artifact. Material and Methods: Thirty dental plaster blocks, each with one of each of mandibular second premolar, first molar and second molar teeth with crowns aligned as in the natural dentition were scanned by CBCT device and analyzed using CS 3D imaging software, before and after the first molar was prepared and restored with dental amalgam, composite resin or glass ionomer cement (GIC), 10 plaster blocks being randomly selected for each restorative material. The reformatted axial, coronal and sagittal scans were then quantitatively assessed for artifact by two calibrated dento- maxillofacial radiologists by comparing the control and restored scans of each plaster block in a blinded manner and documented the slice numbers from which the image became diagnostic. Then, the slice numbers were converted into millimeters away from the restoration. Results: Paired t test, ANOVA and post hoc Tukey tests were used for statistical analyses. The level of significance was set at α = 5%. Depending on the extent, the majority of artifacts produced were as follows: Dental amalgam &gt;Composite resin &gt;GIC. The artifact was most extensive in the coronal section. Streaks and scatter artifacts, linear artifacts extending outward from tooth surface and hypodense halo were predominant. Conclusion: Different dental restorative materials cause various amounts of artifacts in different planes of projection of CBCT image due to differences in density and atomic number.

Due to the low adhesion caused by moisture absorption, the delamination between the underfill and the passivation layer of the chip has been proved to be a critical problem to determine the packaging reliability. In this study, five different silane coupling agents were added to underfill and their reliability at the underfill and passivation layer interface was investigated under hygrothermal conditions. Shear tests at room temperature and high temperature were carried out to evaluate the interfacial adhesion. It was found that after hygrothermal aging, the adhesion of underfill without coupling agent was severely degraded for the passivated layer; however, after adding coupling agent, the coupling agent enhanced the hygrothermal reliability of the interface due to the formation of chemical bonds, especially the silane coupling agent with epoxy and amino groups. It showed good interfacial adhesion under both room temperature and high temperature conditions before and after hygrothermal aging.

Composite materials used in dentistry indicate adverse biological effects in laboratory conditions. One reason for this activity is incomplete conversion of their polymer matrix, favoring chemical instability and release of biologically harmful components to the external environment. The aim of the study was to assess the degree of conversion of restorative materials commonly available on the European market and to examine the cytotoxic effects of their eluates in vitro. Using the Fournier transform infrared spectroscopy (FTIR) technique of analysis, the degree of polymer matrix conversion of 6 restorative materials was examined: Gradia Direct, Arkon, Filtek Z550, Herculite XRV, Tetric Evo Ceram, Charisma, polymerized with LED light. In order to assess the cytotoxicity of eluates of the studied materials obtained after 1 hour , 24 hours and 7 days, the MTT assay was used in cultured 3T3 cells. The results were statistically analyzed at significance level of p=0.05. The conversion degree of the assessed polymers ranged from 31.56% for Tetric Evo Ceram to 75.84% for Arcon. The strongest (p=0.05) cytotoxic effect was demonstrated after 7-day observation of Tetric Evo Ceram eluates, reducing the metabolic activity of cells down to 56%. A positive correlation (r(x, y) = 0.62) between the degree of conversion of composite materials and cytotoxic effects of their eluates on cell cultures was confirmed. 1. Restorative dental materials are chemically unstable in the conditions of the present study. 2. Polymer-based restorative dental materials available on the European market demonstrate cytotoxic properties constituting a potential threat to the patients' health.