镍铬、钴铬合金和纯钛在人工唾液中的耐腐蚀性评价

目的:用电化学交流阻抗谱方法研究钴铬、镍铬合金和纯钛在人工唾液中的耐腐蚀性。方法:用电化学工作站测量出3种金属材料在人工唾液中的电化学阻抗谱(Bode图、Nyquist图),利用ZSimpWin软件对数据进行拟合分析,根据等效电路R(CR)拟合结果来评估3种金属的耐腐蚀性能。结果:从Nyquist图可见,3种材料的容抗弧半径大小依次为纯钛>钴铬合金>镍铬合金;从Bode图见,3种材料均为一个时间常数,即表面均是一个电容层。根据等效电路R(CR),3种材料的电容层无明显区别,但三者的阻抗值均很大,其中纯钛的阻抗值最大,钴铬合金的阻抗值居中,镍铬合金的阻抗值最小。结论:3种材料在人工唾液中均具有良好的耐腐蚀性,其耐腐蚀性能顺序是纯钛>钴铬合金>镍铬合金。     

Evaluation of model and dispersion parameters and their effects on the formation of constant-phase elements in equivalent circuits

It was shown in a previous paper that the distortion induced by local inhomogeneities of equivalent-circuit model parameters in EIS data could be treated in terms of the average, the deviation and higher moments of the parameter distribution. Further refinements of the method are discussed. Evidence is provided that, at a frequently applied equivalent circuit, the lognormal distribution of the time constants can cause constant-phase behaviour in the EIS diagrams over a frequency range of several orders of magnitude.     

Analysis of an impedance function of zinc anodic dissolution

Zinc anodic dissolution has been studied by means of electrochemical impedance spectroscopy (EIS). The kinetic study of the oxidation mechanism has allowed us to propose a theoretical impedance function for this system in deaerated sulphate medium. Relevant information on the faradaic process is provided by analysis of the theoretical impedance function. Kinetic parameters of this system can be calculated from the fitting of experimental data to the faradaic impedance function deduced theoretically. The physical measurements of this function are analysed by means of the dependence of simulated EIS spectra on kinetic parameters.     

Examination of herpes virus DNA sequences for patterns that resemble transposable elements

Herpes viruses are associated with many types of oral tumors and can be tumorigenic in vitro. The mechanisms by which they transform cells remain unknown, but it has been suggested that they contain insertion sequences. Two algorithms were developed to search DNA sequences for the presence of patterns that characterize such elements using either selection or scoring techniques. When randomly shuffled herpes virus sequences were examined each algorithm detected many such patterns but the scoring algorithm found fewer than the selection algorithm. In the herpes virus sequences that are known to contain such patterns the computer techniques found many more than previously reported, indicating that visual inspection alone is not adequate. The frequency of these patterns suggest that although the transforming regions of herpes virus DNA could contain transposable elements experimental confirmation is necessary.     

Examination of herpes virus DNA sequences for patterns that resemble transposable elements

Herpes viruses are associated with many types of oral tumors and can be tumorigenic in vitro. The mechanisms by which they transform cells remain unknown, but it has been suggested that they contain insertion sequences. Two algorithms were developed to search DNA sequences for the presence of patterns that characterize such elements using either selection or scoring techniques. When randomly shuffled herpes virus sequences were examined each algorithm detected many such patterns but the scoring algorithm found fewer than the selection algorithm. In the herpes virus sequences that are known to contain such patterns the computer techniques found many more than previously reported, indicating that visual inspection alone is not adequate. The frequency of these patterns suggest that although the transforming regions of herpes virus DNA could contain transposable elements experimental confirmation is necessary.     

The periodontal differentiation in the phylogeny of teeth–an overview

During the evolution of teeth, different types of periodontal attachment have been developed. On the basis of the comparative histology of periodontal tissues, protoacrodontal, acrodontal, acro-protothecodontal, pleurodontal and thecodontal structures can be distinguished that depend upon the area of attachment (crestal, marginal or socketed type) and the mode of attachment (ankylosis, fibrous or combined type). Due to "phylogenetic memory", changes of the periodontium in health and disease could be interpreted as copies of phylogenetically older patterns. The greatest variations in tooth attachment have originated in acrodont bony fishes and in pleurodont reptiles, whereas the selection for a single thecodont or socketed type was an important event in the evolution of mammals. The detailed structures of cementum, of the fiber apparatus and of the junctional epithelium vary from type to type and within one type. These principal structures are decisive for reaction patterns of degeneration and regeneration. Therefore, comparative periodontology could be an important adjunct to help interpret the natural history of periodontal diseases, to help in the selection of experimental animals and to help provide treatment strategies in both human and veterinary situations.     

Repeatability of head posture recordings from lateral cephalometric radiographs

The mechanisms that control facial growth are still not known. One method for studying these mechanisms is the careful analysis of subjects with normal and aberrant growth patterns using standardized lateral cephalometric radiographs. It has been shown in normal subjects that head posture is related to facial development and that changes in head posture are influenced by changes in nasal respiratory resistance (NRR). In the determination of these associations it is therefore important to assemble cephalometric data from lateral skull radiographs that have been standardized for position as well as for natural head posture. The study demonstrates that a reproducible head posture position exists that can be recorded with a method error of only a few degrees.     

Informatics approaches to improve the quality of dental care

Despite technological advances, challenges exist in US dental care, including variations in quality of care, access and untreated dental needs. The implementation of learning health systems (LHSs) in dentistry can help to address these challenges. LHSs use robust informatics infrastructure including data and technology to continuously measure and improve the quality and safety of care and can help to reduce costs and improve patient outcomes. The use of EHRs and standardized diagnostic terminologies are highlighted, as they allow for the storage and sharing of patient data, providing a comprehensive view of a patient's medical and dental history, and can be used to identify patterns and trends to improve the delivery of care. The BigMouth Dental Data Repository is an example of an informatic platform that aggregates patient data from multiple institutions and is being used to for scientific inquiry to improve oral health.     

A study of external magnetic-field effects on nickel–iron alloy electrodeposition,based on linear and non-linear differential AC electrochemical response measurements

Linear and non-linear electrochemical AC spectrometry (the former better known as electrochemical impedance spectrometry, EIS) studies were performed during Ni–Fe alloy electrodeposition in magnetic fields up to 0.5 T. We could show that by using linear EIS it can be very difficult – if not almost impossible – to identify magnetohydrodynamic effects on the electrodeposition of Ni–Fe alloys. Very poor reproducibility was seen in linear EIS experiments, even in the absence of a magnetic field, due to the inherent non-stationarity of electrocrystallisation processes. Using a non-linear approach we could show that the real and imaginary parts of the total impedance of the system are sensitive to the presence of a magnetic field in the frequency range from 1 to 100 Hz. Some degree of correlation between the applied magnetic field and the second harmonic response of the current density could also be detected at relatively high frequencies (e.g., at 10 and 100 Hz).     

Immobilization of albumin on indium-tin oxide (ITO) surface via isocyanate linkage

Indium-tin oxide (ITO) surfaces have become a very important material for use as a conducting substrate, recently. Immobilization of biological molecule onto the ITO is a fundamental step in the development of biosensors. In this paper, attachment of albumin was carried out using ITO as a support. Albumin was covalently immobilized onto self–assembled monolayer (SAM) of (3-isocyanatopropyl) triethoxysilane (IPTES) on ITO surface. Isocyanato-functionalized organic film was prepared by self–assembling on active ITO surface. After that, human serum albumin (HAS) which was prepared in Phosphate-Buffered Saline Solution (PBS: pH 7.4, 0.1 M), was covalently immobilized on IPTES modified ITO surface. The study here can help us understand the influence of monolayer and electrochemical behavior on ITO surface. Characterization of stepwise changes of active ITO, IPTES/ITO and albumin/IPTES/ITO surfaces were carried out using contact angle (CA) measurements, fluorescence microscopy, atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), respectively.     

Electrochemical impedance spectroscopy in understanding the influence of ultrasonic dental scaling on the dental structure–dental filling interface

The purpose of this study was to investigate the effect of ultrasonic scaling on teeth restored with a light‐cured resin. Ultrasonic scaling is a very popular periodontal therapy among dentists, and used for the removal of dental plaque and calculus in order to reduce and eliminate inflammation. Given the fact that most ultrasonic devices are used at high frequencies to perform scaling, undesirable consequences, such as loss of adhesion and increase in surface roughness, may occur in teeth that have been restored with light‐cured resins. Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy were used to investigate the effects of ultrasonic treatments at the dental material–hard dental tissue interface. After ultrasonic scaling, EIS measurements were performed on a human tooth that had been restored with a light‐cured resin filling. The data were analyzed and the influence of ultrasound was shown after visualization of the hard dental tissues and the dental material as equivalent electrical circuits. The study revealed, through EIS measurements, that ultrasonic scaling affected the resistance of the light‐cured resin filling and dentin, whereas the enamel was affected only slightly. Scanning electron microscopy revealed an increase in roughness of the dental material.     

Characterization of non-aqueous dispersions of carbon black nanoparticles by electrochemical impedance spectroscopy

Understanding fundamental electrochemical characteristics of industrial fluids, lubricants and their contaminants will allow for improvements in monitoring the performance of existent, and the formulation of new advanced industrial fluids and lubricants. This study focusses on the electrochemical characterization of model systems of colloidal dispersions of carbon black (CB), validation of these models, and investigation of applications of electrochemistry for determining the relative effectiveness of dispersants. Utilizing electrochemical impedance spectroscopy (EIS) analysis of industrial colloidal dispersions, an experimental method was developed to study the mechanism of dispersant/carbon black interactions, and the role of these interactions in the formation and stabilization of colloidal dispersions. Experimental EIS parameters such as conductivity, permittivity, critical frequencies of impedance and modulus relaxations, and impedance and modulus values were used in modeling equations describing particle sizes and interaction mechanisms occurring in CB dispersions. Results from the modeling equations show that dispersant micelles averaging 9 nm in diameter were present in solution. The dispersant micelles have a tendency to aggregate and form a loose “network”. In solutions containing CB, dispersants surround CB particles and form a colloidal suspension. An increase in relative concentration of the dispersant leads to a better stability of the suspension and prevents CB agglomeration. The diameter of the suspended CB particles decreases with added dispersant until a stabilization point is reached at approximately 200 nm. The validity of the impedance data and results of the modeling equations were confirmed by other analytical techniques, such as quasi-elastic light scattering and adsorption analysis.     

EIS study of the FeIII/FeII redox couple at a Nafion®-coated Pt electrode

The redox reaction Fe^III + e ? Fe^II is studied at a Nafion^®-filmed Pt electrode using both steady-state and EIS methods. It is shown that the fitting of the EIS experimental data can be greatly improved by using the new concept of a ‘theoretical–experimental hybrid model’, i.e., by introducing experimental data obtained at a bare electrode in the theoretical model for a filmed electrode. It is also shown that a combined steady-state and EIS study cannot lead to a separate determination of the three key parameters of the system: the diffusion coefficient in the polymer film (D_f), the thickness of the film (L), and the partition coefficient between the solution and the polymer (γ), only the two parameters γD_f/L and L²/D_f being obtained from experimental data by a curve fitting procedure. Finally, an exhaustive theoretical EIS study in quiescent solution is also proposed.     

根管治疗约诊间痛发生机制的研究进展

约诊间痛是根管治疗中常见的并发症,其发生的主要原因是根尖周组织在根管治疗过程中受到机械、化学或微生物损害,导致大量炎性介质释放或激活,引发了急性根尖周炎症反应.了解约诊间痛的发生机制将有助于制定有效的预防和控制措施.     

SEM,EDX and EIS study of an electrochemically modified electrode surface of natural enargite (Cu3AsS4)

Enargite electrodes, made from mineral originating in the ‘Salvador’ mine (Chañaral, Chile), have been studied using SEM, EDX, CV and EIS in an alkaline solution for a range of different potentials in the positive sweep direction (PSD) and negative sweep direction (NSD). The results of SEM and EDX have shown that the principal changes in morphology and chemical composition take place on the surface of the electrode for oxidation potentials close to the value that corresponds to the most intense peak in the PSD, where there is clearly formation of a layer of oxidised material with areas of morphology which are irregular and high in oxygen content. These results are in accordance with the findings from XPS studies published previously. The charge transfer resistance and the resistance of the anodic layer of the electrode were determined by EIS measurements; the values depend heavily on the applied potential in the PSD or NSD. These changes are related to the changes on the surface of the electrode studied by SEM and EDX     

外泌体在肿瘤微环境中调控作用的研究进展

非可控性炎症在肿瘤的发生、发展及恶化中扮演着重要的角色。肿瘤微环境本身也是一个非可控性炎症的微环境,肿瘤细胞在慢性、反复轻微的炎性刺激下,会诱导肿瘤微环境的恶化,进而促进肿瘤的恶性进展。关于肿瘤细胞对其周围细胞的调控机制,越来越多的研究聚焦在肿瘤细胞释放的外泌体的信使功能上。而随着微小核糖核酸（ miRNAs）研究的深入,研究者认为miRNAs可以作为信号分子介导细胞之间的通讯。在肿瘤的慢性炎性环境中,肿瘤源性外泌体-miRNAs对周围细胞发挥着重要的调控作用,探索外泌体-miRNAs的形成及作用机制,将为揭示肿瘤微环境中免疫和炎症本质提供依据。     

电化学阻抗法研究口腔含氟环境中纯钛的腐蚀行为

目的：电化学阻抗法研究钛修复材料在口腔含氟环境中的腐蚀性能。方法：采用高级电化学分析仪获得钛在人工唾液和含氟人工唾液中的电化学阻抗谱,利用EIS-Nyquist图、EIS-Bode图及等效电路的拟合解析,系统研究F-对钛腐蚀性能的影响。结果：当人工唾液中F-浓度为0.1%,钛表面氧化膜的阻抗值及相位角无显著变化,当人工唾液中F-浓度达到0.2%时,钛表面氧化膜的阻抗值显著下降,而低频区的相位角下降到30°。结论：电化学阻抗法可以用来研究钛在口腔含氟环境下的腐蚀性能,较高浓度的氟可以对钛产生严重的腐蚀作用。     

Planned change and the future of the dental education system

Dentistry today faces an environment that clearly requires changes in dental education. Future dentists must be prepared to deal with new patterns of dental disease, revised manpower requirements, and new developments in the nature of dental practice. The dental education system can best adapt to this situation by initiating a process of planned change. A well-developed literature in this area provides both a theoretical framework and a practical approach that the dental education system can follow in its planning process. In this paper, the principles of planned change are interpreted in the context of dental schools' characteristic structure, goals, leadership, and communication mechanisms. The traits of successful change and specific strategies for achieving it are offered as a means for the dental education system to build with confidence a productive and healthy future.     

Monitoring acid-demineralization of human dentine by electrochemical impedance spectroscopy (EIS)

Objective

The purpose of this study was to monitor in situ acid-induced demineralization of dentine by using electrochemical impedance spectroscopy (EIS) and correlate the EIS findings with changes in the chemical composition and ultrastructure of dentine.

Method

EIS was used to monitor the process of demineralization of dentine induced by an acid model. Scanning electron microscopy (SEM) was used to examine the ultrastructure, while energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analysis were employed to investigate the changes in the chemical composition of surface dentine with demineralization.

Results

Two kinds of equivalent circuits that matched the histological structure of dentine were used to fit the EIS data. The parameters R_d, which is the resistance of the bulk of dentine layer and R_ct, which is the charge transfer associated with the penetration of electrolyte into the dentinal tubules, decreased with increasing duration of demineralization. SEM images showed that the smear layer on the dentine and peritubular dentine disappeared with demineralization. The EDX results showed that the content of calcium and phosphorus decreased consistently with the decreasing content of HAP as shown by the XRD results. The findings from this study suggested that the changes in R_d and R_ct determined by the EIS corresponded well with the variation in structure and composition of dentine.

Conclusions

EIS could be employed to monitor structural and chemical compositional changes induced by acid-demineralization on dentine surface.     

Pd–P electroless deposition on carbon steel: An electrochemical impedance spectroscopy study

By the combination of two techniques, namely, polarization curves and electrochemical impedance spectroscopy (EIS) it is possible to obtain information about solution/metal surface interactions occurring during Pd–P electroless deposition at the equilibrium potential, on carbon steel. The polarization curves indicate that the deposition reaction does not obey the mixed potential theory. The values of the charge transfer resistance, when compared with those obtained by the equivalent circuit proposed to model the EIS data, indicate that there are changes in the rate-determining step of the reaction over the course of the deposition. The values obtained for the elements of the equivalent circuit that correspond to the film, permit the characterization of the film as a semiconductor. This conduction feature seems to be due to the presence of incorporated phosphorus (≈7wt.%) in the deposit at the end of the deposition process.