Telemetric comparison of centric relation and centric occlusion reconstructions

Two complete fixed prostheses built with the occlusion in centric relation and with occlusion in the subject's existing centric occlusal position were tested with telemetry under conditions of actual use. The findings indicate that the subject did not use the centric relation position but accepted the prosthesis built to her preexisting centric occlusion. These findings are consistent with our previous results of telemetric studies conducted on patients with three-unit fixed prostheses.     

Selective determination of dopamine using unmodified,exfoliated graphite electrodes

Selective determination of a neurotransmitter, dopamine (DA), is achieved in the presence of ascorbic acid (AA) at neutral pH on an inert, unmodified exfoliated graphite electrode. The edge planes, exposed by roughening the surface of the electrode have been found to be very active for electrochemical sensing. A separation of 0.24 V in the oxidation potential and an increase of 100 times in the currents between DA and AA have been observed with the graphite exfoliated at 800 °C. The exfoliation temperature is found to play a major role in determining the activation of the surface and in turn the effective separation of the analytes. This is attributed to the trend in the O/C ratios on the graphite electrodes observed using X-ray photoelectron spectroscopy. The separation is mainly due to the repulsive interactions between the functional groups on the electrode surface and the ascorbate anion. This is confirmed by comparing the point of zero charge (pH_PZC) of the electrode surface determined using pH titration and the pK_a of AA. A very low detection limit of 50 nM of DA in the presence of 100 μM ascorbic acid has been observed using chronoamperometry. The exfoliated graphite is an unmodified electrode and hence just polishing the electrode could expose the active surface. The analytical utility of the exfoliated graphite electrodes for the selective determination of DA in the presence AA is presented.     

Development of amperometric arsine gas sensor using gold-modified diamond electrodes

Amperometric gas sensor of arsine was developed using gold-modified diamond electrodes as the working electrodes. The detection method was conducted in high concentration of H₂SO₄. The reaction was declared based on two oxidation steps, involving oxidation of As³⁻ to As⁰ at mild potential in strong acid, followed by electrochemical oxidation of As⁰ to As³⁺ at gold-based electrodes. Linear calibration curve was observed in the concentration range of 5–50 ppb (r² = 0.985) with detection limit of ∼4.43 ppb (S/N = 3). Current decreasing of measurement was found ∼5.5% for 5 measurements. However, better stability was observed after the 5th measurement, indicated that the sensor could be applied for long time measurement. Investigation to several possible interference gasses, i.e. SO₂, H₂S, NO, NO₂, CO, O₃ and H₂ indicated no significant interference of the gas to arsine measurements.     

Evaluation using sequential trials methods

Dental school faculty members, as well as many practitioners, are interested in evaluating products and procedures used in clinical practice. Research design and statistical analysis, however, can pose problems to some, while others would like to avoid detailed consideration of protocol until after a preliminary investigation. Sequential trials methods provide an analytical structure that is both easy to use and statistically valid.     

Simultaneous determination of phenolic compounds by using a dual enzyme electrodes system

Simultaneous amperometric determination of two phenolic compounds was performed by using a tyrosinase (TYR) electrode and a TYR-peroxidase (POD) bienzyme electrode on the basis of differences in the selectivities for two phenolic compounds between the two enzyme electrodes. Catechol and p-cresol contained in the same solution were determined simultaneously with the present system. The response of the bienzyme electrode was greater than the sum of the response of the TYR electrode and that of a POD electrode. This amplification effect may be responsible for the differences in the selectivities. Amplification mechanisms were also discussed.     

A histologic comparison of effects of electrosurgical resection using different electrodes.

Electrosurgery is a helpful adjunct to restorative dentistry, yet there often is damage to underlying connective tissue. In this study, small loop electrodes demonstrated a wider area of coagulation necrosis than was found with needle electrodes. In all instances, coagulation necrosis as a result of heat was noted. To help minimize tissue damage, very fine wire electrodes should be used, and entry into deep tissue layers should be avoided.     

Time dependent EC′, ECE and EC2E mechanisms at microdisc electrodes: simulations using adaptive finite element methods

In this paper we extend the work in [Electrochem. Commun. 5 (2003) 519] to more complex reaction mechanisms. We use the adaptive finite element algorithm described there to simulate the chronoamperometric current for EC^′ reaction mechanisms (catalytic reaction mechanisms) at inlaid and recessed microdisc electrodes and for ECE and EC₂E reaction mechanisms at microdisc electrodes.     

The reduction of l-cystine hydrochloride at lead using static and rotating disc electrodes

The reduction of the disulphide, l-cystine hydrochloride to the l-cysteine hydrochloride thiol, in 0.1 mol dm^?3 HCl at 298 K, has been studied at pre-treated, circular, 0.50 cm² lead disc electrodes using steady state linear sweep voltammetry, non-steady state voltammetry and controlled potential coulometry. The diffusion coefficient for l-cystine hydrochloride was approximately 4.8 × 10^?10 m² s^?1 from the three techniques. Reduction of the disulphide was irreversible and hydrogen evolution occurred as a competitive reaction at approximately ?1.35 V vs. SCE. Analysis of the mixed control kinetics, using a Koutecky–Levich approach, allowed the relative roles of charge transfer and mass transport to be resolved. Anomalously high Tafel slopes, of typically ?183 mV, were observed due to disulphide adsorption. The charge transfer kinetics are consistent with the first electron gain being rate determining while reaction orders are +1 with respect to both the disulphide and proton concentrations. The mechanism of l-cystine hydrochloride reduction has been critically discussed.     

Electroanalytical determination of sildenafil in Viagra tablets using screen-printed and conventional carbon paste electrodes

This work compares the electroactivity of a conventional carbon-paste electrodes and screen-printed carbon electrodes. Potentiometric sensors responsive to sildenafil citrate (SILC) drug (the active component of Viagra) are described, characterized, compared and used for drug assessment. The proposed carbon paste electrode is fully characterized in terms of plasticizer type, response time, life span, soaking time, titrant, pH and temperature. The electrodes exhibited linear response with a Nernstian slope of 58.20 ± 1 and 58.82 ± 0.5 mV decade⁻¹ for SILC in the concentration range from 1.0 × 10⁻⁷ to 1.0 × 10⁻² and 5.30 × 10⁻⁷ to 1.0 × 10⁻² mol L⁻¹ with good reproducibility for CPE and SPE, respectively. Both CPE and SPE could be used in the pH range 3.0–5.0 and the isothermal coefficient is found to be 0.98 and 0.85 mV/°C, respectively. The limit of detection was found to be 9.0 × 10⁻⁸ and 3.5 × 10⁻⁷ mol L⁻¹ for CPE and SPE, respectively. They were applied to potentiometric determination of SILC in pure state and pharmaceutical preparation under batch conditions. The CPE and SPE sensors display good selectivity for SILC drug over large number of inorganic cations, sugars and amino acids commonly used in drug formulations. The CPE and SPE show high selectivity for the drug under investigation. The results obtained using the fabricated CPE is compared with those obtained by SPE for spiked pharmaceutical samples.     

Predicting clustered dental implant survival using frailty methods

The purpose of this study was to predict future implant survival using information on risk factors and on the survival status of an individual's existing implant(s). We considered a retrospective cohort study with 677 individuals having 2349 implants placed. We proposed to predict the survival probabilities using the Cox proportional hazards frailty model, with three important risk factors: smoking status, timing of placement, and implant staging. For a non-smoking individual with 2 implants placed, an immediate implant and in one stage, the marginal probability that 1 implant would survive 12 months was 85.8% (95%CI: 77%, 91.7%), and the predicted joint probability of surviving for 12 months was 75.1% (95%CI: 62.1%, 84.7%). If 1 implant was placed earlier and had survived for 12 months, then the second implant had an 87.5% (95%CI: 80.3%, 92.4%) chance of surviving 12 months. Such conditional and joint predictions can assist in clinical decision-making for individuals.     

Variations in treatment need using four screening methods

The study models of 100 Grade Seven students were used to compare the Dental Aesthetic Index (DAI), the Dental Health Component (DHC) and the Aesthetic Component (AC) of the Index of Orthodontic Treatment Need (IOTN), and the Danish Ministry of Health (DMH) screening system. The basis for comparison was the agreed subjective assessment of two orthodontists for each subject. Disagreements between the subjective assessment and each screening method were further analysed in an attempt to identify the specific occlusal traits responsible for the disagreement. The DAI under-estimated treatment need in cases with displaced canine teeth, incisor crowding or rotations and increased overbite. The DAI over-estimated treatment need in cases with increased overjet in otherwise well-aligned arches. The DMH guidelines over-estimated treatment need in cases with increased overjet and crowded arches. The DHC was found to be over-sensitive in cases with increased overjet and contact point displacements greater than 2 mm. The AC under-estimated treatment need in cases with excessive overjet and buccally displaced canines, and over-estimated treatment need in cases with spaced arches and deep overbite.     

Diagnosis of adsorption on solid electrodes using semi-integral voltammetry: A generalization via asymptotic analysis

A diagnosis of adsorption on solid electrodes using semi-integral voltammetry, initially proposed by Bowling and McCreery for a reversible charge transfer without coupled chemical reactions, is re-examined in the general case. Towards this aim, we show that an asymptotic analysis of the semi-integrated (or convolved) voltammograms is sufficient to conclude. A straightforward approach is designed which enables an examination of all previous hypotheses available in the literature: reversible or irreversible charge transfer, involvement of adsorbed reactants and/or products of the charge transfer or pure diffusion, and occurrence of coupled chemical reactions. We apply our asymptotic approach to all these cases, and show that the adsorption hypothesis is the only one to yield peak-shaped semi-integrated voltammograms, while monotonically increasing S-shaped semi-integrated voltammograms are obtained in the pure diffusion approximation. We find that the exclusive assumption of adsorption versus pure diffusion is sufficient to lead to discriminating behaviour, as the consideration of all other hypothesis (reversibility of the charge transfer, coupled chemical reactions) does not alter the conclusions. Thus, a hierarchy in the various hypotheses exists, which alludes to the systematic use of semi-integral voltammetry as a practical route to the diagnosis of the involvement of adsorption phenomena in electrochemical processes. Possible restrictions to this proposal are examined, as well as the way in which they may be overcome.     

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目的    研究定量激光荧光技术（DIAGNOdent）、定量光导荧光技术（QLF）和数字成像光纤透照技术（DIFOTI）诊断氟斑牙的效果。方法    2007年11月至2008年3月选择因各种原因拔除的临床诊断为氟斑牙的离体牙20颗,其中10颗为磨牙,10颗为前磨牙。每颗牙根据TF Index给予分级并记录。分别使用DIAGNOdent,QLF 和DIFOTI 3种光学技术分析评价离体氟斑牙,并对所得结果进行比较分析。结果    DIAGNOdent检测最大荧光值与TF-score具有相关性（r = 0.485,P < 0.05）。离体氟斑牙的QLF图像呈现出弥散的灰色阴影,DIFOTI图像呈现出弥漫集中的黑色阴影,且后者更加清晰。结论    3种光学技术均可用于诊断氟斑牙,其诊断效果：DIFOTI>QLF>DIAGNOdent,可作为鉴别龋病和氟斑牙的一种辅助手段。