Modeling the butterfly: the voltammetry of (√3×√3)R30° and p(2×2) overlayers on (111) electrodes

The voltammetry of the formation of (√3×√3)R30° and p(2×2) overlayers on (111) electrodes is modeled by analytical and Monte Carlo techniques. Both ordered structures are formed by second-order order–disorder phase transitions that lead to sharply-peaked ‘butterfly’ features in the voltammogram. The butterflies for both systems are, however, distinctly different and resemble the voltammetry of Pt(111) in sulfuric and perchloric acid, respectively, even though the simulated adlayer structures are not exactly the same as the experimental ones. Some general features of butterfly peaks in voltammetry and their implications are discussed.     

Phospholipid monolayers studied by a combination of cyclic voltammetry and Langmuir techniques at the water ∣ 1,2-dichloroethane interface

Monolayers of distearoyl phosphatidylcholine spread on the water ∣ 1,2-dichloroethane interface have been studied in a novel type of Langmuir trough. Isotherms of the lipid have been measured at controlled potential differences across the interface, and cyclic voltammetry has been applied at a controlled surface pressure. Electrocapillary curves derived from the isotherms agree with the ones measured at true thermodynamic equilibrium. At positive potentials the adsorption of the lipid appeared to be weak while at negative potentials rather stable monolayers were obtained.     

The electrochemical behaviour of the Pr(III)/Pr redox system at Bi and Cd liquid electrodes in molten eutectic LiCl–KCl

The electrode reactions of LiCl–KCl–PrCl₃ solutions at the surface of liquid electrodes, i.e. Cd and Bi, were investigated by electrochemical techniques. The redox potential of the Pr(III)/Pr couple at the liquid electrodes were observed at more positive potential values than those at one inert electrode. This potential shift was thermodynamically analysed by a lowering of activity of Pr in the metal phase. Cyclic voltammetry, using Cd and Bi pools as working electrodes, was conducted in order to study the reaction mechanism. The results suggest a quasi-reversible behaviour of the Pr(III)/Pr electrochemical system at the liquid electrodes, and the values of the kinetic parameters, k⁰ and α as well as the reversible half wave potential, $E_{1/2}^{\mathrm{r}}$, have been obtained. The interdiffusion coefficients of Pr in the metal phases seem to be similar to the diffusion coefficient of Pr(III) in solution. From comparison between the equilibrium potential adopted by a praseodymium electrode immersed in a solution containing Pr(III) ions, and the calculated $E_{1/2}^{\mathrm{r}}$ of the system Pr(III)/Pr–M (being M = Cd or Bi) it has been possible to estimate the activity coefficients of Pr in the Cd and Bi phases. Open circuit chronopotentiometry using Cd or Bi film electrodes was also conducted. Electromotive force, emf, measurements for various intermetallic compounds in two-phase coexisting states were carried out in the temperature range of 673–823 K. The activities and relative partial molar Gibbs energies of Pr were obtained from the measured emf for various Pr–Cd and Pr–Bi intermetallic compounds, PrCd₁₁, PrCd₆, PrCd_4.46, PrBi₂ and PrBi. The relative partial molar entropies and enthalpies of Pr were also calculated from the temperature dependence of the emf. The standard Gibbs energies of formation for the Pr–Cd and Pr–Bi intermetallic compounds were calculated.     

Nicotine and lipopolysaccharide stimulate the production of MMPs and prostaglandin E(2) by hypoxia-inducible factor-1α up-regulation in human periodontal ligament cells

Kim Y‐S, Shin S‐I, Kang K‐L, Herr Y, Bae W‐J, Kim E‐C. Nicotine and lipopolysaccharide stimulate the production of MMPs and prostaglandin E₂ by hypoxia‐inducible factor‐1α up‐regulation in human periodontal ligament cells. J Periodont Res 2012; 47: 719–728. © 2012 John Wiley & Sons A/S Background and Objective: Although hypoxia‐inducible factor 1α (HIF‐1α) is up‐regulated in the periodontal pockets of periodontitis patients, the expression and precise molecular mechanisms of HIF‐1α remain unknown in human periodontal ligament cells (PDLCs). The aim of this study was to explore the effects, as well as the signaling pathway, of nicotine and lipopolysaccharide (LPS) on the expression of HIF‐1α and on the production of its target genes, including cyclooxygenase‐2 (COX‐2)‐derived prostaglandin E₂ (PGE₂), MMP‐2 and MMP‐9 in PDLCs. Material and Methods: The expression of COX‐2 and HIF‐1α proteins was evaluated using western blotting. The production of PGE₂ and MMPs was evaluated using enzyme immunoassays and zymography, respectively. Results: LPS and nicotine synergistically induced the production of PGE₂, MMP‐2 and MMP‐9, and increased the expression of MMP‐2, MMP‐9, COX‐2 and HIF‐1α proteins. Inhibition of HIF‐1α activity by chetomin or knockdown of HIF1α gene expression by small interfering RNA markedly attenuated the production of LPS‐ and nicotine‐stimulated PGE₂ and MMPs, as well as the expression of COX‐2 and HIF‐1α. Furthermore, pretreatment with inhibitors of COX‐2, p38, extracellular signal‐regulated kinase, Jun N‐terminal kinase, protein kinase C, phosphatidylinositol 3‐kinase and nuclear factor‐kappaB decreased the expression of nicotine‐ and LPS‐induced HIF‐1α and COX‐2, as well as the activity of PGE₂ and MMPs. Conclusion: These data demonstrate novel mechanisms by which nicotine and LPS promote periodontal tissue destruction, and provide further evidence that HIF‐1α is a potential target in periodontal disease associated with smoking and dental plaque.     

Effects of early treatment of maxillary incisor crowding by using two bands and four brackets (2×4) mechanotherapy

The purpose of the present study was to investigate effects of early treatment of maxillary incisor crowding on anteroposterior skeletal and dental changes. Treatment group comprised 17 patients with maxillary incisor crowding treated with the two bands and four brackets (2×4) mechanotherapy, and with an initial mean age of 8 years and 10 months. Control group consisted of 17 patients with the same type of malocclusion as the treatment group and with an initial mean age of 8 years and 7 months. Lateral cephalograms in the treatment group were obtained at three time periods: T1, at the start of the 2×4 mechanotherapy; T2, at the end of the 2×4 mechanotherapy; T3, at the end of posttreatment observation. In the control group, lateral cephalograms were obtained at two time periods: T1, at the start of observation; T3, at the end of observation. Ten linear and 10 angular measurements were made for each cephalogram and the cephalometric data obtained were analysed statistically.The significantly large retroclination of the mandibular incisors was found at T1 in both groups compared with Japanese norms, resulting in the obtuseness of the interincisal angle. The resolution of maxillary incisor crowding during T1–T2 produced the retrusive movement of maxillary central incisor tips and the retroclination of mandibular incisors. There were no statistically significant differences for the T1–T3 changes in any linear and angular measurements between both groups. The mandibular incisors were, however, inclined labially during T1–T3 in the treatment group, which were, on the contrary, inclined lingually in the control group. These results suggested that the resolution of maxillary incisor crowding mostly produce the anteroposterior dental effects, and that its effect on the correction of the retroclination of mandibular incisors which was observed at the start of the 2×4 mechanotherapy was not so significant.     

Formation of a nickel hydroxide monolayer on Au through a self-assembled monolayer of 5,5′-dithiobis(2-nitrobenzoic acid): voltammetric,SERS and XPS investigations of the modified electrodes

The formation of self-assembled monolayers (SAM) of 5,5′-dithiobis (2-nitrobenzoic acid), DNBA on gold has enabled further derivatization of the electrode surface with functional moieties anchored to the surface bound molecules. A SAM of DNBA was formed on the Au surface. Nickel ions tethered to the SAM-covered Au surface, were subsequently derivatized electrochemically to yield nickel hydroxide overlayers, thereby showing the possibility of preparing ultra-thin films of metal oxides through solution chemistry. The nickel hydroxide surface coverage obtained on bare and SAM-covered electrodes was estimated from voltammetric peaks and it varied from one monolayer to about 300 monolayers. The formation of a monolayer of nickel hydroxide has been achieved for the first time by electrochemical modification. Further, the modified electrodes were subjected to SERS and XPS studies to understand their surface characteristics. Modified electrodes provide a catalytic pathway involving nickel hydroxide for the electro-oxidation of glucose in alkaline solutions.     

Can poly(acrylic) acid molecular weight mixtures improve the compressive fracture strength and elastic modulus of a glass-ionomer restorative?

Objectives

To optimize the compressive fracture strength (σ) and elastic modulus (E) of a glass-ionomer (GI) restorative using poly(acrylic) acid (PAA) weight average molecular weight (M_w) mixtures.

Methods

174 PAA solutions were prepared (four control PAA M_ws at three PAA concentrations (25, 35 and 45%) (n = 12) and six M_w mixtures (Groups A-F at nine blend ratios and three PAA concentrations (n = 162))). The viscosity (η) of each PAA solution was determined using a digital viscometer. The PAA solutions were hand-mixed with a commercial GI restorative powder (Ionofil Molar; Voco, Cuxhaven, Germany) and σ and E were determined using cylindrical (6 mm height, 4 mm diameter) specimens (n = 20) at 24 h. Data were analyzed using analyses of variance (ANOVA) (three-, two- and one-way) and regression analyses at p < 0.05.

Results

The three- and two-way ANOVAs highlighted significant effects of M_w mixture, blend ratio and PAA concentration (all p < 0.0001) on the η, σ and E data. Regression analyses showed significant increases in η, σ and E (p < 0.0001) with increasing M_w from Groups A to F. There was no significant effect of blend ratio on the σ data for Groups A (p = 0.178), D (p = 0.747) and F (p = 0.107) and on the E data (p > 0.083).

Significance

The current approach to improving the mechanical properties of GI restoratives using PAA M_w mixtures is encouraging, however, further manipulation of the GI restorative system by optimizing PAA M_w mixtures, blend ratios and PAA concentrations is required to elicit further improvements in σ and E without impacting upon the η of the PAA solution.     

Two modifications in the treatment of keratocystic odontogenic tumors (KCOT) and the use of Carnoy’s solution (CS)—a retrospective study lasting between 2 and 10 years

This retrospective study aimed at evaluating the recurrence rates of keratocystic odontogenic tumors (KCOTs) that were enucleated with and without the application of Carnoy’s solution (CS). The study included 36 KCOTs treated between 1996 and 2006. Recurrence rates were investigated in correlation with the respective treatment method applied. Additionally, any damage to the inferior alveolar nerve associated with treatment was analyzed. Treatments consisted of enucleation with (38.9%) or without (61.1%) the application of CS. Median follow-up was 4.5 years. Single enucleation showed a recurrence rate of 50%, but the additional application of CS reduced the recurrence rate to 14.3%. No detrimental effects of CS on the mandibular nerve were detected. Enucleation plus the application of CS reduced the recurrence rate of KCOTs compared with simple enucleation. The application of CS did not cause any damage to the mandibular nerve.     

Load-bearing capacity of screw-retained CAD/CAM-produced titanium implant frameworks (I-Bridge?2) before and after cyclic mechanical loading

Implant-supported screw-retained fixed dental prostheses (FDPs) produced by CAD/ CAM have been introduced in recent years for the rehabilitation of partial or total endentulous jaws. However, there is a lack of data about the long-term mechanical characteristics.

Objective

The aim of this study was to investigate the failure mode and the influence of extended cyclic mechanical loading on the load-bearing capacity of these frameworks.

Material and Methods

Ten five-unit FDP frameworks simulating a free-end situation in the mandibular jaw were manufactured according to the I-Bridge^®2-concept (I-Bridge^®2, Biomain AB, Helsingborg, Sweden) and each was screw-retained on three differently angulated Astra Tech implants (30º buccal angulation/0º angulation/30º lingual angulation). One half of the specimens was tested for static load-bearing capacity without any further treatment (control), whereas the other half underwent five million cycles of mechanical loading with 100 N as the upper load limit (test). All specimens were loaded until failure in a universal testing machine with an occlusal force applied at the pontics. Load-displacement curves were recorded and the failure mode was macro- and microscopically analyzed. The statistical analysis was performed using a t-test (p=0.05).

Results

All the specimens survived cyclic mechanical loading and no obvious failure could be observed. Due to the cyclic mechanical loading, the load-bearing capacity decreased from 8,496 N±196 N (control) to 7,592 N±901 N (test). The cyclic mechanical loading did not significantly influence the load-bearing capacity (p=0.060). The failure mode was almost identical in all specimens: large deformations of the framework at the implant connection area were obvious.

Conclusion

The load-bearing capacity of the I-Bridge^®2 frameworks is much higher than the clinically relevant occlusal forces, even with considerably angulated implants. However, the performance under functional loading in vivo depends on additional aspects. Further studies are needed to address these aspects.     

Electrochemical behaviour of N-aminopyridinium,and the viologens N,N′-diamino-4,4′-bipyridilium and N,N′-bis(4-aminophenyl)-4,4′-bipyridilium in aqueous acid:: towards the formation of polymer hybrids of pyridine and aniline

A new polymer has been prepared by anodic polymerisation of N,N′-diamino-4,4′-bipyridilium as the tetrafluoroborate salt in aqueous acidic at a gold electrode. The polymer was electroactive and conductive, with $\text{D}$ for the inserting counter ion being 8.0×10^?10 cm^?2 s^?1 during reduction and 4.8×10^?10 cm^?2 s^?1 during oxidation. The polymer was not electrochromic, being blue–black at all impressed potentials. Yields of polymer were poor, being particularly so at low pH (0<pH<1). The best pH for electrodeposition was about 2.0. N,N′-diamino-4,4′-bipyridilium was not electroactive at negative potentials. Conversely, N-aminopyridinium yields a blue water-soluble radical on reduction, and electron transfer to N,N′-bis(4-aminophenyl)-4,4′-bipyridilium as the dichloride salt—which has a particularly stable radical cation—yields a thin film of red–black radical-cation salt. Neither of these two latter species are electroactive at positive potentials.     

The specialty of oral and maxillofacial surgery (OMFS) in Europe – Part 2: training environment including the new Union of European Medical Specialists (UEMS) Oral and Maxillofacial Surgery European Training Requirement (OMFS ETR)

OMFS training in Europe has incrementally improved over the last 50 years. However, not all European nations have a formal written curriculum/syllabus, quality indicators, exit examinations, or guidelines for training programmes or trainers. In 2021 the OMFS Section of the Union of European Medical Specialists (UEMS) created an OMFS European Training Requirement (OMFS ETR) to help address these gaps and raise training standards in Europe. This paper includes key lessons from OMFS training programmes across Europe. It also summarises the new OMFS ETR as a comprehensive curriculum and syllabus. The ETR is a resource for nations with dual degree or single medical degree versions of the specialty. More importantly, it can act as a template for the handful of European Economic Area (EEA) nations that do not currently have a recognised OMFS specialty in Directive 2005/36 EU or the European Free Trade Association Treaty. By outlining the breadth and depth of the specialty, the ETR will be useful for competent regulatory authorities as well as OMFS trainees and trainers, patients, and politicians. The OMFS ETR includes key competencies and capabilities alongside training structures and documentation. A free unrestricted Access© database can be downloaded from www.omfsuesm.eu so OMFS experience can be recorded in a similar way across international borders. The OMFS ETR will be a living document. As it is unlikely that OMFS will remain frozen in time, this training document will also evolve. Its true value will become clear as it is used by current and future OMFS surgeons.     

Anti-M(3) muscarinic cholinergic autoantibodies from patients with primary Sjögren's syndrome trigger production of matrix metalloproteinase-3 (MMP-3) and prostaglandin E(2) (PGE(2)) from the submandibular glands

Background

We demonstrated that serum immunoglobulin G (IgG) from patients with primary Sjögren's syndrome (pSS), interacting with the second extracellular loop of human glandular M₃ muscarinic acetylcholine receptors (M₃ mAChR), trigger the production of matrix metalloproteinase-3 (MMP-3) and prostaglandin E₂ (PGE₂).

Methods

Enzyme-linked immunosorbent assays (ELISAs) were performed in the presence of M₃ mAChR synthetic peptide as antigen to detect in serum the autoantibodies. Further, MMP-3 and PGE₂ production were determined in the presence of anti-M₃ mAChR autoantibodies.

Results

An association was observed between serum and anti-M₃ mAChR autoantibodies and serum levels of MMP-3 and PGE₂ in pSS patients. Thus, we established that serum anti-M₃ mAChR autoantibodies, MMP-3 and PGE₂ may be considered to be early markers of pSS associated with inflammation. Affinity-purified anti-M₃ mAChR peptide IgG from pSS patients, whilst stimulating salivary-gland M₃ mAChR, causes an increase in the level of MMP-3 and PGE₂ as a result of the activation of phospholipase A₂ (PLA₂) and cyclooxygenase-2 (COX-2) (but not COX-1).

Conclusions

These results provide a novel insight into the role that cholinoceptor antibodies play in the development of glandular inflammation. This is the first report showing that an antibody interacting with glandular mAChR can induce the production of pro-inflammatory mediators (MMP-3/PGE₂).     

Comparative investigations on the efficacy of articaine 4% (epinephrine 1:200,000) and articaine 2% (epinephrine 1:200,000) in local infiltration anaesthesia in dentistry—a randomised double-blind study

A randomised double-blind study investigated 155 patients with tooth extractions in the mandibular and maxillary jaws for a loss of anaesthetic potency when reducing the concentration of the active in articaine solutions. Tests were performed on the preparations of articaine 4% with a 1:200,000 addition of epinephrine (Ultracain D-S) and articaine 2% with a 1:200,000 addition of epinephrine (Ultracain 2%-Suprarenin). Local infiltration anaesthesia was the chosen method of anaesthesia. The most noticeable difference observed between the two injection solutions concerned the duration of anaesthesia, which was significantly shortened under the low-dose solution. The 4% articaine solution did not prove superior in local anaesthetic effect. Articaine 2% with epinephrine 1:200,000, therefore, can be considered a suitable local anaesthetic for tooth extractions.