Microbiological and clinical effects of an antiseptic dental varnish after mechanical periodontal therapy

The aim of this study was to explore the microbiological and clinical effects of an antiseptic dental varnish when applied to periodontally diseased teeth after mechanical therapy. 20 subjects participated in this placebo controlled, double blind prospective longitudinal study. 2 experimental sites with a pocket probing depth ≥5 mm were chosen in each subject. The control varnish, consisting of ethanol, ethylacetate and polyvinylbutyral, was applied to one of the selected teeth and the test varnish, containing 1% chlorhexidine and 1% thymol in addition, was applied to the other one. Clinical parameters were assessed, and microbiological samples were obtained from the two study sites at baseline (6-10 weeks after completion of conventional periodontal therapy), and 2, 4 and 12 weeks thereafter. The mean PLI at baseline was very low and, therefore, only a minimal potential for a further improvement existed. During the 12-week observation period, the mean PLI increased significantly at sites treated with the placebo varnish, while no similar trend for an increase in PLI was detected in the test sites. The bleeding tendency seemed to remain unaffected by the application of the varnish. On the microbiological level, no relevant differences could be detected between placebo and test sites at baseline, or during the follow-up period. In conclusion, the application of a dental varnish with antimicrobial properties after mechanical periodontal therapy had little effect in subjects with good oral hygiene. © Munksgaard, 1999.link_to_subscribed_fulltex

Properties and thermo-switch behaviour of LDPE mixed with carbon black, zinc metal and paraffin wax

This paper reports on the presence of wax and radiation-induced crosslinking on the morphology, thermal and mechanical properties, as well as electrical conductivity and thermo-switch properties of LDPE containing different amounts of carbon black (CB) or carbon black plus zinc metal as filler. Although the filler was generally well dispersed in the polymer or polymer/wax blend, there were clear indications of the formation of conductive pathways. Different combinations of polymer, wax, CB and zinc filler and radiation induced crosslinking gave rise to different extents of crystallinity and/or chain immobilization, which had an influence on the mechanical and thermo-mechanical properties, and on the electrical conductivity and thermo-switch behaviour. Most importantly, the presence of wax, and CB and CB/Zn fillers, gave rise to increased electrical conductivity. The thermal expansion in the composites did not seem to play a significant role in obtaining larger values of the positive temperature coefficient of resistivity (PTC). We found that the presence of a small amount of paraffin wax significantly increased the PTC coefficients of the LDPE based conductive composites, and that γ-radiation induced crosslinking provided the thermomechanical stability of the amorphous regions in LDPE needed to obtain a high PTC intensity, which would provide a cheap material with good thermo-switch functionality, which is something not observed before

A general synthesis of water soluble upper rim calix[n]arene guanidinium derivatives which bind to plasmid DNA

The reaction of O-alkylated p-aminocalix[n]arenes (n=4, 6, 8) with N,N'-di(tert-butoxycarbonyl)thiourea in the presence of HgCl, and subsequent removal of the protective groups with hydrochloric acid led to the new water soluble calix[n]guanidinium derivatives (p-guanidiniumcalix[n]arenes) 20-23. With the exception of tetraoctyl-p-guanidiniumcalix[4]arene 21, which forms a macroscopic gelatinous aggregate even at very low concentration, all the synthesised guanidinium calixarenes show good solubility in water and sharp NMR signals. Moreover, these compounds are not cytotoxic and bind to plasmid DNA. (C) 2004 Elsevier Ltd. All rights reserved

Scanning Force Microscopy of Upright-Standing, Isolated Calixarene-Porphyrin Heterodimers

A water soluble calixarene [4] arene 1 with four guanidinium substituents on the upper rim and propyl groups below was anchored in the propylamino coating of smooth silica particles, and a tricarboxylate-tripod porphyrin 2 of 2 nm height was attached to these cationic islands. The molecular complex with a height of 3 nm was unequivocally detected on the particles' surface by atomic force microscopy in the tapping mode. Although deposits of 1 (height: 1 nm) and 2 (height: 2 nm) were also evident on the smooth silica particles, 3 nm seems to be the minimal height to identify single objects. The soft surface of the particles not only allowed tight attachment of molecular edge amphiphiles by the hydrophobic effect but also immobilized the particles on the mica surface by amine-silicate interactions

The detection of the early stages of ageing in an LDPE+graphite composite by comparison of dielectric responses induced by sinusoidal and triangular signals

This study describes the possibility of dielectric characterization of the initial stages of ageing in an low-density polyethylene (LDPE) + graphite composite, which is not possible using the standard method of dielectric spectroscopy. It is shown that the differences between the delay angles, Δφ = φTRI – φSIN, obtained using triangular and sinusoidal excitations on the composite samples, shows a maximum, and at the same time the position of this maximum shows more sensitivity to changes in the electrical properties of the material caused by ageing than other dielectric parameters. In order to clarify the applied methodology, a comparative analysis of the dielectric properties of other polymers poly(vinyl chloride) (PVC) and poly(vinyl alcohol) (PVA) and a conductive polymer composite (LDPE + carbon black) with respect to the application of sinusoidal and triangular electrical signals was carried out. Based on the presented results, we believe that the position of the peak in the frequency spectra of the difference between the delay angles obtained by using triangular and sinusoidal signals may be a suitable parameter for the dielectric characterization of polymeric materials

Dielectric spectroscopy of nanocomposites based on iPP and aPS treated in the water solutions of alkali metal salts

In this paper, a new simple and environmentally friendly treatment technique for obtaining polymer nanocomposites with appropriate dielectric properties has been presented. Sheets of isotactic polypropylene and atactic polystyrene were immersed in 3 saturated water solutions of alkali metal salts (LiCl, NaCl, and KCl) at 2 fixed temperatures (23 degrees C and 90 degrees C), and 3 DC electrical potentials (+4kV, -4kV, and ground potential) were applied. A quantification of alkali metals in the polymer sheets was conducted by inductively coupled plasma optic emission spectrometry. The obtained concentration values were from 7.3810(-9)mol/cm(3) to 1.2510(-7)mol/cm(3). The qualitative analysis of potassium distribution in the polymer matrix was conducted by time-of-flight secondary ion mass spectrometry cross-sectional record. The relative dielectric constant (epsilon) of samples was investigated in the frequency range from 20Hz to 9MHz at the constant temperature of 22 degrees C. Stable values of epsilon in fully measured frequency range were observed for both pure and treated samples. Next, the results of the dielectric spectroscopy measurements were compared and established the kind of treatment that provided the highest value of epsilon. The relationship between the concentrations of alkali metals and the values of relative dielectric constant was determined for the samples obtained by a treatment at 90 degrees C and +4kV

DNA Condensation and Cell Transfection Properties of Guanidinium Calixarenes: Dependence on Macrocycle Lipophilicity, Size, and Conformation

Calix[n]arenes functionalized with guanidinium groups at the upper rim and alkyl chains at the lower rim bind to DNA, condense it, and in some cases, promote cell transfection depending on their structure and lipophilicity. Atomic force microscopy (AFM) studies indicate that upon DNA binding the hydrophobic association of the lipophilic chains of cone guanidinium calix[4] arenes drives the formation of intramolecular DNA condensates, characterized by DNA loops emerging from a dense core. Furthermore, hexyl and octyl chains confer to these calixarenes cell transfection capabilities. Conversely, larger and conformationally mobile calix[6]- and calix[8] arene methoxy derivatives form intermolecular aggregates characterized by "gorgonlike" structures composed of multiple plectomenes. These adducts, in which interstrand connections are dominated by electrostatic interactions, fail to promote cell transfection. Finally, calix[4] arenes in a 1,3-alternate conformation show an intermediate behavior because they condense DNA, but the process is driven by charge-charge interactions

Ionic diffusion in iPP: DC electrical conductivity

This study provides a new insight into the relationships between absorption and adsorption processes that occur during the treatment of iPP in aqueous solutions of metal-chloride salts, as well as the impact of these processes on the electrical conductivity of this nonpolar polymer. The polypropylene films (0.5 mm) were exposed to three-day treatments in aqueous solutions of chlorine salts of some alkali and transition metals at temperatures of 22 C and 80 C. The treatments induced an increase in the electrical conductivity of iPP, up to 800%. DC conductivity is not directly proportional to the concentrations of metals in the treated films due to the complex relationships between diffusion and adsorption processes. The experiment was set up to simulate the real-world conditions and the study provides practical knowledge on the stability of the electrical conductivity of iPP under exposure to aqueous solutions. The influence of electric aging on the electrical conductivity of the treated films was also examined.This work was supported in part by the Ministry of Education, Science and Technological Development of the Republic of Serbia, by the Ministry of Scientific and Technological Development, Higher Education and Information Society of the Republic of Srpska (project: 19.032/961-112/19) and by the National Research Foundation, South Africa.Scopu