Evaluation of the Erosive Potential of Selected Isotonic Drinks: In Vitro Studies

BACKGROUND

Isotonic drinks are an important component of the diet of athletes. Sports drinks cause the body to maintain proper hydration and supplement minerals which are lost in sweat during excessive exercising. Aside from the benefits of isotonic drinks, it is important to be aware of the harmful effects of citric acid within the products, which could cause enamel erosion.

OBJECTIVES

The aim of the study was to evaluate the erosive potential of sports drinks using confocal scanning laser microscopy (CLSM).

MATERIAL AND METHODS

The studies measured the change of surface roughness of the dental enamel after etching using Isostar, Powerade and Gatorade drinks, and Fortuna orange juice. Measurements were repeated after 1, 2 and 3 h of exposure to the selected liquid. The evaluation of calcium compound contents was carried out using the complexonometric method.

RESULTS

The surface roughness measurements of dental enamel showed that the lowest values of the parameters Ra and Rz were obtained for Isostar and orange juice. The research of the calcium content in the selected beverages showed the highest value in Isostar (320.0 mg/L) and the lowest in Powerade (40.0 mg/L) and Gatorade (21.0 mg/L).

CONCLUSIONS

Our study confirms that Isostar is the safest sports drink, among the analyzed beverages, for athletes, because it causes the least erosive changes in dental enamel. It is recommended to supplement beverages to reduce their potential for erosion using calcium compounds.

Frictional Behaviour of Composite Anodized Layers on Aluminium Alloys

Three variants of the micro arc oxidation (MAO) technique have been used to treat a 2017A alloy surface. The first variant was a pure anodized layer, the second an anodized layer with SiC embedded nanoparticles and the third an anodized layer with Si₃N₄ nanoparticles. Tribological tests were performed for all variants, on three samples for every case. Friction coefficients and wear rates were calculated on the basis of experiments. The pure anodized layer manifested friction coefficient values within the range of 0.48 ÷ 0.52 and a wear rate in the range ~10^-15 m³N^-1m^-1. SiC nanoparticles improved the tribological properties of the layer, as indicated by a reduction of the friction coefficient values to the range of 0.20 ÷ 0.26 with preserved very high resistance against wear (wear rate ~10^-15 m³N^-1m^-1). Si₃N₄ particles embedded in anodized layer deteriorated the tribological properties, with a reduction in the resistance against fatigue and wear, intensification of friction forces and a change in the nature of friction contact behavior to more abrasive-like nature (friction coefficients ranging from 0.4 to 0.6 and wear rates ~10^-14 m³N^-1m^-1).

Comparison of Mechanical and Barrier Properties of Al2O3/TiO2/ZrO2 Layers in Oxide-Hydroxyapatite Sandwich Composite Coatings Deposited by Sol-Gel Method on Ti6Al7Nb Alloy

In this study, coatings of different oxides (TiO2, Al2O3, ZrO2) and hydroxyapatite (HAp) as well as sandwich composite hydroxyapatite with an oxides sublayer (oxide+HAp) were deposited on Ti6Al7Nb alloy using the sol-gel dip-coating method. The coatings were characterized in terms of morphology (optical microscope), surface topography (AFM), thickness (ellipsometry), and crystal structure (XRD/GIXRD). The mechanical properties of the coatings-hardness, Young's modulus, and adhesion to the substrate-were examined using nanoindentation and scratch tests. The barrier properties of the coatings against the migration of aluminum ions were examined by measuring their concentration after soaking in Hank's balanced salt solution (HBSS) with the use of optical emission spectrometry of inductively coupled plasma (ICPOES). It was found that all the oxide and HAp coatings reduced the permeation of Al ions from the Ti6Al7Nb alloy substrate. The best features revealed an Al2O3 layer that had excellent barrier properties and the best adhesion to the substrate. Al2O3 as a sublayer significantly improved the properties of the sandwich composite HAp coating.

Amorphous AlN films grown by ALD from trimethylaluminum and monomethylhydrazine

The great interest in aluminium nitride thin films has been attributed to their excellent dielectric, thermal and mechanical properties. Here we present the results of amorphous AlN films obtained by atomic layer deposition. We used trimethylaluminum and monomethylhydrazine as the precursors at a deposition temperature of 375-475 °C. The structural and mechanical properties and chemical composition of the synthesized films were investigated in detail by X-ray diffraction, X-ray photoelectron spectroscopy, electron and probe microscopy and nanoindentation. The obtained films were compact and continuous, exhibiting amorphous nature with homogeneous in-depth composition, at an oxygen content of as low as 4 at%. The mechanical properties were comparable to those of AlN films produced by other techniques.

Formation and Mechano-Chemical Properties of Chromium Fluorides Originated from the Deposition of Carbon-Chromium Nanocomposite Coatings in the Reactive Atmosphere (Ar + CF4) during Magnetron Sputtering

The literature analysis did not indicate any studies on fluorination tests of carbon nanocomposite coatings doped with transition metals in a form of nanocrystalline metal carbide in amorphous carbon matrix (nc-MeC/a-C). As a model coating to investigate the effect of fluorination in a tetrafluoromethane (CF4) atmosphere, a nanocomposite carbon coating doped with chromium-forming nanocrystals of chromium carbides in a-C matrix (nc-CrC/a-C) produced by magnetron sputtering from graphite targets and using a Pulse-DC type medium frequency power supply was chosen. After the deposition of the gradient chromium carbonitride (CrCN) adhesive sublayer, the fluorination of the main coating was conducted in a reactive mode in an (Ar + CF4) atmosphere at various CF4 content. It was observed that the presence of CF4 in the atmosphere resulted in a reduced amount of chromium carbides formed in favor of chromium fluorides. Thus far, this is an observation that seems unnoticed by the carbon coatings researchers. Fluorine was assumed to bond much more readily to carbon than to chromium, due to the stability of tetrafluoromethane (CF4). The opposite seems to be true. The mechanical properties (nano-hardness and Young's modulus) and tribological properties in the 'pin-on-disc' friction pair are presented, along with the analysis of bonds occurring between chromium, carbon, and fluorine by means of X-ray photoelectron spectroscopy (XPS).

Qualitative Research of Composite Graphene Membranes Using the Electric Mode in SEM and AFM

The development of new graphene-based materials necessitates the application of suitable material imaging techniques, especially for the identification of defects in the graphene structure and its continuity. For this purpose, it is natural to use one of the main properties of graphene-electrical conductivity. In this work, we prepare a 9 cm2 large-area monolayer graphene membrane on porous scaffolding sealed with either GO or rGO. Then, we use electrostatic force microscopy (EFM) AFM mode along with SE and AEE SEM modes to characterize the as-prepared graphene membranes thoroughly. The combination of SEM-AEE and AFM-EFM techniques not only assesses the quality of graphene itself but also characterizes the selectivity and effectiveness of masking graphene layer defects by applying GO or rGO. This makes these methods valuable in optimizing the production of advanced graphene nanocomposites such as semipermeable membranes.

Experimental-computational approach to investigate elastic properties of struvite

The research presented in the paper concerns the elastic properties of struvite. The article combines theoretical and experimental research. Experimental studies were carried out on struvite single crystals grown in sodium metasilicate gel by single diffusion. This unique method leads to obtaining crystals of sufficiently large size to conduct, for the first time, experimental measurement of elastic properties of monocrystalline struvite. Using the nanoindentation method, the Ez = 29.1 ± 0.7 GPa value of the component of Young's modulus was determined for a struvite single crystal. In addition, the elastic constants C11, C22, and C33 were determined using micro-Brillouin spectroscopy. Theoretical calculations of the abovementioned properties have been carried out by employing density functional theory methods. Scaling of the theoretical elastic constants leads to obtaining good agreement with the experimental values. Values of the Ex and Ey components of the Young's modulus, not available from the experimental nanoindentation technique, have been determined theoretically as 23 GPa and 27 GPa, respectively. Differences in the values of elastic components and Young's modulus components are related to the layered crystal structure of struvite and directional character of the hydrogen-bonding pattern.