ABSTRACT
New intercalation compounds CrxZrSe2 were synthesized and thoroughly studied. Cr atoms were found to occupy the positions both tetrahedrally and octahedrally coordinated by the Se atoms in the interlayer gap. The magnetic properties and electrical resistivity were studied in the temperature ranges of 2.4-300 K and 80-340 K, respectively. The compounds change their behavior from semiconducting (x = 0.1) to metallic (x > 0.1). The magnetic interaction strongly depends on the Cr content and temperature. The spin-glass state with antiferromagnetic interaction exists at T < Tcrit for CrxZrSe2 with x ≤ 0.2, while at x ≥ 0.3 ferromagnetic contribution arises as well. The single crystals of CrxZrSe2 were grown to study the electronic structure of the materials. A combination of the X-ray photoelectron spectroscopy (including that across Cr 2p-3d and Zr 3p-4d resonance) and X-ray absorption spectroscopy methods allowed to propose the location of the Cr 3d-states in the Se 3p-Zr 4d energy gap.
ABSTRACT
The basis of modern tooth whitening systems is the use of a whitening gel, which usually contains hydrogen peroxide or carbamide peroxide. The study included 81 patients aged 22 to 35 years with a tooth color A2 and a darker color on the Vita Classic scale. The purpose of our research was to identify a new approach to whitening teeth to improve safety and gentleness. To perform this, we assessed the effect of the tooth whitening procedure on the mineral composition of the oral fluid. A new approach to the teeth whitening procedure was to use a mouth retractor and a tool for aspirating the whitening gel, which we developed. Before the procedure, a protective film-forming aerosol, which included sodium ascorbate, was applied. After the tooth whitening procedure, the enamel was remineralized with a sealing liquid for 14 days. The concentrations of calcium and phosphorus in the oral fluid were determined using a spectrophotometer with a set of reagents (Human). The results obtained indicate that the new approach to the teeth whitening procedure contributed to less pronounced changes in the concentrations of calcium (+29.07, p < 0.001) and phosphorus (-14%, p < 0.001) in the oral fluid immediately after the procedure and in combination with the standard procedure for teeth whitening; immediately after this procedure, the calcium concentration increased by 74.4% (p < 0.001), and the phosphorus concentration decreased by 23.07% (p < 0.001). The use of remineralizing agents led to a faster recovery of the initial levels of calcium and phosphorus in the oral fluid.
ABSTRACT
One of the most important functions of the oral fluid is to maintain oral homeostasis. In-office teeth whitening systems are able to change the mineral metabolism and the activity of a number of enzymes in the oral fluid, but there are conflicting data in publications about this. The aim of this study was to compare the effect of Opalescense Boost, ZOOM Advance POWER, and ZOOM Phillips White Speed, which contain different percentages of hydrogen peroxide, on the performance of oral fluid. After the procedure of whitening teeth with the studied in-office systems, the concentration of calcium in the oral fluid increased, and the activity of alkaline phosphatase decreased. Calcium levels returned to baseline values after 30 days, and alkaline phosphatase activity returned after 14 days. There was no significant difference in the changes in calcium concentration and alkaline phosphatase activity between different tooth whitening systems. Chemical teeth whitening with the Opalescense Boost system caused the largest change in the activity of superoxide dismutase in the oral fluid compared to the ZOOM Advance POWER and ZOOM Phillips White Speed photocatalytic teeth whitening systems. An increase in the activity of superoxide dismutase by +75.5% was shown immediately after the procedure of teeth whitening with the Opalescense Boost system, which indicated an increase in the power of antioxidant defense mechanisms. To assess the effectiveness and safety of using various whitening systems, it is possible to study the dynamics of the activity of superoxide dismutase, which reflects the processes of antioxidant protection of the oral cavity.
