Effect of Preheating on Mechanical Properties of Different Commercially Available Dental Resin Composites

Background: This study aimed to reveal the effect of preheating on the surface microhardness and shear strength of composite materials used in the restoration of posterior teeth. Methods and Results: There were 3 composite materials under the study: Estelite Posterior, Harmonize and Filtek Z550. To make static and dynamic tests of them, 120 filling samples were prepared. Of those, 60 samples were for surface hardness measurements and 60 samples were used to evaluate the shear strength of composite materials. We formed 12 study groups with 10 filling samples in each. Samples made off Estelite Posterior, Harmonize™, and Filtek™ were designated with E, H, and F capital letters, respectively; the "VH" abbreviation indicated static Vickers hardness testing and "SS" was assigned for dynamic shear testing; mark (°) was used when preheating was applied. Filling samples were made of heated (up to 60°C) and room-temperature (23-25°C) composite materials. The filling samples of EVH, EºVH, HVH, HºVH, FVH, and FºVH groups were subjected to a surface microhardness test. The samples of ESS, EºSS, HSS, HºSS, FSS, and FºSS groups were subjected to shear-strength assessment of materials. The surface microhardness of filling samples was measured using a ПMT-3 Vickers hardness tester and the Vickers hardness number (VHN) was calculated. Dynamic tests were carried out using an UltraTester machine (Ultradent, Inc., USA) and shear test method until the shear-strength (SS) filling sample had completely failed. After analysis of the obtained results, it was found that preheating had enhanced the surface hardness and mechanical strength of the composite materials used in the study. However, the positive influence of preheating was significant only in the EVH-EºVH, ESS-EºSS, HSS-HºSS, and FSS-FºSS groups in 1.21, 1.09, 1.33, and 1.16 times, respectively. In the HVH-HºVH and FVH-FºVH groups, the identified differences were not of significance despite the improvement in mean values at 1.08 and 1.1 times. Conclusion: Preheating of light-curing resin-based composites is not equally effective for static and dynamic mechanical properties of materials for dental restoration. Preliminary laboratory tests could have helped before their clinical use

Human plague: An old scourge that needs new answers

Yersinia pestis, the bacterial causative agent of plague, remains an important threat to human health. Plague is a rodent-borne disease that has historically shown an outstanding ability to colonize and persist across different species, habitats, and environments while provoking sporadic cases, outbreaks, and deadly global epidemics among humans. Between September and November 2017, an outbreak of urban pneumonic plague was declared in Madagascar, which refocused the attention of the scientific community on this ancient human scourge. Given recent trends and plague’s resilience to control in the wild, its high fatality rate in humans without early treatment, and its capacity to disrupt social and healthcare systems, human plague should be considered as a neglected threat. A workshop was held in Paris in July 2018 to review current knowledge about plague and to identify the scientific research priorities to eradicate plague as a human threat. It was concluded that an urgent commitment is needed to develop and fund a strong research agenda aiming to fill the current knowledge gaps structured around 4 main axes: (i) an improved understanding of the ecological interactions among the reservoir, vector, pathogen, and environment; (ii) human and societal responses; (iii) improved diagnostic tools and case management; and (iv) vaccine development. These axes should be cross-cutting, translational, and focused on delivering context-specific strategies. Results of this research should feed a global control and prevention strategy within a “One Health” approach

Weathering the storm: Self-efficacy, social support processes, and health-related coping strategies among the Detroit-area widowed

Research has indicated that bereavement associated with the loss of a loved one may result in depression, a decline in social relationships, and poorer health amongst the bereaved. Studies on bereavement suggest that bereaved persons try to have continuity of roles in their lives and eventually recover from the loss of a loved one. The current study examines whether widowed persons engage in health-related coping strategies (H-RCS) (ie. smoking, drinking, and exercise) as an initial result of spousal loss. Using the Stress and Coping Model posited by Lazarus and Folkman (1984), it is hypothesized that widowed persons with greater levels of social support, religiosity, income, self-efficacy, and self-rated health will be less likely to engage in health-related coping behaviors than their counterparts. The current study utilizes secondary data from the Changing Lives of Older Couples study (CLOC), a prospective study of bereavement, and Ordinary Least Squares, Negative Binomial Regression, and Logistic Regression to analyze the proposed relationship between widowhood and health-related coping strategies across three available waves of data collected 6 months, 12 months, and 18 months after spousal loss. Findings reveal that bereavement is indeed related to engagement in H-RCS, although this effect is moderated primarily through self-efficacy. More specifically, bereavement influenced physical inactivity and health behavior at Wave 1 and generated higher daily cigarette consumption by Wave 3. The only exception was in the Wave 3 regression equation where lower levels of bereavement predicted physical inactivity. This finding suggests that low bereavement may actually be deleterious to health depending on the type of health-related coping strategy examined. No significance was found between bereavement and any health-related coping strategy by Wave 2 and across all significant bereavement models there was no significant alcohol effect. The most pronounced effect for bereavement outcomes were for physical inactivity models at Waves 1 and 2. The results of this study do not provide support that bereaved adults engage in alcohol consumption as a result of spousal loss. However, findings do reveal that the widowed may be particularly susceptible to engaging in H-RCS 6 months and 18 months after spousal loss

AWARENESS ABOUT THE HOMER OR THE SUBJECTIVE AND COGNITIVE ASPECTS OF THE PROBLEM

The article tells the story and literary credo of the Russian poet V.A. Zhukovsky, who translated part of Homer's “Iliad” into Russian. He was known in the eyes of his contemporaries as the owner of the most advanced worldview. He was a renowned teacher, poet and translator, well acquainted with the works of German thinkers and philosophers

SERIAL AND SHUNTABLE RESISTANCE OF CIGS SOLAR PHOTO-ELECTRIC MODULE IN THE CONDITIONS OF REAL SOLAR LIGHTING AT VARIOUS TEMPERATURES

The current-voltage characteristics of the solar photovoltaic module, based on a thin-film polycrystalline semiconductor binary compound Cu(In, Ga)Se2, under real solar illumination (Prad=780 ± 30 W/m2), in the temperature range of 25 °C-50 °C, have been studied and the values of serial and shunt resistance are determined. It has been established that with increasing temperature, the magnitudes of the series and shunting resistance of the solar photovoltaic module decrease, which is most likely due to the modulation of the resistance of the n-CdS buffer front layer

Postural Control in Lowlanders With COPD Traveling to 3100 m: Data From a Randomized Trial Evaluating the Effect of Preventive Dexamethasone Treatment

Objective: To evaluate the effects of acute exposure to high altitude and preventive dexamethasone treatment on postural control in patients with chronic obstructive pulmonary disease (COPD). Methods: In this randomized, double-blind parallel-group trial, 104 lowlanders with COPD GOLD 1-2 age 20-75 y, living near Bishkek (760 m), were randomized to receive either dexamethasone (2x4 mg/d p.o.) or placebo on the day before ascent and during a 2-day sojourn at Tuja-Ashu high altitude clinic (3100 m), Kyrgyzstan. Postural control was assessed with a Wii Balance BoardTM at 760 m and one day after arrival at 3100 m. Patients were instructed to stand immobile on both legs with eyes open during five tests of 30 s each, while the center of pressure path length (PL) was measured. Results: With ascent from 760 to 3100 m the PL increased in the placebo group from median (quartiles) 29.2 (25.8 ; 38.2) to 31.5 (27.3 ; 39.3) cm (P< 0.05); in the dexamethasone group the corresponding increase from 28.8 (22.8 ; 34.5) to 29.9 (25.2 ; 37.0) cm was not significant (P=0.10). The mean difference (95% CI) between dexamethasone and placebo groups in altitude-induced changes (treatment effect) was -0.3 (-3.2 to 2.5) cm, (P=0.41). Multivariable regression analysis confirmed a significant increase in PL with higher altitude (coefficient 1.6, 95% CI 0.2 to 3.1, P=0.031) but no effect of dexamethasone was shown (coefficient -0.2, 95% CI -4.0 to 3.6, P=0.925), even when controlled for several potential confounders. PL changes were related more to antero-posterior than lateral sway. 22 of 104 patients had an altitude-related increase in the antero-posterior sway velocity of >25%, what has been associated with an increased risk of falls in previous studies. Conclusions: Lowlanders with COPD travelling from 760 to 3100 m revealed postural instability 24 h after arriving at high altitude, and this was not prevented by dexamethasone

Table_1_Postural Control in Lowlanders With COPD Traveling to 3100 m: Data From a Randomized Trial Evaluating the Effect of Preventive Dexamethasone Treatment.docx

<p>Objective: To evaluate the effects of acute exposure to high altitude and preventive dexamethasone treatment on postural control in patients with chronic obstructive pulmonary disease (COPD).</p><p>Methods: In this randomized, double-blind parallel-group trial, 104 lowlanders with COPD GOLD 1-2 age 20–75 years, living near Bishkek (760 m), were randomized to receive either dexamethasone (2 × 4 mg/day p.o.) or placebo on the day before ascent and during a 2-day sojourn at Tuja-Ashu high altitude clinic (3100 m), Kyrgyzstan. Postural control was assessed with a Wii Balance Board^TM at 760 m and 1 day after arrival at 3100 m. Patients were instructed to stand immobile on both legs with eyes open during five tests of 30 s each, while the center of pressure path length (PL) was measured.</p><p>Results: With ascent from 760 to 3100 m the PL increased in the placebo group from median (quartiles) 29.2 (25.8; 38.2) to 31.5 (27.3; 39.3) cm (P < 0.05); in the dexamethasone group the corresponding increase from 28.8 (22.8; 34.5) to 29.9 (25.2; 37.0) cm was not significant (P = 0.10). The mean difference (95% CI) between dexamethasone and placebo groups in altitude-induced changes (treatment effect) was -0.3 (-3.2 to 2.5) cm, (P = 0.41). Multivariable regression analysis confirmed a significant increase in PL with higher altitude (coefficient 1.6, 95% CI 0.2 to 3.1, P = 0.031) but no effect of dexamethasone was shown (coefficient -0.2, 95% CI -0.4 to 3.6, P = 0.925), even when controlled for several potential confounders. PL changes were related more to antero-posterior than lateral sway. Twenty-two of 104 patients had an altitude-related increase in the antero-posterior sway velocity of >25%, what has been associated with an increased risk of falls in previous studies.</p><p>Conclusion: Lowlanders with COPD travelling from 760 to 3100 m revealed postural instability 24 h after arriving at high altitude, and this was not prevented by dexamethasone.</p><p>Trial Registration:clinicaltrials.gov Identifier: NCT02450968.</p