Biomimetic Whitening Effect of Polyphosphate-Bleaching Agents on Dental Enamel.

This in vitro study investigated the extrinsic tooth-whitening effect of bleaching products containing polyphosphates on the dental enamel surface compared to 10% carbamide peroxide (CP). Eighty human molars were randomly allocated into four whitening-products groups. Group A (control) was treated with 10% CP (Opalescence). The other groups with non-CP over-the-counter (OTC) products were group B = polyphosphates (iWhiteWhitening-Kit); group C = polyphosphates+fluoride (iWhite-toothpaste); and group D = sodium bicarbonate (24K-Whitening-Pen). L*, a*, b* color-parameters were spectrophotometer-recorded at baseline (T0), one day (T1), and one month (T2) post-treatment. Changes in teeth color (ΔEab) were calculated. Data were analyzed using ANOVA and the Bonferroni test (α = 0.05). Groups A, B, and D showed significant differences in ΔL*&Δa* parameters at T1, but not in Δb* at T0. Group C showed no difference for ΔL*, Δa*, Δb* at T0 and T1. Group A showed differences for ΔL*, Δa*, Δb*, at T2, while groups B, C, and D had no difference in any parameters at T0. At T1, ΔEab values = A > D> B > C (ΔEab = 13.4 > 2.4 > 2.1 > 1.2). At T2, ΔEab values increased = A > B > C > D (ΔEab = 12.2 > 10.6 > 9.2 > 2.4). In conclusion, the 10% CP and Biomimetic polyphosphate extrinsic whitening kit demonstrated the highest color change, while simulated brushing with dark stain toothpaste and a whitening pen demonstrated the lowest color change at both measurement intervals

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Experimental and Theoretical Analysis of Mechanical Properties of Graphite/Polyethylene Terephthalate Nanocomposites

In this work, graphite nanoplatelets (GNP) were incorporated into poly (ethylene terephthalate) (PET) matrix to prepare PET-GNP nanocomposites using a melt compounding followed by compression moulding and then quenching process. Both static and dynamic mechanical properties of these quenched materials were characterized as a function of GNP contents using dynamic mechanical thermal analysis (DMTA) and tensile machine, respectively. The results demonstrated that the addition of GNP improved the stiffness of PET significantly. Additionally, the maximum increase in the storage modulus of 72% at 6 wt.% GNP. The incorporation of GNP beyond 6 wt.% into PET decreases the storage moduli, but they remain higher than pure PET. The observed reduction could be due to agglomeration, resulting in poorer dispersion and distribution of higher levels of GNP into the PET matrix. In contrast to the results for moduli, tensile strength and elongations at break reduce with increasing the GNP content. For example, tensile strength reduced from ∼46 MPa (neat PET) to ∼39 MPa (−15%) for the nanocomposites containing 2 wt.% GNP. This reduction is accompanied by a decline in elongation at break from ∼6.3 (neat PET) to ∼3.4 (−46%) for the same nanocomposites. Such reductions are followed by a gradual decrease in upon further addition of GNP. These reductions indicate that increasing GNP loadings, results in brittleness in nanocomposites. In addition, it was found that quenched PET and composite samples were not fully crystallized after processing and therefore (cold) crystallized during the first heating cycle DMTA, as indicated by a rise in storage moduli above the glass transition temperature during the DMTA first heat. Furthermore, mathematical models based on non-linear theories are developed to capture the experimental data. For this, a set of mechanical stress-strain data is used for model parameters’ identification. Another set of data is used for the model validation that demonstrates good agreements with the experimental study

Use of YouTube as a Learning Modality for Clinical Procedures among Dental Students in Riyadh, Saudi Arabia—A Cross-Sectional Study

Social media like YouTube are increasingly used by students as a learning tool. The aim of this study was to examine the use of YouTube videos as a means of learning clinical procedures among dental students in Riyadh, Saudi Arabia. A cross-sectional observational study was conducted among dental students from six dental colleges in Riyadh, Saudi Arabia. Among the total of 331 dental students who responded to this survey, 93.9% (n = 308) reported that they had used YouTube for dental learning. A total of 65.30% (n = 201) of the respondents strongly agreed that they find videos of clinical procedures on YouTube helpful as a learning tool. A total of 54.40% (n = 180) agreed that they always refer to YouTube videos to prepare for a clinical procedure that they have never done before. A total of 75.3% (n = 232) reported that they most commonly watched clinical procedures related to restorative dentistry, 67.2% (n = 207) for fixed prosthodontics procedures, 65.3% (n = 201) for endodontic clinical procedures, and 62.3% (n = 192) for removable prosthodontics videos. A total of 50.60% (n = 156) strongly agreed that YouTube videos are helpful in relating theoretical knowledge with clinical knowledge. A total of 50.30% (n = 155) reported that it is important to have faculty guidance regarding useful YouTube videos on dental procedures. A total of 91.90% (n = 283) participants would like their dental school to post tutorials or videos for clinical procedures on YouTube. Even after increased availability of online videos, a majority of dental students felt that YouTube videos suggested by faculty were more valuable than videos identified through normal searching

Comprehensive Review of the Properties and Modifications of Carbon Fiber-Reinforced Thermoplastic Composites

Carbon fiber-reinforced polymers are considered a promising composite for many industrial applications including in the automation, renewable energy, and aerospace industries. They exhibit exceptional properties such as a high strength-to-weight ratio and high wear resistance and stiffness, which give them an advantage over other conventional materials such as metals. Various polymers can be used as matrices such as thermosetting, thermoplastic, and elastomers polymers. This comprehensive review focuses on carbon fiber-reinforced thermoplastic polymers due to the advantages of thermoplastic compared to thermosetting and elastomer polymers. These advantages include recyclability, ease of processability, flexibility, and shorter production time. The related properties such as strength, modulus, thermal conductivity, and stability, as well as electrical conductivity, are discussed in depth. Additionally, the modification techniques of the surface of carbon fiber, including the chemical and physical methods, are thoroughly explored. Overall, this review represents and summarizes the future prospective and research developments carried out on carbon fiber-reinforced thermoplastic polymers

Exploring the Potential Biological Activities of Pyrazole-Based Schiff Bases as Anti-Diabetic, Anti-Alzheimer’s, Anti-Inflammatory, and Cytotoxic Agents: <i>In Vitro</i> Studies with Computational Predictions

In this innovative research, we aim to reveal pyrazole-based Schiff bases as new multi-target agents. In this context, we re-synthesized three sets of pyrazole-based Schiff bases, 5a–f, 6a–f, and 7a–f, to evaluate their biological applications. The data from in vitro biological assays (including antioxidant and scavenging activities, anti-diabetes, anti-Alzheimer’s, and anti-inflammatory properties) of the pyrazole-based Schiff bases 5a–f, 6a–f, and 7a–f showed that the six pyrazole-based Schiff bases 5a, 5d, 5e, 5f, 7a, and 7f possess the highest biological properties among the compounds evaluated. The cytotoxicity against lung (A549) and colon (Caco-2) human cancer types, as well as normal lung (WI-38) cell lines, was evaluated. The data from the cytotoxicity investigation demonstrated that the three Schiff bases 5d, 5e, and 7a are active against lung (A549) cells, while the two Schiff bases 5e and 7a exhibited the highest cytotoxicity towards colon (Caco-2) cells. Additionally, the enzymatic activities against caspase-3 and Bcl-2 of the six pyrazole-based Schiff bases 5a, 5d, 5e, 5f, 7a, and 7f were evaluated. Furthermore, we assessed the in silico absorption, distribution, metabolism, and toxicity (ADMT) properties of the more potent pyrazole-based Schiff bases. After modifying the structures of the six pyrazole-based Schiff bases, we plan to further extend the studies in the future

Endophytic bacterium Bacillus subtilis (BERA 71) improves salt tolerance in chickpea plants by regulating the plant defense mechanisms

Plant growth-promoting endophytic bacteria can stimulate the growth, nutrient acquisition, symbiotic performance and stress tolerance of chickpea plants under saline soil conditions. The aim of this study was to investigate the stress-adaptive mechanisms of chickpea plants mediated by Bacillus subtilis (BERA 71) under saline conditions. Inoculation with BERA 71 enhanced plant biomass and the synthesis of photosynthetic pigments and reduced the levels of reactive oxygen species (ROS) and lipid peroxidation in plants under conditions of stress. Furthermore, the activities of ROS-scavenging antioxidant enzymes (superoxide dismutase, peroxidase, catalase and glutathione reductase), the levels of non-enzymatic antioxidants (ascorbic acid and glutathione) and the total phenol content were increased in stressed plants during bacterial association. The bacteria decreased sodium accumulation and enhanced the nitrogen, potassium, calcium and magnesium content in the plants. The suppression of ROS generation and of lipid peroxidation and the accumulation of proline in BERA-71-inoculated plants enhanced the membrane stability under salinity stress and non-stress conditions

Enhancing the Performance of a Metal-Free Self-Supported Carbon Felt-Based Supercapacitor with Facile Two-Step Electrochemical Activation

Carbon felt (CF) is an inexpensive carbon-based material that is highly conductive and features extraordinary inherent surface area. Using such a metal-free, low-cost material for energy storage applications can benefit their practical implementation; however, only limited success has been achieved using metal-free CF for supercapacitor electrodes. This work thoroughly studies a cost-effective and simple method for activating metal-free self-supported carbon felt. As-received CF samples were first chemically modified with an acidic mixture, then put through a time optimization two-step electrochemical treatment in inorganic salts. The initial oxidative exfoliation process enhances the fiber’s surface area and ultimately introduced oxygen functional groups to the surface, whereas the subsequent reduction process substantially improved the conductivity. We achieved a 205-fold enhancement of capacitance over the as-received CF, with a maximum specific capacitance of 205 Fg−1, while using a charging current density of 23 mAg−1. Additionally, we obtained a remarkable capacitance retention of 78% upon increasing the charging current from 0.4 to 1 Ag−1. Finally, the cyclic stability reached 87% capacitance retention after 2500 cycles. These results demonstrate the potential utility of electrochemically activated CF electrodes in supercapacitor devices

Impact of Hybrid Fillers on the Properties of High Density Polyethylene Based Composites

The main objective of this work is to develop a variety of hybrid high-density polyethylene (HDPE) micro- and nanocomposites and to investigate their thermal, mechanical, and morphological characteristics as a function of number of fillers and their contents percentage. In this study, 21 formulations of the composites were prepared using fillers with different sizes including micro fillers such as talc, calcium carbonate (CaCO3), as well as nano-filler (fumed silica (FS)) though the melt blending technique. The morphological, mechanical, and thermal properties of the composite samples were evaluated. The morphological study revealed negligible filler agglomerates, good matrix&ndash;filler interfacial bonding in case of combined both CaCO3 and FS into the composites. Sequentially, improvements in tensile, flexural and Izod impact strengths as a function of fillers loading in the HDPE matrix have been reported. The maximum enhancement (%) of tensile, flexural and impact strengths were 127%, 86% and 16.6%, respectively, for composites containing 25% CaCO3 and 1% FS without any inclusion of talc filler; this indicates that the types/nature, size, quantity and dispersion status of fillers are playing a major role in the mechanical properties of the prepared composites more than the number of the used fillers