Materials and Methods for All-Ceramic Dental Restorations Using Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) Technologies-A Brief Review.

The materials used in dentistry for the fabrication of all-ceramic restorations have undergone great and rapid developments over the last two decades. Among the most common ceramic materials in dentistry are those based on zirconium and lithium disilicate. Due to the properties of these materials, they are in great demand in the field of dental restoration production. Thus, dental restorations that will use those materials are commonly machined in CAD/CAM systems, which offer the possibility of manufacturing all-ceramic dental restorations in a very short period of time. This article reviews the modern materials in the field of all-ceramic dental restorations, their manufacturing processes, as well as what determines which ceramic materials are used for the production of CAD/CAM blanks and their production technology.

3Y-TZP/Ta Biocermet as a Dental Material: An Analysis of the In Vitro Adherence of Streptococcus Oralis Biofilm and an In Vivo Pilot Study in Dogs.

The surface adhesion of bacterial cells and the in vivo biocompatibility of a new ceramic-metal composite made of zirconium dioxide and tantalum were evaluated. Within the framework of an in vitro study using the crystal violet staining and colony counting methods, a relatively similar adhesion of Streptococcus oralis to the 3Y-TZP/Ta biocermet (roughness Ra = 0.12 ± 0.04 µm) and Ti-Al6-V4 titanium alloy (Ra = 0.04 ± 0.01 µm) was found. In addition, in an in vivo preliminary study focused on the histological analysis of a series of rods implanted in the jaws of beagle dogs for a six-month period, the absence of any fibrous tissue or inflammatory reaction at the interface between the implanted 3Y-TZP/Ta biocermets and the new bone was found. Thus, it can be concluded that the developed ceramic-metal biocomposite may be a promising new material for use in dentistry.

The topological soliton in Peierls semimetal Sb.

Sb is a three-dimensional Peierls insulator. The Peierls instability gives rise to doubling of the translational period along the [111] direction and alternating van der Waals and covalent bonding between (111) atomic planes. At the (111) surface of Sb, the Peierls condition is violated, which in theory can give rise to properties differing from the bulk. The atomic and electronic structure of the (111) surface of Sb have been simulated by density functional theory calculations. We have considered the two possible (111) surfaces, containing van der Waals dangling bonds or containing covalent dangling bonds. In the models, the surfaces are infinite and the structure is defect free. Structural optimization of the model containing covalent dangling bonds results in strong deformation, which is well described by a topological soliton within the Su-Schrieffer-Heeger model centered about 25 Å below the surface. The electronic states associated with the soliton see an increase in the density of states (DOS) at the Fermi level by around an order of magnitude at the soliton center. Scanning tunneling microscopy and spectroscopy (STM/STS) measurements reveal two distinct surface regions, indicating that there are different surface regions cleaving van der Waals and covalent bonds. The DFT is in good agreement with the STM/STS experiments.

Could the Propionic Acid Treatment in Combination with Metformin be Safe for the Small Intestine of Diabetic Rats?

BACKGROUND: Effects of propionic acid (PA) on the cellular and molecular processes in the small intestine under type 2 diabetes mellitus (T2DM)-induced endoplasmic reticulum (ER) stress remain incompletely studied. OBJECTIVES: The aim of the study was to assess the state of unfolded protein response (UPR) system in the small intestine of diabetic rats and to explore PA's influence on metformin treatment. METHODS: Male Wistar rats were divided into 1) control and 2) T2DM groups, and groups receiving (14 days, orally) 3) metformin (60 mg/kg), 4) PA (60 mg/kg), and 5) PA+metformin. Western blotting, RT-PCR, and transmission electron microscopy were performed. RESULTS: We found that T2DM induced elevation of ER intermembrane space and UPR overactivation based on increased GRP78, ATF6 and PERK levels in small intestine. Metformin treatment led to a further UPR activation. PA supplementation partially restored enterocytes functioning via normalization of ATF6 and PERK content, while IRE1 level reached the maximum value, compared to all groups. The most pronounced effect of adaptation to the T2DMinduced ER stress was observed after combined metformin and PA action. In particular, decreased ER intermembrane space in enterocytes was detected compared to separate metformin and PA administration, which was accompanied by restored GRP78, PERK and IRE1 levels. CONCLUSION: Our study proves the safety of additional therapy with propionic acid in combination with metformin for the functional state of small intestine. Due to its ability to modulate UPR signaling, PA may be considered a safe and perspective candidate for supportive therapy in T2DM, especially for neuroprotection.

Adsorption Ability of Graphene Aerogel and Reduced Graphene Aerogel toward 2,4-D Herbicide and Salicylic Acid.

Within this work, new aerogels based on graphene oxide are proposed to adsorb salicylic acid (SA) and herbicide 2,4-Dichlorophenoxyacetic acid (2,4-D) from aqueous media. Graphene oxide aerogel (GOA) and reduced graphene oxide aerogel (rGOA) were obtained by freeze-drying processes and then studied by Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) analysis. The influence of contact time and the concentration of the adsorbates were also assessed. It was found that equilibrium for high adsorption is reached in 150 min. In a single system, the pseudo-first-order, pseudo-second-order kinetic models, Intraparticle diffusion, and Elovich models were used to discuss the detail of the aerogel adsorbing pollutant. Moreover, the Langmuir, Freundlich, and Temkin adsorption models were applied to describe the equilibrium isotherms and calculate the isotherm constants.

Prediction of pathogenic single amino acid substitutions using molecular fragment descriptors.

MOTIVATION: Next Generation Sequencing technologies make it possible to detect rare genetic variants in individual patients. Currently, more than a dozen software and web services have been created to predict the pathogenicity of variants related with changing of amino acid residues. Despite considerable efforts in this area, at the moment there is no ideal method to classify pathogenic and harmless variants, and the assessment of the pathogenicity is often contradictory. In this article, we propose to use peptides structural formulas of proteins as an amino acid residues substitutions description, rather than a single-letter code. This allowed us to investigate the effectiveness of chemoinformatics approach to assess the pathogenicity of variants associated with amino acid substitutions. RESULTS: The structure-activity relationships analysis relying on protein-specific data and atom centric substructural multilevel neighborhoods of atoms (MNA) descriptors of molecular fragments appeared to be suitable for predicting the pathogenic effect of single amino acid variants. MNA-based Naïve Bayes classifier algorithm, ClinVar and humsavar data were used for the creation of structure-activity relationships models for 10 proteins. The performance of the models was compared with 11 different predicting tools: 8 individual (SIFT 4G, Polyphen2 HDIV, MutationAssessor, PROVEAN, FATHMM, MVP, LIST-S2, MutPred) and 3 consensus (M-CAP, MetaSVM, MetaLR). The accuracy of MNA-based method varies for the proteins (AUC: 0.631-0.993; MCC: 0.191-0.891). It was similar for both the results of comparisons with the other individual predictors and third-party protein-specific predictors. For several proteins (BRCA1, BRCA2, COL1A2, and RYR1), the performance of the MNA-based method was outstanding, capable of capturing the pathogenic effect of structural changes in amino acid substitutions. AVAILABILITY AND IMPLEMENTATION: The datasets are available as supplemental data at Bioinformatics online. A python script to convert amino acid and nucleotide sequences from single-letter codes to SD files is available at https://github.com/SmirnygaTotoshka/SequenceToSDF. The authors provide trial licenses for MultiPASS software to interested readers upon request.

Investigation of Tribological Characteristics of PEO Coatings Formed on Ti6Al4V Titanium Alloy in Electrolytes with Graphene Oxide Additives.

Coatings with a thickness from ~40 to ~50 µm on Ti6Al4V titanium alloys were formed by plasma electrolytic oxidation (PEO) in a silicate-hypophosphite electrolyte with the addition of graphene oxide. The PEO treatment was carried out in the anode-cathode mode (50 Hz) at a ratio of anode and cathode currents of 1:1; their sum density was 20 A/dm2, and the treatment's duration was 30 min. The effect of the graphene oxide's concentration in the electrolyte on the thickness, roughness, hardness, surface morphology, structure, composition, and tribological characteristics of the PEO coatings was studied. Wear experiments, under dry conditions, were carried out in a ball-on-disk tribotester with an applied load of 5 N, a sliding speed of 0.1 m·s-1, and a sliding distance of 1000 m. According to the obtained results, the addition of graphene oxide (GO) into the base silicate-hypophosphite electrolyte leads to a slight decrease in the coefficient of friction (from 0.73 to 0.69) and a reduction in the wear rate by more than 1.5 times (from 8.04 to 5.2 mm3/N·m), with an increase in the GO's concentration from 0 to 0.5 kg/m3, respectively. This occurs due to the formation of a GO-containing lubricating tribolayer upon contact with the coating of the counter-body in the friction pair. Delamination of the coatings during wear occurs due to contact fatigue; with an increase in the concentration of GO in the electrolyte from 0 to 0.5 kg/m3, this process slows down by more than four times.

Adsorption Removal of Mo(VI) from an Aqueous Solution by Alumina with the Subsequent Regeneration of the Adsorbent.

Industrial wastewater is the main source of an excessive amount of molybdenum (Mo) in natural ecosystems. It is necessary to remove Mo from wastewater before it is discharged into the environment. Molybdate ion(VI) is the most common form of Mo in natural reservoirs and industrial wastewater. In this work, the sorption removal of Mo(VI) from an aqueous medium was evaluated using aluminum oxide. The influence of such factors as the pH of the solution and the temperature was evaluated. Three adsorption isotherms, namely, Langmuir, Freundlich and Temkin, were used to describe the experimental results. It was found that the pseudo-first order kinetic model better fits the kinetic data of the adsorption process, and the maximum Mo(VI) adsorption capacity was 31 mg/g at 25 °C and pH 4. The thermodynamic parameters indicated that the process of Mo(VI) adsorption on Al2O3 was exothermic and spontaneous. It was shown that the adsorption of Mo strongly depends on pH. The most effective adsorption was observed at pH values below 7. Experiments on adsorbent regeneration showed that Mo(VI) can be effectively desorbed from the aluminum oxide surface into a phosphate solution in a wide range of pH values. After the desorption of Mo(VI) in a phosphate solution, alumina was found to be suitable for repeating the procedure at least five times.

TCR-Pred: A new web-application for prediction of epitope and MHC specificity for CDR3 TCR sequences using molecular fragment descriptors.

The search for the relationships between CDR3 TCR sequences and epitopes or MHC types is a challenging task in modern immunology. We propose a new approach to develop the classification models of structure-activity relationships (SAR) using molecular fragment descriptors MNA (Multilevel Neighbourhoods of Atoms) to represent CDR3 TCR sequences and the naïve Bayes classifier algorithm. We have created the freely available TCR-Pred web application (http://way2drug.com/TCR-pred/) to predict the interactions between α chain CDR3 TCR sequences and 116 epitopes or 25 MHC types, as well as the interactions between ß chain CDR3 TCR sequences and 202 epitopes or 28 MHC types. The TCR-Pred web application is based on the data (more 250 000 unique CDR3 TCR sequences) from VDJdb, McPAS-TCR, and IEDB databases and the proposed approach. The average AUC values of the prediction accuracy calculated using a 20-fold cross-validation procedure varies from 0.857 to 0.884. The created web application may be useful in studies related with T-cell profiling based on CDR3 TCR sequences.

Assessment Effect of Nanometer-Sized Al2O3 Fillers in Polylactide on Fracture Probability of Filament and 3D Printed Samples by FDM.

In this paper, a mathematical model for the description of the failure probability of filament and fused deposition modeling (FDM)-printed products is considered. The model is based on the results of tensile tests of filament samples made of polyacrylonitrile butadiene styrene (ABS), polylactide (PLA), and composite PLA filled with alumina (Al2O3) as well after FDM-printed products of "spatula" type. The application of probabilistic methods of fracture analysis revealed that the main contribution to the reduction of fracture probability is made by the elastic and plastic stages of the fracture curve under static loading. Particle distribution analysis of Al2O3 combined with fracture probability analysis shows that particle size distributions on the order of 10-5 and 10-6 mm decrease the fracture probability of the sample, whereas uniform particle size distributions on the order of 10-1 and 10-2 mm do not change the distribution probability. The paper shows that uneven distribution of Al2O3 fillers in composite samples made using FDM printing technology leads to brittle fracture of the samples.

Evaluation of the Role of the Activating Application Method in the Cold Sintering Process of ZnO Ceramics Using Ammonium Chloride.

The influence of the method of applying the activating additive ammonium chloride and its concentration on the density and microstructure of zinc oxide ceramic obtained by cold sintering at 244 °C was investigated. The activating agent was applied by two methods: impregnation and subsequent autoclave treatment. When the powder was activated by the impregnation method, the crystal sizes remained at the initial level of 0.17-0.19 µm. After the autoclave treatment, the crystal sizes increased to 0.31-0.53 µm. Samples of cold sintering ZnO with relative density up to 0.96 and average grain sizes 0.29-0.86 µm were obtained. ZnO powders and ceramic samples were analyzed using SEM, TGA/DSC, and XRD to reveal the effect of the powder activation method and cold sintering conditions on the material microstructure. The effect of ammonium chloride concentration on grain growth and microstructure of ceramic samples is shown. It was found that the average grain size of ceramic samples with an increase in additive concentration passes through a minimum. In cold sintering of the autoclave activated powder, the effect of reducing the average grain size was observed. The results of this work are discussed on the basis of the idea of the solid-phase mobility of the crystal structure arising when interacting with an aqueous medium.

Experience in the Application of Augmented Reality Technology in the Surgical Treatment of Patients Suffering Primary and Recurrent Pelvic Tumors.

Surgical treatment of locally spread tumors in pelvic organs remains an urgent and complicated oncological problem. The recurrence rate after radical treatment ranges from 15.1% to 45.2%. The key to successful and safe surgical intervention lies in meticulous planning and intraoperative navigation, including the utilization of augmented reality (AR) technology. This paper presents the experience of clinically testing an AR technology application algorithm in the surgical treatment of 11 patients. The main stages of the algorithm are described. Radical operations incorporating intraoperative AR technology with favorable outcomes were performed on eight patients. One patient underwent a palliative intervention, while two patients did not undergo surgery. The testing of the algorithm for the application of AR technology in the surgical treatment of primary and recurrent pelvic tumors demonstrated both a technical possibility and reproducibility of this algorithm and the AR technology itself in clinical practice.

Rheological Characterization and Printability of Polylactide (PLA)-Alumina (Al2O3) Filaments for Fused Deposition Modeling (FDM).

This article presents the study of the rheological properties and the printability of produced ceramic-polymer filaments using fused deposition method (FDM) 3D printing technology. Powder mixtures with an alumina content of 50 to 70 vol.% were fabricated by a wet processing route. A series of rheological experiments of the obtained mixtures were conducted in the temperature range from 200 to 220 °C for the commercial polylactide (PLA) powder and from 200 to 240 °C for ceramic-polymer, which corresponds to the recommended temperatures for 3D printing of commercial PLA filaments. The composition with the maximum content of alumina leads to a powdery material in which the molten polymer is insufficient to measure the rheological properties. In spite of this, the filaments were prepared from all the obtained mixtures with a tabletop single-screw extruder, the diameter and surface profile of which were analyzed. As the ceramic content increased, the diameter and surface roughness of the filaments increased. Therefore, it was only possible to print an object from a filament with the lowest ceramic content. However, the print quality of the 3D printed objects from the fabricated ceramic-polymer filament is worse (imperfect form, defects between layers) compared to the commercial PLA filament. To eliminate such defects in the future, it is necessary to conduct additional research on the development of printing modes and possibly modify the software and components of the 3D printer.

Peculiarities of γ-Al2O3 Crystallization on the Surface of h-BN Particles.

The main goal of the present work was to synthesize a composite consisting of h-BN particles coated with a γ-Al2O3 nanolayer. A method was proposed for applying nanocrystalline γ-Al2O3 to h-BN particles using a sol-gel technique, which ensures the chemical homogeneity of the composite at the nano level. It has been determined that during crystallization on the h-BN surface, the proportion of spinel in alumina decreases from 40 wt.% in pure γ-Al2O3 to 30 wt.% as a result of the involvement of the B3+ ions from the surface nitride monolayers into the transition complex. For comparison, nano-alumina was synthesized from the same sol under the same conditions as the composite. The characterization of the obtained nanostructured powders was carried out using TEM and XRD. A mechanism is proposed for the formation of a nanostructured γ-Al2O3@h-BN composite during the interaction of Al-containing sol and h-BN suspension in aqueous organic media. The resulting composite is a promising model of powdered raw materials for the development of fine-grained ceramic materials for a wide range of applications.

The Influence of Surface Texturing of Ceramic and Superhard Cutting Tools on the Machining Process-A Review.

Machining is an indispensable manufacturing process for a wide range of engineering materials, such as metals, ceramics, and composite materials, in which the tool wear is a serious problem, which affects not only the costs and productivity but also the quality of the machined components. Thus, the modification of the cutting tool surface by application of textures on their surfaces is proposed as a very promising method for improving tool life. Surface texturing is a relatively new surface engineering technology, where microscale or nanoscale surface textures are generated on the cutting tool through a variety of techniques in order to improve tribological properties of cutting tool surfaces by reducing the coefficient of friction and increasing wear resistance. In this paper, the studies carried out to date on the texturing of ceramic and superhard cutting tools have been reviewed. Furthermore, the most common methods for creating textures on the surfaces of different materials have been summarized. Moreover, the parameters that are generally used in surface texturing, which should be indicated in all future studies of textured cutting tools in order to have a better understanding of its effects in the cutting process, are described. In addition, this paper proposes a way in which to classify the texture surfaces used in the cutting tools according to their geometric parameters. This paper highlights the effect of ceramic and superhard textured cutting tools in improving the machining performance of difficult-to-cut materials, such as coefficient of friction, tool wear, cutting forces, cutting temperature, and machined workpiece roughness. Finally, a conclusion of the analyzed papers is given.

Granulation of Silicon Nitride Powders by Spray Drying: A Review.

Spray drying is a widely used method of converting liquid material (aqueous or organic solutions, emulsions and suspensions) into a dry powder. Good flowability, narrow size distribution, and controllable morphology are inherent in powders produced by spray drying. This review considers the granulation factors that influence the final properties of the silicon nitride dried powders. The first group includes the types of atomizers, manifolds, and drying chamber configurations. The process parameters fall into the second group and include the following: inlet temperature, atomizing air flow, feed flow rate, drying gas flow rate, outlet temperature, and drying time. Finally, the last group, feedstock parameters, includes many factors such as feed surface tension, feed viscosity, solvent type, solid particle concentration, and additives. Given the large number of factors affecting morphology, particle size and moisture, optimizing the spray drying process is usually achieved by the "trial and error" approach. Nevertheless, some factors such as the effect of a solvent, dispersant, binder, and sintering additives considered in the literature that affect the Si3N4 granulation process were reviewed in the work. By summarizing the data available on silicon nitride powder production, the authors attempt to tackle the problem of its emerging demand in science and industry.

Practical Application of Augmented/Mixed Reality Technologies in Surgery of Abdominal Cancer Patients.

The technology of augmented and mixed reality (AR/MR) is useful in various areas of modern surgery. We considered the use of augmented and mixed reality technologies as a method of preoperative planning and intraoperative navigation in abdominal cancer patients. Practical use of AM/MR raises a range questions, which demand suitable solutions. The difficulties and obstacles we encountered in the practical use of AR/MR are presented, along with the ways we chose to overcome them. The most demonstrative case is covered in detail. The three-dimensional anatomical model obtained from the CT scan needed to be rigidly attached to the patient's body, and therefore an invasive approach was developed, using an orthopedic pin fixed to the pelvic bones. The pin is used both similarly to an X-ray contrast marker and as a marker for augmented reality. This solution made it possible, not only to visualize the anatomical structures of the patient and the border zone of the tumor, but also to change the position of the patient during the operation. In addition, a noninvasive (skin-based) marking method was developed that allows the application of mixed and augmented reality during operation. Both techniques were used (8 clinical cases) for preoperative planning and intraoperative navigation, which allowed surgeons to verify the radicality of the operation, to have visual control of all anatomical structures near the zone of interest, and to reduce the time of surgical intervention, thereby reducing the complication rate and improving the rehabilitation period.

Investigation of MAO Coatings Characteristics on Titanium Products Obtained by EBM Method Using Additive Manufacturing.

Coatings with a thickness from 27 to 62 µm on electron beam melted Ti-6Al-4V have been formed by micro-arc oxidation (MAO) in a silicate-hypophosphite electrolyte. MAO tests in the anode-cathode mode (50 Hz) with an anode-to-cathode current ratio of 1:1 and sum current densities 10 and 20 A/dm2 were carried out. The duration of the MAO treatment was 30 and 60 min. The effect of the processing parameters on the structural properties of the MAO treated coatings was studied. The current density and treatment time significantly affect the coating thickness and surface roughness. The values of these characteristics increase as the current density increases. The effect of thermal cycling tests on surface morphology, thickness and roughness, and elemental and phase composition of MAO coatings was analyzed. After 50 cycles of thermal cycling from +200 °C to -50 °C, no cracking or delamination of coatings was observed. Coatings formed in 30 min at a current density of 20 A/dm2 turned out to be the best in terms of such indicators as surface morphology, thickness, and roughness.

Evaluation of Mechanical and Electrical Performance of Aging Resistance ZTA Composites Reinforced with Graphene Oxide Consolidated by SPS.

This paper presents a study of Al2O3-ZrO2 (ZTA) nanocomposites with different contents of reduced graphene oxide (rGO). The influence of the rGO content on the physico-mechanical properties of the oxide composite was revealed. Graphene oxide was obtained using a modified Hummers method. Well-dispersed ZTA-GO nanopowders were produced using the colloidal processing method. Using spark plasma sintering technology (SPS), theoretically dense composites were obtained, which also reduced GO during SPS. The microstructure, phase composition, and physico-mechanical properties of the sintered composites were studied. The sintered ZTA composite with an in situ reduced graphene content of 0.28 wt.% after the characterization showed improved mechanical properties: bending strength was 876 ± 43 MPa, fracture toughness-6.8 ± 0.3 MPa·m1/2 and hardness-17.6 ± 0.3 GPa. Microstructure studies showed a uniform zirconia distribution in the ZTA ceramics. The study of the electrical conductivity of reduced graphene oxide-containing composites showed electrical conductivity above the percolation threshold with a small content of graphene oxide (0.28 wt.%). This electrical conductivity makes it possible to produce sintered ceramics by electrical discharge machining (EDM), which significantly reduces the cost of manufacturing complex-shaped products. Besides improved mechanical properties and EDM machinability, 0.28 wt.% rGO composites demonstrated high resistance to hydrothermal degradation.

Processing and Characterization of Spark Plasma Sintered SiC-TiB2-TiC Powders.

SiC-TiB2-TiC composites with matrices consisting of semiconductor material (SiC), conductive materials (TiB2-TiC), or their combination were fabricated by spark plasma sintering (SPS) at 2000 °C in a vacuum under a pressure of 80 MPa for 3 min. The composition and microstructure of the obtained composites were studied by X-ray diffraction and a scanning electron microscope equipped with an energy-dispersive detector. The flexural strength, Vickers hardness, and fracture toughness of SPSed samples were determined. Based on the observations in this work, three variations of the sintering process were proposed with different matrix compositions. The dense (99.7%) 60SiC-25TiB2-15TiC vol.% sintered ceramic composites exhibited the highest strength and hardness values of the studied composites, as well as a fracture toughness of 6.2 MPa·m1/2.