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The aim of this work was to find the influence of the addition of low amount of hydrophilic and hydrophobic TiO2 nanoparticles on compressive strength, microhardness and rheological properties of flowable dental composite material. Specimens were prepared by adding 0.05; 0.2 and 1 wt. % of hydrophilic and hydrophobic 20 nm TiO2 nanoparticles. These specimens were compared to non-modified control specimens in compressive strength and microhardness. Furthermore, their rheological properties were determined. The optimal nanoparticle loading was 0.2 % hydrophobic TiO2, resulting in significantly higher compressive strength and microhardness than those of the control specimen group. Mechanical properties of flowable composites reinforced with hydrophilic and hydrophobic TiO2 at higher loadings are lower than those of control specimens, which is the result of nanoparticle agglomeration. TiO2 nanoparticles addition resulted in the decrease in viscosity in all specimens except for the specimewn with 1% hydrophilic TiO2 nanoparticles. In accordance to the obtained results, hydrophobic nanoparticle addition results in a more resistant and durable material, combined with an increased flowability compared to a non-modified composite.

Although polymethylmethacrylate (PMMA) is widely used as a denture base material, its disadvantages include low strength and low thermal conductivity. The effects on thermal conductivity, flexural strength, thermal diffusivity, and elastic modulus of adding Al2O3 and SiC powders in different volumes to PMMA were investigated. A total of 60 specimens were prepared in 10 groups (five groups for the thermal conductivity test and five groups for the flexural strength test (n:6). The specimens were immersed in water for 30 days before the testing. Thermal conductivity values were measured by the transient hot bridge (THB) method, and flexural strengths were measured by the 3-point bend test. A significant difference was found in thermal conductivity, flexural strength, thermal diffusivity and elastic modulus values between independent groups (P < 0.001) using the Kruskal-Wallis test. The Kruskal Wallis 1-way ANOVA was used for the post hoc tests after Kruskal Wallis (á=.05). The thermal conductivity of PMMA increased significantly with the addition of 15% SiC and 15% Al2O3. The flexural strength values decreased significantly with the addition of 10% SiC and 15% Al2O3. The thermal diffusivity values increased significantly with the addition of 10% and 15% SiC. The Young modulus of PMMA decreased when 10% SiC, 10% Al2O3 and 15% Al2O3 were added. Environmental scanning electron microscope (ESEM) showed that ceramic powders were dissipated in PMMA. The addition of 15% SiC powders to PMMA increased thermal conductivity without significantly reducing flexural strength. This study helped determine the optimum volumes for the use of SiC and Al2O3 powders. Knowledge of the importance of this variable will help in more effective modification of denture base resin with SiC and Al2O3 powders to improve heat transfer without adversely affecting strength.

Renewability, recyclability and biodegradable contents are similar to glass fibers in natural fiber reinforced polymer composites (NFRP) which have definite mechanical properties. The interface of polymer matrix and natural fibers results the composites to achieve superior properties of products. Researchers have extended their product designs and production techniques by using renewable materials such as jute fiber, cotton fiber, silk fiber, etc. which are enormous and used in the manufacture of durable industrial goods of high-end quality. This paper reviews the current developments and the brief findings needed in literature, concentrating on the mechanical properties and applications of NFRP.

In esthetic restorative dentistry, resin composites are generally encountered. Because of their excellent biocompatibility, lack of taste, odour, tissue discomfort, and toxicity, insolubility in body fluids, ease of use, good clinical/ aesthetic properties, stable colours, optical characteristics, efficient pigmentation, low cost, and repairability, they are becoming more common. Currently used composite resins have some flaws, particularly inconsistent mechanical properties. For a long time, particles of various sizes have been used as fillers to enhance these properties. In prosthodontics, poly(methyl methacrylate) (PMMA) is commonly used as a dental base material. It does, nevertheless, have several weaknesses, including low strength and weak thermal properties. The effects of different sizes of alumina (Al2O3) particles on the poly(methyl ethacrylate) (PMMA) denture base were determined in this experiment. PMMA powder was blended with Al2O3 added to methyl methacrylate (MMA).For PMMA polymeric materials strengthened with Al2O3 (40 nm, 140 nm and 0.3-0.8 μm) in various concentrations, the mechanical properties were studied.Also, the synergetic influence of the three nanoparticle sizes in the resin matrix was studied.Furthermore, thermogravimetric (TGA) analysis and water absorption and solubility characteristics of the composites prepared were also examined. Among the most significant properties to be obtained for good denture materials is high mechanic properties, water absorption and solubility, since they have different attributes in the aqueous condition of the oral cavity. Results showed clear properties optimization, especially for the size-hybrid alumina composites.

Abstract: The presented experimental research aims to compare the degradation degree of five different types of surgical sutures used in clinical practice and to discuss the influence of local pH on the degradation of a suture material. The surgical sutures were tested in terms of stability and hydrolytic biodegradation in Phosphate Buffer Saline (PBS) solution varying the pH and the immersion time of the samples in the liquid medium. The surface properties, structural characteristics and the effects of hydrolytic biodegradation on the mechanical properties were studied using Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Degradation degree and Tensile Strength tests, respectively.

The article presents the optimization of a production process with the help of FDM technology of a fertigation pump prototype that does not require other energy source than that given by the flow and pressure of water for irrigation. In the research presented in this article specimens of PETG material are tested in terms of mechanical properties by using a tensile test equipment. The results of these tests are used to dimension and simulate with finite element the component elements of the pump.

Previous studies have shown that marine drug propylene glycol alginate sodium sulfate (PSS) plays important roles in human diseases. This study mainly explored the effects of PSS on hyperglycemia and hyperlipidemia in diabetic db/db mouse models. The db/db mice were randomly divided into 5 groups (n=12), which were model control group (distilled water), positive control group (metformin), PSS low, medium, and high dose groups (PSS25, PSS50, PSS100) and normal control group (C57/BL, distilled water). The mice in each group had free diet and water for 90 days. During the experiment, food intake was recorded every day and body weight was recorded weekly. In addition, fasting blood glucose and glycosylated hemoglobin levels were measured regularly. Finally, the contents of triglyceride (TG), low-density lipoprotein (LDL-c), high-density lipoprotein (HDL-c) and total cholesterol (TC) in the serum of mice were determined. PSS can significantly reduce fasting blood glucose and glycosylated hemoglobin levels in db/db mice, and improve insulin sensitivity. Moreover, PSS can reduce the fat accumulation of db/db mice and significantly improve the blood lipid level of db/db mice. PSS can significantly improve the symptoms of glucose and lipid metabolism disorders in db/db mice.

An original functionalization strategy is proposed here to design chitosan (CS)-based cryogels with ethylenediaminetetraacetic acid (EDTA) moieties. Cryogels with aligned micro-sized tubular structures were further engineered through an unidirectional freezing approach. Attachment of EDTA groups onto CS chains was proved by 1H-RMN and FT-IR spectroscopy. The formation of EDTA-functionalized 3D porous CS-based cryogels was demonstrated by several methods of characterization (FTIR spectroscopy, optical microscopy, SEM, porosity measurements, swelling behavior, copper (II) retention capacity). The sorption tests pointed out the high potential of EDTA-functionalized CS-based cryogels for heavy metal ions retention.

The purpose of this research is to study and develop the formulation of a rheological law for composite materials with elasto-plastic behaviour in cold compression. Starting from the generally known relationships in literature, the hypoelastic model proposed for the composite materials behaviour (as powder materials) has been developped/explained, ensuring the understanding of the research. The hypolastic theory has been used for modeling the continuous transition from elastic to plastic state for a powder material. The material behaviour is described through an isotropic tensor relationship between the deformation speed tensor, Cauchy’s stress tensor and its derivative in relation to time (the Jaumann’s derivative). Only the linear part has been used from the general form of the law which depends on scalar functions. The calculations lead to relationships depending on five parameters which are identified according to experimental data. A numerical simulation of the stress-strain evolution during the simple compression of a diepressed powder sample is made; the numerical simulation has been validated by the experimental results.

The paper presents the study on the static mechanical properties of PLA (Polylactic Acid) produced with entry-level additive technologies using three printing directions. During the experimental work were tested a total of 15 “dog bone” ASTM D638-14 standard specimens made from additively manufactured polymer (PLA) through FDM (Fused Deposition Modelling) technique, where the material and rectilinear pattern infill geometry and infill percentage of 100% were constant and the printing orientation was varied. Usually technical data sheets that are delivered by filament materials producers include the most satisfactory data which are valid for only one specific printing direction. The printing direction is deliberately selected, in such way that the best material characteristics are achieved. In addition to this matter, as the additive manufacturing market grew significantly in the past couple of years, the filament production market showed a consequential growth. The aftermath of this expansion had a direct impact towards the quality and costs of the filaments used for 3D printing, in order to satisfy both the low-end and high-end users. Therefore, in this frame, the present research provides entry-level additively manufactured PLA performances showing significant changes depending on the different printing directions and determine the build orientation influence on the mechanical properties, in the aim of providing aid for both mechanical designer and product manufacturer at the stage of the printed product mechanical properties.