Volume 60, Issue 1

Abstract: Bromelain, a natural substance sourced from pineapples, was found effective in various colds, in preventing heart attack and respectively in excess weight. On the other hand, it is well-known that pineapples juice increases the gastric acidity and respectively the people with hemophilia, internal bleeding must also be very careful in consuming this fruit. The objectives of this study were to obtain and to characterize a drug delivery system used for the transmembrane transfer of bromelain. The samples based on polyurethane matrices with and respectively without bromelain were synthesized and characterized by measurements of pH, encapsulation efficacy, cumulative drug release in a degradative media and in simulated gastric acid, electron microscopy and by modern techniques such as Zetasizer, cytotoxicity assay, and various non-invasive skin irritation assessment. The results indicate the obtaining of polyurethane matrices with mean sizes between 322-342 nm and neutral pH, that have a medium stability against the clusters formation tendency and a medium drug release rate. The non-irritative potential and the results on their cytotoxicity are important evidences that can be used for the further clinical trials of the polyurethane carriers.

Abstract: Lignin fiber/epoxy resin compositeused for energy absorbing was prepared by atmospheric stirring method. Quasi-static compressive mechanics tests were implemented by using the electronic universal mechanics tester (WDW-100KN) under ambient conditions to analyze the compressing behavior of the matrix material and composite at the strain rate of 10-2s-1 .Scanning electron microscope (SEM) was used to observe the microstructure of the composite after quasi-static compression damage. The results showed that when the ratio of epoxy resin and curing agent was 3:1, the internal structure of the matrix material was more uniform with smoother cross-section, which represented better mechanical properties. It was found that the addition of lignin fiber changed the compression characteristics of the matrix material, resulting in a strengthening stage appeared. At the same time, when the lignin fiber content was 2% or 3%, the composite could absorb more impact energy and delay crack generation, which met the performance requirement of energy absorbing materials.

Abstract: This study aimed to evaluate the efficacy of disinfectant solutions on Candida albicans (C. albicans) for different types of denture materials. A total of 144 specimens (10x10x2 mm) were obtained from three different materials: autopolymerized acrylic resin, heat-cured acrylic resin, and hard relining material (n = 6). Three disinfectant solutions were used: 100% white vinegar, 2% chlorhexidine digluconate (Saver) and denture cleaning tablets (Corega). The specimens were placed on Eliza plates and 1.5 mL of Yeast Extract Peptone (YPD) was added to each well. Then, 30µL of candida culture was added to the wells. Next, the specimens were incubated at 37°C at 80 rpm for 48 h. Disinfectants were added to the Eliza plates. For all specimens, the disinfectants were replaced with 2 mL of sterile water and kept at 100 rpm for 30 min. Then, 0.1 mL of the liquid was taken and inoculated into the pads containing YPD medium. After incubation, the candida colony growth on the pads was measured. Scanning electron microscope (SEM) images were taken from randomly selected specimens from each group. Statistically significant differences (𝑃 [ 0.05) were found between the disinfectant method groups and the control group for the three types of denture materials. The 2% chlorhexidine gluconate (Saver) disinfectant was the most effective for C. Albicans ATCC 60193 and oral isolate of C. Albicans for all three of the tested denture materials. The effect of cleaning of tabs (Corega) and white vinegar was found to be similar.

Abstract: Biomass fibers are promising materials for applications in modern vehicles. They have great economic and ecological significance, as well as a great potential in the fabrication of composite materials due to the relatively high level of strength and rigidity, low density, availability, recyclability, and biodegradability. In this context, the focus is on the development of automotive brake pad materials from sustainable sources. This work refers to the investigation of the behavior of composite materials made of biomass fibers, phenolic resin, graphite and aluminum oxide. These materials are intended to be used for brake pads on automobiles with moderate efficiency. For this purpose, three recipes of composite materials with different percentages of coconut fiber and wood powder were developed in laboratory. The physical and mechanical as well as functional properties of these composite materials with varying amounts of biomass fibers are examined in this paper. The best performances in this terms was obtained for the composite material containing the highest amount of wood powder and the lowest amount of coconut fiber.

Abstract: The waste recycling of epoxy resin-based fiber reinforced plastics is an important topic of current environmental protection. This work investigated the potential engineering benefits of applying simply crushed recycled epoxy resin-based fiber reinforced plastic in structural concrete. In this paper, the mixing and mechanical properties of concrete products with crushed and recycled waste epoxy plates instead of some fine aggregate were studied experimentally. Three kinds of recycled crushing materials with different particle sizes below 4mm, 4mm to 9mm, and 9mm were used to prepare 10 groups of concrete samples with different proportions by replacing sand with 5, 10, and 15% volumes, respectively. The results showed that the density of the recycled plastic concrete was reduced and the slump of the concrete was increased, with the increase of the recycled crushing materials, and the mechanical properties of concrete were improved within the 5%-10% admixture, and the best results of comprehensive mechanical properties were achieved when the admixture was 10% and the particle size was 4-9mm. These results indicated that it is feasible to replace concrete fine aggregates with recycled crushing materials of waste epoxy plate, and this study not only explores a new way to recycle waste epoxy resin-based fiber reinforced plastic, but also reduces the over-exploitation of sand natural resources, which have a high social and economic value.

Abstract: The purpose of this study was to evaluate the effect of finishing/polishing systems on the translucency parameter (TP) of resin composites after accelerated artificial aging (AAA). Four composite resins (Filtek Z250, Admira, IPS Empress Direct, Clearfil Majesty Esthetic) were evaluated. Thirty samples were prepared with each resin composite and divided into three subgroups: control (Mylar strip), disc (Optidisc), and rubber (Dimanto) (n=10). The spectrophotometer was used to determine color measurements. TP was calculated the using the CIEDE 2000 formula. Data were analyzed using Generalized Lineer Model (p[0.05). The three factors (composite resin, finishing/ polishing, and AAA) had no statistically significant influence on the TP. However, composite and finishing/polishing influenced the TP. Filtek Z250 showed the lowest TP values and the IPS Empress Direct showed the highest TP values before and after AAA. Polished groups showed higher TP values than control groups before and after AAA. IPS Empress Direct with Dimanto had higher TP values than other groups (except for IPS Empress Direct with Optidisc); Filtek Z250 with finishing/polishing groups showed lower TP values than other groups. Composite type and finishing/polishing systems influenced TP values. Unfinished groups exhibited lower TP values than finished groups. There was no difference in TP values between finishing/polishing systems (Dimanto and OptiDisc).

Abstract: The etiology of maxillofacial injuries is represented by car accidents, human aggression, and work-related trauma. Trauma to the maxillofacial area requires a complex treatment that involves functional and aesthetic rehabilitation. To restore the functionality of the damaged areas, a correct surgical technique is necessary along with the use of the ideal prostheses for a better reconstruction. Along with the development and improvement of facial fractures osteosynthesis techniques, an attempt was made to identify the right material to complete these surgical methods. We analyze in this paperwork the benefits of polyetheretherketone-based materials in the prosthetics of different facial fractures in comparison with other materials like titanium.

Abstract: The increasing concern for the protection of the environment, through the use of renewable natural resources, has led in the last decades to the realization of a number of natural polymers or hybrids to be able to replace petroleum-based polymeric materials. Rosin is a low-cost wood resin extracted from conifers. In this paper, based on FTIR and Raman analyses, the spectra of natural Rosin resin and some hybrid resins with volume proportions of 45, 55 and 65% Rosin were studied. Some mechanical properties such as modulus of elasticity, elongation at break, tensile strength were determined from stress-strain diagrams obtained from tensile stress. Increasing the volume proportion of Rosin leads to a decrease in stiffness and strength properties and obtaining a visco-elastic behavior.

Abstract: Industrial vacuum cups are used for lifting, holding and moving a wide variety of automated applications for handling semi-finished products and parts made of a wide range of materials - metal, glass, plastic, paper, wood, etc. and are used in a variety of industries. This paper presents some of the authors` theoretical and experimental research on the maximum lifting force that different types of vacuum cups can achieve. The study was carried out on the basis of sizing recommendations made by manufacturers and dealers of these types of vacuum cups. The specially designed experimental stand was installed on the universal material testing machine LBG 100 kN and allowed the practical determination of these lifting forces provided by various types of industrial vacuum cups. Lifting force measurements were carried out with the AXIS FB 1k digital dynamometer attached to the machine. Vacuum cups of 3 different shapes and made of 3 different materials were used, using different vacuum depressions - 0.3 bar, -0.5 bar, -0.7 bar and -0.9 bar. The research aimed to determine by measurement the maximum lifting force of these types of vacuum cups applied to steel parts. The results obtained for these forces were compared with the calculated theoretical values, with the manufacturer’s recommended dimensioning values, and comparative conclusions were also drawn on the maximum lifting force provided by the different types of industrial vacuum cups studied.

Abstract: The use of digital technology has become a useful and also a preferred process in the realization of dental prosthetic restorations, because through it, superior quality dental prostheses are obtained in terms of aesthetics, accuracy of execution and durability. CAD/CAM technology is changing all aspects of dentistry, making dental restoration processes much easier and more efficient for dentists, patients and dental technicians. The materials that can be used to manufacture dental restorations designed using Exocad software depend on the type of restoration (crowns, bridges, veneers, etc.) and the manufacturing method (milling with a 3-, 4-, or 5-axis CAM device); available materials include: PMMA (polymethyl methacrylate) and zirconia. Using digital technology, in this study we performed 6 fixed prosthetic restorations, of which 5 unidental restorations (5 dental crowns) and 1 pluridental restoration (a 4-element dental bridge); of the 6 prosthetic restorations, 3 restorations will be fixed by cementing on dental abutments, and 3 restorations will be fixed by screwing on implants. Digital technology allows the use of higher quality materials, resulting in more resistant and more aesthetic prosthetic restorations; helps reduce the occurrence of errors; obtaining a better marginal adaptation and a perfect adaptation to the anatomical structures of the patient`s teeth.

Abstract: Biodegradable bio composites with potential applications in medical implants were prepared with starch content by in situ polymerization technique using polyurethane prepolymers. (PU) and acrylamide (AAM) monomers. The structure and properties of bio composites were evaluated. FT-IR spectroscopy showed bonding between N=C=O functional group terminated polyurethanes confirmed improved compatibility of prepolymers, AAM, starch and bio composites. The DSC data are the glass transition (Tg) of the bio composite and ordinary polyacrylamide (PAAM) network. By incorporating starch and polyurethane in the form of an interpenetrating network into a polyacrylamide network, mechanical and thermal properties of bio composites due to higher crosslink density given by hard segment content. We studied the swelling behavior of both bio composites and individual PAAM networks under different pH conditions to validate their biocompatibility and potential use in biomedicine setting. The hydrolytic stability of biocomposites and PAAM networks was investigated using phosphate buffer. Hydrolytic stability of biocomposites was found to be higher comparison with PAAM network. Morphological analysis of the samples showed uniform distribution and good interfacial adhesion. Improves sample biodegradability it was revealed by the soil runoff test.

Abstract: The materials of the given article are devoted to the problem solution associated with one of the processing plastic waste methods by adding various fillers in order to obtain the final product for the thermal insulation materials manufacture. The researches were conducted using the UPR (unsaturated polyester resin) samples made of EPS (expanded polystyrene) plastic waste and crushed recycled polyethylene from greenhouse film waste with various types of wood waste from carpentry workshops. The tests have revealed that when EPS is added to the unsaturated polyester mixtures, the EPS thermal conductivity coefficient decreases with a slight decrease in density, which gives the wide opportunities to use EPS waste as an additive for UPR and expands the ways of its potential industrial application, and the addition of styrene to the compositions containing 10% of styropor causes a clear decrease in thermal conductivity characteristics and a slight decrease in the density of these mixtures. The values of the thermal conductivity coefficient and the density of the low-density polyethylene material increase with the wood powder percentage raising used as an organic filler.

Abstract: Main goals like technical innovation, costs and respect for the environment urge us to discover finer, lighter, biodegradable, and more «intelligent» materials in their functionality. The development of industrial design is motivated by criteria such as the environment, sustainability, the need for lightweight products, manufactured with fewer components and integrating various functions. As experts in new materials and technologies for the development of innovative products, we work closely with international research institutes as part of our projects. We want to create materials that combine such properties in the most efficient way, interacting with their close environment and the environment in general and, based on their features, to be transformed through various processes in completely different materials. The goal of our work is to compare different existing materials with a new bio-based material using quantifiable measurement indicators and sensory measurement indicators. The purpose of this article is to provide a few elements that can be used as a guide in establishing a quantitative impact assessment strategy based on the use of sensory evaluation techniques. In the framework of our presentation, we will focus mostly on comparing the materials via a metrological tool for quantifying tactile characteristics likely to be correlated to the `ground truth` that constitutes a sensory profile.

Abstract: Can polymer-infiltrated florapatite glass ceramic produced from waste materials, such as clam shell and soda lime silicate glass, be used in prosthetic rehabilitation? The purpose of this study is to investigate the effect of Si/Ca ratio on the mechanical properties of Nb-Bi-Ce doped polymer-infiltrated fluorapatite ceramic networks (PICNs) produced from clam shell (CS) and soda lime silicate (SLS) glass by conventional melt-quench technique, used as a dental ceramic. PICNs comprising Si/Ca at four different weight percentage ratios: 1.27% (PICN-1), 2.15% (PICN-2), 4.12% (PICN-3) and 12.6% (PICN-4) were prepared (n=10). The powder mixtures in four different ratios were compressed in a rectangular prism shaped mold and subjected to equal pressure from all sides in a cold isostatic press, followed by heat treatment at 750C for 3 h. Then complete vacuum infiltration was done with a polymer mixture then low temperature firing was applied leading to the formation of the PICNs. Wear behavior and 3-point bending properties were evaluated and specimens were analyzed using scanning electron microscopy (SEM). The friction and wear properties were determined by means of a pin-on-disk tribotester. Since the flexural strength test did not show normal distribution, Kruskal Wallis test was performed in independent groups, p[0.05. There is a significant difference of flexural strength values between the groups (p=0.032), it was determined that the difference was between the PICN-1 and PICN-4 groups (p=0.037). In the analysis of wear scar, abrasion grooves were also observed. The results of this study showed that high Ca and Si content in CS and SLS glass, respectively, encourages the use of waste materials in the production of PICNs intended to be used in prosthetic rehabilitation. The composition of PICNs produced from waste materials affected flexural strength and wear behavior. Increasing the Si/Ca ratio was found to support the mechanical properties of experimental PICN and that experimental PICNs can be considered as high potential candidates for dental applications.