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This paper is part of a larger study that aims to evaluate the biomechanical behaviour of mandibular bone and periodontal splinting systems subjected to different occlusal forces by means of electric resistive tensometry (ERT). The research was based on the following premise: the degree of bone resorption and periodontal type of splint influence the deformation of the mandibular bone. The study was conducted in two stages: first, the validation of the mandibular dental arch model, which is the subject of the present article, and second, the evaluation of mandibular bone strain in case of different types of bone loss and periodontal splints, which is the subject of a second article.

Polyurethane foam wastes is one of the environmental problems for which are not still the efficient solutions of valorization. This paper presents the possibility of recovering polyurethane foam waste by obtaining some new materials with sound absorption properties. The polyurethane foam wastes were ground and mixed, in proportion of 0, 3, 5, 7 and 12 wt%, with bicomponent polyurethane foam as a binder, resulting 5 new materials. The sound-absorbing properties of the new materials have been determined and it can be observed that the sound-absorbing properties of rigid polyurethane foam with closed pores can be improved by adding polyurethane foam waste to its structure. In addition, the mechanical properties and thermal conductivity of the new materials were studied.

The fragility fracture fixation confronts with the major problem of implant loosening due to the altered bone structure. Techniques used to fragility fracture stabilization includes metals devices, cements or adhesives. Different types of cements and adhesive can be obtained by chemical manipulation in order to provide a more efficient transition between the metal surface and the real bone. Thus, by selecting the appropriate chemical composition and ration between the components, synthetic cement and adhesive can provide a proper interface that ensure a perfect cohesion between the implant material and the natural bone. Most of the studies point the benefit of these synthetic materials in improving screw fixation strength. That is why, currently, the synthetic materials used in prosthesis are improved by associating with natural components of the bone, such as hydroxyapatite. For osteoporosis, which is characterized by demineralization, the association of the implanted material with hydroxyapatite is expected to be a suited solution for bone matrix regeneration after implantation. The aim of the current study was to assess the mechanical properties of orthopedic screws coated with a new polyurethane acrylate polymer containing hydroxyapatite in order to improve the stability of the screw for the subsequent fixation of the fragility fracture. To test the efficiency of the new hydroxyapatite containing polymer, the mechanical behavior of the coated screws was evaluated. Our data show that the augmented screw can be obtained by incorporating lower hydroxyapatite concentrations.

In order to evaluate the possibility of reuse of some mixed waste from plastic and paper, composite samples of both HDPE and PP basis were made with different filler contents of crushed postage envelope waste. From the morphostructural characterization (SEM images) of the samples obtained it was observed that the HDPE and PP samples had had a homogeneous single-phase structure in contrast to the composite samples with filler from mixed plastic and paper waste. The latter, have a biphasic heterogeneous structure in which the cellulose particles are uniformly distributed. Determinations performed through the dielectric spectroscopy technique indicated that the cellulose content of the composite samples leads to a systematic increase of the dielectric losses (up to about 40% for the HDPE samples, respectively about 30% for the samples with PP), the increases being in direct correlation with the cellulose content of the composite.Mechanical determinations have shown that the average values of tensile strength recorded on the achieved samples, systematically decrease at the increase in the chips content of the samples - decreases up to 10% at an addition up to 15% chips from the waste are explained by the substantially lower mechanical strength of waste paper than that of the HDPE, respective PP.

The present paper describe the production and characterization of novel collagen films containing propolis encapsulated in chitosan nanoparticles, for biomedical applications such as cutaneous wound healing. Structural and morphological details were investigated by ATR FTIR spectroscopy, SEM and nanoindentation measurements, revealing the collagen fibers aligned in a quasi-parallel distribution, which might be favorable for biomedical applications. Moreover, the vibrational marker bands of propolis were well preserved in the final polymeric mixture, indicating the stability of bioactive compounds upon the encapsulation procedure. The antibacterial effect depends on the nanoparticles concentration in collagen film, the effect being more evident with respect to E. coli than S. aureus. The antioxidant capacity monitored by CUPRAC assay, indicated a synergic effect of chitosan nanoparticles matrix and propolis extract, incorporated in collagen films.

Soil pollution with plastics represents a great threat to plants, animals, but especially to humans, as a very small quantity of the plastic which is discarded daily is recycled or incinerated in waste facilities, much of it reaching landfills where their decomposition lasts up to 1000 years and during this time the toxic substances penetrate the soil and the water. If, initially, the pollution with plastics has been identified and recognized in the aquatic environment, recent studies show that plastics residues exist in huge quantities in the soil. The present study focuses on the analysis of factors that pollute soil, so the various studies that have been carried out claim that soil pollution with plastic is much higher and increases in an aggressive manner, being estimated to be 4 to 23 times higher than water pollution with plastics, and the accumulation of microplastics in the soil has a negative impact on soil biota. Thus, once the plastic material accumulates in the soil, it is assimilated to organic matter and the mineral substitutes of the soil and persists for several hundred years.

In the recent years, the electric vehicles have drawn great attention worldwide as a feasible solution for clean transportation. The charging infrastructure for electric vehicles is expanding throughout the world, encouraged by large investments from the automotive industry, to reduce carbon emissions. The purpose of this paper is to design the shell of an electrical vehicle charger by using polymeric composite materials. The manufacturing technology is proposed and the analysis of the product behaviour during the wind action in extreme conditions is presented. The paper includes studies and research regarding the design, the manufacturing and the simulation for the action of wind upon the product’s walls. The simulations are performed for the actual used material (ordinary sheet steel) and for the proposed composite material in order to compare the results. The composite material seems to be an adequate solution for the electric charger shell.

The damages and casualties inflicted by mine and IED attacks in security challenging areas generated a strong and quick response from nations all over the world. As a part of this response several national and private research facilities increased their efforts in identifying and implementing new ways or technologies to enable blast wave mitigation. The current paper aim to investigate the opportunity of using polyurea coated steel plates as a possible new blast mitigation approach, as suggested by several investigators. In order to objectively conclude about the ability of polyurea coated plates to sustain locally blast loads several experimental tests were performed according to STANAG 4569 demands for a 1/6 scaled plate structure. In order to numerically validate the experimental results several Autodyn simulations were set-up. The numerical and experimental results exibits a fair correlation, both pointing towards a dismiss of the idea of using polyurea coated steel plates as structural and cost effective blast mitigation approach.

Designing a sample to be made by FDM 3D printing is a fundamental problem in further studies related to such printed structures as material properties vary depending on filament orientation and G-code particularities. Samples designed to simulate wall structures inside 3D printed parts have been tested to allow separate evaluation of key components in such parts. Results show a very long plastic region in filaments without imperfections. As filament strands break steps of similar values appear in the reaction force measured by the machine.

The aim of our study was to determine the wear resistance of vacuum-formed retainers (VFRs) made out of polyethylene terephthalate glycol (PETG), from four different manufacturers (Essix, Leone, Erkodent, Bio-Art), under high load forces (600 N), for 10000 cycles. Forty thermoplastic sheets were divided in four groups, each group consisting of a set of ten sheets from each manufacturer, thermoformed on two matching study models with an ideal occlusion. The Instron 8874 equipment was used to simulate the accelerated wear of VFR surfaces. The surfaces of the VFRs were visually inspected using a KEYENCE VHX-600 digital microscope, but this proved difficult because of the surface shine. 3D models were generated using a GOM industrial laser surface scanner. Several wear areas were identified, having various degrees of roughness, with no evident tear points or perforations. One-way ANOVA analysis showed no statistically significant differences in net mass loss between the four groups.