Volume 55, Issue 1

Abstract: The paper is treating the strength analysis of the main deck structure of an inland navigation catamaran for 30 passengers. The main deck should have high stiffness and high strength to resist to external loading and endure high stresses from combined bending and torsion loads. Different materials for sandwich structure of the deck have been analysed by using the Finite Element Method in order to determine the solution which accomplish better designing criteria regarding allowable stress and deformations and total weight.

Abstract: Nowadays scientific researchers aim to develop new material designs for space structures that can withstand the harsh conditions in space environment. Another goal is to reduce the weight and the launching cost of the structures. A solution to those needs is to integrate fiber reinforced polymers in spacecraft structural components. Radiation shielding is a requirement that has to be met by the materials used to manufacture space structures. Protons are one of the many charged particles that can influence the integrity of materials in space. In the present study three material designs were developed and their ability to shield proton beam irradiation was evaluated. The material designs consist in advanced composite materials (carbon fiber reinforced polymers - CFRPs) that integrate the concept Low Z - High Z - Low Z (tantalum foil) and metallic coatings. Simulations were performed to determine the penetration depth of an ion beam (energy 15 MeV) in the proposed material designs. It was observed that the beam’s penetration depth through a CFRP sample with Ta foil (sample’s thickness 2.08 mm) was about 75% of the sample’s thickness, 58% for CFRP sample with Babbitt coating (sample’s thickness 2.28 mm), 56% for the CFRP sample with Zn coating (sample’s thickness 2.28 mm) and 55% for the CFRP sample with Zn/Monel coating (sample’s thickness 2.28 mm). It seems that the proposed material designs provide ion beam protection similar with an aluminum sample of 2 mm thickness. The experimental procedure confirmed the results obtained from the simulations, all the material designs providing protection in case of proton beam irradiation with an energy of 15.8 MeV.

Abstract: The cloves are antiseptic, antiparasitic, antibacterial, antifungal, antiviral, anesthetic, analgesic, anti-inflammatory, tonic, carminative, anti-ulcer, antithrombotic, antioxidant and anti-cancerous. They contain eugenol, tannins and flavonoids that also help to strengthen the vein wall. This paper presents the obtaining and the characterization of a polyurethane drug delivery system which can be used for the transmembrane transport of eugenol in oral therapies. The products were analyzed by pH and solubility measurements, thermal decomposition and zetasizer tests and they were applied on mice skin to evaluate their harmfulness. The results suggest that were obtained neutral pH structures with low solubility and a good thermal stability, with sizes between 241 and 289 nm and no toxicity effect was found in the case of studied samples.

Abstract: The paper presents the polystyrene reinforcing effect of some styrene-diene block-copolymers on the physical-mechanical characteristics and thermal degradation stability of the associated composites.

Abstract: The studies presented in this article are based on the variation of some constructive parameters on various types of materials for a prehension system jaws. The pneumatic actuation prehension system is part of the structure of a manipulator integrated within a teaching platform for installation. In the tests, the varied parameters were the following: the type of plastic material, the way of printing on the 3D printer bed, the degree of fill (the density) and the geometric shape. The experimental tests have resulted in an optimal version of the prehension system jaws.

Abstract: The pneumatic elastic elements are widely used in the secondary suspension of modern railway vehicles due to their important advantages compared to the conventional ones. In the present paper, the modelling and analysis of the pneumatic suspension is approached, taking into account the main elements, pneumatic enclosures and rubber elements. The analysis performed investigates the influence of relevant parameters on suspension stiffness and on its dynamic response.

Abstract: This paper describes the evaluation of the aging process of some polymeric painting materials subjected to a thermal treatment in electro insulating fluids, based on natural esters (vegetable oils). The paint layers surface morphology was comparatively characterized by FESEM technique, prior to the exposure, and after 1000 h of exposure to vegetable oil, heated at 130oC. The results show a substantial increase in the pulling resistances for all the painting materials subjected to this investigation, especially in the presence of the Kraft insulating paper and copper foil (inserted compulsory to emulate the actual working environment), due to an increase in the painting material adhesion, as well as an increase of the tensile strength of the paint layer. These findings may open new theoretical and practical research prospects, particularly in the field of preliminary treatments for materials used for heavy duty industrial transformers.

Abstract: The development of new classes of dental materials determined the apparition of reinforced polymers, as BioHPP and Trinia, used for core in non-metallic prosthetic restorations, including in implants non-metallic superstructure. The purpose of the study was to present the results of the comparative clinical trials referring to the use of BioHPP and Trinia resins as core in fixed prosthetic rehabilitation. The researches were performed on 33 patients in which we realized 71 fixed prosthetic restorations. According to the six evaluation criteria used in research, we conducted biannual monitoring meetings over two and half years period for registrations of comparative results in the use of these two reinforced polymers as core. The results of the study demonstrated that both type of these materials exhibit a certain degree of elasticity and presents many advantages, therefore these represent a beneficial acquisition in patients oral health.

Abstract: Implants and biomaterials used in hard and soft oral tissue augmentation are very complex, but predictable to use nowadays, as the technological advances haven’t skipped this field of medicine. Cases that were impossible to treat with implant retained fixed prosthesis some years ago, have become the daily practice of oral surgeons and dentists around the world. The new user-friendly products, together with simplified protocols, increased the practitioners’ predictability and success rate, thus the biomaterial industry took a huge leap forward. As the biomaterial industry keeps developing continuously, making better and safer products, the surgical and prosthetic protocols evolve and change as well. On this matter, the implant placement has become safer, using digital surgical guides. Guided implant placement doesn’t just allow the practitioner place the implant in the patient’s bone, but, moreover, it helps him place it in the correct, 3D, prosthetic position. And, thus, guiding the future bone augmentation and regeneration as well, accordingly. So, the implant placement has shifted from bone-orientated to prosthetic-orientated, offering at the same time a better primary stability for the implants, due to the prior planning. The present clinical study aims to analyze the outcome of the digital guided protocol. Unlike the free-handed surgery, the digital guided surgery allows dentists and oral surgeons to place implants according to the future prosthetic position of the crowns, even in conditions of alveolar ridges with bone resorption. Moreover, it makes possible the “one day implant” concept, the dental technician being able to create the provisional crown/s in advance, knowing precisely the future position of the implant placement. So, at the time of the surgery, the provisional crown is also put in place, guiding the soft and hard tissue healing and also giving the patient a greater satisfaction.

Abstract: The purpose of this study was to evaluate the behavior of four restorative materials in non-carious cervical lesions when subjected to exterior stresses of different magnitude. A plane model reproducing a vestibular and lingual section of the lower canine was created. The finite elements are of a two- dimensional type (2D) - quadrilater. Four restorative materials were used: Vitrebond, Dyract AP, Vitremer, Fuji IX. All materials were considered to be isotropic and elastic. Nodal charges were of 40 degrees to vertical, applied on the vestibular side at h=8.993mm to gingival crest, of increasing magnitudes:20, 40, 60, 80, 100, 120, 140, 160 N. The results of this study showed that after restoration stress values in all the elements are (with minimal differences) similar to those in the healthy tooth; a correct restoration leads to normal functioning of the tooth. It can be considered that particular types of restoring materials should be used in particular lesions to be restored, depending on the location of the lesion and the elastic characteristics of the materials and tooth structure. A correct restoration leads to normal functioning of the tooth.

Abstract: The development and increase use of the endoscopic techniques in endonasal surgery has encouraged the practice of endoscopic dacryocystorhinostomy as a trustworthy alternative to external dacryocystorhinostomy. The purpose of the present paper is to provide another insight into transnasal endoscopic dacryocystorhinostomy by proposing the fitting, at the end of the intervention, of a conformational stent model with aspiration made out of medical silicone similar to a Montgomery tube.

Abstract: In this study, newly developed polymeric composites based on poly(3-hydroxybutyrate) (PHB), cellulose fibres (CF) and plasticizer (bis[2-(2-butoxyethoxy)ethyl] adipate) (DBEEA) were subjected both to microorganism’s action in controlled conditions, and to soil’s action by sample burial. The weight loss of PHB based composites at 60 days exposure were determined in comparison with neat PHB. The weight variation for PHB based composites buried in a natural soil at 45 days and 90 days was monitored. DSC-differential scanning calorimetry and SEM -scanning electron microscopy analysis were performed on the tested composites after 90 days of soil burial. It was found that the introduction of cellulose fibres into PHB leads to the increase of biodegradability of composites.

Abstract: In recent years, the inorganic nanoparticles played an important role in the membrane technology due to their special properties, most notably being the hydrophilicity/hydrophobicity modification of the active surface of the membrane. In this paper, the polymer used for membrane manufacturing was polysulfone (PSf) via phase-inversion method. The composite PSf membranes were prepared by blending zinc oxide (ZnO), titanium dioxide (TiO2) nanoparticles and ZnO/TiO2 nanohybrid with three concentrations. Retention of Congo red dye, distilled water permeability, relative flux and relative flux reduction were tested in order to study the effects of the nanoparticles in the membrane matrix. SEM, EDX, porosity, roughness, contact angle, tensile strength and elongation measurement were conducted in this article, also. Compared with control PSf, ZnO/PSf and TiO2/PSf membranes, the experimental results indicated that the ZnO/TiO2/PSf nanohybrid membrane presents the best overall properties, including permeability, retention, and antifouling ability. ZnO/TiO2/PSf membrane exhibits a percentage increase in permeability of 254% and retention of 64.58 % relative to that of the control PSf membrane.

Abstract: The seven curcumin derivatives were deposited on palygorskite in order to obtain hybrid materials. The fluorescence emission spectra of the obtained materials show a decrease in fluorescence intensity relative to the respective dyes, due to the environments around the dyestuff molecules created in the host matrices. Absorption studies show the best adsorption on the inorganic matrix, for the compounds with the hydroxyl groups. Correlating fluorescence spectra of hybrid materials with the results for absorption spectra of the dyes adsorbtion on the surface of the clay lead to the conclusion that a high percentage of the adsorbed dye had the effect of fluorescence quenching. Thus, it was confirmed that the fluorescent properties of hybrid materials depend on the interactions established between the fluorescent dyestuff and the inorganic network.

Abstract: The present paper reports the first attempt to synthesize bicomponent hydrogels based on methacryloyl derivatives of gelatin (GelMA) and mucin (MuMA) with different compositions, with potential as wound dressings. While gelatin is widely investigated and used to fabricate scaffolds and coatings stimulating cell interactions and tissue regeneration, mucin - a macromolecule which covers the wet epithelia - remains yet under exploited as biomaterial. The influence of MuMA content on various parameters such as the affinity for aqueous media, stability in simulated physiologic media and the rheologic behavior was investigated. Also, the preliminary assessment of the drug release potential and biocompatibility were performed. The materials’ water uptake capacity and rheologic behavior depend on the pH value of the incubation media, while their composition influences the drug release capacity and cells-scaffold interactions.

Abstract: This work presents some of researches performed by the authors on execution of plastic parts required for repair works specific to certain machines and plants. Authors focused especially on the repair and reconditioning of certain assemblies which include various machine parts: special spacers, machine-tools guides and toothed gears. Methods shown herein are very simple, accessible even to small workshop and they do not require special equipment, thereby involving minimal expenses. The use of simple programs allow fast and low-cost execution of parts with an accurately determined geometry.

Abstract: Prosthetic mesh implants in hernia repair are frequently used based on the fact that lower recurrence rates are detected compared to anatomic repair. In latest years, researchers tried to answer weather there is an ideal mesh material for abdominal hernia repair. The studies tried to compare resistance, bio-tolerance, rates of recurrence and infection of several materials used in alloplasty. The results are far from pointing an unique ideal chemical structure of mesh. In our study, we compared the results of a cohort of 265 patients operated in 2010 and 2011 in our clinic for complicated abdominal incisional hernias. We compared the results of polypropylene mesh vs. polyester. Polypropylene mesh proved significantly better for preventing hernia recurrence and showed a lower shrinkage rate.

Abstract: Combining technological development in the laparoscopic field alongside the increase of surgeon’s experience in partial nephrectomy, have extended the indications of laparoscopic nephron sparing surgery to more complicated cases, increasing the role of suture materials in obtaining a good collecting system closure and hemostasis, with short warm ischemia time and low postoperative complications rate. Suturing materials are continuously developed combining new and unique designs with novel synthetic materials in order to fulfill surgeon’s exigence.

Abstract: The aim of the paper is to identify the of optimal plastic type used in obtaining thoraco-lumbar orthoses - used in the treatments of comminutive fracture, of burst fracture type of the vertebrae in the lumbar area. For this purpose, with the help of Finite Element Analysis (FEA), a theoretical study was carried out on the influence of elastic properties of plastics, used in the achieving of lumbar orthoses, on the state of tension and on the local displacements of the bone fragments from the traumatized area under the condition of the movement from the base of extension and flexion. In the study the force of flexion, the force of extension and the elastic modulus of plastic material varied on three levels. The theoretical results obtained were completed with clinical trials carried out on a total of 26 patients who suffer thoraco-lumbar comminutive fracture, burst fractures type, at vertebra T11 and were immobilized in Boston-type plastic orthoses made of: polypropylene (PP), rigid vinyl polychloride (PVC-D) and polytetrafluoroethylene (PTFE). As a result of observations, it was found that the use of an orthesis made from rigid plastic material, although it appears higher stresses in the traumatized zone, the displacements of bone fragments are smaller, the pains is higher in the fractured zone, the angle of kyphosis (LKA) close to the normal value and a better mobility of the spine (ODI indicator).

Abstract: The metal complexes and amine compounds are the most frequent categories of catalysts used in polyurethanes synthesis. Unfortunately, all auxiliary substances added to a synthesis increase the toxicological risk of final products used in a therapy. In the present study, polyether-urethane (PU) microstructures with and without catalyst were obtained. These structures were characterized by the measurement of samples’ pH, of their size and stability, were obtained and the skin irritation potential. The results show that samples with a neutral pH, PU microstructures with sizes between 120 and 165 nm and with a medium stability. It was found that the microstructures from syntheses with catalyst present increased values of skin irritation.

Abstract: Water is an important element of life, while every industry in its processes uses an important amount of water. Following processes, the water is contaminated and requires water treatment technologies. Unconventional methods to wastewater treatment, in the last years, use membrane technology as one of the most reliable processes for contaminants removal. In this article, the influence of the different concentrations of polysulfone (PSf) on the polymeric membranes properties was studied. These membranes were obtained through phase inversion method and with different polymer concentrations: 23, 25, 27 and 30 wt.%. The performance of the membranes was studied by pure water flux, permeability and retention. It has been observed that by increasing the polymer concentration, the pure water flux and the permeability will decrease. Retention was determined using methylene blue, which is one of the most utilized dye from industry and it could be observed that by increasing the polymer concentration the retention degree of the pollutant also increases. In order to explain the evolution of membrane permeability at different polymer concentrations, surface hydrophilicity by contact angle method and cross-section SEM imaging were used.

Abstract: Since the time of their introduction into medical practice, biomesh were criticized for their lack of tissue integration and the rejection due to the organism reaction for an element that is not autologous. The mechanisms by which these changes of contact between the tissue and the foreign material were produced were initially incompletely understood, but over time the involvement of the immune system mediated by the cellular or humoral local inflammatory reaction was established.

Abstract: Graphene oxide and graphite filled polyester composites were prepared by using conventional melt-mixing methods in order to improve tribological performance of polyester. It was investigated friction stability, microhardness, friction coefficient, and specific wear rate of the composites in details. It was found that the presence of graphite and graphene oxide influenced friction coefficient and wear rate of the composites. Graphene oxide decreased wear rate with increasing of test speed and graphite decreased wear rate for composite for all speeds. Tribological performance of the polyester/graphene composites is mainly attributed to bigger thermal conductivity for graphene, which can easily dissipate the heat which appears during the friction process at bigger forces. The positive influence of graphite on coefficient of friction (COF) of the composites is the result of the clivage of graphite layers during the loadings due to van der Waals weak bonds between the graphite layers.

Abstract: Materials based on acrylic resins are commonly used in dental practice. These are obtained through various technologies, which determine the chemical, physical and biological properties of the final product, which can influence the inflammatory processes in the periodontal tissue. To evaluate the effects of these materials, we identified the concentrations of TGFb1 and IL8 in crevicular fluid in 23 patients with temporary dentures made of polymethyl methacrylate by two polymerization methods: (1) a product processed immediately prior to application, wherein the polymerization of the material occurs in the oral cavity; and (2) a product processed in the dental laboratory from a prepolymerized block (block-type PMMA), and applied directly into the patient’s mouth. The results of our study revealed a significant correlation between the IL-8 inflammation marker and the clinical parameters in the periodontal tissue exposed to the polymerization of the material in the oral cavity.

Abstract: This paper presents the development and characterization of polymer composites based on natural rubber, crosslinked using two types of vulcanization systems, as follows: the classical method using sulfur and curing accelerators and the method using peroxide in the presence of a polyfunctional monomer - trimethylolpropanetrimethacrylate. The composites were made with 0 parts to 100 parts rubber (phr) and 40 phr filler content. The physical-mechanical characteristics of resulting composites depend on the crosslinking method and on the composition. The mechanical parameters of materials were derived by processing the transmissibility curves, derived for samples with known dimensions and density. The main vibration frequencies and the quality factor, derived in the vicinity of resonances, allow to derive the elasticity and internal damping of materials.

Abstract: The main aim of this study was to prepare and characterize polymeric nanoparticles containing two cardiovascular active pharmaceutical ingredients: valsartan (VAL) and amlodipine besylate (AML). Six formulations were evaluated with different ratios of AML:VAL:PLGA (1:16:17, 1:16:34, and 1:16:51) and different stirring speed (1200 and 2400 rpm). Encapsulation efficiency (EE, %) and particle size analyses were performed to characterize and optimize the formulation. All loaded nanoparticles showed a high EE (%), nano-size, negative x-potential and a high homogeneity.

Abstract: Utilization of computer-aided design/computer-aided manufacturing (CAD/CAM) rapidly increases in dental medicine. Making of computer-engineered complete denture is based on scanning of patient data, designing of prosthesis and milling or rapid prototyping. This is digital denture, term that includes innovative devices, software programmes and corresponding materials. Industrially polymerized cross-linked polymethyl methacrylate (PMMA) is the material used for fabrication of digital denture. The aim of this study is to analyze the different cross-linked PMMA used for fabrication of CAD/CAM complete denture.

Abstract: The study aimed to assess the changes of the surface roughness induced by some acidic beverages on indirect restorative materials by using profilometry. Twenty samples of three composite resins (Ceramage, SR Adoro, Luna-Wing) and three ceramics (IPS In Line, Hera Ceram, Reflex Dimension) immersed in three acidic beverages (Red Bul, wine, Coca Cola), for 5 minutes, three times daily, 14 days. The control samples were immersed in artificial saliva during the study periode. After the end of the erosive cycles and before to determine the surface roughness of the samples in the study groups, all the samples were immersed in artificial saliva for 18 hours. The surface roughness was determined in relation to the baseline surface using profilometer Perthometer_M1 (Mahr Gottingen GmbH, Germany). The immersion of the indirect restorative materials tested in the three acidic beverages lead has resulted to changes in their surface roughness. The most aggressive was wine, followed by Coca Cola, and Red Bull.