Volume 53, Issue 2

Abstract: This study presents a novel strategy for the modulation of the stop band of a polymer photonic crystal by utilizing the pattern on the surface of a written DVD. Thus, fluorescent dye doped polymer colloids (305 nm) capable to self-assemble have been obtained through soap-free emulsion polymerization and deposited on the surface of the DVD, both the top and bottom. The resulting films were investigated by SEM, UV-Vis and fluorescence spectroscopy. Depending on the design of the surface, the modification of the band gap, as well as the emission properties of the photonic crystals were observed.

Abstract: The study samples were taken Meliodent self-curing acrylic partial denture acrylics and flexible acrylate Bre.flex, used in manufacturing. The aim of the study was to observe if the irradiation of deployable dentures, there are changes in the structure of the material. Samples were subjected to irradiation at three different values of power (500, 650, and 750 W) and three different time intervals (2, 3, or 5 min), and was later examined by electron microscopy in comparison with control samples of the same material. After the microwave irradiation of materials it is made partial dentures and analysis using scanning electron microscope found no changes notable in the studied areas.

Abstract: In this paper, some of the ionized forms and aggregated forms of tetrasulphonated porphyrin TPPS4, have been separated by passing it through a composite polymer membranes of polysulfone type with N-methyl-pyrolidone and magnetite. The aqueous solutions of TPPS4 at different pH values have been prepared, characterized and passed through the membrane, leading to the conclusion that the acidic or alkaline solutions have been transformed into neutral form with certain therapeutic properties in photodynamic therapy.

Abstract: This paper is a brief characterization of composite materials and experimental system used for the measurement of heat transfer in a multilayer Board with the help of thermocouples. Also determine the temperatures, thermal gradients, thermal flows, in stationary mode, within a range of 570 s for a plate of composite materials (aluminium foil, expanded polystyrene, extruded polystyrene, universal adhesive).

Abstract: Vocal rehabilitation in patients with total laryngectomy can be done by using a phonatory prosthesis. The functioning principle of a speaking prosthesis is based on the existence of one-way valve from the trachea to the esophagus that allows the exhaled air to enter the residual pharynx and produce the voice. One of the possible complications that can occur during this process is represented by the aspiration of the prosthesis into the trachea. The aim of this paper is to present the design of a safety device, made of polydimethylsiloxane, which should prevent the tracheal aspiration of the phonatory prosthesis during primary or secondary insertion or during the replacement procedures.

Abstract: Drug delivery systems are used to protect unstable pharmaceutical active substances, to modify the characteristics of the loaded drug or to deliver the active ingredient to its specific receptor. In this study, polyurethane-based particles were obtained and the influence of stirring speed during the synthesis, the drying speed of products as well as the chain extender/polyol ratio were determined in order to describe the characteristics of the new particles. The final particles were elongated in shape and stable up to 280oC. We established that the drying speed did not influence in a noticeable manner the particles size and led to the formation of a dispersed system in which the constituents presented a high tendency to form clusters or conglomerates. The results suggested that the stirring speed during the synthesis and the chain extender/polyol ratio may be used as two important parameters which can influence the particles sizes without affecting other characteristics. In vivo evaluation on mice skin model did not reveal any damaging properties of the newly synthesized particles.

Abstract: The high content of organic matter of surface waters represents a real danger for aquatic fauna, even if their toxicity is low. Such a high rate of biodegradation leads to oxygen depletion of the waters in question and thus the suffocation of aquatic fauna. The elimination of these disadvantages by using purge technologies of catalytic oxidation may be a viable solution. The oxidation process of pollutants in wastewater that contain glycerol or molasses was performed on nanostructured catalysts based on Fe, Mn and Fe-Mn mixed. The catalysts were prepared by precipitation-coprecipitation of selected precursors and they were characterized by determination of particle size distribution. Measurements for the determination of particle size distribution were carried out using the method of dynamic light scattering. The oxidation process was conducted in a batch reactor equipped with air bubbling system, in suspension of catalysts. Efficiency of oxidation process of wastewater loaded with glycerol or molasses is expressed by biochemical oxygen demand. Compared to Mn or Fe catalyst, the Fe-Mn catalyst favors an advanced treatment of wastewater that contain glycerol or molasses by oxidation with air.

Abstract: Adhesive cements (that chemically adhere to both the tooth and the restoration material) are considered to be a highly specialised group of composite cements. They involve a three-step procedure (acid etching, bonding agents or silane and composite resin), like cements using acid etching technique and have similar physical properties as the latest. The purpose of this study was to statistically analyse the values of the adhesive bond between dental tissue and ceramic, using three types of cements (both commercial products and a product from Romania) and one type of ceramic. The separate combinations were studied in order to identify the weakest link of the interface of dental-tissue-ceramic in terms of shear bond strength. The adhesion values recorded at the interface of cement-enamel for Dualcim and Nexus cements were significantly different from those recorded for Variolink cement. The highest resistance to adhesion was recorded to the interface cement Variolink – dentin, the average being 16.19 MPa.

Abstract: This paper presents a model for the numerical simulation of Charpy test, using together Smoothed Particle Hydrodynamics (SPH) Method and Finite Element Method. Numerical simulation of the mechanical tests require the use of special material models, so the material fracture to be also simulated. The new numerical method, SPH Method, in fact a version of the Free Particle Method, presents some important advantages among which no material failure criterion to be used. Our proposed model is a model combining the FEM and SPH Model: only the specimen is modeled only by particles. The numerical results are compared with the results using only FEM and finally with the experimental data. Avoiding the material models, in fact the failure criterion, by SPH method presents a great advantages because any material model (Plastic-kinematic, Johnson-Cook, Modified Johnson-Cook, Picewise linear plasticity etc.) involves knowledge about some material constants. This aspect is very important and in the same time, very difficult. The numerical model together with some theoretical fundamentals of the SPH Method could be more then an invitation for using the SPH Method, it could be an available model able to inspire the researchers in their work. The paper is finished after some conclusions.

Abstract: PETG (polyethylene terephthalate) is a very popular plastic material when it comes to manufacturing invisible orthodontic appliances. These devices are very common nowadays because they provide an esthetic treatment alternative to braces. This type of plastic material has several indications in orthodontics: manufacturing night guards, positioners, orthodontic aligners, invisible single-layer/multi-layer thermoplastic retainers, bite splints, space maintainers, mini trays, fluoride trays, growth guiding splints, etc. The polyethylene foils provide resistant wear and rigid devices, with no substantial elastic deformation, capable of assuring a reliable orthodontic treatment.

Abstract: The paper presents the development of a cross-ply composite material reinforced with carbon fibers and epoxy matrix (CFRP). Specimens cut from composite plate have been tested in tensile, using a testing machine with hydraulic grips, assisted by full-field strain measurements equipment. Using tensile tests and ultrasounds technique, were determined the nine elastic characteristics of the orthotropic material. During tensile test, at a certain level of stress, inside the specimen, small cracks appear. These cracks become more numerous and larger with increasing of stress. A portion of a specimen without cracks and with cracks respectively, subjected to tensile, were simulated by Finite Elements Analysis (FEA). For this analysis, the composite material was considered homogeneous and orthotropic. The simulation of cracks presented inside the specimens at different stress levels has been realized using X-ray pictures. Based on the FEA determinations, the stress state in the vicinity of the cracks was determined.

Abstract: In the paper, I have brought in a method whereby a body with rheological behaviour is associated to a dynamic-equivalent Kelvin model. The equalization is made so that the forced vibration caused for Kelvin model by a harmonic external impulse is identical to the forced vibration caused in the case of the studied rheological model. It was experimentally determined the elasticity modulus and damping factor for samples with Dammar bio-matrix, reinforced with silk, flax or hemp fabric. Modifying samples dimensions, It was studied the vibrations frequency effect on the studied mechanical properties.

Abstract: The aim of this research is to develop plastic pyrotechnic compositions with a high level of moldability while maintaining safety and performance features specific to usual plastic bonded pyrotechnic compositions. In this view, theoretical and experimental studies have been performed in order to determine the characteristics of three new plastic pyrotechnic compositions and to establish their agreement with energetic materials safety and performance essential principles. These formulations have been designed to accomplish special requirements, such as processing performances, i.e. good malleability for hand packing or molding at room temperature, and pyrotechnic effects, i.e. illuminating or smoke signaling.

Abstract: Removable partial dentures (PDs) are an affordable and effective treatment option in patients with partial edentations.This aim of this study is to evaluate the differences, in the terms of patient’s compliance, in restoration of partial edentations through three types of PDs, achieved of Meliodent-Kulzer acrylic resin, Valplast® polyamide resin, respectively of BioDentaplast-Bredent acetal resin. Investigations were carried out on 78 patients (3 groups of 26 patients), to which were performed 101 PDs (35 of Meliodent-Kulzer, 33 of polyamide Valplast®, respectively 33 of BioDentaplast-Bredent) and after the accommodation period with the dentures, six assays of compliance have been conducted. The results of the research have demonstrated that PDs made of flexible materials were far more favourable than those made of Meliodent acrylic resin, and PDs with BioDentaplast framework presented the best impact. The ascertained differences are relevant in the treatment of partial edentation, for choice of the best option for one of these three polymeric denture base materials.

Abstract: This paper presents the results of the research work performed by the authors aiming at highlighting and quantifying the reinforcement effects (restoring of the mechanical strength) on transmission pipelines, generated by applying composite material sleeves in the areas in which the steel pipes of these lines have local surface defects (metal loss – like flaws). The models proposed to that purpose have been confirmed by performing some experimental programs, the first one consisting of the examination of the behaviour of some full-scale steel pipe specimens, with metal loss – like flaws (made by machining), on which reinforcing wraps made of composite material have been applied (with polymeric matrix and fiberglass fabric), subjected to internal pressure loading, up to bursting, and the second one aiming at the determination of the state of stress and strain in the pipelines on which reinforcing wraps made of composite material have been applied and which are subjected to internal pressure loading, in the elastic range. The items discussed and the results presented in the paper are mainly useful for the development and qualification of the composite materials repair systems for the transmission pipelines, according to the requirements of the standards ASME-PCC2 and ISO 24817.

Abstract: The growing utilisation of carbon materials increases the waste generation. Therefore, the development of new composites using recycled carbon fiber reinforced polymer (rCFRP) within the present study was driven by environmental and economic factors. Six configurations of new polymeric matrix composites were developed and evaluated by mechanical tests (flexural, compression and interlaminar stress), microscopic and thermal analysis. Four configurations of composites were obtained by filling the matrix with rCFRP powder and fibrous elements mixture, the reinforcement phase being produced by grinding carbon fiber reinforced polymer (CFRP) waste. The new composite configurations showed an increase in mechanical properties with rising the reinforcement fraction. The samples analyzed by stereomicroscopy reveled a fairly homogeneous distribution of the reinforcement in the matrix for 5%wt. up to 30%wt., whereas thermal analysis showed no significant changes in the glass transition temperatures of developed materials. Two configurations of composites were obtained by chemical etching of the matrix and recovering carbon fiber woven, used subsequently as reinforcement phase for new composite configurations. The same method was used for determining the volume fraction of CFRP composite constituents. Initial results demonstrate that recycled carbon remains a highly satisfactory engineering material. These results showed that recycled FRP composites can be used to develop new less demanding composite materials or improve some properties of FRP composites.

Abstract: The textile polymeric composites define a class of advanced materials, utilising fabrics as reinforcement. The geometry, as well as the structure of textile reinforced polymeric composites, are much more complex than that of composites reinforced with unidirectional fibres. The mechanical properties of textile reinforced composites are influenced by several parameters such as fibre material, the internal geometry of the fabric, number of counts, size of gap between adjacent yarns, height of woven layer, undulation and thickness of the composite lamina. Each of these factors can influence the structural behaviour and can be modelled based on its specific length scale. This paper is focused on the modelling procedures of the in-plane stiffness characteristics, specific to satin reinforced laminated composites. The method used is a compromise between the continuous and pure discrete approaches and it is associated with a mesoscopic analysis of the repetitive unit cell (RUC). The elastic properties of the textile reinforced polyester composite, using S glass fibre, arranged in satin reinforcement, are determined and analysed taking into account the variation of two characteristic geometric parameters, namely the width and the height of the reinforcing tow.

Abstract: This paper reports the fabrication of spherical particles developed as bone tissue regenerative biomaterials. Inspired by the extracellular matrix of hard tissues, the particles were generated through the mineral loading of a macromolecular matrix consisting in a bicomponent hydrogel (interpenetrated polymer networks based on gelatin and alginate). The study describes the effects of the peptide-polysaccharide ratio on the morpho-structural features, water affinity, and interaction with MG-63 osteoblast-like cells.

Abstract: The management of laryngeal trauma represents one of the most challenging problems for an ENT surgeon. The alternatives vary from a “wait and see” approach to extensive and immediate reconstructive interventions, but in all cases the risk of laryngeal stenosis remains high. This translates into a poor quality of life for the patients and increased costs for the health system. The use of a resorbable plate for the reconstruction of the affected cricoid has the advantages of requiring a single intervention and enabling the patient to return to his normal activities in a shorter period of time. It is why we present this method of approach, which can be a viable alternative in managing these difficult cases.

Abstract: The aim of this study was to point out the effect of elaboration parameters on the structure and electrochemical stability of a bioinspired hybrid film chitosan with hydroxiapatite (HAp) on Ti50%Zr alloy. The new hybrid films based on chitosan and hydroxiapatite were elaborated electrochemically using various ratio between components and different temperature and time of electrodeposition. The electrodeposition electrolye was a mixture of (NH4)2HPO4 , Ca(NO3)2 and chitosan. The structure was identified by Fourier transform infrared (FTIR) spectroscopy, and the morphology associated with elemental analysis were evaluated by scanning electronic microscopy (SEM) and X ray diffraction. Surface characterization was completed with contact angle measurements. Electrochemical tests in physiological solution (NaCl 0.9%) potentiodinamic polarization curves (tafel plots procedures). Based on experimental data we can conclude that the hybrid coating with higher HAp concentration is the most stable.

Abstract: Mixed mode four-point testing is performed on polyurethane foams. This paper presents only the results on the stress intensity factors (SIFs) obtained experimentally for a density of 325 kg/m3, although tests were done for three foam densities. An asymmetric four-point bending setup was used for determining the critical SIFs in Mode I and Mode II, and discussions on the influence of the initial crack length on the SIF values are done. As initial crack length is increased the theoretical predictions give a better comparison to experimentally obtained results.

Abstract: Composite materials based on synthetic leathers from Polyvinyl Chloride and Polyurethane with knitted fabric support are increasingly used in many sectors of industry. Two synthetic leathers have been analysed both through experimental and analytical methods in order to evaluate their elastic properties. The analytical evaluation of material elasticity was conducted based on a micromechanical approach, taking into account the Krenchel’s coefficient for Polyester fibre orientation and based on the analytical models of Leaf and Glaskin and Chamis. Experimental data was gathered using microscopic analysis and the mechanical impulse excitation test method. Results showed a good correlation with that from the experimental study. Thus, it was confirmed that the Leaf and Glaskin model and the Chamis model have a good accuracy in prediction of fibres orientation and respectively elastic properties of synthetic leather based on plain jersey.

Abstract: Various techniques have been proposed for the fabrication of surgical guide templates in orthodontics. The objective of this paper is to review the associated literature and recent advancements in this field, based on design concept , materials and technique.

Abstract: The surface relief map changes induced by methyl methacrylate (MMA) chemical treatment to the flat ridge lap area of the acrylic teeth in order to improve the bond strength to the denture base resin acrylic tooth interface, was investigated with a scanning electron microscopy (SEM), a classical non-invasive investigation method. The ridge lap area of 20 artificial acrylic molars was milled to flat. The samples were randomly assigned in two experimental groups, ten samples pertaining to each one of the groups. The flat surfaces of the acrylic molars were submitted to a different treatment. Group 1: (control group), no chemical treatment; Group 2: Chemical treatment with methyl methacrylate. Each specimen was submitted to SEM investigation with SEM: HITACHI TM3000 Scanning Electron Microscope. The SEM imaging captured data depicted obvious changes of the surface relief aspect of the samples treated with methyl methacrylate compared to control group. Acrylic teeth chemical treatment with methyl metahcrylate generates surface topography changes, visible in SEM imaging, topography aspects responsible for the improved adhesion of acrylic teeth to denture base resin.

Abstract: Recently the removal of trace element using biodegradable polymers is important. This paper involves preparation and evaluation of chitosan/ polyethylene glycol blend served as a heavy metal removal system. The author prepared various blending system with different composition ratios and different crosslinking density. Experimental results indicated that swelling degree and thermal property of the blend film were correlated with blend ratio and crosslink density. The blend film was then investigated its metal-binding performance. Copper sorption capacity was one of major potential applications in a field of wastewater treatment.

Abstract: Rubber is increasingly used in the industry of railway rolling stock, as elastic and damping element for the suspension of the vehicle or buffer and draw-gear devices. The simplicity of design, the lack of some special maintenance operations for the rubber elements and the high degree of shock and longitudinal oscillations absorption led to its increasingly use to shock isolators in order to equip railway vehicles.

Abstract: A challenge of actual research in the field of epoxy resin composites is to find paths to modify the basic properties of these polymers but keeping unchanged their excellent mechanic properties when is about epoxy resins. One valuable way is to find appropriate solvents that are compatible with the used polymer and able to solvate specific salts such as using the solution to place metallic ions inside the polymer matrix. Such an attempt might be followed by solvent removal by various physical processes having as effect the presence of metallic ions in the polymer network with possible effects regarding the transport phenomena. There are some well-known solvents as 1,4-Dioxane, 1-Methyl-2-Pyrrolidinone and N,N-Dimethylformamide that can be used also as metallic complexes precursors and their effect on the properties of an epoxy resin should be known. Present study is concerning with the modifications induced by the use of above mentioned organic solvents together with glucose and starch as an attempt to create nano-structures inside the polymer. For this study three epoxy resins had been used and tribological behaviour had been studied on a TRM 1000 tribometer from Wazau (Germany).

Abstract: The aim of our study was to establish the level of calculus and dental tissue loss, together with the quality of the dental root surface after the instrumentation performed by three techniques applied in the causal treatment of the periodontal disease – the Gracey curettes, the ultrasonic scaler and the reciprocating systems with Periotor inserts. The in vitro study was conducted on 33 extracted teeth by periodontal pathological reasons which were randomly distributed in three sample groups: group 1 (instrumentation with Gracey curettes), group 2 (ultrasonic piezoelectric scaling) and group 3 (instrumentation with reciprocating system). The quantitative evaluation of hard tissue loss after instrumentation was done by weighing each tooth before and after performing the procedure. For the qualitative analysis of the instrumented root surfaces we applied the Roughness Loss of Tooth Substance Index (RLTSI). The greatest weight loss in the samples was registered by Group 1 (Gracey curettes), but there were no statistically significant differences between the mean values of the weights between the study groups. The mean values of the RLTSI score were significantly different between groups 1 and 3, with better scores for the reciprocating system. Therefore, the results of our in vitro study revealed the fact that the scaling in deep pockets with the Periotor inserts was the least aggressive method, followed by the ultrasonic scaler and the Gracey curettes.

Abstract: The aim of this study is to demonstrate that tanned waste leather can be successfully incorporated in cement matrix and the resulted composite material can be proposed as construction material. The composite leaching tests for total chromium (maximum concentration registered = 2.76 mg/kg), which is the most used tanning agent, shown low levels in leachate lower than maximum allowed concentration MAC for non-hazardous waste (MAC = 10 mg/kg). The study proposes a new environmentally friendly recycling method for tanned leather waste.

Abstract: The effect of zinc oxide-eugenol material (Cariosan, Spofa Dental) on resin-based restorative materials (a composite resin - Premise, Kerr Company, a compomer - Dyract Extra, Dentsply, a giomer - Beautifil, Shofu) hardness was investigated. Surface hardness was evaluated using a digital microhardness tester (Micro-Vickers Hardness System CV- 400DMTM, CV Instruments Namicon). In contact with eugenol-based cement the hardness values of all tested materials significantly decreased. After cement storage in artificial saliva for 1 and 7 days, the hardness values of all three resin-based materials registered a significantly increase when compared to the samples where the materials were placed in contact with eugenol-based cement immediately after setting, but still significantly lower when compare to the samples having no contact with eugenol-based cement.

Abstract: Wool as important row material in textile processing is the oldest fibre used by people to make fabrics. In order to make products corresponding to market requirements, use of the increasingly fine wool fibres has expanded. This type of fibre is mainly imported. In order to establish optimal conditions for the experiment was chosen a central compose rotatable program, second order, with two independent variables: partial draft and spindles speed at spinning machine. Using data obtained with the program have established the optimum parameters of the spinning process. The paper examines the optimization of the spinning process of a yarn made by 100% wool, sort 70’s Nm 52.

Abstract: The lack of drug specificity for inner ear structures and the side effects of systemic administration have determined the treatment strategies to evolve from systemic administration to local application of drugs. The disadvantages of systemic or local administration of drugs for the inner ear, have led to the development of nanoparticles with specific activity. The study presents current research advances regarding the use of nanoparticles (liposomes, PLGA, dendrimers, silica or magnetic nanoparticles, etc.) in inner ear pathology treatment.

Abstract: One important direction for the mechanical behavior study of the materials is the fracture surface evaluation. This work makes a qualitative interpretation of the fracture surface from some Zircaloy-4 SEM microfractographies by using the fractal analysis technique. By reason of the current research, we introduce for the first time some new algorithms, most of them based on Box Counting methods and variations for 2D and 3D structures. The Box Counting algorithm is an efficient algorithm to compute the Fractal Dimension and can be applied directly on gray-levels images.

Abstract: In accordance with ISO 4049/2000 Standard, the alleged radioopaque restorative materials must have a radioopacity value similar or higher with an aluminum layer of the same thickness. Depth polymerization of RDC represents half the depth of hardening under experimental conditions. European Standard requires a minimum of 0.5 mm for opaque diacrylic cements, 1 mm for opaque shades of restorative materials, respectively 1.5 mm for the other materials [11]. The aim of this study is to measure the radioopacity of different nanocomposite materials and coordinate this with the material’s performance.

Abstract: The aim of our scanning electron microscopic study was to evaluate the cleaning efficiency of irrigating solutions used in endodontic treatment regarding smear layer removal from the root canal dentin walls. Ethylenediaminotetraacetic acid (EDTA)17%, citric acid(CA)10% and chlorohexidinegluconate (CHX)2% solutions were tested as final irrigants after endodontic treatment. The study was conducted on extracted teeth, divided in four groups according to the irrigation protocol used. The specimens were analyzed by scanning electron microscopy and the amount of smear layer present at apical, middle and coronal level was recorded, based on a scoring system. Data were statistically analyzed using Kruskal-Wallis and Friedman test and the level of significance was set at p[0.05. At the coronal and middle thirds we recorded no statistically significant difference between EDTA and CA regarding the smear layer removing capacity. Final irrigation with 10% CA proved to be more efficient than 17% EDTA in smear layer removal at apical level of the root canal, with p[0.05 (p=0.036), which is an important area for disinfection in endodontic treatment.

Abstract: HY zeolite (solid acid) doped poly (aniline) has been synthesized through oxidative polymerization of aniline with ammouim peroxydisulfate used as an oxidant in aqueous medium. The influence of HY zeolite contents (5wt %, 10 wt %, 15wt %, 20wt % and 50 wt %) on the conductivity characteristic, thermal stability, and specific surface area of poly (aniline)/ HY zeolite composites was performed. All samples were characterized by FTIR, UV-Vis, XRD, TGA and SEM techniques. The electrical conductivity was measured using a four-probe method and it was found to be equal to 2.2 S/cm. FTIR spectra has confirmed the presence of poly (aniline) in the form of conducting emeraldine salt and suggest significant interaction of poly(aniline) with HY zeolite.