Volume 56, Issue 4

Abstract: Two types of biocomposite materials are made (original fabrication recipes) containing different resins as base: version A with natural resin and version B with polyester resin. For both of them the reinforcement element is a natural one namely fir needles. The samples are mechanically tested by compression in order to obtain the stress-strain curves and the elasticity longitudinal modulus.

Abstract: Natural polymers are biodegradable and biocompatible and can be used as carriers of pharmaceutical active compounds, with good results for the enhancement of their stability characteristics.Plant extracts of the Cariophyllaceae family are of great interest due to antioxidant, anti-inflammatory, carminative, anticancer, antibacterial, antifungal, antiviral properties, and more recently, the ability to inhibit intestinal carboxylation and reduce obesity by complex mechanisms.The aim of our study was tocharacterize the Stellaria media aqueous extract from the point of view of total polyphenols (using Folin-Ciocalteu method) and antioxidant capacity, as well as the efficiency of inclusion of Stellaria extract in calcium chloride alginate beads by two different methods. In the same time, the size of alginate microcapsules was investigated along with the released efficiencyfrom the polymeric matrix in different biological fluids.Two different methods for encapsulation of Stellaria media extract were developed in this work, using calcium alginate beads. Encapsulating efficiency shows a better approach within the method in which the extract was in situ encapsulated in “pearls”-shaped beads.

Abstract: One of the major disadvantages of epoxy resins when they are used to impregnate a fabric or when they are used to obtain laminates is their rigidity that leads in loading conditions to the matrix fracture followed by breaking of fabric due to a shearing mechanism in which the two free parts of the matrix fracture acts as a scissor. During the design of a composite material or structure such behavior of the matrix has to be taken into account and the problem could be solved if the rigidity of the matrix is reduced. The present study is about changing the value of this parameter by using an organic polymer solvent and a thermoplastic polymer to modify the basic properties of an epoxy resin. At this time an analysis of thermal properties of polymer blends is done to determine the effect of solvent and thermoplastic polymer presence inside the epoxy matrix.

Abstract: The extension of use of light advanced polymer composites from structural parts of an aircraft to all kinds of components of the engine is presently very limited by the knowledge of both technological development process and materials behaviour during service. The paper comes to meet an area of interest for many researchers and large integrators and manufacturers, by presenting the first steps made into the manufacturing of a carbon fiber reinforced composite blades for a centrifugal compressor impeller. An existing metallic reference impeller was redesigned, air flow studies were achieved to establish new design performances, precursors (type, volume fraction, architecture, distribution) were defined for the CFRP (Carbon Fiber Reinforced Polymer), stress analyses were performed on proposed structural materials configurations. Furthermore, the paper award an important section to manufacturing process stages, the manufacturing technology used and first developed trials. It was concluded that an entire impeller CFRP (Carbon Fiber Reinforced Polymer) manufacturing can and shall be the next step of the study, using autoclave technology.

Abstract: Orthodontic appliances usually require the joining of different stainless-steel parts in order to achieve adequate control over tooth movement during the active treatment. The aim of this study was to assess the tensile and shear breaking force of the joints between forty orthodontic bands and forty attachments (buccal tubes), joined by laser and TIG welding, without filler material. For the laser welding technique, we used an XXS Laser (OROTIG) welding unit and for the TIG welding technique, a PUK D2 (LAMPERT) welding unit. The tensile and shear breaking force of the welded joints was determined using the Z010 Zwick/Roell testing machine. The independent-samples t-test showed statistically significant differences between the laser and TIG groups for both the tensile and the shear breaking force tests, the laser welded samples having better mechanical strength than the TIG welded samples. For practical use, under normal loading forces, both techniques are suitable for this particular application in orthodontics. In patients with parafunctional habits, that could develop higher bite forces, the failure of the welded joints might occur if the welding surface is not increased, especially for the TIG welding technique.

Abstract: Bulk metallic glasses (BMGs) represent a viable alternative for replacing classic materials used in medical devices. This paper presents the research conducted in order to obtain copper based BMGs using two different chemical compositions: Cu48Zr47Al5 and Cu45Zr45Al5Ag5. The samples were obtained by copper mold casting and their structure and properties were investigated using X-Ray diffraction (XRD), differential scanning calorimetry (DSC) and optical microscopy.

Abstract: The analysis of reinforced polymers is one of the most important sources of information for materials properties designers. In this regard, due to their intrinsic properties, the fabrics play an essential role when they are used as reinforcement elements. The composites properties can be designed by alternating various types of fabrics, by modifying the orientation of every reinforcement layer, by modifying the matrix properties or by choosing the matrix. This study regards the tensile behavior of four fabric reinforced composites with four different epoxy resins as matrix. All the materials have the same reinforcement structure but the matrix is, in each case, another epoxy resin and more two classes of materials had been studied one is containing the natural polymerized matrix materials and the other one the materials that had been thermally treated according to technical sheet of each polymer. The tests were done one year after the materials formation.

Abstract: Either considering chemical munitions or chemical improvised explosive devices, the armies should be able to counter their effects from two different perspectives: the agent used and the way to disperse it. While the agent to be delivered can be more or less lethal, the real factor that gives efficiency to the attack is the manner the agent is delivered. The state-of-the-art tested garment indicate that current knowledge regarding protective equipment for chemical warfare agents remains very limited. In this context, the present study aimed at the possibility of using the MWCNT-OH-based polyurea-composite material, obtained by our group in a previous study, in the field of protection against hazardous chemicals.

Abstract: The increased demand for energy sources is the driving force to convert organic compounds into alternative fuels. Plastic waste disposal affects the environment, since they are not easily recycled and, during the recycling process, they can produce waste ash, heavy metals, or potentially harmful gas emissions. In the plant design for plastic converting into fuel, the chemical reactor is one of the advanced equipment in the field of chemical and process engineering. This study emphasizes the feasibility of pyrolysis process for valorisation plastics by producing energy-efficient products. In this respect, samples of polypropylene, polyethylene and polystyrene were used as models and subjected to pyrolysis processes at 450 °C, in the presence of two types of mesoporous silica materials, MCM-41 and SBA-15, using a modern developed reactor. The use of mesoporous materials increased the calorific value of the obtained oil and gas, thus improving the economic potential of the process end products. This study dealt with the extraction of oil from plastics termed as plastic pyrolysis oil (PPO) and plastics pyrolysis gas (PPG), with a composition rich in different types of hydrocarbons and they can be marketed at much cheaper rates compared to that present in the market.

Abstract: For more than half a century, the use of plastic in agriculture has given farmers opportunities for growing fruits and vegetables regardless of the season, and at the same time achieving better quality compared to open-field cultivation. The use of plastics, through various specific techniques, helps reduce the consumption of various resources such as water, energy, fertilizers or pesticides.We could say that without these plastics a significant amount of cultivated fruits and vegetables could not be harvested in early conditions and could not be preserved and conditioned in controlled parameters.Plastic is a very important material for economy but also in everyday life. The use of plastic in agriculture has increased from year to year, thus contributing to both the increase of agricultural production and the improvement of the quality of food.Plastics are a wide range of synthetic or semi-synthetic materials that are used for various purposes. In the plastic industry, are used raw materials, such as cellulose, coal, natural gas, salt and, of course, crude oil. Plastics are extremely versatile materials and are ideal for a wide range of applications for industry as well as for consumers.

Abstract: Single walled carbon nanotubes (SWCNT) and multi walled carbon nanotubes (MWCNT)/ vinyl ester nanocomposites with three different contents of carbon nanotubes (CNTs) have been prepared by the simple melt-compounding method. A fine and homogeneous dispersion of CNTs throughout vinyl ester resin has been noticed by SEM images. Two mechanical tests (compression and three point bending test) show that, compared to neat vinyl ester resin, compression modulus and compression strength of the nanocomposites have been significantly improved by about 9% and 14%, respectively, when incorporating only 0.15 wt.% MWCNTs. Furthermore, thermal behavior of SWCNT and MWCNT/ vinyl ester nanocomposites has been investigated and discussed based on differential scanning calorimetry (DSC) and thermo- mechanical analysis (TMA). Glass transition temperature (Tg) and coefficient of thermal expansion (CTE) have been increased and decreased, respectively, with increasing of CNTs content.

Abstract: The bulk metallic glasses composites are a new class of bulk metallic glasses (BMGs), containing an amorphous metal matrix and reinforcing materials of metallic or ceramic nature in order to obtaining the desired combination of mechanical properties including strength, hardness, ductility and toughness. Composite materials of cylindrical form with the diameter of 10 mm and 5 mm in height were successfully prepared by hot-pressing of Zr – based glassy alloy powder and Fe – based nanocrystalline alloy powder in different volume fraction. The samples obtained were structural investigated by scanning electron microscopy and X-Ray diffraction and mechanically characterized by hardness and compression tests. It was found that increasing the volume ratio of the Fe-based nanocrystalline alloy up to a certain value leads to an increase in hardness and mechanical compressive strength.

Abstract: Flame straightening is a technology process used to eliminate deformations. This method relies on local heating of the material to correct geometry or damaged parts. In the local automobile services its main use is for repairs of less critical deformed components. The maximum temperature and thermal gradient, heating time, cooling rate and number of heating cycles affect the mechanical properties since local heating can alter material microstructure. The aim of this research was to determine the mechanical characteristics of thin steel plates repaired by local heating associated with plastic deformation (similar to hot working) and cold straightening (similar to local cold working) for automotive side and door panels made of structural steel. Thin sheet plates, 0.9mm thickness, were deformed by impact and repaired by local heating using the flame and induction heating then plastically deformed while hot as well as straightened without heating. The heat repaired samples were studied by light microscopy to determine microstructure change and samples were tensile tested to determine their mechanical characteristics. Local excessive grain growth generates anisotropy, the assembly behaves as a composite material with regions that show significant plastic deformations while others little or no deformations at al. Without procedures adjusted to each material repairs involving heating are to be avoided, cold working should be employed when replacement is not possible.

Abstract: This study comprises the studies performed on six in vivo failed centromedullary fixation devices, three made of stainless steel 316L and three of titanium alloy Ti-6Al-4V. Fractographic studies were performed using stereomicroscopy and scanning electron microscopy while metallographic studies were performed by light microscopy. Loading mode which caused failure was inferred based upon surface fracture topography and light microscopy studies were performed to observe if abnormal microstructures or inclusions could be the cause of the failure. In all cases the chemical composition was according to standard specifications and the microstructures appeared normal with low inclusionary content. The mode of failure was found to be fatigue and the crack initiation site was on the implant surface on roughness features and surface induced defects.

Abstract: The aim of this study is to investigate the effect of alloplatic graft and platelet rich fibrin (PRF) , alone or in combination, on bone regeneration in Wistar rats femural defects. Bone defects were prepared in adults male of 20 Wistar rats. In a group of ten, the defect was filled with synthetic ceramic graft as an alloplastic graft; the others 10 were grafted with this alloplastic graft mixed with PRF. All animals were sacrificed on the 90th postoperative day and the femural bones were removed, histologic sections were prepared and the experimental sites were examined microscopically. Histologic examination revealed more new bone formation in the defects filled with alloplastic graft mixed with PRF than in the defects grafted with alloplastic graft alone. The platelet rich fibrin combination effectively induces new bone formation.

Abstract: Most of the fixation implants for tibia fracture are made of various metallic alloys based on titanium or even stainless steel. But modern technologies and advanced materials offer endless opportunities of using polymers combined with various fillers to enhance and adjust mechanical properties in order to be as suitable and convenient for any patient.

Abstract: Polylactic acid (PLA) is one of the most extensively used biodegradable aliphatic polyester produced from renewable resources, such as corn starch. Due to its qualities, PLA is a leading biomaterial for numerous applications in medicine as well as in industry, replacing conventional petrochemical - based polymers. The purpose of this paper is to highlight the mechanical properties, such as tensile stress, of pure PLA specimens in comparison with PLA based-composites, with three different added materials in PLA mass: Copper, Aluminum and Graphene, as well as the influence of filament angle deposition on these properties. In order to check if the the filling density of the specimen influences the ultimate tensile stress (UTS), three different filling percentages (60%, 80% and 100%) have been chosen in the experimental tests. In this context, the mechanical characteristics of four different filament types based on PLA material, starting from pure PLA to PLA with Aluminum, Copper or Graphene filler are compared. Understanding and controlling these parameters is essential for the successful use of PLA and PLA-based composites in different areas such as medical applications, sport equipments and light industry.These tests have been performed due to the fact there is a lack of information concerning the mechanical properties. In the scientific literature, such information is only available for expensive printing systems; for open source printers (as those used in these tests), the information is poor and for some new materials, even inexistant. According to the technical specifications, for an expensive printer the cost may exceed 3000 Euros, with a minimum layer resolution of 100 m, this type of printer can reliably reproduce many 3D objects accurately, in quiter conditions.

Abstract: This work are made for determine the possibility of generating the specific parts of a threaded assembly. If aspects of CAD generating specific elements was analysed over time in several works, the technological aspects of making components by printing processes 3D through optical polymerization process is less studied. Generating the threaded appeared as a necessity for the reconditioning technology or made components of the processing machines. To determine the technological aspects of 3D printing are arranged to achieve specific factors of the technological process, but also from the specific elements of a trapezoidal thread or spiral for translate granular material in supply process are determined experimentally. In the first part analyses the constructive generation process of a spiral element. In the second part are identified the specific aspects that can generation influence on the process of realization by 3D DLP printing of the two studied elements. The third part is affected to printing and determining the dimensions of the analysed components. We will determine the specific value that can influence the process of making them in rapport with printing process. The last part is affected by the conclusions. It can be noticed that both the orientation and the precision of generating solid models have a great influence on the made parts.

Abstract: The purpose of this study was to assess the accuracy of two 3D printed dental models manufactured after intraoral/IO and extraoral/EO scanning. A dental study model (KaVo Dental GmbH/Germany) was used as a reference for this research; this model was scanned with an industrial scanner (XT H 225 ST/Industrial CT scan/Nikon Metrology Inc./U.S.A.) and a reference STL file was generated (coded M1). Two 3D printed models (Form2/FormLabs Inc./U.S.A.) were produced via IO scanning (TRIOS 3 Battery Cart/3 Shape/Denmark), respectively via EO scanning (Swing Dental Scanner/Dof Inc./South Korea) of the reference dental model. The 3D printed models obtained were scanned with the industrial scanner, resulting in other two STL files (coded M2, respectively M3). All the STL files obtained (reference M1; M2; M3) were compared in pairs, using a 3D analysis software. Good results were achieved in obtaining 3D printed dental models via IO or EO scanning, yet, the 3D printed dental model obtained via IO scanning (M3) showed slightly improved dimensional compatibility with the reference model (M1) in comparison with the 3D printed dental model manufactured via EO scanning (M2).

Abstract: In recent years, in many areas of civil engineering applications, fuzzy logic models have been used. The aim of this paper is to develop a fuzzy logic model to predict the adhesion stress in polymer concrete. Availability of experimental data was required to develop the relationship between the mixture variables of polymer concrete and its measured properties. The basic parameters considered in this study were epoxy resin, silica fume, aggregate sort I and aggregate sort II dosage. Using Mamdani fuzzy model, with the said parameters, we effectively predicted the adhesion stress in polymer concrete accurately by taking into account the parameters of the problem. In these circumstances, data can be acquired in a short period of time without wasting material, with decreased design cost, all this without attempting experiments and thus saving time. This study showed that the model used has a good prediction and generalization capacity with acceptable errors.

Abstract: The article presents the process by which, with the help of 3D printing technology, the piston of the differential injection device was produced using ABS material. It was made with fused filament fabrication (FFF) technology, and the smoothing process was used to improve the surface quality. The piston is part of a complex equipment for underground fertilization of agricultural crops.

Abstract: At young ages the spinal column, which is the central support system of the human body, is susceptible to malformations, especially if the children are sitting in an incorrect position for long period. Our study examines the case of several elementary school students from a developed rural area. The aim of this study to analyze the impact of long sitting hours (5-6 hours) in incorrect position at on the normal standing up position at elementary school students. The study group for our study consisted of 80 elementary school students were recruited from a local rural elementary school. Each student was evaluated using a Kinect based system to determine their general standing up position. For 14 weeks, twice a week, each student has executed 5 type of Schroth exercises to improve their general body position. The first evaluation has shown that the students general standing up position is affected from the long sitting hours in the school benches. Most of them have shown misalignments at the shoulder and hip levels. In many cases one of the shoulders was higher than the other and the same is true for the hips as well. After 14 weeks of physiotherapy based on Schroth exercises the miss alignments were reduced to a bare minim. The results have shown that long sitting hours in incorrect positions can affect the spinal column and the standing up posture of the human body. In many cases malicious postures start to develop from childhood. If not treated they can transform in hyper-kyphotic and scoliotic postures which can induce other complications. If these malicious postures are observed in early stages of the children and with only 2 hours a week of physiotherapy based on Schroth exercise the postures can be corrected and the hyper-kyphotic and scoliotic postures can be avoided.

Abstract: Finite element analysis is the most commonly used methods in orthopedic biomechanical research. The study aims at improving the common understanding of the behavior of the pelvis and the biomechanics of the pelvic ring in a healthy and osteoporosis configuration. We performed a finite element analysis using the ANSYS program. The study mainly focused on bones and the joints and the complex modelling of the ligaments was ignored. The results of our study showed that the stress distribution of the pelvis with osteoporosis was changed compared with normal pelvis. In addition to, in the healthy bone, where the maximum stress values are concentrated around the obturator foramen (anterior arch of the pelvic ring), in the osteoporotic bone, the maximum stress also appear at the posterior arch of the pelvic ring (especially in the sacrum.

Abstract: The topic of this paper refers to the influence of the plasticizer and the processing mode upon the characteristics of the poly(vinyl chloride) (PVC) composites. Thereby, in this study two types of industrial plasticizers were used to highlight their influence upon the properties of final composites. The employed lubricant was stearic acid, the most common and cheapest additive used in the industry for cables manufacturing. For economic reasons, calcium carbonate of 2 m size was used as reinforcing agent. Further on, two sets of samples were prepared, targeting the influence of the processing mode upon the properties of final composites. Beside the structure (by FT-infrared), thermal behavior (thermal analyses and differential scanning calorimetry) and mechanical properties (dynamic mechanical analyses, tensile strength and elongation at break) of PVC composites, the limiting oxygen index (LOI) and the overall morphology of the samples were also investigated.

Abstract: Our study’s goal was to underline the differences between the girls’ and the boys’ representative in terms of age, in what concerns the moving speed and the effort perception during the dynamic balance when walking on the slackline throughout the activities specific for the Development through Education and Adventure (DEA). The results have shown the fact that the boys have a better speed movement on the slackline rather than the girls, allowing us to conclude that the boys’ dynamic balance is superior to the girls’ balance on both studied age categories. Perceiving the physical effort through heart rate is different according to age category when walking on the slackline for the groups of the study.

Abstract: The main goal of this research study was to understand the role of the vegetable oil in the obtaining process of nanoparticles by emulsion solvent evaporation method, respectively the effect of the vegetable oil upon the final characteristics of hybrid PLGA-pomegranate vegetable oil (PMG) nanoparticles. Colloids with mean diameter around 125.6 nm (PLGA-np) and 141.7 nm (PLGA-PMG-np) were obtained. It was noted that the addition of the vegetable oil has a key role in the primary emulsification process leading to hybrid colloids with improved the uniformity (PdI) and stability of hybrid nanoparticles.

Abstract: Ephedrine is an illicit drug, classified as precursor for methamphetamine, which is also used as stimulant, appetite suppressant, decongestant or asthma. In this study, novel molecularly imprinted polymer (MIP) films were prepared by sol-gel derived techniques, using N-(2-aminoethyl)-3-aminopropyltrimethoxysilane as functional monomer, to recognize ephedrine from aqueous solutions. The films were obtained by air-spraying the precursor solutions, with various concentrations of monomer and template, on glass supports. Infrared, thermogravimetry, ellipsometry, optic and atomic force microscopy analyzes of films provided information regarding the effect of molecular imprinting upon the physical properties of films. Further on, batch rebinding evaluation indicated that thinner films present high affinity for ephedrine, resulting in 6.2 imprinting factor after 15 minutes of contact, which attests the ability of the novel MIP films to recognize and rebind ephedrine.

Abstract: In this study a fluid elastomer was applied by two different methods on a martensitic stainless steel substrate, in order to obtain coatings for protection against cavitation. The investigations regarding the resistance to cavitation erosion of the elastomeric coatings were carried out by the indirect vibratory method using the values of the cumulative erosion (material loss) developed during a testing period of 600 minutes with a 20 kHz ultrasonic vibrator at a peak-to-peak amplitude of 50 μm. The experimental results obtained in the laboratory have been processed statistically. They clearly pointed out that the deposition method significantly influences the cavitation resistance of the elastomer.

Abstract: This paper describes a hip implant model designed to assess the Fused Deposition Modeling (FDM) process for manufacturing investment casting master patterns. In addition, an indirect approach toward manufacturing master pattern via silicone rubber moulding in conjunction with 3D Printing process manufactured hip implant master pattern has been investigated. The dimensional accuracies of the manufactured AM master patterns and the wax pattern are presented. Finally, cost and lead time comparisons carried out between FDM ABS pattern manufacturing, indirect pattern manufacturing via silicone rubber moulding and conventional pattern manufacturing by metal mould are also presented.

Abstract: Nowadays world is exposing a continuous spreading of composites applications and, as a consequence an enforcement of scientist efforts toward such materials design, testing and modelling. Since polymer reinforced materials are covering a huge area of applications it is obvious that the researchers interest is oriented to these materials study in all its aspects. Fabric reinforced polymers represent a very attractive solution from the manufacturers’ point of view, especially in the case of thermoset polymers where the lay-up method is the most used to form composites. This study is about tensile behavior of lamina or plies of thermoset matrix fabric reinforced materials. The aim of the study is to determine the role of the matrix and the role of fabric (fibers type, specific weight) on the tensile response to gather valuable information regarding the design of layered materials.

Abstract: The purpose of this article is to present an overview of the trend of using, on a wider scale, plastics in the automotive industry. It is presented the realization of PLA-TPU-Blends with a biogenic mass greater than 90%, by mixing thermoplastic Polyurethan (TPU) with Polylactid-Acid (PLA) at IKT University of Stuttgart. In order to estimate the possibilities of use of bio-materials made from PLA and TPU, the properties were compared with standard thermoplastics such as Polypropylen (PP), Polyethylen (PE), Polyamid (PA), as well as with better performing materials from the engineering thermoplastics range. PBT, ASA and their derivatives. Notable are the properties of PLA-TPU-Blends compared with standard thermoplastics PP, PE, PA. The results show PLA-TPU-Blends superiority in Yeld strength compared to the types of Polypropylene homopolymer (PP-H), block-copolymer (PP-B) and randompolymer (PP-R), the properties being adaptable by flexible modification of the ratio between the components, according to the requirements of the application. Using suitable additives to make components compatible, there were created blends which were partially cross-linked, but their properties remain of thermoplast. When reinforcing PLA-TPU-Blends with fibers (glass and natural), the components also react with the groups (-OH) on the fiber surface, thus making a good connection between fibers and blends, which prevents the so-called pull-out-effect. PLA-TPU-Blends reinforced with natural fibers can be used to make the interior body elements of vehicles. The paper also presents a comparison between bio-materials made at IKT University of Stuttgart with Polyethylen (PE) and other industry standard bio-materials.

Abstract: The article presents the technology and process, whereby a small-scale demonstration model and the real-scale prototype of vertical axis wind turbine blades are produced using rapid prototyping technology (3DP) and GFRP surface coatings, which help to improve the mechanical properties. In the end of the article the results of the production process and the advantages of combining these technologies are presented.

Abstract: Explaining the phenomena occurring at the level of relative friction surfaces has become increasingly complex and often contradictory. Research over time has shown that the friction coefficient for a friction coupler is not a constant magnitude, as Amonton-Coulomb has stated, its values being dependent on a multitude of factors (normal load, slip rate, the nature of the material, the state of lubrication, etc.). The laws of the two are considered to be valid only under conditions of dry rubbing and elastic deformation of the surfaces in contact. The present paper proposes in the first part a study on the theoretical expression of the coefficient of friction. The experimental part of the paper highlights the variation of the coefficient of friction with the speed, loading and processing of the contact surface. It was made on a tribological stand of pin / disc type, and the coupler used was polymeric material called Turcit (for disc) / general purpose steel (for pine).

Abstract: The aim of our study was to evaluate fracture resistance of the PMMA complete dentures and to make a comparison between the classic acrylic maxillary complete dentures and the metal-reinforced ones, in terms of fracture resistance during function and to compare the fracture pattern of the two groups of complete dentures. We used maxillary complete dentures made of heat-processed acrylate, 5 exclusively and 5 in which a metal-cast net in the form of a mesh was inserted after being casted, worn by patients for a period of 5 years. A bilateral progressive force was applied to the PM2-M1 area until the samples failed, recording the force value at which the first change occurred. A Universal Loading Machine was used. The results were analyzed using the ANOVA method. For the classic acrylic complete dentures group, the minimum fracture force value was 1060 N, the maximum fracture force value being 2443 N. For the reinforced complete dentures group, the minimum fracture force value was 3320 N, the maximum value being 3760 N. Statistical analysis of data using the ANOVA shows that the results are statistically relevant, with a p value of 0.000137 (p[0,05). All the dentures from the classic acrylic complete dentures group fractured presenting two or more fracture lines, most of them involving also fractures on the acrylic teeth and breaking into multiple pieces, while all the dentures from the reinforced complete dentures group fractured presenting one or two fracture lines, most of them without detachable fragments and involving also fractures on the acrylic teeth.

Abstract: FDM is 3D printing technology using mainly PLA and ABS as filament materials. PP has close characteristics to PLA and, due to that, is a potential material for for deposition. Paper aims to analyse the behaviour of PP during heating cycle specific to 3D printing process. Macroscopic and microscopic analysis of the deposited strings have been performed. They revealed less stiffness of the PP deposition comparing to PLA, which is due to the lower viscosity of PP. DSC Thermal analysis has been done at it revealed a 30% higher heat flux in PP comparing to PLA and that increases its fluidity. It was recorded a difference between the elongation viscosity of the PP filament and the PP deposited by FDM process. After 5s the deposited PP proves higher values for the elongation viscosity. Dynamic shear rheology measurements the was applied on samples deformed under 210 kN at 190oC. It has been found that the PP requires lower storage energy and that means that it has a lower viscosity for the entire range of applied frequencies. In the same time, the complex viscosities prove different behavior. To improve the control of the deposition shape, it is necessary to reduce the extrusion temperature with 4-5%. That leads to economy in power consumption.

Abstract: PLGA (poly-lactic-co-glycolic acid) nanoparticles represent an important synthetic biocomponent that has the potential to be a promising carrier of drugs, proteins, nucleic acids, due to its biodegradability and minimal side effects. The aim of our study was to observe the antioxidant effect of vitamin E loaded in PLGA nanoparticles administered over a period of 3 weeks in Wistar rats treated with a hypercaloric diet. Glutathione (GSH) and malondiadehyde (MDA) biomarkers determined from liver lysate were analyzed to evaluate the oxidative stress (OS) induced by the hypercaloric diet. The results of our study revealed a statistically significant increase for GSH and vitamin E in group 2 of Wistar rats receiving hypercaloric diet and a daily dose of vitamin E versus group 1 (p[0.005). The antioxidant effect of vitamin E was also observed by the statistically significant decrease of MDA in group 2 of Wistar rats compared with group 1. The daily dose of vitamin E has improved the liver redox status of group 2 Wistar rats.

Abstract: The paper presents an analysis regarding the use of ERTALON 4.6 polyamide in high thermal shock systems. The behavior of ERTALON 4.6 polyamide mounted on high thermal shock systems was studied using high speed thermal imaging cameras. In the same time its mechanical proprieties were studied with the purpose to determine if it can withstand the stresses that occur during rifle firings.

Abstract: Treatment of crown root fracture is complex and requires an accurate diagnostic and treatment plan. The purpose of this article is to report a case of a maxillary central incisor with a crown-root fracture with pulp exposure treated and rehabilitated with the preservation of pulp vitality using a micro-pulpotomy and pre-mixed bioactive endodontic cements followed by zirconia restauration, a bioinert ceramic material, milled using CAD/CAM technology. The preservation of pulp vitality using premixed bioceramic materials, ensures the continuation of dentinogenesis with its benefits, higher resistance of radicular walls against fracture, smaller diameter of apical foramen as well as creating conditions over time for a post retained crown with better aesthetic results.

Abstract: The thermochemical stability of a MOL (mineral oil) electroinsulating mineral oil was studied by the gas chromatography technique, compared with a Voil (vegetable oil) electroinsulating fluid based on natural esters (oil), exposed to a longer (1000 hours) thermal treatment (110 ± 5 °C) in contact with the core transformer plate (silicon steel sheet) both blank and covered by immersion with three different types of lacquers (L-G epoxide, L-528 alkyl epoxy-melamine copolymer and L-S polyurethane). Experimentally it was noted that during the thermal treatment applied and in contact with the silicon steel sheet, the investigated oils have produced mainly C2H4, CH4 and H2. The total amount of flammable gases formed in Voil (vegetable oil) is about 7.5 time lower than in MOL. It has also been found that the lacquer coating of the silicon steel sheet does not change the mechanism of gas formation processes in the investigated oils, as well as the fact that the oxygen content of the investigated oils decreases monotonously during the thermal treatment applied due to either the formation of CO2 and CO and the oxidation processes of investigated lacquers.

Abstract: The article presents a promising technology for medical applications - additive technology by thermoplastic extrusion. Some conceptual models for knee prostheses of different constructional forms have been made using FDM technology. Different materials, including biocompatible, were considered and different 3D printing equipment was used to choose the variant with the most optimal characteristics. These conceptual models can have various beneficial applications in medicine, improving the quality and functionality of personalized prostheses.

Abstract: Periodontal diseases are inflammatory diseases that cause lesions of the dento-periodontal system and can even lead to the loss of teeth. A successful treatment of periodontal diseases includes procedures aimed at reducing inflammation, by mechanical and chemical means, which have the role to decrease the pathogenicity of microorganisms found in the bacterial plaque. The study was conducted on a group of 50 patients, of whom a control group of 25 patients followed conventional periodontal treatment, while the other 25 patients received magnesium-terpene therapy by using polymeric thermoforming mouth custom trays, along with conventional periodontal treatment. The statistical and clinical assessment of the study revealed the efficiency of the magnesium-terpene active gel for the treatment of periodontal disease.

Abstract: Patients with total atrioventricular block are of particular interest and prone to severe prognosis unless treated with emergency cardiac pacing. We evaluated different types of leads and their impact on the myocardium, according to the fixation type and pacing method.. A pacemaker patient has a different depolarization pattern and a single chamber pacemaker, has by definition, an intracardiac desynchronization and a different electro-mechanical coupling activity. The presence of late potentials is an independent prognosis factor for cardiac death and electrical vulnerability, especially after myocardial infarction(MI). Late potentials recorded as magnitude vector are the expresion of late depolarization of the surrounding tissue and represent the morfological substrate for reentry. Thus, the incidence of late potentials after pacemaker implant, represents the expresion of electrical vulnerability of the stimulated right ventricular myocardium. In order to deeply study the parameters of magnitude vectors, we noticed the appearance of late potentials during the transitory stimulation in acute atrioventricular block and a restoration of vector normal parameters, after conduction recovery and sinus rhythm conversion.

Abstract: A bone defect with standard dimensions and localization is produced. Inside this defect a polymer (collagen sponge) impregnated with growing factors, i. e. bone morphogenetic protein – BMP, is introduced. For the witness lot, the same defect is produced, in which the same polymer is introduced, but without any growing factors. It is found that the growing factor not only remains at the initial site, but also has effect on the bone regeneration process. A mathematical model is constructed using a field theory of multifractal type based on the spontaneous symmetry breaking mechanism to exploit such dynamics in biostructures. This mechanism contains all the informational “ingredients”: the multivalent logic based multifractal bit, the algorithm based networks through spatial cnoidal modes of oscilation, etc. In such context, the evolution of all biostructures, through a mechanism that mimics a 3D biological printer, can become operational.

Abstract: Sutures are classified into non-absorbable and absorbable, and mechanical properties of these materials vary by the composition. In this study we analyze four different types of sutures used commonly in surgery: silk, nylon, polyglycolic acid (PGA) and polytetrafluoroethylene (PTFE). The materials were chosen to represent a wide range of suture material categories: absorbable and nonresorbable, monofilament and multifilament, natural and synthetic in order to assess their mechanical properties but also the bacterial adherence to each type. The objective of this study was to measure the total bacterial adherence by using real time PCR at 7 days postop and to analyze the antibacterial and mechanical properties comparatively depending on the type and composition of sutures. Tensile properties such as maximum tensile load, elongation rate, stiffness and energy absorbed before breakage were taken into consideration. Experimental determination pointed out that the average total bacterial load was lowest for PTFE and highest for silk. The results of the study are useful in choosing an appropriate suture wire according to the mechanical properties taking into account the bacterial load of the surgical site in order to aid in tissue repair.

Abstract: This work presents an experiment aimed at determining the concentration of heavy metals found in the water resources of natural receivers. Heavy metals are very dangerous both for the aquatic life environment, influencing the health of the respective living beings and for the human health especially if there is an open contact between the human and the respective water source. Due to the different technological processes of the treatment plants, the wastewater, however, contains a high concentration of heavy metals, which means that those technological processes do not fully comply with the legal requirements. A good, viable solution that is being researched more and more at present is the use of types of polymeric membranes, suitably adapted in ultrafiltration processes of wastewater. Many of today`s advanced researches focus on investigating the retention of heavy metals by membranes. The purpose of this work is to determine the concentration of the main heavy metals such as Fe2+, Zn2+, Cu2+, Pb2+, Ni2+, Mn2+, etc. and other elements such as: Fluorides, Nitrites NO2-N, Phosphates PO4-P, Ammonium NH4-N etc, both before using an organic membrane of PAN from hollow fibers and after cessation of the ultrafiltration experiment to determine the % of the respective metals. can be removed after the ultrafiltration process. The results of the analyzes carried out during the experiment showed that some of the above mentioned chemical elements can be retained by more than 85 % so that a membrane of PAN can reduce the degree of pollution of the waste water, especially where the waste water is directly discharged into natural source of water. At the same time, 14 chemical elements present in the waste water were analyzed and after determining the concentration of the heavy metals after the completion of the experiment it can be confirmed that the use of polymeric membranes is and will be a viable solution for the purpose of protecting the environment and health.

Abstract: A mathematical model regarding water filtration with a nanofiltration (NF) titanium dioxide ceramic membrane is presented. The experiments aimed to use the excitation-emission matrix (EEM) spectroscopy method to highlight the existence of humic acid (HA) in water, before and after the NF process. Following the established operating conditions, experiments were performed for each quantity of AH separately, leaving the installation to work at the appropriate parameters for 15 minutes. for each quantity of AH. The analyzes for EEM fluorescence were performed using the FP-8300 spectrofluorimeter. The collected samples were analyzed with Spectra Manager II software on fluorescence intensity (au - arbitrary units), with an emission wavelength (nm) between 460 and 640 nm and with an excitation wavelength (nm) between 350 and 600 nm. Following the experiments carried out, mathematical correlations were established between the parameters that influence the filtering process and the studied parameters. It is worth mentioning that as a result of the experiments carried out, a number of 20,450 values were obtained, which were used for the elaboration of mathematical models. These models, for sets of values of the order of tens of thousands, verified both from the point of view of the real values and from the point of view of the regression coefficients (coefficients close to the value 1), demonstrate the quantity and the very good quality of the experimental data, respectively of the measured and calculated sizes. In order to validate the generated equations, they were subjected to checks, the difference being obtained between the value obtained by experimental means and the value obtained within the mathematical model. And the value of the resulting relative error, gives information on the accuracy (truth) of the mathematical model, so that it can be extended to other experiences. It turns out that this method cannot quantitatively determine the value of a parameter, but it can highlight the presence and differences between two samples.

Abstract: The clinical success of any indirect prosthodontic restoration is strongly related, among other numerous factors, to the fixing procedure. The technological deficiencies into the inlay cementation lead to defects, either in depth or on surface, which often cause failures. The longevity of inlays depends, to a large extent, on the quality of the dental-prosthetic joint. This marginal adaptation is influenced by the thickness and the type of the luting cement. The aim of this study is a comparative analysis on the behavior of the luting cement for composite resin and ceramic inlays in two different solutions: ANFOR-type artificial saliva and a 20% citric acid solution. Fixing composites are the material of choice for works with high aesthetic potential, our study revealing that their depreciation and alteration is reduced, even in aggressive environments. Cementation seems to be the most critical step, and its long-term success relies on adherence to the clinical protocols.

Abstract: Iron-based amorphous alloys are characterized by so-called soft magnetic properties. Unfortunately, the geometry of iron-based amorphous materials significantly limits the applicability of these materials. One way to expand the use of these materials is to make composites based on them. As part of this work, rapid-cooled alloys were produced using the injection casting method. On their basis, magnetic composites with the addition of a non-magnetic binder were produced. The results of the structure (XRD) and magnetic properties (VSM) tests of the produced materials are presented. The research results have shown that the decisive impact on the magnetic properties of composites is the fact of the separation of magnetic particles with a non-magnetic binder. In this case, the influence of exchange interactions is dominated by dipole interactions.

Abstract: 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.

Abstract: 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.

Abstract: 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.