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The maxillo-facial reconstructive surgery very often uses regular shape biocompatible material plates which are fastened by screws to the rest of the bone. The choice of optimal plate for each case, especially in risk cases, should be made primarily according to surgeon medical experience but also following a strength analysis of the various existing plates. The analysis of mechanical structures by using the finite element method highlights the resistance, the risky areas in case of possible demands such as the jaw’s pressure on the mandible, allowing the physician to optimize the restorative solution. Keywords: finite element, osteosynthesis

The choice of denture artificial teeth is made up onto several criteria regarding both aesthetics and functionality. Of these, colour stability is one of the determining factors. Colour stability of materials used in aesthetic prosthetic restoration is important for the long-term success of the treatment. Our study was conducted to compare colour stability of different acrylic artificial teeth available on the market and usually used in manufacturing partial and full dentures in Romania and to find a ranking of staining ability of different solutions with which artificial teeth could come into contact lately, during function or cleaning phases. For this study were purchased six boxes of identical front superior acrylic denture teeth from four different manufacturers, coded by letters V, M, R and S). These teeth were immersed in various liquids such as red wine, Coca Cola, black tea, coffee, which we considered to be ingested frequently by the largest part of the population. Our study shows that, of the four analyzed drinks, the most colouring is coffee. The same operator determined the color coordinates using the Easy-Shade intraoral spectrophotometer. The results were expressed using CIELAB colour notation system. Color difference was expressed as DE*. A device was made for constant positioning the tooth versus the Vita Easy Shade spectrophotometer rod used to determine colour changes in the central third of the buccal area. The acrylic prefabricated teeth suffered various colour changes in contact with those drinks, with magnitudes depending on the type of the liquid and the acrylic teeth chosen. We compared colour stability of two batches of homolog teeth, first unmodified and second grinded and polished in the dental laboratory, from which the most affected were R and M where this colour change occurs in three of the four kinds of drinks in which we have made the immersion. Washing the dentures with soap and water reduced differences in colour caused by contact with any type of these drinks. Keywords: color stability, denture, acrylic teeth, staining drink

Longevity of fixed partial dentures fiber-reinforced composite restorations is dependent upon many different factors, including material, maxillary or mandibular arches, patient- and dentist-related. 25 metal polymeric and 25 integral polymeric fixed partial prosthesis were obtained for this study. The Rx investigation was performed by using the Fona X 70. The possible defects were investigated with the DIAGNOcam using the transillumination method. In contrast to conventional technology with an interdental light source, DIAGNOcam practically uses the entire tooth as a light propagation medium. the transillumination investigation detects more defects trapped in the polymeric materials in 20 from the 25 metal ceramic fixed partial prosthesis and in 16 from the considered 25 integral polymeric fixed partial prosthesis. In conclusion, a noninvasive evaluations method, such as transillumination, has a great capability to evaluate the internal structure of the polymeric material used for the fixed partial prosthesis considered. Most of these defects were identified in the occlusal, cervical and connector’s areas of the fixed partial prosthesis and then could lead to fractures and failures of the prosthetic treatment. Keywords: polymeric fixed partial prosthesis, transillumination, non-invasive method, material defect

The paper focuses on the development of composite materials based on bacterial cellulose and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV). Natural composites were obtained from bacterial cellulose membranes and chloroform copolyester solutions (various mass ratios). The composite membranes were characterized by FT-IR spectroscopy, X-ray diffraction, SEM morphology, contact angle measurements and thermogravimetric analysis. Cellulose nanofibrils coating and/or precipitation with PHBHV particles was observed. The biocompatibility of composite materials was assessed by using L929 mouse fibroblast cells monolayers. Possible applications of these composite materials are focused on blood vessel engineering and/or wound dressing management. Keywords: bacterial cellulose, polyhydroxyalkanoates, composites, tissue engineering

Bimetallic Pd-Ag nanoparticles (NPs) were obtained by polyol method in the presence of poly (vinylpyrrolidone), PVP, as capping agent. The reduction of silver and palladium precursors was performed in argon inert atmosphere by successive reduction, or coreduction approach. In the successive reduction, AgNO3 solution was injected in the ethylene glycol solution of PVP at 140°C, followed by the injection of [Pd(NH3)4]Cl2 solution. The obtained bimetallic Pd-Ag NPs exhibited cluster structure, with the surface reach in silver. The NPs size was in the range of 30 – 58.5 nm with the average dimention of 41.5 nm. The coreduction approach consists in the hot injection of both metal precursors as complex ammine dissolved in ethylene glycol. By this method, smaller Pd-Ag NPs with the average sizes in the range 16 – 30 nm were obtained, depending on the synthesis parameters. The influence of metal cations : PVP molar ratio, metal cations concentration, Ag : Pd atomic ratio and the reduction temperature on the composition and morphology of the bimetallic NPs was studied. For both reduction approaches, based on the experimental data, two different reduction patways were proposed. Keywords: bimetallic nanoparticles, Ag, Pd, PVP, polyol method, coreduction, successive reduction

This study was focused on the synthesis of some new hybrid materials based on poly(amidoamine) dendrimer and halloysite designed for 5-Fluorouracil encapsulation. Different techniques like Spectroscopic methods (FTIR, XPS and UV-Vis) and thermogravimetric analysis were used to characterize the hybrid materials. The morphology of the hybrid materials was pointed out using Scanning Electron Microscopy ( SEM) analysis. The obtained results showed that the drug encapsulation efficiency of the hybrid materials was strongly influenced by the interactions between dendrimer-halloysite and drug molecules. Keywords: dendrimer, halloysite, 5-fluorouracil, UV-Vis, X-Ray Photoelectron Spectroscopy

Direct photoreduction and photosensitization are powerful approaches for the in-situ synthesis in a polymer matrix. A silver–acrylate nanocomposite was prepared using a novel one-pot strategy involving simultaneous photoinduced reduction and free radical polymerization processes. The fabrication of metal nanocomposite was performed using an acrylate functionalized oligomer (polyethylene glycol 600 diacrylate) and a silver salt (AgNO3). The formation of Ag-nanoparticles was followed by UV–Vis spectroscopy which shows a surface plasmon band at a wavelength range between 410 and 440 nm. Transmission electron microscopy revealed that the synthesized nanoparticles were spherical in shape with a diameter between 5 to 20 nm. The polymerization process was followed quantitatively by infrared spectroscopy, monitoring the disappearance of the characteristic bands for the acrylate double bonds (1410 cm-1). The optimum conditions for obtaining the silver-polymer nanocomposites have been determined (silver precursor concentration, molar ratio silver precursor/photoinitiator, irradiation time and intensity). A reaction mechanism was proposed to explain the polymerization rate dependence on the silver cations content. Keywords: Silver nanoparticles, photo polymerization, acrylate, nanocomposites

In this paper, data on Melana-type polyacrylonitrile fibres dyeing with Crystal violet (CV) - triphenylmethane dye- in the presence of maleic acid copolymers with vinyl acetate (NaM-VA) or styrene (NaM-S) are presented. Mathematical models of the studied dyeing processes have been developed and the necessary information on their significant factors is produced by means of experiment planning methods, known as Design of Experiment (DoE) or Experimental design. Optimal correlations between the application conditions and the colour differences obtained on Melana-type fibre have also been studied. Keywords: Melana fiber, Maleic copolymers, Crystal violet dye, Color differences, Statistic modeling, Optimization process

Difficulty to objectively determine the moment of bone fracture consolidation by classical imaging methods makes necessary the development of a method that will allow establishing, by objective criteria, the moment in which biomechanical loading of the injured bone segment may be permitted. We propose a method based on the approximation between bone diaphysis and a beam, analysing its behaviour under frequency excitation at one end and measuring the vibrations at the other end. Variation of parameters measured in the structurally sound structures compared to the fractured ones, as well as the possibility to analyse their evolution in the presence of osteosynthesis materials used for the surgical treatment of fractures is ascertained. The existence of composite plastic materials of which the used anatomical bone mould for this experiment is made simulates the real pathological situation, which allows extending the determinations to clinical cases. Key words: bone, fracture, mould, polyurethane, osteosynthesis material, composite material

The paper presents a comparative analysis between the performances of pressure sensitive adhesives based on polychloroprene rubber and hybrid acrylic adhesive. The analysis was based on peel, shear and tensile tests for the assemblies on various substrates. Adhesion work was also determined from the contact angles and superficial tensions. The values of the adhesion work confirm the results obtained with the above mentioned tests. Keywords: pressure sensitive adhesives, polychloroprene-based rubber, hybrid acrylic adhesives