Browse Articles

Dental sealants are a specific prophylactic alternative for fissures with an irregular morphology. The aim of this in vitro study was to evaluate dye penetration around three materials recommended for fissure sealing with a different composition. Thirty teeth were sealed according to manufacturer’s instructions as follows (n=10): Group I, light-cured unfilled resin-based sealant, Admira Seal® (Voco GmbH); Group II, light-cured filled resin-based sealant, Fotoseal® (S.C.Remed Prodimpex S.R.L., Bucharest, Romania); Group III, resin modified glass ionomer sealant without varnish, GC Fuji Triage® (GC Corporation). The teeth were thermocycled, then immersed in 0.5% basic fuchsine dye for 24 h. The teeth were sectioned buccal-lingually in order to obtain one section per tooth in the middle of the occlusal surface and the sections were examined at 40x with an inverted microscope. Dye penetration was recorded (mm) using specific software and related to the total length of the sealed fissure. Average values for each group were subjected to statistical analysis by Student’s t and Kolmogorov-Smirnov tests (p[0.05). Significantly less dye penetration was recorded for both resin-based sealants compared to the resin modified glass ionomer sealant, with no difference between the filled and the unfilled resin sealant (p=0.34). The resin-based sealants were more effective in sealing the fissures than the resin modified glass ionomer cement sealant.

Numerous problems are seen in the general lifestyle and health of young adults with noscomially acquired HIV between 1987-1990, a peculiarity of the HIV infection in Romania. One of these problems is immunity alteration as reflected in the oral pathology of these patients. This study evaluates the impact that the HIV infection has on the oral health of infected young adults. The current observational, case-control study compares the caries experience and the impact on oral health quality in 114 HIV positive young adults versus a control group, using the Decay-Missing-Filled (DMF) Index and the oral health profile, obtained using by OHIP-14 questionnaire method.

This paper presents the development, operation and testing of a modular small sizes original stand, its main modules made of plastics, intended for tests on blades and rotors in the structure of experimental models of hydraulic turbines. The stand includes a water tunnel consisting of demountable and sealed sections of which the majority, of various shapes and sizes, are made of composite material type fiberglass reinforced polyester, FRP, and one of them, rectangular cross-section, is made of transparent and resilient Plexiglass. Through the shapes of sections, quality of interior surfaces and quality of plastics used, the water tunnel allows creating in its transparent section a forced, permanent and continuous circulation of water, of adjustable speed in the range 0.05 ... 1.1m/s. The results of tests conducted on an experimental model of water turbine by use of this stand demonstrate the economic and technical advantages of using plastics in building these types of testing tools.

Equal Channel Angular Pressing (ECAP) is the most emblematic technique for producing bulk nanostructured materials and ultrafine grained materials (UFG) through severe plastic deformation. In this study, we examined a 6063-T1 aluminum alloy, subjected to ECAP processing at room temperature for one, three, six and nine passes respectively, using a 90° die and the processing route BC. The as-received and ECAP processed samples were firstly analyzed in OES experiments, the accumulated equivalent strain being also estimated based on ECAP die geometry and on the number of passes. All specimens were investigated as well in XRD tests for phase identification. Williamson-Hall method was used for evaluating the crystallite size and the lattice strain. Some correlations with the main processing parameters were also established.

The low biodegradability of petroleum-based plastic materials led to the search for novel biodegradable plastics. In this way, a team of German researchers developed, produced and marketed a material that can help the environment, in terms of 100% biodegradability and renewability, contributing to a more efficient use of resources. The trade name proposed by the team is “liquid wood” and is a high-quality thermoplastic material. It brings together the wood and plastics processing industries, in order to make products with complex design geometry and to process warm material wood (lignin and natural fibers) using the same technique and equipments just like for conventional thermoplastic materials. This paper presents analyses of bending test behavior in case of Arboform L, V3 Nature -“liquid wood” (A-LW) and Arboform reinforced with Aramid Fibers (A-LWAF). The results were compared with technical literature and some plastic materials in case of requirement for greater stiffness of material. Keywords: bending test, Arboform, bending strength, flexural modulus

Metallic iron nanoparticles were synthesized by the hydrazine reduction method in three experimental versions. The average size and particle size distribution obtained by the three versions was determined with a particle size measurement system making use of dynamic light scattering. The presence of the aromatic solvent and anti-caking additive influences the average size and size distribution of the particles. The metallic iron nanoparticles obtained in the three experiments were used in the treatment of waters containing a 6.8 mg/l concentration of hexavalent chromium. Reduction of hexavalent chromium concentrations as well as total chromium, COD and TSS depend on pH and reaction times. Thus, the optimal conditions requires for Cr6+reduction, for obtaining values lower than 0.1 mg/l, are: the pH value of 11, a duration of the process 10 hours. Keywords: nanoparticles, chromium, wastewater, chemical oxygen demand, biochemical oxygen demand

The paper deals with the synthesis of compounds based on standard epoxy resin/ modified epoxy resin with different molar ratios of glycols and with the characterization of cured products to investigate the influence of the addition of various amounts of modified resin on the compound flexibility as compared to standard epoxy resin. Modification of epoxy resins with glycols results in a wide range of specific properties superior to neat epoxy resin. These properties are highlighted by characterizing the products obtained using various types of glycols and different standard resin/ modified resin weight ratios by physical- mechanical analyses and Dynamic Mechanical Analyses (DMA). Keywords: glycol-modified epoxy resins, glass transition, dynamical properties and mechanical properties

This research is based on the study of the chemical polymerization of nanocomposites based conductors polypyrrole PPy(Cl) and the HY Zeolite type Faujasite as reinforcements, at room temperature and atmospheric pressure using FeCl3 as initiator of the reaction and dopant at the same time. After characterization commodity we methods primarily on the polymerization of pyrrole with different molar ratios of [FeCl3] / [Pyrrole] in an aqueous medium, followed by a series of characterizations for the polymers obtained. Won the right ratio was used for the preparation of nanocomposites PPy (Cl) / HY Zeolite. After each synthesis, the developed product is characterized by FTIR, SEM, UV-Vis, XRD, and electrical conductivity in order to confirm the success of the process of synthesis and study their properties to specific applications envisaged. Keywords: nanocomposite, polypyrrole, zeolite HY, conductor polymer

Coatings obtained on cellulose fabrics with nonionic dyes – silica hybrids have been investigated. Composition of the impregnation bath and parameters having a major influence on coloring properties were studied in relationship with washing and light fastness. It was found that cotton can be coated with organic-inorganic nonionic dyes - silica hybrids exhibiting fair washing and light fastness. Properties of the coated materials can be controlled by variation of parameters affecting sol obtaining procedures or impregnation conditions. The presence of only one trialkoxysilane group per chromogen makes the formation of a highly crosslinked silica network to be difficult. The partial condensation of DR1-PTES (Disperse Red 1 dye covalently linked to 3-isocyanatopropyltriethoxysilane) to the stage of oligomeric structures, together with the existence of silanol and unhydrolyzed alkoxysilane groups can explain leaching behavior of the coatings obtained with this type of hybrid materials. Keywords: nonionic dyes, silica hybrids, surface coating, cotton fabrics, sol-gel process

This paper presents the synthesis of some acrylic monomers with pendant carbazole groups. They were copolymerized with N-octyl methacrylate to obtain organic photosensitive materials used in the production of holograms with electrophotographic methods. Keywords: N-vinylcarbazole, N (2-hydroxymethyl carbazole), N-carbazolyl methlacrylate, octylmethacrylate