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The present study evaluates the marginal adaptation of fixed partial prosthesis made from resin composite. The main goal is to obtain restorations with excellent aesthetics and extremely high quality which increase the lifetime of the prosthesis system - dental structures. The method allowed the observation of defects that might occur during the technological processing, as well as their correction. It was used the 3D Shape software with which have been achieved scans for the virtual presentation the marginal adaptation. Following the investigation it was showed, that the cementation is extremely important, the errors occurring in this phase are influencing of the final results and behaviour. Composite resin fixed partial prosthesis are restorations which through a correct technology can compete with the ceramic fixed partial dentures. Keywords: aesthetic restoration, marginal adaptation, defects, 3D Shape software

In the last years, researches regarding the manufacture of polyamide parts using selective laser sintering process have developed increasingly more because of the advantages this materials offer. This paper was focused on a comparative study about the mechanical proprieties and surface roughness of parts manufactured by Selective Laser Sintering (SLS) from PA2200 powder. Tested parts were achieved on DTM Sinterstation 2000 Machine and EOS Formiga P 100 Machine. The results obtained lead to the conclusion that the mechanical proprieties obtained for the test parts made at 7,5W laser power on DTM Sinterstation 2000 Machine, are close to the results obtained for the test parts made at 30W on EOS Formiga P 100 Machine. Keywords: Polyamide, Selective Laser Sintered, mechanical proprieties, roughness

The concern for quality assurance and improvement of the manufacturing processes of plastic materials is of great interest to industry companies offering the guarantee to ensure the conformity, performance, competitiveness and profitability. This paper addresses the importance of improving the quality of plastics manufacturing processes, on high (flow) performance. It illustrates the application of the “Six Sigma” statistical method for injected products that have certain defects / nonconformities, especially dimensional manufacturing. Keywords: plastic products, quality, six sigma, manufacturing process, efficiency

The bile duct system has two distinct components: one intrahepatic and another extrahepatic. Both components are subject to large anatomical variability. Knowledge of intraparenchimatous bile duct system distribution is particularly useful for planning and performing major surgical resection and liver transplantation. For this reason, the training of students and medical residents must use liver corrosion casts. On the 130 pieces of hepatic corrosion casts, a percentage of 80.75% of cases have modal typology, homologated by Terminologia Anatomica (1998). On a percentage of 19.25% of the studied cases were found major variations of the intrahepatic bile duct system (classified into four morphological types). In 16.15% of cases, the posterior branch in his passage to the left hepatic duct intersects the main portal fissure. Medial and lateral branches showed no major variations on the studied material. Use of human intrahepatic bile duct system corrosion casts with major anatomical variations, can compensate for lack of clinical material in training of medical students and residents. Keywords: corrosion casts, intrahepatic bile duct system, major variations, training

Chitosan (CHI) and poly(acrylic acid) (PAA) polyelectrolyte multilayers were constructed onto silica microparticles with particle diameter of 40 – 60 mm (Daisogel type). The multilayers were subject to two post-treatment strategies: (i) immersion in an aqueous solution with pH = 2.4 for 5 min, followed by immersion for 1 min in water and thermal treatment at 120oC for 60 min and (ii) cross-linking with glutaraldehyde for 60 min. The sorption properties for a cationic dye were investigated taking methylene blue (MB) as a model. The reusability of (CHI/PAA)n multilayers deposited onto Daisogel microparticles in the consecutive sorption/desorption cycles of MB was investigated as a function of the number of double layers and the post-treatment strategy. Keywords: polyelectrolyte multilayer; chitosan; poly(acrylic acid); methylene blue; silica

The aim of the study was to compare using atomic force microscopy the surface roughness of three types of composite resins after finishing and polishing procedure with three different systems. A hybrid (Valux Plus, 3M ESPE), a microhybrid (Filtek Z 250, 3M ESPE) and a nonohybrid (Herculite XRV Ultra, Kerr) composite resins were chosen for this study. A number of 28 samples having 10 mm in long ,7 mm in width and 2 mm in high of each composite resin were obtained. The samples were equally split in 4 groups. In control group 7 specimens of each material received no finishing and polishing treatment after being cured under plastic matrix strip. In the first study group 7 samples of each material were finished using fine, safe end taper tungsten carbide bur, 7 samples were finished using superfine needle diamond bur and 7 samples used diamond impregnated one stage polisher. The surface of all composite samples was analyzed using atomic force microscopy. The results were expressed as root mean square surface roughness (nm). The results were statistically analysed using ANOVA and post hoc Bonferroni test at a 0.5 significance level. Significantly differences were obtained in the surface roughness of all three tested composite resins after finishing and polishing when comparing to surface roughness from control group. The one-step diamond abrasive polisher leaded to a significant lower surface roughness for all three composite resins when comparing to the surface roughness when tungsten carbide bur or diamond bur were used. Surface roughness of Valux Plus was higher than that observed for Filtek Z 250 or Herculite XRV Ultra, irrespective of the system used for finishing and polishing. The surface roughness of composite resins is in relation with the type of composite resin and the type of finishing and polishing system. The one-step diamond abrasive polisher was more efficient in obtaining smooth surface when comparing to tungsten carbide bur or diamond bur. The nanohybrid composite resin has a lower surface roughness when comparing to microhybrid and the hybrid composite resin after finishing and polishing. Keywords: composite resins, surface roughness, AFM, finishing and polishing system

The polymer foils, obtained from pure and coloured (with cycloimmonium ylids) poly (vinyl) alcohol (PVA) gel, are studied from the optical anisotropy point of view. The dried foils were stretched under heating and their optical birefringence was measured for different degrees of stretching. The changes in the birefringence were correlated with the stretching degree of the polymer foils. The influence of the cycloimmonium ylid structural peculiarities on the coloured foils’ anisotropy is also discussed. Keywords: cycloimmonium benzoyl anilido-benzoyl methylids, optical birefringence, stretched coloured and pure PVA foils

Within this paper an experimental analysis of an advanced composite U-beam pultruded profile based on isophtalic polyester resin reinforced with unidirectional glass fibres and overlay veil has been carried out to determine its most important mechanical properties. Tensile tests have been accomplished on specimens cut from the pultruded profile along and transverse to the fibers direction. Over thirty mechanical properties including Young’s moduli, stiffness, load-extension as well as stress-strain distributions determined at maximum load, maximum extension and at break have been determined on a Lloyd Instruments LS-100KPlus materials testing machine. Typical failure mechanisms such as fibres pull-out and delaminations have been noticed. The tests show that this kind of unidirectional glass fibers-reinforced isophtalic polyester resin with overlay veil obtained in the putrusion process is suitable for a large range of applications from the automotive and aerospace industry and put into evidence its strong anisotropy. Keywords: Pultrusion, Isophtalic polyester resin, Mechanical anisotropy, Tensile tests, Stiffness

The article presents the importance of using polymer additives in the hydraulic fluid flow, to reduce the friction, to reduce the linear pressure losses, to increase the flowing velocity, to reduce the pumping energy, to increase the efficiency of the hydraulic machines. The article highlights the Toms effect in hydraulic industrial applications. Its also shows experimental results on single stage centrifugal pump operating with additives in water in different poly acryl amide concentration, highlighting the significant increase of the pump efficiency when the concentration does not affect the fluid viscosity. The pump efficiency increased with 8-10% when the polymer additives concentration was 0,04%. Experiments were performed in Hydraulic Laboratory of University Politehnica of Bucharest. Enhancing theoretical and experimental research in this area, based on the viscosity and elasticity anisotropic properties of the polymer additives solutions, can be created new premises for hydrodynamics and hydro power applications. Keywords: polymer additives, hydraulic performances, centrifugal pumps

The goal of this paper is to study the creep behaviour of multi-walls carbon nanotubes (1, 3, 5 wt.% MWCNTs) filled polypropylene (PP) through the instrumented indentation technique. Two types of the 3-step indentation test were considered to analyse viscoelastic behaviour through sharp indentation at room temperature. Under the loading conditions, the PP/MWCNTs samples present a time-independent plastic behaviour which must be considered not to under/overestimate the viscoelastic properties. The ratio of residual indentation depth to the maximum indentation depth at peak load calculated from the initial portion of the unloading curve was over 0.7 and demonstrated the plastic character of tested materials. The indentation hardness and modulus calculated from the slope at the unloading curve were changed due to the presence of plastic deformation from the loading phase, to the load intensity and hold time. The local distribution of carbon nanotubes lead to the variation in creep response and also, in the mechanical properties of material. Calculating the creep rate, a better creep response was offered by the higher concentration of carbon nanotubes during the indentation test at peak load of 1 N. A 3-step standard indentation test (Oliver and Pharr method) was considered to avoid the influence of the duration from the holding phase on the mechanical parameters. We found that a holding phase of 40 seconds was enough to have a negligible influence of creep on the indentation modulus for 5 wt.% of MWCNTs sample. Keywords: indentation, creep, carbon nanotubes, indentation hardness, indentation modulus