Browse Articles

The surface effect of nano- and microscale structures of some orthopedic materials, containing nano hydroxyapatite (HAP) and collagen type I (COL), on the interactions of osteoblasts with the surface of these materials is investigated and analyzed. The size and shape of inorganic particles are examined by TEM, SEM and AFM imaging. The surface morphology of collagen self-assemblies is also explored by AFM and SEM observations. Results show that the effect of the surface structure is significant on cell behaviour and can be correlated with cell constructs on these materials in cell culture. Keywords: orthopedic materials, surface structure, osteoblasts, TEM, SEM, AFM

The paper deals with a comparison of the surface roughness of WPC (Wood Plastic Composite) after the machining (turning). Turning was performed with constant speed rotation and constant depth of cut. The goal of this paper was the observed change of average maximum height Rz (roughness average Ra) with change of feeds (interval of feed f=0.1 to 0.61mm) and design recommendations resulting from acquired knowledge. Keywords: Wood Plastic Composite, machining, surface roughness

Polymeric fixed partial prosthesis represents an important part of the prosthetic treatment. Their presence in the oral cavity could lead to fracture them and to alter the final prosthetic treatment. Time Domain Optical Coherence Tomography can be used as a noninvasive evaluation method and 3D reconstructions which could generate a real forecast on those prosthesis in the oral cavity environment. Keywords: polymeric fixed partial prosthesis, optical coherence tomography, non invasive method, material defect

This paper refers to the preparation of durable performance concrete using superplasticizer additives. The study revealed the influence of polymer additives on the nature and concentration of physical and mechanical characteristics of concrete obtained as compared with a standard concrete (without additives). Keywords: concrete, polymeric additives, superplasticizers, lignosulfonates, ether polycarboxylates

The paper focuses on the experimental evaluation of acoustic properties of biodegradable composite materials with textile inserts used for products with a protective role in the urban habitat. The materials used in this study are obtained from mixed wood and textile waste bonded together with ecological binders. In order to determine the absorption and reflection coefficients, the samples were tested using the impedance tube Bruel & Kjaer type, 4206 A, with a frequency range between 100 - 3200 Hz. It was concluded that the tested specimens have shown a high absorption coefficient for the frequency range between 800 – 2800 Hz. It was also noticed that the values of absorption coefficient depended on the type and quantity of binders. Based on the experimental results, the composition of the tested materials will be improved in the future in order to obtain a good absorption of the sound at low frequencies. Keywords: absorption, reflection, composite, frequency, impedance tube

Engineers, biologists and surgeons face a special task when they design procedures, components and systems to replace tissues damaged beyond any limits, caused by disease or trauma. It has been proven that titanium and its alloys have an excellent biocompatibility, that’s why many studies have been made on them, in order to enhance their biomedical applicability. In this paper, the wear behavior of HEMA was analyzed, for use as a cartilage substitute , in experimental models in vivo for testing under conditions very close to reality for two new materials, Ti12Mo and Ti25Nb25Ta alloys. Keywords: titanium alloy, synovial fluid, HEMA

The role of the concentration of the components of the alkaline electrolyte for chemical (electroless) coating of cobalt has been investigated with respect to the rate of their deposition on flexible organic support (polyterephthalate). It has been proved that with the increase in the concentration of Co2+ ions in the solution the rate of deposition is growing up. The influence of the concentration of NaH2PO2, used as a reducing agent, has been studied in regard to the kinetics of deposition and with respect to the morphology of the cobalt coating, as well as the effect on the quantity of the phosphorus co-deposited in the coating. In the course of the study on the influence of the buffering components (NH4Cl and H3BO3) in the working electrolyte, preventing the undesired liberation of cobalt hydroxide, on the kinetics of reduction of the cobalt ions, their optimal concentrations have been ascertained. It has been found that the increase in pH and in the temperature of the studied electrolyte determined an increase in the rate of reduction of the cobalt ions, whereupon the optimal values have been selected. Keywords: chemical deposition, cobalt, coating, organic substrate

Dental restoration materials act as a local irritating factor superimposed to the bacterial factors, and the inflammatory and immune response of the marginal periodontal tissue leads to replacement of the functional structures with granulation tissue that continues to grow in size, while the subgingival dental plaque is heading to the lateral and apical areas. We evaluated morphologically and immuno-histochemically the marginal periodontium adjacent to the fixed metallic-alloyed prostheses (Cr-Ni), composite resins (Cromasit) and ceramic (Vita-Ceram), but also some of the patients with periodontitis which were not associated with prosthetic devices. By the morphological analysis of the periodontal components we reported structural microscopic alterations closely correlated with macroscopic changes observed during clinical examination. We observed a direct relationship between the proportion of inflammatory infiltrate / collagen fibers according to the type of material adjacent to the periodontal tissue. By immunohistochemical evaluation we observed that regeneration and re-epithelizing process appear to be delayed by: persistent inflammatory infiltrate in the epithelial spurs, the presence of fibrinous exudate, fibro-purulent and blood cells on the surface of mucosa. Immunohistochemical investigation in marginal periodontitis watched the evaluation of the immunoreactivity in the periodontal morphological substrates toward the proliferation markers of the gingival epithelium (Ki-67), as well as the mesenchymal reactions specific to the healing process in periodontal lesions (CD -31). The morpho-pathological changes of the periodontal tissue are more profound in the presence of the dental prostheses than in the patients without any such devices and also the regenerative epithelial capacity of the damaged periodontium is more reduced in patients with prostheses than in those without. Keywords: dental materials, parodontium, imunohistochemistry, morphopathology

In this study, the chemical modification reaction of polystyrene (PS) with maleic anhydride (MA) in the presence of borontrifluoride (BF3) catalyst in chloroform was examined. The modified polystyrene containing (-COCH=CHCOOH) fragments in phenyl rings was characterized by IR and 1H-NMR spectroscopy. In addition, TGA, AFM analyses and contact-angles for polystyrene and the modified polystyrene were performed. The effects of polystyrene concentration, maleic anhydride concentration, catalyst concentration, solvent volume and temperature on the modification reaction were investigated by determining the amount of the carboxyl group fixed to the aromatic ring of polystyrene. Some kinetic parameters such as the reaction rate, the rate constant, the activation energy for the modification reaction were calculated. Keywords: polystyrene, maleic anhydride, chemical modification, reaction kinetics

The article presents and discusses experimental data regarding synthesis and characterization of epoxy resins modified with glycols of different molecular weight, synthesized in a 2: 1 molar ratio resin / glycol. The synthesis of epoxy resins modified with glycols was examined by using the spectrophotometer (FT-IR methods) against analytical (chemical) methods, by determining the content of the epoxy groups in time. Furthermore, in order to determine the influence of the glycol nature on the characteristics of the resulted resins, they were cured by using an aromatic polyamine hardener such as 4.4’-diaminodiphenylmetane (DDM), and the resulted epoxy resins were characterized by using both conventional mechanical analyses and the dynamic mechanical analyses (DMA). From the DMA determinations we noticed that resin flexibility increases in the same time with the polieteric chain length. Keywords: epoxy resin, glycol, glass transition, dynamical properties, mechanical properties