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Plastic materials based on biopolymers are of great importance in biomedical field. In this article, chitosan was investigated to elucidate the impact of the surface topography parameters and wettability on its interaction ability with certain biological molecules. The physicochemical properties of chitosan in acetic acid environment are analyzed by molecular modeling to predict some of the films properties. Morphology images show a hill–valley-structured surface of nanoscale level, with low surface bearing properties and valley fluid retention. Wetting features were determined for evaluation of the balance between the adhesion and cohesion forces acting at the biointerface. wetting or dewetting behavior of chitosan with several biological media.

This work was aimed at synthesizing the N, N`-isophthalic bis(piperonylic acid) dihydrazide (PAID) to be as a new crystallization accelerator for poly(L-lactide) (PLLA), and a detailed investigations of the non-isothermal crystallization, melting behavior, thermal decomposition behavior and mechanical properties of PLLA nucleated by PAID were performed applying differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and electronic tensile tester. The melt-crystallization proved that the PAID could act as a heterogeneous nucleating agent to significantly promote the crystallization in cooling, even the crystallization was still able to be accelerated upon the fast cooling at 50 oC/min. The final melt temperature was another crucial factor for PLLA’s melt crystallization, and when the final melt temperature was 170 oC, the onset crystallization temperature and melt-crystallization enthalpy was almost up to 150 oC and 56.8 J/g upon cooling of 1 oC/min, respectively. Furthermore, the chemical nucleation was proposed to be the nucleation mechanism of PAID for PLLA via the preliminary theoretical calculation. For the cold-crystallization, the addition of PAID exhibited an inhibition for the crystallization of PLLA, but the total crystallization process depended on the heating rate and PAID concentration. The single melting peak after cooling of 1 oC/min indicated that the crystallization had been thoroughly completed in cooling. Additionally, the single melting peak with different locations after full crystallization resulted from the different crystallization temperatures. A comparison in the onset decomposition temperature implied that the presence of PAID only slightly decreased the thermal stability of PLLA. The mechanical testing showed that, in contrast with the elongation at break, the existence of PAID enhanced the tensile strength of PLLA.

The article presents the influence of accelerated UV ageing on the structural properties of selected polymer materials. In this study, 3 types of materials from a group of thermoplastics known as PP30T, PE, POM were used. The test samples were prepared by injection moulding. In turn, an accelerated UV ageing process (600 h) was carried out in the UV Test chamber with fluorescent lamps characterized by a wavelength of 313 nm. Changes in the structure of the tested materials were observed by using an optical microscope. Measurements of gloss on the surface of primary samples that were exposed to UV rays were also taken. In addition, the structure of primary and aged samples was tested by differential scanning calorimetry (DSC). The conducted studies have demonstrated the impact of UV radiation on the changes in the surface layer of tested materials.

In this study, the composites of ceramic waste filler polyester were produced with ceramic waste as the filler and unsaturated polyester resin as the matrix. Various weight of filler loads (particle size [180 µm) were used; 0, 28.5, 41 and 50 wt% in view to better understand the effect of filler content on the mechanical, thermal properties and water absorption of the composites. Additionally, Fourier transform infrared spectroscopy was used to characterize the samples, from the findings, it is noticed an increase in the level of porcelain powder decreased the flexural strength and Hardness and increased the density. The results of water absorption have shown the composites absorbs fewer water. Thermal degradation indicates that the composite is more resistant to temperature than unsaturated polyester matrix due to the effect of porcelain powder incorporated. Moreover, the results reveal an opportunity for using the ceramic waste as filler in unsaturated polyester resin formulation.

Thermal behavior of hybrid epoxy composites reinforced with different types of plain weave fabrics and ply orientation at various angles was investigated in this research. It was analyzed their thermal linear expansion coefficient and specific heat measured with Thermomechanical Analyzer (TMA) and Differential Scanning Calorimeter (DSC) respectively. Also, in this paper was studied the influence of carbon black - aramid powder and carbon black - barium ferrite mixtures added into epoxy matrix between certain plies of the hybrid composites. The experimental results showed that the addition of filler mixtures led to a significant decreasing of thermal expansion coefficient and specific heat of the hybrid epoxy composite with carbon outer plies. It was recorded a good structural stability in case of hybrid carbon-glass composite in the temperature range of 40-60°C.

In the last two decades, both general and oral health status became more important for individuals, being associated to their quality of life, social provenance and income. Society’s evolution is associated to high expectations regarding edentulous and decays treatment. Metal filling such as gaudent or amalgam have been replaced by aesthetic materials, to achieve similarity to the patient’s genuine biological tissue. Along with the aesthetic demand, dental materials have to fulfill biocompatibility and mechanical properties proximate to healthy soft either hard tissues. Composite materials have the advantages of accomplishing biological and mechanical demands and to be accessible financially, compared to ceramics. Composites are classified according to the main monomer, filling, particles’ dimension, addition of external molecules, this entirety having a direct influence on materials’ properties. The objective of this prospective interventional in vitro study was to evaluate biomechanical properties of four different hybrid composites: Premise direct™ – Premise indirect™ (Kerr, Orange, California, USA), Gradia® Direct (GC, Alsip, Illinois, USA) and Ceramage® (SHOFU Dental, Ratinger, Germany). Vickers microhardness, compressive strenght, direct tensile strenght, water absorption and solubility were assessed. The results showed that microfilled hybrid composites UDMA (urethane dimethacrylate)-based monomer had the highest evaluations regarding Vickers microhardness, compressive strenght and tensile strenght, whereas water absorption was the highest for nanofilled hybrid Bis-GMA (bisphenol A-glycidyl methacrylate)/TEGDMA (triethylene glycol dimethacrylate), and solubility for microfilled hybrid UDMA based monomer.

The purpose of modern dental medicine is to prevent dental caries and promote minimally invasive techniques at the expense of invasive methods. Dental sealants are largely recommended for occlusal surfaces protection, but concerns are related about microleakage at material-enamel interface. This in vitro study aimed to investigate the association between chemical structure, sealing capacity and marginal infiltration for 2 fluoride F containing commercially available resin-based sealants: Pit&Fissure® Sealant (DMP) and Fissurit FX® (Voco) in order to achieve a better description and ensure adequate material selection in every day practice. An optimal resin-based sealant should mimic the structural, physical and mechanical characteristics of enamel. The main difference between the sealing materials tested is based on the amounts of inorganic filler and on the various shapes of the particles in the filler. Pit&Fisure® Sealant express less attachment at enamel interface, higher sorption and greater water solubility, when compared to Fissurit FX®. The better sealing capacity of Fissurit FX® can be described by the homogeneity of the material and the very small size of the inorganic fillers. Dental materials properties used as pit and fissure sealants are sensitive to mechanical, thermic and chemical stress from oral cavity. Regular dental check-up can detect the presence and integrity of sealant and ensure preventive effect in time.

The study was performed on a number of 48 plastic molds, obtained by injection of Technovit 7143. Technovite is a self-curing resin based on methyl methacrylate. Technovite no longer requires the use of dyes that can adversely affect the polymerization process and has a short polymerization time, making corrosion possible shortly after injection.

The prognosis of the prosthetic rehabilitation is linked to the proper transfer of the clinical data to the dental laboratory, in the digital or conventional workflow. The aim of the present study was to compare the dimensional accuracy of analog and digitalized models, focusing on the influence of impression polymeric materials on the final digital model. Methods: The master model with standard reference points and the three groups of test models, obtained by alginic acid polymer impression (group A) and condensation-cured poly(dimethyl siloxane) in two impression techniques (1-step putty/light-body-group 1T, 2-steps putty/ light-body-group 2T), were measured in four standardized points before and after digitization. The differences from the master model and between the pair analog and digital models was calculated and statistically analysed using Mann-Whitney tests (2 groups), and one-way Anova (3 groups) with post-hoc Tukey`s Test was applied for pairwise analysis (á=0.05). Results: All analog and digitalized model tests showed altered dimensions from the master model. A general reduction of the digitalized models, in sagittal and transversal dimensions, was observed, comparing to the reference model. The impression material was a significant factor influencing dimensional accuracy. Conclusions: a statistically significant difference was found between most of the models and the master model. However, through digitalization, some of the errors were compensated. The digital models from alginic acid polymer group (group A) registered the highest trueness, with no statistically significant difference (P > 0.05) from the reference model.

The aim of this paper is to investigate the resistance to flexure of traditional and modern dental acrylic prosthetic bases. The practical utility of the laboratory studies carried out in this research is to apply the physical properties of plastic in medical technology, for improved clinical practice. The clinical utility of this research on prosthetic acrylic bases resistance is reflected in the quality of life of patients, the quality of mastication and durability of the prosthesis. Material and methods: experimental research, using a mechanical test machine. The results were analysed through quantitative methodes. Statistical correlations were made in the final experimental part. In conclusion, the values obtained in our experiments are comparable with those found in scientific literature. This fact enables us to recommend the use of the injection molding technique in clinical practice in our country, as well as the abandonment of the traditional manual stuffingpressing process.