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This paper presents our experiments on obtaining and characterizing polymeric composites based on wood sawdust and natural rubber. Natural rubber was crosslinked both through a classic method – using benzoyl peroxide at high temperature, and an unconventional method at room temperature – electron beam irradiation. Physico-mechanical properties such as hardness, modulus at 100% elongation and tensile strength indicate a significant improvement as a result of adding wood sawdust to blends. Better results have been obtained using crosslinking by electron beam irradiation. The crosslinking rates of samples, measured using the Flory-Rehner equation increase as the amount of wood sawdust in blends increases and as the electron beam irradiation dose increases. The swelling parameters of samples significantly depend on the amount of wood sawdust in blends, because the latter has hydrophilic characteristics. Key-words: natural rubber, wood sawdust, irradiation, physico–mechanical characteristics, crosslink density, swelling parameters

The bond strength of the root canal sealers to dentin and core material seems to be a very important property for maintaining the integrity and the seal of root canal filling. This in vitro study aimed to evaluate and compare the bond strength of three different root canal sealers. Forty five extracted single-root human teeth were prepared using ProTaper system. Teeth were divided into three groups (n=15) for obturation using AH Plus, RealSeal and a new, experimental endodontic sealer containing hydroxyapatite. Each tooth was obturated using warm vertical condensation technique in the apical third and gutta-percha injection in the middle and coronal thirds of the root canal. All teeth were sectioned transversally at the apical and middle thirds into 1 mm thick discs. Push-out tests were performed using a universal mechanical testing machine (Lloyd Instruments – LR5k plus). The maximum load at failure was recorded and divided by the area to obtain the bond strength in MPa. Using a stereomicroscope (STEMI 2000 C Zeiss, Jena, Germany), at a magnification of 20x, the interface where the obturation failure occurred was identified. Statistical analysis was performed and the result showed non significant differences between the three endodontic sealers at each level obturation. Also, the stereomicroscopic analysis showed a good adhesion to dentin for all sealers. The experimental sealer adhesion is comparable to that of the two consecrated materials. Keywords: push-out test, bond strength, endodontic sealer, root canal obturation

Profiled steel sheeting dry board (PSSDB) consists of steel sheeting that are connected to a dry board using self-drilling and self-tapping screw to form a light composite structure. This study focuses on PSSDB that uses 12 M geopolymer concrete infill with half-sized dry-board infill (GPCHB). The detected weakness of the profiled steel sheeting on this PSSDB system is due to the relatively easy occurrence of local buckling on its structure as it reaches an ultimate load, especially on the top flange. This study aims to analyze the relationship between stiffness and deflection at the mid-span of PSSDB systems using different parameters. Results show that the panel with 12 M GPCHB has 107% and 40% increase in rigidity compared with those of the control (without infill) and full board normal concrete panels, respectively. Mid-span deflection is also reduced to 52%. In conclusion, stiffness increases and deflection decreases when 12 M GPCHB is used in the panel. Keywords: composite structure, geopolymer concrete, weakness, local buckling, stiffness

Film forming polymer solutions for skin wound dressing were developed and characterized. Film forming solutions were prepared by adding polyvinyl alcohol (PVA) and poly (hydroxy) urethane (PHU) in different proportions into a well tolerate volatile solvent. The formulations were in vitro evaluated according to five criteria. Two formulations have proved the ability to form polymeric film. Evaluation of the tensile strength, contact angle and swelling index were made for these formulations. The results showed a positive response of the formulations to be used for skin wound dressing. Keywords: integrity on skin, swelling index, tensile strength, surface polarity

The challenge of the chondral lesions treatment has been considerably answered with the development of non-cellular scaffolds. Among the most frequently used, the scaffolds based on Hyaluronic Acid and, respectively, collagen derived polymers are the subject of our comparative research. The present paper highlights some particularities related to their intrinsic physical properties such as adhesiveness, microstructure and cellular permeability and concludes that the two alternatives present qualitatively similar outcome and effectiveness. Keyword: hyaluronic acid polymer scaffold, collagen scaffold, chondral lesions, osteoarthritis

The mechanism of action and adverse reactions of 52 mg levonorgestrel-releasing intrauterine system and also level of pain during the insertion and techniques of anesthesia or analgesia for this procedure have been well documented. On the opposite pole the 13.5 levonorgestrel-releasing intrauterine system has been recently launched in Europe. To our knowledge there are no studies correlating the device design and biomaterials, mechanism of action, surgical technique and level of pain during the insertion of levonorgestrel-releasing intrauterine systems. This study was undertaken in order to determine whether there is a different level of pain during the insertion of 52 mg levonorgestrel-releasing intrauterine system compared to 13.5 mg levonorgestrel-releasing intrauterine system, considering the mechanism of action and the structural and dimensional discrepancies between the two intrauterine devices. Keywords: Levorgestrel-releasing intrauterine systems, device design, mechanism of action, level of pain during the insertion

The liver segmentation is determined by the distribution of the vascular and ductal hepatic elements; from this, the hepatic portal vein (HPV), the central element of liver afferent pedicle, is the most important. The posterior branch (PB) is serving right lateral division (RLD) of the liver and presents the lowest morphological variability. On a total of 125 pieces of liver corrosion casts, one examined the intraparenchymal distribution of portal PB and the segmentation of RLD. Regarding the intraparenchymal distribution of the branches in the RLD of the liver, we showed four distinct morphological types: Type I (77.6% of cases) in which the PB bifurcate symmetrically in branch of segments VI and branch of segment VII; Type II (8.8% of cases) in which the PB bifurcate in branch of segment VII and an inferior branch, that bifurcate branch of segment VI and branch of segment VIA; Type III 12.8% of cases) in which the PB bifurcate in branch of segment VI and a superior branch, that bifurcate in branch of segment VII and branch of segment VIIA; Type IV (0.8% of cases) in which the PB trifurcate in branch of segment VI, branch of posterior intermediate segments, and branch of segment VII. Knowledge of these morphological types of portal PB is important for clinical and surgical practice. Keywords: corrosion casts; hepatic portal vein; posterior branch; variability; morphological typologies

Fiber reinforced composites (FRC) are used in periodontal therapy for stabilization of mobile teeth with compromised bone support. The type of fiber and the type of composite have a great influence on mechanical properties of FRC. The specimens made of different FRC systems were subject to a three-point bending test. The results indicate that the specimens which exerted the best ratio between high deflection, low flexural modulus and medium flexural strength have the best indications to be used in periodontal therapy. Regarding the fracture pattern, the FRC recommended for splinting are those that separate in two discrete parts while maintaining an intact polyethylene fiber. This aspect allows intraoral repairs, increasing the life-span of the periodontal splints. Keyword: fiber reinforced composite, periodontal splint, three-point bending test

The purpose of this study is to assess the effects of artificial saliva with different pH on the wearing of glass ionomer cements. We used three types of glass ionomer cements and three immersion environments. We have prepared a total of 96 samples. We used 6 artificial saliva samples for each environment. Each sample was immersed in the storage solution to a specific pH. Storage solution was changed on days 1, 7, 14 and 28. Glass ionomer cements are influenced by the storage media, showing significant changes in the case of an acidic environment (in our case, artificial saliva with different pH). As long as the material is tolerated and protected by the tooth structure, resistance to abrasion will be satisfactory. Keywords: glass ionomer cements, pH, artificial saliva, wearing

A number of inventions, and theoretical and experimental research allowed to increase the thermal homogenous melt flow-rate delivered by the screw. On the other hand, quality of the extruded product depends on geometrical considerations of the extrusion head and on a large scale on the rheological behaviour (viscous and elastic) of the polymer melt. Non-harmonizing the design of the screw-barrel unit with the construction of the extrusion head can lead to low-quality products. In this paper, the extrusion head working field was drawn based on limitations imposed by the screw-barrel unit, i.e.: maximum flow-rate assuring required melt thermal homogeneity; - maximum flow-rate for which the heating system on the barrel (and screw, eventually) assures the extrusion temperature; -minimum flow-rate corresponding to screw diameter. Keywords: extruder head working field, extruder performance, rheological behaviour, screw-barrel unit