Browse Articles

The pneumatic elastic elements are widely used in the secondary suspension of modern railway vehicles due to their important advantages compared to the conventional ones. In the present paper, the modelling and analysis of the pneumatic suspension is approached, taking into account the main elements, pneumatic enclosures and rubber elements. The analysis performed investigates the influence of relevant parameters on suspension stiffness and on its dynamic response.

This paper describes the evaluation of the aging process of some polymeric painting materials subjected to a thermal treatment in electro insulating fluids, based on natural esters (vegetable oils). The paint layers surface morphology was comparatively characterized by FESEM technique, prior to the exposure, and after 1000 h of exposure to vegetable oil, heated at 130oC. The results show a substantial increase in the pulling resistances for all the painting materials subjected to this investigation, especially in the presence of the Kraft insulating paper and copper foil (inserted compulsory to emulate the actual working environment), due to an increase in the painting material adhesion, as well as an increase of the tensile strength of the paint layer. These findings may open new theoretical and practical research prospects, particularly in the field of preliminary treatments for materials used for heavy duty industrial transformers.

The development of new classes of dental materials determined the apparition of reinforced polymers, as BioHPP and Trinia, used for core in non-metallic prosthetic restorations, including in implants non-metallic superstructure. The purpose of the study was to present the results of the comparative clinical trials referring to the use of BioHPP and Trinia resins as core in fixed prosthetic rehabilitation. The researches were performed on 33 patients in which we realized 71 fixed prosthetic restorations. According to the six evaluation criteria used in research, we conducted biannual monitoring meetings over two and half years period for registrations of comparative results in the use of these two reinforced polymers as core. The results of the study demonstrated that both type of these materials exhibit a certain degree of elasticity and presents many advantages, therefore these represent a beneficial acquisition in patients oral health.

Implants and biomaterials used in hard and soft oral tissue augmentation are very complex, but predictable to use nowadays, as the technological advances haven’t skipped this field of medicine. Cases that were impossible to treat with implant retained fixed prosthesis some years ago, have become the daily practice of oral surgeons and dentists around the world. The new user-friendly products, together with simplified protocols, increased the practitioners’ predictability and success rate, thus the biomaterial industry took a huge leap forward. As the biomaterial industry keeps developing continuously, making better and safer products, the surgical and prosthetic protocols evolve and change as well. On this matter, the implant placement has become safer, using digital surgical guides. Guided implant placement doesn’t just allow the practitioner place the implant in the patient’s bone, but, moreover, it helps him place it in the correct, 3D, prosthetic position. And, thus, guiding the future bone augmentation and regeneration as well, accordingly. So, the implant placement has shifted from bone-orientated to prosthetic-orientated, offering at the same time a better primary stability for the implants, due to the prior planning. The present clinical study aims to analyze the outcome of the digital guided protocol. Unlike the free-handed surgery, the digital guided surgery allows dentists and oral surgeons to place implants according to the future prosthetic position of the crowns, even in conditions of alveolar ridges with bone resorption. Moreover, it makes possible the “one day implant” concept, the dental technician being able to create the provisional crown/s in advance, knowing precisely the future position of the implant placement. So, at the time of the surgery, the provisional crown is also put in place, guiding the soft and hard tissue healing and also giving the patient a greater satisfaction.

The purpose of this study was to evaluate the behavior of four restorative materials in non-carious cervical lesions when subjected to exterior stresses of different magnitude. A plane model reproducing a vestibular and lingual section of the lower canine was created. The finite elements are of a two- dimensional type (2D) - quadrilater. Four restorative materials were used: Vitrebond, Dyract AP, Vitremer, Fuji IX. All materials were considered to be isotropic and elastic. Nodal charges were of 40 degrees to vertical, applied on the vestibular side at h=8.993mm to gingival crest, of increasing magnitudes:20, 40, 60, 80, 100, 120, 140, 160 N. The results of this study showed that after restoration stress values in all the elements are (with minimal differences) similar to those in the healthy tooth; a correct restoration leads to normal functioning of the tooth. It can be considered that particular types of restoring materials should be used in particular lesions to be restored, depending on the location of the lesion and the elastic characteristics of the materials and tooth structure. A correct restoration leads to normal functioning of the tooth.

The development and increase use of the endoscopic techniques in endonasal surgery has encouraged the practice of endoscopic dacryocystorhinostomy as a trustworthy alternative to external dacryocystorhinostomy. The purpose of the present paper is to provide another insight into transnasal endoscopic dacryocystorhinostomy by proposing the fitting, at the end of the intervention, of a conformational stent model with aspiration made out of medical silicone similar to a Montgomery tube.

In this study, newly developed polymeric composites based on poly(3-hydroxybutyrate) (PHB), cellulose fibres (CF) and plasticizer (bis[2-(2-butoxyethoxy)ethyl] adipate) (DBEEA) were subjected both to microorganism’s action in controlled conditions, and to soil’s action by sample burial. The weight loss of PHB based composites at 60 days exposure were determined in comparison with neat PHB. The weight variation for PHB based composites buried in a natural soil at 45 days and 90 days was monitored. DSC-differential scanning calorimetry and SEM -scanning electron microscopy analysis were performed on the tested composites after 90 days of soil burial. It was found that the introduction of cellulose fibres into PHB leads to the increase of biodegradability of composites.

In recent years, the inorganic nanoparticles played an important role in the membrane technology due to their special properties, most notably being the hydrophilicity/hydrophobicity modification of the active surface of the membrane. In this paper, the polymer used for membrane manufacturing was polysulfone (PSf) via phase-inversion method. The composite PSf membranes were prepared by blending zinc oxide (ZnO), titanium dioxide (TiO2) nanoparticles and ZnO/TiO2 nanohybrid with three concentrations. Retention of Congo red dye, distilled water permeability, relative flux and relative flux reduction were tested in order to study the effects of the nanoparticles in the membrane matrix. SEM, EDX, porosity, roughness, contact angle, tensile strength and elongation measurement were conducted in this article, also. Compared with control PSf, ZnO/PSf and TiO2/PSf membranes, the experimental results indicated that the ZnO/TiO2/PSf nanohybrid membrane presents the best overall properties, including permeability, retention, and antifouling ability. ZnO/TiO2/PSf membrane exhibits a percentage increase in permeability of 254% and retention of 64.58 % relative to that of the control PSf membrane.

The seven curcumin derivatives were deposited on palygorskite in order to obtain hybrid materials. The fluorescence emission spectra of the obtained materials show a decrease in fluorescence intensity relative to the respective dyes, due to the environments around the dyestuff molecules created in the host matrices. Absorption studies show the best adsorption on the inorganic matrix, for the compounds with the hydroxyl groups. Correlating fluorescence spectra of hybrid materials with the results for absorption spectra of the dyes adsorbtion on the surface of the clay lead to the conclusion that a high percentage of the adsorbed dye had the effect of fluorescence quenching. Thus, it was confirmed that the fluorescent properties of hybrid materials depend on the interactions established between the fluorescent dyestuff and the inorganic network.

The present paper reports the first attempt to synthesize bicomponent hydrogels based on methacryloyl derivatives of gelatin (GelMA) and mucin (MuMA) with different compositions, with potential as wound dressings. While gelatin is widely investigated and used to fabricate scaffolds and coatings stimulating cell interactions and tissue regeneration, mucin - a macromolecule which covers the wet epithelia - remains yet under exploited as biomaterial. The influence of MuMA content on various parameters such as the affinity for aqueous media, stability in simulated physiologic media and the rheologic behavior was investigated. Also, the preliminary assessment of the drug release potential and biocompatibility were performed. The materials’ water uptake capacity and rheologic behavior depend on the pH value of the incubation media, while their composition influences the drug release capacity and cells-scaffold interactions.