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Polyurethanes are used in many areas of bioengineering as they are biocompatible and present various mechanical properties according to the needs of each application. Necuron is a polyurethane that has been valued in many areas of industry. This paper presents compressive and three point bending testing done on three types of Necuron (840, 1020, 1300) with the purpose of evaluating its mechanical properties in order to use Necuron as a new material for transtibial prostheses. Results have shown Necuron 1300 to be a good candidate to fulfill this goal. Still there is need of further experimental programs to obtain reliable statistical information regarding the mechanical properties of Necuron. Keywords: Necuron, compression, bending, transtibial prostheses

The aim of this study is to determine the bonding resistance of orthodontic brackets in accidental conditions i.e. bites from very hard materials which may occur in a normal activity. Many studies had been developed concerning the integrity of orthodontic systems and the strength of various pairs of brackets and adhesives in controlled conditions. In orthodontics many patients were returning to treatment, especially in the period immediately after the installation of orthodontic system as a result of failure of brackets. This failure is a consequence of patients’ natural habits on biting food despite medical recommendations. For this study bovine rib bone were used to simulate the human tooth and a certain pair adhesive-bracket. Pretests were developed in order to identify the behaviour of organic material and the results were satisfying. Unlike other studies in this study the shear resistance of the adhesive was analyzed using an universal testing machine with a load on the bracket. Since the study concerns with accidental detachment of the bracket the experimental parameters were set as close to the natural conditions. The results are encouraging the development of further studies on various pairs adhesive-bracket using bovine bone as human teeth simulator since its results are fitting data reported by other authors following numerical or empirical studies on human teeth. The use of bovine bone ensures the reproduction of the tests without having the care of teeth collection. Keywords: orthodontics, adhesive, bracket, shear strength

The aim of this study is to analyze the stress generated by the shrinkage of lutting materials in restorative therapy with indirect composite inlays; we follow the way of the tension transmission from the lutting material to the restoration and to the dental tissues. In our study it was used a virtual construction of an upper first molar, created with the Finite Element Method. Our conclusions demonstrate that the shrinkage of the lutting resin influence the fracture resistance of the restored teeth, and, of course, the longevity of the indirect inlays. Keywords: indirect inlays, composite shrinkage, polymerization stress, prosthesis structure, dental treatment

Removable partial dentures are widely and successfully used in the rehabilitation of partial edentulous patients. These types of dentures can be made from PMMA (poly methyl methacrylate resin) or polyamides, both types of materials having their advantages and disadvantages. Evaluation of these removable partial dentures is accurate only if are considered all the parameters. Computer-Aided Engineering (ANSYS) software is used with a 3D Computer-Aided Design (3D CAD) solid geometry and simulates the behaviour of solid bodies under thermal or structural loading conditions. ANSYS automated the Finite Element Analysis (FEA) technologies and deliver the results listed. All considered criteria materialized by Numerical Simulation concept serve as guides for a qualitative evaluation of known design requirements. Keywords: PMMA, ANSYS, 3D CAD, FEA

The aim of this study was to evaluate the effects of one in-office and two home bleaching agents on the surface roughness of a hybrid, microhybrid and nanohybrid composite resin. Three composite resins (Valux Plus, 3M ESPE, Filtek Z 250, 3M ESPE, and Herculite XRV Ultra, Kerr) and three bleaching agents (Opalescence PF, Ultradent Products, Perfect Bleach, Voco, and Perfect BleachOffice +, Voco) were chosen for this study. Twenty eight samples of each composite resin were prepared and were equally split in 4 groups: 7 samples were stored in distilled water (control group), 7 samples were subject to 17% carbamide peroxide gel (Perfect Bleach) action for 3 h a day, 7 days, 7 samples were subject to 15% carbamide peroxide gel (Opalescence PF) action for 3 h a day, 7 days and 7 samples were subject to 35% hydrogen peroxide gel (Perfect BleachOffice +) action two times for 15 min . After cleaning the samples were submitted to roughness evaluation using atomic force microscopy (AFM). Bleaching agents that contain 35% hydrogen peroxide and 17% or 15% carbamide peroxide increased the composite resins surface roughness. The hybrid resin recorded the highest roughness after bleaching, followed in descending order by microhybrid and nanohybrid composite resins. Keywords: bleaching agent, composite resin, roughness evaluation, carbamide peroxide, atomic force microscopy

The aim of the present paper was to investigate the chemical corrosion in various solutions, of a commercial resin based restorative nano-filled composite. 20 samples of a nanocomposite Filtek Supreme XT (3M ESPE) were immersed for 30 days in Ringer (physiological solution), Fusayama artificial saliva, and Afnor artificial saliva. After that, they were examined by scanning electron microscopy and energy-dispersive X-ray spectroscopy. It resulted that the corrosion is mainly due to the pitting, micrometric holes being observed. Also, preferred directions of corrosion resulted, as consequence of micro-scratches formation during the samples preparation. The oxygen content generally increased due to the oxides formation, while carbon, silicon and zirconium normalized atomic percents decreased, showing the corrosion both of the polymeric matrix and of the filler particles. Micro-holes size statistics revealed quantitatively the degree of corrosion and agrees well with the changes of chemical composition. Keywords: nanofilled composite, pitting corrosion, artificial saliva

The aesthetic composite inlay or ceramic ones are useful for restoring posterior teeth affected by decay processes. The choice of the inlay type can sometimes be a challenge for the dentist. The aim of this study is to identify the optimal type of an inlay used for second-class cavities that can assure a good long-term prognosis of dental restoration. In order to achieve this study, it was performed a 3D analysis of stresses recorded in a premolar restored with a composite inlay and a ceramic inlay, the simulation being done by finite elements method (FEM) using ANSYS program. The study results showed that stresses registered in the tooth restored through ceramic inlay are more favourable than those recorded in the case of the tooth restored with composite inlay. Keywords: dentistry, restoration, FEM, composite material, tooth-restoration

Facial epistasis represent facial prosthetic components made of acrylic or silicone plastics, which have no other function than to rebuild the lost region of the face in order to partially restore the physiognomy. A mandatory step in the manufacturing process of epistasis is represented by fingerprinting the tissue defect and the entire facial region and making a study model as basis for designing the epistasis . Keywords: facial episthesis, prosthetic components, acrylic or silicone plastics

Metal-composite crowns or metal-polymeric crown are an intermediary option from the mechanical and esthetical characteristics between acrylic resin and ceramic materials. Same as in the case of other types of fix partial dentures, the esthetic veneer may present fissures or fractures. The replacement of a fix partial denture is time consuming and involves high costs. In specific clinical cases, the metal-composite fix partial dentures can be repaired with plastic materials like diacrylic composite resin. Metal-acrylic and metal-ceramic fix partial dentures can also take advantage of the diacrylic composite resin in similar situations- fracture. The repairing maneuver can be considered temporary for a longer period of time. The key of reparation’s success is the interface integrity between the two materials. Imagistic investigation methods, like Atomic Force Microscopy gives important information about the surface roughness of different materials. The purpose of the present study is the investigation of the new interface obtained after the direct reparation of metal-composite crowns with diacrylic composite resins. Keywords: crown, acrylic resins, ceramic materilas

This paper is about obtaining polyolefin composites with antibacterial properties for the manufacture of hollow blown bodies (vials, bottles, jars) used for the packaging of medical products, cosmetics and food. As main polymer, it was used polypropylene, and as biocide active agent, it was used silver chloride deposited on a support of titanium dioxide or of silica. Antimicrobial silver was added as a premix, using for this purpose the co-polymer ethylene-1-octene. Hollow bodies were obtained by extrusion-blowing and were tested for their mechanical properties and biocompatibility. Keywords: polypropylene, co-(ethylene-1-octene), hollow blown bodies, extrusion