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This workpaper presents the assessment of the interaction between the dimension of glycol-modified polyethylene terephthalate (PETG) and the attrition of occlusal appliances by determining the degree and area of attrition of dental mouth guards made of PETG plates of different sizes: 0.8mm, 1mm, 1.2mm, 1.5mm, 2mm, 2.2 mm thick. The samples were made by thermoformed using the Erkoform device and inserted into the oral cavity subjects. The evaluation was made 2 weeks, 4 weeks and 6 weeks later. For evaluation it was used coloured occlusal spray. The best results were obtained with the 2 mm thick, but in our study the occlusal appliances with 1,2 mm had good results too. Keywords: occlusal appliances, glycol-modified polyethylene terephthalate (PETG), thermoformed

In order to obtain an ideal smile design for our today subjects, more often the dental treatment requires interdiciplinarity. Recent advances in dental materials and techniques promote the opportunity of bonding orthodontic attachments to surfaces other than enamel, like porcelain crowns, veneers, or bridges. This study aims to compare tensile bond strengths of metal brackets bonding to porcelain fused-to-metal crowns, using two different luting cements (RelyX™ Unicem U200 by 3M ESPE, respectively Blugloo by Ormco) and the same surface conditioning system, as well as to determine the findings’ statistical value. The results evaluated by ANOVA, Tukey and Kruskal-Wallis tests indicated no statistically significant differences among the two cements in terms of tensile bond strength. Keywords: metal brackets, ceramic crowns, tensile bond strength, luting cements

The specific parameters describing the flows of Bingham type rheological fluids through a circular pipe, under the action of a pressure gradient in the direction of the movement are established, using the Non-Standard Scale Relativity Theory approach. In such context, an analytical solution and a numerical application (for KELTAN 4200 — an etilene-co-propilene copolymer) are obtained. The friction effort has two components, one of specific fluid gliding, the other of shearing, depending on transverse speed gradient. In the central area of the fluid movements a particles agglomeration (fluid stopper) occurs, defined by a constantly moving structure. Keywords: rheology, friction effort, polymers, fluid stopper, speed

Shape memory alloys are often used in applications where corrosion resistance property is very important. We can obtain a thin polymer layer using pulsed laser deposition on a nitinol wire with many applications in medical field. The polymer and the shape memory element with a non-metallic thin layer on the surface were analyzed by structural and chemical point of view using scanning electrons microscopy and X-ray dispersive energy analyze. Thermal insights were realized using a differential scanning calorimeter to analyze the polymer behaviour before and after deposition process. Preliminary results on the deposition set-up and the physico-chemical properties of the thin layer are presented and discussed below. Keywords: Shape memory alloys, thin polymer layer, pulsed laser deposition, PMMA

In the following work a correlation was inferred of the effects of material behaviour in different zones of the extruder screw channel with a number of process parameters. Calculus of the average temperature variation of the processed material with length and depth of the screw channel allows effective positioning of intense mixing zones, resulting in enhanced melt thermal homogeneity and product quality. Relationships for the flow-rate of the feeding zone, the specific power and the efficiency of the extrusion process allow the overall performance calculus of the extruder. To increase process efficiency one must reduce the heat loss, Ql which results in energy savings and the decrease of thermal pollution of the environment. It becomes thus possible to replace a certain number z of actual extruders with diameter D, each with a total installed power Nt,1 and flow-rate Gm,1, with a single extruder of the same diameter D assuring a flow-rate Gm = z . Gm,1 and whose total installed power is Nt [ z . Nt,1. Heat lost through the external surface of the heating system of z extruders (z . Q1,l) is higher than that of a single modern extruder. Consequently, process efficiency in the up-graded extruder is higher than that of the extruders, resulting in diminished energy related expenses and cost of the mass unit of extruded product along with less environment pollution. Keywords: extrusion process; extruder performance; output; extruder efficiency; thermal pollution; energy

This paper tackles a ligno-cellulosic composite, whose basic matrix is made out of hemp hurds and mineral binders, as regards the percentage participation of the hurds in the structural stability and thermal-transfer capacity, for a plate- or block-shaped product. The studies, corroborated with laboratory research, aim at ascertaining the use of these products both as lining and as filling material, in the sandwich-type structures, in civil engineering; the materials basis specific to constructions can thereby be achieved, in a wide range, in terms of the thermal-insulation capacity and, implicitly, of the energetic consumption typical of civil, industrial, agro-zootechnical engineering. Keywords: hemp hurds, mineral binders, thermal conductivity

An important desirable effect of endodontic therapy is to induce the repair of periradicular tissues and to stimulate the cementogenesis. Endodontic perforations interfere with these goals, therefore, the discovery of an ideal material for perforations repair, with high biocompatibility, has become a necessity. The study is based on the comparative analysis of the biochemical profile of the animals implanted with three materials used in endodontics, at 7, 30 and 60 days after intervention, for Ca, P and Mg evaluation. Keywords: stomatognathic system homeostasis, biocompatibility, biochemical profile, Ca, P and Mg evaluation, biomaterials, dental treatments

One of the aspects determining the speed rate, and therefore the economic viability, of an injection molding process is the efficiency of the heat transfer between the injected part and the mold. The quicker the temperature of the part drops below the threshold value at which it can be ejected from the mold, the sooner the mold can be closed and the injection of next part can begin. In this article is presented the solution to the highly constrained structural design optimization problem of maximizing the heat exchange surface area of the cooling system of an injection mold, an exercise aimed at increasing the speed of an existing molding system. The author described how a systematic design search via an evolutionary heuristic specifically designed for such highly constrained design problems can yield substantial increases in cooling area, while allowing the relatively straightforward implementation of the constraints that ensure the functionality of the system. Keywords: Evolutionary optimization, Injection molding process, Punctuated equlibrium, Cooling system

Geopolymer has good bonding structure of amorphous inorganic polymer which has excellent bonding agent properties and shows high bond strength in an early stage. Therefore, inorganic material like geopolymer which have advantages in previous research and has potential in replacing the organic materials in coating application. The chemical composition of the geopolymer materials which were metakaolin, ground granulate blast slag (GGBS) and fly ash contain mostly Silica (Si) and Aluminium (Al) which were possible source material for the manufacture of geopolymer coating. Based on Si:Al ratio and water:cement ratio were the important factor in the process of geopolymer coating which Si:Al of 3.5 and water:cement ratio of 0.25 gave the best result in strength in geopolymer coating. The common techniques for coating method that have been used were brush, spraying and dipping. From previous research, coating method influenced the greater result in fire proofing materials and high temperature. For compositions with Si:Al = 2.5 the adhesive strength was > 3.5 MPa while for Si:Al=1 and 2 only weak adhesion to the metal substrates was achieved in metakaolin based geopolymer coating. Fly ash geopolymer coating has improved the compressive strength of the coatings materials as high as 40 MPa with the high sintering temperature, 1500°C. Thermal expansion measurements in metakaolin geopolymer coating of the Si:Al = 2.5 composition revealed expansion of up to 6% at 800 °C, while for Si:Al = 1 and Si:Al = 2 compositions up to 4% shrinkage was observed. Keywords: Alkali Activated Binder, coating, geopolymer, XRF, XRD, SEM

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