Background: The need for the whitening effects of toothpastes became primary for most users. Changes in the surface roughness of restoration materials after tooth brushing are inevitable, and the abrasion is known to increase the possibility of dental plaque accumulation. Aim of the study: To evaluate in vitro surface roughness changes of different dental restorative materials after tooth brushing simulation. Material and methods: Fifty specimens of two composite materials (Evicrol, Super-Cor), two glass ionomer materials (Glassfill, Kavitan Cem) and a silicate cement (Fritex) were prepared according to the manufacturer’s instructions. Each group of specimens was divided in three subgroups for tooth brushing simulation: using two different types of toothpaste and without toothpaste. Before and after 153 hours of tooth brushing simulation with a custom-made device, the surface roughness was measured with a surface roughness tester. Statistical analysis was performed after collecting the data. Results: All materials exhibited changes in surface roughness after the use of both toothpastes. The self-curing composite showed the less change and glass ionomer materials showed the greatest changes in surface roughness. Conclusions: The surface changes of dental materials depended on their composition and the cleaning procedure. Although self-curing composite was the most resistant to surface changes, its surface roughness values were high. Light-curing composite presented the lowest surface roughness values, even after brushing with toothpastes. The “medium” labeled toothbrush caused significant changes without toothpaste on the surface of light-curing composite, glass ionomer and silicate cement materials.
The metering shaft of the drilling machine is driven from the impeller. The standard traditional gearbox, the Norton gearbox, provides a constant rotating motion between the impeller and the metering shaft. Manufacturers have started to replace this gearbox with an intermittent rotating movement. Using the stepless variable speed gearbox, the speed of the metering shaft and thus the seed rate is set steplessly. The aim of the thesis is the mathematical modeling of the intermittent rotating motion of the seed drill of a particular drilling machine, and the creation of a striping model.
Today’s industry relies not only on raw material processing, but also on information. The huge amount of data obtained during the production process of goods and services; as well as information about the context of the production processes has made it necessary to account for, methodize, analyze and react in order to achieve a competitive market share. Fortunately, this technological leap has been able to support the above process, but the presence of those new technologies requires adequate preparation from the point of view of human resources too.
The presented research is designed to meet a particular challenge facing the industry. Its aim is to automate the process of friction coefficient determination, using a method that enables quick and easy repeatability of measurements developed by S.C. Plasmaterm S.A in Târgu Mureş.
The Mixed CAD Generating Method, developed by the first author and presented in previous papers, is able to generate gear teeth gaps from a special points cloud. The generation method requires only a few specific points from the cutting edges of the generating tools. These points can be obtained in a first approach through a simple drawing of the cutting edges. The drawings can use either mathematical equations, or simply the construction and design principles of the cutting tools. In the case of multi-edge cutting tools of a higher level of complexity, or in case of the absence of the edge equations, there exists a simpler approach. It consists in building a solid model, or obtaining the solid model of the tools from the tool’s designer or manufacturer. In these cases, the generating points are downloaded from the solid model. This paper presents two possibilities of obtaining these points with usual CAD methods.