Technological advances are closely related to the development of new materials and their processing and manufacturing technologies. In the dental field, the high complexity of the geometrical designs of crowns, bridges and other applications of digital light processing 3D-printable biocompatible resins is the reason for the need for a deep understanding of the mechanical proprieties and behavior of these materials. The aim of the present study is to assess the influence of printing layer direction and thickness on the tensile and compression proprieties of a DLP 3D-printable dental resin. Using the NextDent C&B Micro-Filled Hybrid (MFH), 36 specimens (24 for tensile strength testing, 12 for compression testing) were printed at different layer angulations (0°, 45° and 90°) and layer thicknesses (0.1 mm and 0.05 mm). Brittle behavior was observed in all specimens regardless of the direction of printing and layer thickness for the tensile specimens. The highest tensile values were obtained for specimens printed with a layer thickness of 0.05 mm. In conclusion, both printing layer direction and thickness influence mechanical proprieties and can be used to alter the materials’ characteristics and make the final printed product more suitable for its intended purposes.
Introduction. Musculoskeletal disorders (MSDs) caused by incorrect working posture among dentists is a serious issue and one that leads to decreased productivity and quality of life.
Aim. The aim of this study was to evaluate the impact of MSDs caused by postural errors in dental healthcare professionals on the body’s center of gravity through a new and innovative technique – baropodometry.
Methods. In this study we included 3 oral healthcare specialists with over 20 years experience of practicing in orthostatism, with confirmed work-related MSDs, and performed a baropodometric analysis on them.
Results. According to the analysis, all 3 test subjects had alterations of the body’s center of gravity, with uneven distribution of pressures on the feet being recorded by the baropodometer.
Conclusion. In an effort to maintain a good field of view and workplace in orthostatism, the subject is forced to adopt an non-ergonomic position that leads to uneven weight distribution, shifted center of gravity that eventually cause musculoskeletal disorders.
The lifetime cost evaluation of a seal must take into account all expenses throughout its operation. The thermodynamic aspects of mechanical face seals (MFSs) analyzed using FEM for various pairs of materials and their correlation with wear, reliability, and economic feasibility have not been researched in the literature. The MFSs analyzed in this paper were manufactured by ROSEAL S.A. for use in water pumps. The materials of the primary seal rings used by manufacturers were taken into account. The operating conditions were as follows: n = 3000 rpm, water temperature = 80 °C, and pressure = 0.1 MPa. In our study, we focused on the thermodynamic phenomena occurring in the MFS. The thermodynamic simulation was run using the FEM software MSC Nastran. Maps of the temperatures and the heat flow in the primary seal rings, for the two types of MFS and for different pairs of materials, were obtained using FEM analysis. The results highlight that the flow rate of leaks increases linearly with the angular speed of the pressure ring and is independent of the materials used in the primary seal.
Either due to trauma, extraction or congenital factors, the absence of teeth has aesthetic, functional, financial and psychological consequences. The aim of the current study is to assess an individualized polymeric 3D printed digitally planned surgical guide designed to achieve precision and predictability in non-standard mini-implant orthodontic cases. Twenty-seven patient records with missing anterior teeth were selected from the database of a private clinic in Timisoara, Romania. Based on the analysis of the cases included in the research, a surgical guide for the insertion of mini-implants as provisional crown support was designed. An FEM simulation was performed using the Abaqus numerical analysis software. Finite element simulation revealed the maximum displacements and stresses that occur in the surgical guide. Mini-implant supported provisional crowns can be a simple and low-cost method to increase patient self-esteem and compliance with the orthodontic treatment. Computer aided mechanical simulation is a useful tool in analyzing different polymeric surgical guide designs before being used in clinical situations in order to avoid failure.
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