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.

Musculoskeletal disorders (MSDs) are among leading factors for early retirement of dental practitioners while the application of ergonomic principles is often overlooked during dental education. The article aims to assess the need for dental ergonomics modules as an integrated part of the dental school curriculum and to quantify the significance and role of ergonomics in reducing musculoskeletal stress generated while undergoing dental training. The study design consisted of a three-part original close-ended multiple-choice questionnaire carried out among 75 sixth year students from “Victor Babeş” University of Medicine and Pharmacy, Timişoara, Romania. Questions focused on the basic knowledge of theoretical ergonomics, the ISO 11226 standard and means of improvement in undergraduate ergonomics training. Most students had an average level of knowledge regarding dental ergonomic principles. Data analysis showed that 62.16% agree that the information received in the second-year dental ergonomics course was helpful in regard to time organization. A high percentage (86%) also understood the correct positioning of the patient while performing dental procedures. Although implementation of ergonomic principles in the early dental training years has a high influence in the prevention of MSDs, students do not fully understand the impact this subject has on their future careers.

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.

The composite attachment loss during orthodontic clear aligner therapy is an adverse event that commonly happens in clinical practice and can affect the overall outcome and length of treatment. The aim of our research is to provide a basis for the further study of an innovative digital protocol and application method for orthodontic aligner attachments. Two 3D models were designed, one based on the proposed protocol and the other on the conventional method for aligner attachment application. Four attachment shapes were used to identify the maximum values for the von Mises equivalent stresses, the maximum displacements values and the areas in which these values were recorded through FEM analysis. The results of the mechanical simulation show lower values of von Mises stress recorded in the 3D printed attachments assemblies, independent of their shape, when simulated under the same boundary and load conditions. The trapezoidal prism shaped 3D printed model has a 3.7 times smaller displacement value (0.088 [mm]) compared to the adhesive resin model (0.326 [mm]). In conclusion, the proposed protocol for aligner attachments and the introduction of innovative materials is a promising method of solving conventional attachment problems in current orthodontic treatments.

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.