Objectives: Rapid development of digital technologies and 3D printing provide new tools for orthodontic indirect bonding. The purpose of this in-vitro study is to evaluate the clinical acceptability of hard CAD/CAM indirect bonding tray. Material & Methods: Ten soft silicone transfer trays and ten hard CAD/CAM trays were produced and 200 brackets were placed on them. The brackets were then transferred to twenty SLA-printed models by indirect bonding. These models were scanned and digitally compared to the reference model by three-dimensional superimpositions (GOM software). The linear and angular measurements were collected and analysed. Results: For the CAD/CAM trays, 100% of the mesiodistal, vertical and transverse measurements of incisors were within the clinical acceptable range of the American Board of Orthodontists (ABO) standards. More specifically, the clinically acceptable linear measurements were between 97 to 100% for silicone trays while they were between 89 to 100% for CAD/CAM trays. The clinically acceptable angular measurements varied between 87% and 100% for the silicone trays and between 79% and 100% for the CAD/CAM trays. Silicone trays were more precise than CAD/CAM trays. The difference was significant for all linear and angular measurements. Conclusions: While the CAD/CAM group shows clinically acceptable results according to the ABO, silicone remains to be more precise than CAD/CAM for transfer trays and is therefore still the reference. Clinical relevance: We demonstrate here that the orthodontic indirect bondings, whether they are realized using silicone transfer trays or CAD/CAM trays, are clinically acceptable in terms of the repositioning accuracy of brackets.

International audienceErosion and corrosion result in potential material loss. The erosion is a physical phenomenon but corrosion is chemical one. The study of these two phenomena, as functions of time and temperature, would lead to a better understanding of glass surface damage. Results allow one to determine the effects of immersion time, temperature of the water bath and residual stresses generated by Vickers indentation on the radial crack and topography of the imprint on the surface of a soda-lime silica glass. Water corrosion effects are different at the imprint corner and the radial crack tip as compared to edges and faces

International audienceSurface finish determines service life of glass workpieces. Therefore, an extensive polishing phase is usually performed to limit the local irregularities. In this paper, we propose to investigate the influence of the grinding parameters on the surface finish of glass samples in order to limit the damages at the earlier stage of the machining process. A central composite design of experiments has been used to define experimental tries that consist of up-grinding or down-grinding glass samples with various feed rate, depth of cut, and wheel speed values. Roughness parameters derived from the Abbott-Firestone curve R(k), R(vk), and the material ratio 100-Mr2 have been used to characterize the surface finishes of the ground glass samples. Using the design of experiments, surface responses have been modeled for each roughness parameter to investigate the influence of the cutting parameters. Abbott-Firestone parameters allow a relevant characterization of the glass samples surface finishes. Feed rate increase led to deeper valleys, thus providing a rough surface finish that could potentially shorten workpieces service life. On the contrary, increasing depth of cut tend to reduce valley depth. Wheel speed has shown minor influence on the surface finish. Up-grinding could help obtain less deep valleys than with a down-grinding. However, up-grinding also increases the cutting forces and induces vibrations that led to an increase of the core roughness and eventually to the fracture of the glass sample during the machining. In a material removal context-in opposition with polishing-feed rate should be carefully chosen since it is the most influential parameter on the surface finish. To maximize productivity while obtaining low-valleys surface finishes, an appropriate strategy would consist in down-grinding with a low feed rate, a high depth of cut, and a high wheel speed. [DOI: 10.1115/1.4004317

This paper presents a multidiscipline approach to propeller engineering. Surface ®nish is a stringent constraint for propeller blade hydrodynamic performance and leads manufacturers to add a polishing phase in the manufacturing process, therefore increasing the realization costs. A combined approach involving the de®nition of tool paths relevant to both domains, manufacturing and hydrodynamics, could improve the process by avoiding the polishing phase. To build such a strategy, relationships between the machined surface ®nish and hydrodynamic performance must be understood. A study has been carried out on the in¯uence of roughness heights and lays on the hydrodynamic performance of bidimensional hydrofoils.