Effect of cavity shape on microstructural evolution of pure aluminum in electrically-assisted solidification.

Grain refinement is a crucial issue in metallic materials. One of the emerging techniques to obtain equiaxed grains is to apply an electric current to the liquid metal during solidification. With this view, in this paper, the effect of electric current on the solidification behavior in various cavity shapes of mold was investigated. Cylinder-, cube-, and cuboid-shaped cavities designed to have similar cavity volume were used. By applying an electric current during the solidification of liquid aluminum, the grains were effectively refined with a grain size of approximately 350 µm for all three types of cavities. The circulating flow of liquid aluminum was observed to have a similar shear rate intensity in all three types of cavities, which is known to be sufficiently high (over hundreds of s-1) to induce dendrite fragmentation resulting newly generated nuclei. Dispersion of nuclei on unsolidified aluminum appeared differently according to the shape of the cavity, which influences final shape of refined zone. The area fraction of refined zone was affected by the relative relationship between the solidification completion time and the electric current application time. This study will provide insight to control of process parameters when electrically-assisted solidification is applied to a real product with a complex shape.

Bone regeneration in the maxillary sinus using an autologous fibrin-rich block with concentrated growth factors alone.

PURPOSE: The purpose of this study was to evaluate the predictability of new bone formation in the maxillary sinus using an autologous fibrin-rich blocks with concentrated growth factors (CGFs) alone as an alternative to graft material. MATERIALS AND METHODS: A total of sixty-one sinus grafts were consecutively performed using the lateral window approach. After making replaceable bony window, the sinus membrane was elevated to make a new compartment. After 113 implants (average 13 mm high) with 11 different systems were placed simultaneously, the collected fibrin-rich blocks with CGFs alone were inserted in the sinus. To seal the lateral window, the bony window was repositioned. Radiographic, clinical, and histologic evaluation was performed to verify sinus augmentation. RESULTS: No significant postoperative complications developed. New bone consolidation in all augmented maxillary sinus was observed along the implants on plain radiographs and on cone-beam computed tomograms. The success rate of implant was 98.2% after an average of 10 months loading. CONCLUSION: Fibrin-rich blocks with CGFs act as an alternative to bone grafting and can be a predictable procedure for sinus augmentation.

Powder based additive manufacturing for biomedical application of titanium and its alloys: a review.

Powder based additive manufacturing (AM) technology of Ti and its alloys has received great attention in biomedical applications owing to its advantages such as customized fabrication, potential to be cost-, time-, and resource-saving. The performance of additive manufactured implants or scaffolds strongly depends on various kinds of AM technique and the quality of Ti and its alloy powders. This paper has specifically covered the process of commonly used powder-based AM technique and the powder production of Ti and its alloy. The selected techniques include laser-based powder bed fusion of metals (PBF-LB/M), electron beam powder bed fusion of metals (PBF-EB/M), and directed energy deposition utilized in the production of the biomaterials are discussed as well as the powder fed system of binder jetting. Moreover, titanium based powder production methods such as gas atomization, plasma atomization, and plasma rotating electrode process are also discussed.