Pressure slip casting is used for the production of technical ceramics in an industrial scale. The expansion to further applications started only a few years ago in order to minimize processing time. Especially, the processing of slips with a small particle size is a major challenge. But small particle sizes are a crucial requirement for highly mechanically loaded components like dental restaurations.
IKTS scientists were able to manufacture multilayer blanks for dental restaurations by pressure slip casting. Gradients in color and translucency of the natural teeth were implemented already in the liquid shaping process. The tailored mixing of slurries with different dopants allows for a smooth gradient without the formation of visible layers.
After the selection of a suited mold material, optimized process parameters for the preparation of the slurries by agitator bead mills were selected. A specially designed pressure slip casting cell allowed for the generation of a homogeneous and dense microstructure with good mechanical properties. The mean particle size of the slurries was 0.18 µm. Subsequently, process dependencies such as the influence of the solid loading (55-75%) and the casting pressure (15-25 bar) on the density and the microstructure were investigated. During the casting process, the well defined addition of slurries with different doping resulted in the generation of multicolored blanks with a height of 20 mm. These components meet the high standard in terms of gradient in color and translucency. At the interface of the differently doped slurries, no inhomogenity was found after sintering. Besides the good aesthetics, the multicolor blanks can also convince with very good mechanical properties (biaxial strength 1050 MPa). Final experiments on the machining with a dental milling machine proofed the good suitability of the blanks to be manufactured to multicolor restaurations.