Microstructure of etched "IPS Empress" heat-pressed ceramics observed by SEM.

A valuable characteristic of the "IPS Empress" used for producing all ceramic dental restorations is that it is a prefired ceramic ingot. The ingot is heated, softened and press-injected into the cavity, and ceramic restorations are fabricated by the lost wax casting method. The leucite crystal present in the ingot are scattered and distributed into the glassy phase in a more homogeneous manner through this pressing procedure, and the resulting ceramics are of higher flexural strength than conventional ones. The present study was carried out to clarify the microstructure of Empress ceramics by etching, and to observe the etched surface by scanning electron microscopy, in comparison with several other conventional ceramics. It was shown that the form and distribution of the leucite crystals in Empress ceramics are quite different before and after pressing, and that the staining and layering ceramics are also different from conventional ceramics. The method of surface treatment of ceramics prior to etching, such as fracturing or grinding, the kind of etching material used, the concentration and the etching time are important factors for revealing, observing and evaluating the microstructure of ceramics containing leucite crystals.