[Qualitative studies on the surface crystallization of dental glass ceramics (Dicor)].

The crystallization of enstatite at the surface of Dicor glass during 'ceramization' is proved by electron microscopy and x-ray diffraction. Microprobe measurements demonstrate a loss of potassium and an uptake of calcium in the outer region of the glass-ceramic after ceramization due to an ion exchange between glass and ceramization investment. This investment consists of gypsum and leucite. A thermal analysis reveals the decomposition of gypsum in the range of the ceramization temperature. Calcium diffuses into the surface of the glass while simultaneously potassium leaves the glass. The altered composition allows the crystallization of enstatite.