| This article studied an intrinsically colored microcrystalline glass-ceramic containing tetrasilicic fluormica as the predominant crystal phase, which was eminently suitable for use in dental CAD/CAM systems. Machinability in this glass ceramic was good and it exhibited a yellow coloration in visible light and fluoresce with a blue coloration while being exposed to ultraviolet radiation.The yellow coloration was produced through the incorporation of a color package comprising 2%~5%CeO2, and 0.5%~1.0%Tb2O3. The yellow coloration demanded close control over many factors including amount of fluorine, ratio of Mg2+ to K+ and heat treatment process. The preferred heat treatment was 65Q癈 for 1 h, plus lOOCX? or 1050癈 for 3h or 4 h, and the ratio of Mg2+ /2K+ in composition should be in the range of 1.0-2.0.A new method that allowed simultaneous control of the morphologies and distribution of the structural elements was proposed. Tetrasilicic fluormica seed crystals, combined with alignment of the seed particles by gel casting allowed high strength and homogeneous distribution of fine crystalline constituent in mica glass ceramic. The occurrence of opacification during heat treatment also decreased.This material had the substantial drawback that it can only be produced in limited shades. Furth study should be done to develop other machinable materials.
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