Structure, chemical durability and microhardness of glass-ceramics containing apatite and leucite crystals

Glass-ceramics based on SiO2-Al2O3-K2O-Na2O-CaO-P2O5 prepared by controlled crystallization of glass are studied. Glass melted from a batch of high pu rity raw materials was quenched and milled. The powder was heat treated at 850 degrees C, 900 degrees C and 1150 degrees C for 1 h, quenched in water, milled, formed and sintered at 1000 degrees C for 1 min. The study focused on the phases of crystallization and microstructure of both heat treated a nd sintered samples. Microhardness and chemical durability were measured of glass-ceramics produced by sintering. Leucite and needle-shaped fluorapati te crystals were developed, The microstructure changed depending on heat-tr eatment and sintering temperatures. The chemical durability and microhardne ss of glass-ceramics prepared for restorative dental applications are influ enced by the properties of the bulk glass. (C) 2000 Elsevier Science B.V. A ll rights reserved.