Effect of P۲O۵ on Crystallization Behavior and Chemical Resistance of Dental Glasses in the Li۲O-SiO۲-ZrO۲ System

Commercial dental lithium disilicate based glass-ceramics containing various amounts of P۲O۵ were synthesized. Regarding the crystallization behavior and physico-chemical properties of the glasses, the optimum percent of P۲O۵ was determined.as ۸ %wt. Crystallization behavior of the glasses was investigated by X-ray diffraction (XRD) and differential thermal analysis (DTA). The micro-hardness and chemical resistance of both glass and glass-ceramic searies were also determined. According to our results, lithium phosphate was precipitated prior to crystallization of the main phases, i.e lithium meta silicate and lithium disilicate. This early precipitation led to evacuation of residual glass phase from lithium ions, which caused increasing the viscosity of glass and so shifting of crystallization to higher temperatures. In addition, increasing in P۲O۵ amounts and consequently increasing in Li۳PO۴, led to significant decrease in the crystallite size and aspect ratio  of crystals. Furthermore, while the chemical resistance of the glasses was decreased with P۲O۵, it was increased with P۲O۵ after heat treatment process. The chemical solubility of these three glass-ceramics was between ۲۰۸۰~۱۱۸۸ μg/cm۲.

Keywords:

Glass-ceramic , Lithium-disilicate , Nucleacen agent , P۲O۵ , morphology , Chemical solubility