Properties of lithium disilicate glass-ceramic obtained from rice husk silica

Abstract

Objectives: Lithium disilicate glass-ceramic used as dental prosthesis and glasses based on the Li 2O-SiO2 system has been investigated by substitution of the commercial high-purity SiO2 (Fluka) by silica obtained from rice husk. Methods: Powder mixtures based on stoichiometric composition of 66SiO2:33Li 2O(in mol%), were melted and glasses were obtained. The effect of the SiO2 substitution on phase formation, microstructure, cytotoxicity and chemical property were determined and discussed. Investigations were carried out by means of differential thermal analysis; X-ray diffractometry, X-ray fluorescence (for comparison between rice husk and high-purity SiO2 powders), cytotoxicity analysis and scanning electron microscopy. Results: Amorphous and transparent glasses were obtained after melting. These glassceramics, presented Tg near to 480°C and crystallization peak at 660°C, in both compositions and Li 2Si 2O5 as crystalline phases after heat-treatment. The cytotoxicity analysis show that both material, lithium dissilicate with high-purity and rice husk silica, not presented cytoxicity behaviour. The X-ray fluorescence analysis showed that the rice husk silica has high-purity, despite present oxide iron in greater proportion than commercial high-purity silica, what can leads to color alterations. Conclusions: Still without glass crystallization, the biological effects are going in a satisfactory way. The analysis will repeated for the crystallized glasses. The substitution of high-purity commercial silica by rice husk silica is a quite promising technique for dental prosthesis of lithium disilicate. The CNPq (Brazil), by the process 142994/2009-0, supports this work realization.