Chemical strengthening of dental ceramics by ion exchange has hitherto only been confirmed for feldspathic porcelains. The objective of this study was to examine whether the strength of lithium disilicate glass-ceramics can be increased by ion exchange as well. A lithium disilicate glass-ceramic material was treated in different molten salts. The concentration gradients of the relevant ions in the surface layer were investigated by means of electron probe microanalysis and secondary ion mass spectroscopy. Characteristic strength and Weibull modulus data were determined. An increase in strength of 25% was achieved by treatment in potassium nitrate. The chemical analyses revealed that the increase in strength resulted from an exchange of potassium for lithium ions. We conclude that ion-exchange treatments can increase the strength of lithium disilicate glass-ceramics. The improved material could be used for highly stressed applications, such as posterior crowns or inlay-retained bridges, with higher mechanical reliability.
(c) 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008.