Phase Formation, Mechanical Strength, and Bioactive Properties of Lithium Disilicate Glass–Ceramics with Different Al(2)O(3) Contents

Owing to its excellent mechanical properties and aesthetic tooth-like appearance, lithium disilicate glass–ceramic is more attractive as a crown for dental restorations. In this study, lithium disilicate glass–ceramics were prepared from SiO(2)–Li(2)O–K(2)O–P(2)O(5)–CeO(2) glass systems with various Al(2)O(3) contents. The mixed glass was then heat-treated at 600 °C and 800 °C for 2 h to form glass–ceramic samples. Phase formation, microstructure, mechanical properties and bioactivity were investigated. The phase formation analysis confirmed the presence of Li(2)Si(2)O(5) in all the samples. The glass–ceramic sample with an Al(2)O(3) content of 1 wt% showed rod-like Li(2)Si(2)O(5) crystals that could contribute to the delay in crack propagation and demonstrated the highest mechanical properties. Surface treatment with hydrofluoric acid followed by a silane-coupling agent provided the highest micro-shear bond strength for all ceramic conditions, with no significant difference between ceramic samples. The biocompatibility tests of the material showed that Al(2)O(3)-added lithium disilicate glass–ceramic sample was bioactive, thus activating protein production and stimulating the alkaline phosphatase (ALP) activity of osteoblast-like cells.