Lithium-zirconium silicate glass-ceramics for restorative dentistry: Physicochemical analysis and biological response in contact with human osteoblast

The main aim of this study was to evaluate the physicochemical and biological behavior of (LZS) lithium-zirconium and (LZSA) lithium-zirconium-alumina silicate glass-ceramics. LZS and LZSA silicate glass-ceramics were produced from commercial raw materials by melting (1550 °C/2 h) followed by water-cooling casting. The obtained glass frits were milled by a two-step process (dry and wet milling) up to achieve 5–10 μm particles. The milled powder was uniaxially pressed (50 MPa) and later fired at 900 °C/2 h (LZS) and at 850 °C/2 h (LZSA). Specimens were characterized by physical, chemical, thermal, and cell culture assays. Crystalline phases such ZrSiO₄ and residual quartz and lithium metasilicate (Li₂SiO₃) was found in the LZS group microstructure while LZSA showed a mixture of ZrSiO₄ and β-spodumene (LiAlSi₂O₆). Materials showed different thermal behavior and mechanical properties. LZS silicate glass ceramics revealed higher fracture toughness and Young's modulus values than those recorded for LZSA silicate glass-ceramics. A higher percentage of osteoblast cell proliferation and mineralization was detected on LZS surfaces when compared to LZSA surfaces. The chemical composition, microstructure, thermal behavior, and mechanical strength of LZS and LZSA silicate glass-ceramic can be adjusted for manufacturing of prosthetic structures for oral rehabilitation. Also, the interaction of glass-ceramics with human cells and tissues can be enhanced by increasing the content of bioactive ceramic materials such as silica or by adding additional bioactive compounds such as beta-tricalcium phosphate.