Design of Join Glass Composition for Layered All-Ceramic Restorations

Development of new joining glasses tailored to layered all‐ceramic dental restoration systems is described. These new glasses were developed to meet the requirements for dental restorations, including coefficient of thermal expansion (CTE) matching in the 100°–500°C range, wetting characteristics, densification temperature for fritted glass layers, radio‐opacity, color, and lead‐free composition. Glasses in the BaO–Al2O3–Na2O–B2O3–SiO2 system were investigated for their biocompatibility, chemical stability, and suitable calculated glass transition temperature (Tg), and dilatometric softening point (Td). Appen additivity factors and Fluegal's database were used to estimate CTE, Tg, Td, and E (elastic modulus) and select compositions in the CTE range 6.00 × 10−6–10.4 × 10−6/K for application to common dental alumina and zirconia ceramic systems. A sol–gel approach was used to produce homogenous glass precursors covering a wide range of compositions. Melting, firing, and quenching the compositions were required to form dense, uniform, transparent layers.