Microstructure and Thermal Expansion properties of some Leucite glass-ceramics

Methods: Three groups of leucite glass-ceramics: (Group 1) IPS Empress Esthetic; (Group 2) Ceramco 3 Dentine; (Group 3) Optimal Dentine and (Group 4) experimental glass-ceramic were studied. Disc specimens (14mm diameter x 2mm thickness) were fabricated by heat pressing or sintering according to the manufacturers' instructions. Specimens were characterized using X-Ray diffraction analysis (XRD), Energy dispersive X-Ray analysis (EDS), Dilatometry and Secondary electron imaging (SEM) with quantitative phase analysis. Compositional glass data and EDS data was used for TEC predictions using Appen Factors.

Results: Tetragonal leucite was detected in all leucite glass-ceramics studied. Mean leucite particle sizes were (Mean ± SD µm): (Group 1) 1.7±2.0; (Group 2) 8.1±13.2; (Group 3) 5.5±9.7 and (Group 4) 0.6±0.4. Leucite area fraction (%) was: (Group 1) 31.2; (Group 2) 30.4; (Group 3) 36.5 and (Group 4) 19.5. TEC values of the glasses calculated using Appen Factors corresponded well with Dilatometry measurements. Glass-ceramic predictions using EDS data and Appen factors did not correlate well with TEC measurements.

Conclusions: The experimental glass-ceramic had a smaller leucite particle size than the commercial glass-ceramics studied. Glass TEC calculated using Appen factors maybe a useful tool for glass design.