Spectrophotometric examination of the optical properties of lithium-silicate glass-ceramics with different substrates

Abstract

Creating esthetic, natural-looking crowns and fixed partial dentures (FPD) is highly affected by the experience of the dental technician even today. The aim of this in vitro study is to examine the optical properties of glass-ceramics of different translucency and thickness, combined with try-in pastes and substrates of different shades. Glass-ceramic specimens were produced of VITA Suprinity (VITA Zahnfabrik) zirconia-reinforced lithium-silicate ceramic, shade A1 T (low translucency) and HT (high translucency), in 0.5 mm; 1.0 mm; 1.5 mm; 2.0 mm; 2.5 mm thickness. Nine types of substrates (cobalt-chromium alloy, copper alloy, zirconia, and six shades of VITA Simulate Material) and three shades of Variolink Esthetic try-in pastes (Ivoclar Vivadent) were used to make 270 different combinations of layered specimens. PerkinElmer® LAMBDA 1050 UV/Vis/NIR Spectrophotometer was used in this study. The device measures the reflectance spectrum by which the L*a*b* and ΔE values can be calculated based on the CIEDE2000 formula. ΔE value indicates the color difference between two colors. Averages were compared to the reference specimen. ΔE values of layered specimens have been decreasing by the thickening of the lithium-silicate ceramic. The highest ΔE values were measured beside metal and zirconia substrates. The effect of different try-in pastes was below the perceptibility threshold (ΔE 0.8). ΔE of the reference substrate was zero, proving the precision of the measurement. The optical properties of lithium-silicate glass-ceramic specimens are significantly affected by the shade of the substrate, the thickness, and translucency of the ceramic; however, the effect of try-in paste shades is not significant.