Color Stability of IPS Empress 2 Glass-Ceramic after Heat-Pressing and Heat-Treatments

열가압 및 열처리에 따른 IPS Empress 2 Glass-Ceramic의 색 안정성

This study was performed to investigate the color stability of IPS Empress 2 glass-ceramic after heat-pressing and/or heat-treatments. Three types of IPS Empress 2 ingots (shade 100, 300, 500) were tested. For this study, three groups were prepared as follows: group 1 is as-received material, group 2 is heat-pressed material, and group 3 is fully heat -treated material. The color of the specimens was measured with a colorimeter. The data were statistically evaluated with one-way ANOVA and Scheffe's multiple test. The results obtained were as follows: 1. IPS Empress 2 glass-ceramic demonstrated less color stability according as the shade is lighter. Namely, the shade 500 showed the lowest color shifts and the shade 100 showed the greatest color shifts after heat-pressing and heat-treatments. 2. In the cases of shade 100 and 300, the changes of ${\Delta}E^*$ were affected mostly by the changes of $L^*$ and $b^*$. 3. In ${\Delta}E^*$ of the shade 100, there were significant differences among the group 1, 2, and 3 (P<0.001). 4. In ${\Delta}E^*$ of the shade 300, there were significant differences between the group 1 and 2, and the group 1 and 3 (P<0.001). 5. In ${\Delta}E^*$ of the shade 500, there was significant difference only between the group 1 and 3 (P<0.001).