Sherif Sultan

Heat-pressed lithium disilicate (LDS)-based glass–ceramic ingots are widely used for the fabrication of dental restorations. Repressing or repeat processing the remaining parts of these ingots has been reported to not adversely affect their mechanical properties. However, there is not enough information on the stainability of crowns constructed from these repeated heat-processed LDS ceramic ingots. Seventy-two identical ceramic crowns were constructed from three different repeated heat-processed LDS ceramic ingots representing three groups (n = 24): E-max (Ivoclare), Lisi (GC), and Celtra (Dentsply Sirona). Each group was subdivided into two subgroups (n = 12) representing experimental (coffee) and control groups. Color changes were assessed according to the CIE L * a * b * system and measured initially, after coffee staining and after brushing. All groups were susceptible to staining; however, they showed different behaviors with respect to the three axes of the CIE L * a * b * system. In general, immersion in coffee followed by brushing decreased the staining of all tested ceramic crowns to the acceptability threshold of color change (ΔE = 2.7). Routine brushing of coffee-stained ceramic crowns made from repeatedly processed LDS, LDS-HDM, and ZLS ceramic ingots restored their color to clinically acceptable levels.