Color stability of lithium disilicate ceramics after aging and immersion in common beverages

Statement of problem. The color of an esthetic restoration and its color stability are important for long-term success. However, the impact of common beverages on lithium disilicate ceramic is not well known. Purpose. The purpose of this in vitro study was to investigate color variations of lithium disilicate ceramics after thermocycling (TC) and immersion in commonly consumed beverages. Material and methods. A total of 288 specimens (1x10x10 mm) were fabricated from IPS e-max computer-aided design (CAD) (n=72), IPS e-max CERAM ([CER] n=72), IPS e-max Press with glazing ([PG] n=72), and IPS e-max Press without glazing ([PNG] n=72) according to the manufacturer's instructions. Each group was divided into 4 subgroups (n=18): TC, coffee, black tea, and red wine, Thermocycling was performed at 21 900 cycles at 5 degrees C, 37 degrees C, 55 degrees C, and 37 degrees C (3 years' clinical simulation), whereas the specimens were soaked in the staining solutions for up to 54 hours (3 years' clinical simulation). Color parameters L*, a*, and b* were assessed with an ultraviolet-visible spectroscopy recording spectrophotometer. Color difference (Delta E) was calculated using the equation [Delta E= [(Delta L*)(2) + (Delta a*)(2) + (Delta b*)(2)](1/2)]. Intraexaminer reliability was assessed by using the intraclass correlation coefficient. Two-way analysis of variance was used for the analysis of Delta E, and the parameters L*, a*, and b* were analyzed with linear mixed models for repeated measurements and the Bonferroni pair-wise comparison test (alpha=.05). Results. Parameters SE, L*, a*, and b* were significantly affected by the interaction between material and treatment (P<.001). A Delta E > 1 was recorded for PG with tea, wine, and coffee, PG after TC and CER after TC. For L*, greater reduction was observed for PNG with tea and CER after TC, whereas for a* significant changes were positive (to red shades), except for PNG with TC, where PNG with wine showed the greatest positive change. For b*, significant changes were negative (to blue shades) except for PNG with tea and coffee and CAD with tea. Conclusions. All groups demonstrated color changes below the clinically perceptible level (Delta E<3.7), except PNG in tea which showed statistically significant color differences (Delta E>4). CAD presented higher color stability compared with the nonglazed Press specimens.