Influence of resin cement on color stability when tuting lithium disilicate and zirconia restorations A spectrophotometry study

Aim: To evaluate the influence of resin cement on the color stability of lithium disilicate and zirconia restorations immersed in coffee after aging. Materials and methods: Eighty maxillary premolars were classified into eight groups (n = 10) based on restorative material type (lithium disilicate or zirconia), resin cement type (G-CEM LinkForce; GC Corporation or Panavia SA Cement Plus Automix; Kuraray Noritake Dental), and preheating temperature (25 degrees C or 54 degrees C). Following tooth preparation, each restoration was bonded to its corresponding substrate. Using a reflectance spectrophotometer, Commission Internationale de l'Eclairage (CIE) tristimulus values were detected and calculated (D65 standard illumination, 10-degree observer angle). All specimens were aged (240,000 load cycles followed by 10,000 thermal cycles), then immersed in coffee (18 h). Following that, the second measure-ments of the color coordinates were determined. The total color differences were measured, and the data were statistically analyzed (alpha = 0.05). Results: The temperature had a significant effect on Delta L' (P < 0.001), Delta C' (P < 0.001), and Delta H' (P < 0.001). The lithium disilicate restorations were more color stable than the zirconia restorations. Also, there was a significant difference (P = 0.047) between the LinkForce (2.28 +/- 0.48) and Panavia SA (2.15 +/- 0.46) cement. The restorations cemented at a temperature of 54 degrees C (1.76 +/- 0.11) showed significant color differences (P < 0.001) compared with those cemented at a temperature of 25 degrees C (2.67 +/- 0.15). A three-way analysis of variance (ANOVA) test revealed that the interaction between the ceramic material, cement type, and temperature had no statistically significant effect (P = 0.611) on the color stability of the ceramic restorations. Conclusions: Cement type has a significant effect on the color stability of lithium disilicate and zirconia restorations. Cement at a temperature of up to 54 degrees C enhances the color stability of lithium disilicate and zirconia restorations.