Resin cement color stability and its influence on the final shade of all-ceramics.

OBJECTIVES: Adhesive resin cements may go through internal discoloration, which may show-through and affect the appearance of translucent all-ceramic restorations. This in vitro study evaluated the amount of resin cement color change and its effect on the final shade of the all-ceramics.
METHODS: Three different resin cements in both light and dual-cure forms were included in the study (Nexus-2/Kerr; Appeal/Ivoclar Vivadent; Calibra/Dentsply). All resin cements contained veneered (IPS Empress Esthetic, ETC1 shade, 20 mm × 1 mm ingot discs) and uncovered groups (n=10/group), all luted on white backgrounds (acetalpolyoxymethylene/Delrin(®)). Curing was performed according to ISO standards with a calibrated LED curing-light (Flashlite 1401). Samples were stored in 37°C distilled water at dark. Spectrophotometric baseline color measurements (Color Eye 7000A) were performed from the samples' top surfaces at 24h (D65 illuminator). Samples were subjected to 65 h of accelerated ageing (Atlas Ci4000). Further color measurements from the same areas were recorded in CIEL*a*b* coordinates where a ΔE data above 3 was accepted as visible discoloration (OptiviewLite-1.9software). Statistical analysis was performed using a nested random effects model and Tukey's post hoc analysis.
RESULTS: Light-cure groups showed better color stability in all three resins but only in Appeal resin cement, the dual-cure group discolored significantly more (p<0.001). More discoloration was recorded on uncovered cement groups that represented the exposed cement at the margins. There was no visible color change (ΔE>3) through the ceramic surface on any veneered group.
CONCLUSIONS: All resin cements showed varying degrees of discoloration after accelerated ageing however their actual color change was partially masked by the ceramic. Dual-cure resin cements may affect aesthetics on restoration margins if directly exposed.