Evaluation of shade matching in the repair of indirect restorative materials with universal shade composites.

Purpose: To evaluate color differences in repair of indirect ceramic and resin nanoceramic CAD/CAM blocks with two universal shade composites after different surface preparations. Materials and methods: 120 samples were prepared from IPS Empress and GC Cerasmart270 CAD/ CAM blocks and thermocycled (5000 cycles, 5°C-55°C). Initial colors of sample surfaces were measured using a spectrophotometer. Rectangular prism-shaped cavities were prepared and repaired with Tokuyama Universal Bond/Omnichroma and G-Multiprimer/G-Premio/Essentia Universal following surface preparation with aluminum oxide, Cojet, and bioactive glass (Sylc). Repaired samples were thermocycled (5000 cycles) and color measurement was performed. Color coordinates L*a*b* were recorded, and color differences were calculated using the CIELab formula. Color differences between pre-and post-repair (ΔE1) and between post-repair and post-aging (ΔE2) were determined. Data were analyzed using Three-way ANOVA with a significance level set at p<0.05. Results: ΔE1 values in all subgroups exceeded the threshold of 3.3. No significant difference was found between the surface preparation processes regarding ΔE1 values. There was no significant difference between the composites and bonding agents in ΔE1 values, except for Cerasmart/Sylc and Empress/Sylc groups. No statistically significant difference was detected in ΔE2 values between the surface preparation treatments in all groups. (p >0.05). Conclusion: Color match of the universal shade composites, which are preferred to increase the esthetic satisfaction and to simplify repair procedures, were found above the acceptable threshold. Post-aging color stability of universal shade composites was below the acceptable threshold.