Color Stability of Microhybrid Composite Resins Depending on the Immersion Medium.

Objective:  The aim of this study was to assess the color stability of two microhybrid composite resins after immersion in different coloring solutions for 4 weeks.

Materials and methods:  Sixty disc-shaped samples (2 mm in thickness and 10 mm in diameter) were prepared according to ISO standard 4049. Two composite resins were used: Filtek Z350 XT (3M ESPE) and Harvard Restore (Harvard Dental International GmbH). After initial color measurements, five samples of each resin were immersed in artificial saliva, Turkish coffee, lemonade, black tea, Coca-Cola 0%, and green tea for 4 weeks. The spectrophotometric measurements were carried out after 24 hours of immersion in the various solutions and then weekly, using a VITA Easyshade Advance 4.0 spectrophotometer (CIE L*a*b* system). Statistical analysis was carried out with SPSS 25.0 software.

Results:  The two composite resins tested revealed discoloration after immersion in all the drinks at a variable immersion period showing different color behaviors. The one-way analysis of variance showed a significant difference in the values of brightness (L), in chromaticity from green to red (a), in chromaticity from blue to yellow (b), and in the color (ΔE) of the two materials at different time intervals. The greatest color change in all the groups was caused by coffee followed by lemonade and black tea followed by green tea, Coca-Cola 0%, and artificial saliva.

Clinical significance:  The importance of color stability of dental restorations is crucial for dental professionals and patients. Indeed, the quality of a restoration is considered from both a functional and esthetic points of view. The information obtained from this study should prove useful for clinicians to make informed decisions in selecting the best materials for their patients' esthetic restorations.

Conclusion:  The Harvard Restore showed a better colorimetric behavior compared with the Filtek Z350. Coffee, black tea, and green tea had the most marked effects on the discoloration of composites, especially on Filtek Z350. Coca-Cola 0% showed a similar behavior to artificial saliva.