Properties of Composite Resins Early After Curing: Color Stability, Degree of Conversion, and Dimensional Stability

Objectives: This study assessed the degree of conversion (DC), color, and dimensional stability, of three composite resins early after curing. Materials and Methods: This study was conducted on X-tra fil, Filtek Z250, and Filtek Ultimate composites. To measure DC, the absorption spectra of composites before and after curing (immediately, 15 min, 2 h, 6 and 24 h, 1 week, and 1 month) were recorded by ATR-FTIR. Fifteen specimens were fabricated for each composite and assigned to two experimental groups (15 min immersion in coffee immediately and 2 h after curing) and a control. The CIE L ^{⁣ ∗} a ^{⁣ ∗} b ^{⁣ ∗} color parameters of each specimen and color change (∆E) were measured at the aforementioned time points. Dimensional changes were measured by a digital micrometer. Respective ANOVA and Tukey tests were used for analysis. p  < 0.05 was considered significant. Results: All composites exhibited an increased DC and expansion over time (p  < 0.001). At 1 month, the ∆E of composites immersed in coffee after 2 h was not significantly from the control group. In the immediate coffee immersion group, X-tra fil experienced significantly greater ∆E than Filtek Ultimate (p = 0.02). No other significant differences were found. Conclusion: Time of exposure to coffee after curing had a significant effect on the color stability of X-tra fil only. X-tra fil showed minimum dimensional changes after 1 month.