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

## TL;DR

This study examined how three types of composite resins change in color, conversion, and size shortly after being cured, especially when exposed to coffee.

## Contribution

The study provides new insights into the early post-curing behavior of composite resins under coffee exposure.

## Key findings

- All composites showed increased degree of conversion and expansion over time.
- X-tra fil had significantly greater color change when immersed in coffee immediately after curing.
- X-tra fil showed minimal dimensional changes after one month.

## Abstract

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.