Determination of the degree of conversion, the diffuse reflectance, and the color stability after different aging processes of gingiva-colored composite resins.

Abstract

To determine the degree of conversion (DC) and spectral diffuse reflectance of four different gingiva-colored composites and to evaluate their color stability after various aging processes. The gingiva-colored composites were assigned to four experimental groups (Anaxgum (AG), Crea.lign paste Gum (CB), Gradia Gum (GR), SR Nexco Gum (NC)). A total of 120 disc-shaped specimens (10 × 2mm) (n = 30/group) were polymerized in a Teflon mold. The nature of chemical bonding was studied by Fourier transform infrared spectroscopy (FTIR). Diffuse reflection spectra of the polymerized specimens were gathered using an ultraviolet-visible-near infrared (UV-Vis-NIR) spectrophotometer. Specimens subjected to aging methods were divided into three subgroups (n = 10): ultraviolet aging, hydrothermal aging, and autoclave aging. Color differences (ΔE*ab and ΔE00 ) were determined by colorimetry before and after aging. The statistical analysis was done using a two-way ANOVA along with paired sample t-test and Bonferroni's post hoc test. Conversion degrees varied between 26.9% and 59.7% and all groups showed 3 or 4 maxima at different positions in the visible region of the spectrum. Both ΔE*ab and ΔE00 values were significantly different from the groups of different brands for all types of aging processes. Similarly, there were significantly different ΔE*ab and ΔE00 values according to the aging procedure for all groups of particular brands, except for ΔE00 of SR Nexco Gum (NC). The aging procedures resulted in significant color differences between similar shades of four commercial gingiva-colored composites. The composite resins showed different degrees of conversion and diffuse reflectance spectra. The aging conditions tested affected the color stability. Patients with gingiva-colored indirect restorations should be informed about time-dependent discoloration.