Effects of treatment with aqueous and acid-based coloring liquid on the color of zirconia.

ABSTRACT

STATEMENT OF PROBLEM: To preserve the mechanical property of color-treated zirconia for optimal restoration longevity, aqueous colorants have been developed as an alternative to acid-based coloring agents. However, little is known regarding the effects of aqueous colorants on the color of zirconia. PURPOSE: The purpose of this in vitro study was to compare the effect of aqueous coloring liquids with acid-based coloring liquids on the color of zirconia. MATERIAL AND METHODS: Eighty monolithic zirconia specimens (10×10×2 mm) were fabricated and divided into 4 groups according to their color treatment unshaded zirconia (control), precolored zirconia, aqueous coloring liquid on zirconia, and acid-based coloring liquid on zirconia. The shaded zirconia specimens were further divided into 3 subgroups based on the number of coloring applications used (1, 3, or 6). The International Commission on Illumination (CIELab) color coordinates were measured by spectrophotometry. RESULTS: Significant differences in the CIE a∗ and b∗ values were observed between the specimen groups treated with the aqueous coloring liquid and the acid-based coloring liquid (P<.001). Increasing the number of colorings resulted in an increase in the CIE a∗ and b∗ values and a decrease in the CIE L∗ values in all the groups (P<.001). CONCLUSIONS: Treatment with aqueous coloring liquid on zirconia produced a greater redness or yellowness compared with treatment with acid-based coloring liquid. The coloring of zirconia lowered its brightness and imparted a red/yellow hue.